2012 Vol. 30, No. 2
Display Method:
2012, 30(2): 205-218.
Abstract:
Santanhu Basin, located in northeast of Xinjiang, China, was developed a contenental rift basin from Late Carboniferous to Middle Permian. On the outcrop and the drilling cores of the basin, layers of sublacustrine hydrothermal deposits from which six of them were sampled, were found in the thick mudstones in Lucaogou Formation(P2l), Middle Permian. The hydrothermal samples can be divided into two types: the first type is formed of analcime, sanidine, orthoclase, dolomite and ankerite.The carbonates were detected of concentrating iron and manganese. The second type is formed of analcime, quartz, and carbonates. Most analcime was observed to be xenomorphic block or amorphous gelatinoid otherwise from automorphic tetragonaltrisoctahedron under the SEM. Major elements of all samples were characterized as being rich in SiO2, Al2O3，Na2O，and poor in TiO2. Trace element of the samples show enrichemnt of highly incompatibility elements, such as Ba, Rb, K, Ta, Sr, Zr and Hf, and are lack of Th, Nb, and Ti relatively. The ratios of Sr/Nd = 44.73~831.78, Nb*=0.02~0.17. ΣREE= 7.33 ~20.619 μg/g, LaN/YbN=2.50 ~16.00, LREE/HREE=4.77～11.20. δEu varies from0.6 to 0.99 which shows negative anomalism to primitive mantle , however, δCe value which varies from 0.96 to 1.04 shows the similarity to primitive mantle. The major and trace elements (includes REE) reveal the distinct differences with the basalts and trachytoids of Permian in the same basin, and also disagree with the average value of Upper Crust. 87Sr/86Sr = 0.705 118~0.706 438, 143Nd/144Nd =0.512454~0.512713，εNd=0.81～3.84. Isotope composition indicates that mantle materials may participate in the hydrothermal fluid with which the hydrothermal minerals were deposited. By the analysis of the lithology, geochemistry, and Sr, Nd isotope, the characteristics of the samples suggest that they are an assemblage of hydrothermal rocks which are related to the hot springs exhalation at the lake bottom in Santanghu continental rift basin. Besides the Crust and meteoric components, the hydrothermal fluid of the rocks was probabely composed of the substance sourced from deep earth.
Santanhu Basin, located in northeast of Xinjiang, China, was developed a contenental rift basin from Late Carboniferous to Middle Permian. On the outcrop and the drilling cores of the basin, layers of sublacustrine hydrothermal deposits from which six of them were sampled, were found in the thick mudstones in Lucaogou Formation(P2l), Middle Permian. The hydrothermal samples can be divided into two types: the first type is formed of analcime, sanidine, orthoclase, dolomite and ankerite.The carbonates were detected of concentrating iron and manganese. The second type is formed of analcime, quartz, and carbonates. Most analcime was observed to be xenomorphic block or amorphous gelatinoid otherwise from automorphic tetragonaltrisoctahedron under the SEM. Major elements of all samples were characterized as being rich in SiO2, Al2O3，Na2O，and poor in TiO2. Trace element of the samples show enrichemnt of highly incompatibility elements, such as Ba, Rb, K, Ta, Sr, Zr and Hf, and are lack of Th, Nb, and Ti relatively. The ratios of Sr/Nd = 44.73~831.78, Nb*=0.02~0.17. ΣREE= 7.33 ~20.619 μg/g, LaN/YbN=2.50 ~16.00, LREE/HREE=4.77～11.20. δEu varies from0.6 to 0.99 which shows negative anomalism to primitive mantle , however, δCe value which varies from 0.96 to 1.04 shows the similarity to primitive mantle. The major and trace elements (includes REE) reveal the distinct differences with the basalts and trachytoids of Permian in the same basin, and also disagree with the average value of Upper Crust. 87Sr/86Sr = 0.705 118~0.706 438, 143Nd/144Nd =0.512454~0.512713，εNd=0.81～3.84. Isotope composition indicates that mantle materials may participate in the hydrothermal fluid with which the hydrothermal minerals were deposited. By the analysis of the lithology, geochemistry, and Sr, Nd isotope, the characteristics of the samples suggest that they are an assemblage of hydrothermal rocks which are related to the hot springs exhalation at the lake bottom in Santanghu continental rift basin. Besides the Crust and meteoric components, the hydrothermal fluid of the rocks was probabely composed of the substance sourced from deep earth.
2012, 30(2): 219-230.
Abstract:
As a kind of chemical rock, the porosity and permeability of carbonate rock is influenced obviously by diagenesis. Dissolution is directly related to the quality of carbonate reservoir. The solubility of carbonate minerals in the buried environments is closely controlled by the chemistry of groundwater, the temperature, pH value and so on. According to the chemical thermodynamics theory, Gibbs freeenergy change ΔG of the equilibrium reaction of calcite and dolomite can be calculated to judge the dissolution trend of calcite and dolomite. Thermodynamic models of the reactions between the minerals and groundwater were established in a closed system. This theoretical model is used in the northern part of Tarim Basin to evaluate the dissolution trend of the CambrianOrdovician under the buried condition. The calculated results of ΔG from the reactions between carbonate rock and formation water are almost negative in the study area, which indicates that the buried environment is favorite for the dissolution of carbonate rock in the CambrianOrdovician. Gibbs freeenergy of Cambrian dolomite is less than Ordovician limestone, and that means dolomite is easier to dissolve than limestone in this deeply buried condition. This conclusion is also supported by cores and previous experimental simulation. Calculation results in Yuqi area are also negative, which implies the strong precipitation of calcite in the caves in this region does not happen in present condition. This conclusion also can be proved from the cores of the CambrianOrdovician.
As a kind of chemical rock, the porosity and permeability of carbonate rock is influenced obviously by diagenesis. Dissolution is directly related to the quality of carbonate reservoir. The solubility of carbonate minerals in the buried environments is closely controlled by the chemistry of groundwater, the temperature, pH value and so on. According to the chemical thermodynamics theory, Gibbs freeenergy change ΔG of the equilibrium reaction of calcite and dolomite can be calculated to judge the dissolution trend of calcite and dolomite. Thermodynamic models of the reactions between the minerals and groundwater were established in a closed system. This theoretical model is used in the northern part of Tarim Basin to evaluate the dissolution trend of the CambrianOrdovician under the buried condition. The calculated results of ΔG from the reactions between carbonate rock and formation water are almost negative in the study area, which indicates that the buried environment is favorite for the dissolution of carbonate rock in the CambrianOrdovician. Gibbs freeenergy of Cambrian dolomite is less than Ordovician limestone, and that means dolomite is easier to dissolve than limestone in this deeply buried condition. This conclusion is also supported by cores and previous experimental simulation. Calculation results in Yuqi area are also negative, which implies the strong precipitation of calcite in the caves in this region does not happen in present condition. This conclusion also can be proved from the cores of the CambrianOrdovician.
2012, 30(2): 231-239.
Abstract:
The diagenetic evolution modes of clastic rocks in deep formation of Paleogene in the main areas of Jiyang subbasin are researched through thinsection analysis, scan electricity microscope observation, Ro test, and reservoir physical parameters analyses, etc and combining histories of tectonic development. It is recognized that there are six types of diagenetic evolution modes mainly affected by tectonic setting, reservoir pressure and fluid environment in it. There are early moderatestrong overpressure, moderatestrong compaction, cementation and dissolution with the multiple medium diagenetic evolution mode and the diagenetic evolution mode of late moderatestrong overpressure, strong compaction, cementation and strong dissolution with acidic medium on the weak steep slopes or gentle slopes. The strength of reservoir compaction is mainly affected by the formation time of the overpressure and the fluid environments are controlled by different tectonic setting in these cases. There are diagenetic evolution mode of normal pressure or weak overpressure, moderatestrong compaction, cementation and strong dissolution with the acidic thermal fluid and diagenetic evolution mode of weakmoderate overpressure, little strong compaction and cementation and strong dissolution with the acidic thermal fluid in the deep sags. Thermal fluid which enhances the dissolution of acid soluble components is the main influencing factor of these diagenetic evolution modes. There are diagenetic evolution mode of moderatestrong compaction, cementation and weak dissolution with acdic medium and diagenetic evolution mode of strong cementation, weak moderate dissolution with multiple medium in normal pressure condition on the steep slopes. The multiple medium which results from early deposition water, late diagenetic water and mixture of both is the main influencing factor in these cases. It's considered that the stratum and buried depth is the primary factor of the diagenetic alteration of the deep formation in Jiyang subbasin, Paleogene, and the tectonic position is the basic premise of diagenetic pressure and fluid field characteristic. The deep thermal fluid has different effects on reservoir evolution in different fluid fields. Multiple diagenetic environment of acidalkaline alternating increases the number of secondary porosity and affects vertical distribution of secondary porosity, but preservation rate of the original porosity in multiple diagenetic environment is more than 5% lower than that in acidic diagenetic environment.
The diagenetic evolution modes of clastic rocks in deep formation of Paleogene in the main areas of Jiyang subbasin are researched through thinsection analysis, scan electricity microscope observation, Ro test, and reservoir physical parameters analyses, etc and combining histories of tectonic development. It is recognized that there are six types of diagenetic evolution modes mainly affected by tectonic setting, reservoir pressure and fluid environment in it. There are early moderatestrong overpressure, moderatestrong compaction, cementation and dissolution with the multiple medium diagenetic evolution mode and the diagenetic evolution mode of late moderatestrong overpressure, strong compaction, cementation and strong dissolution with acidic medium on the weak steep slopes or gentle slopes. The strength of reservoir compaction is mainly affected by the formation time of the overpressure and the fluid environments are controlled by different tectonic setting in these cases. There are diagenetic evolution mode of normal pressure or weak overpressure, moderatestrong compaction, cementation and strong dissolution with the acidic thermal fluid and diagenetic evolution mode of weakmoderate overpressure, little strong compaction and cementation and strong dissolution with the acidic thermal fluid in the deep sags. Thermal fluid which enhances the dissolution of acid soluble components is the main influencing factor of these diagenetic evolution modes. There are diagenetic evolution mode of moderatestrong compaction, cementation and weak dissolution with acdic medium and diagenetic evolution mode of strong cementation, weak moderate dissolution with multiple medium in normal pressure condition on the steep slopes. The multiple medium which results from early deposition water, late diagenetic water and mixture of both is the main influencing factor in these cases. It's considered that the stratum and buried depth is the primary factor of the diagenetic alteration of the deep formation in Jiyang subbasin, Paleogene, and the tectonic position is the basic premise of diagenetic pressure and fluid field characteristic. The deep thermal fluid has different effects on reservoir evolution in different fluid fields. Multiple diagenetic environment of acidalkaline alternating increases the number of secondary porosity and affects vertical distribution of secondary porosity, but preservation rate of the original porosity in multiple diagenetic environment is more than 5% lower than that in acidic diagenetic environment.
2012, 30(2): 251-263.
Abstract:
Changpu Formation of lower Jurassic outcropped in Haifeng, Guangdong province is a set of shallow marine clastic deposits, composed of shoreface sandstones and turbidite deposits in the muddy shelf environment. The particle size analysis of sandstones shows that the probability cumulative curve of shoreface sandstone represents twostage and the frequency histogram is a single peak, and cumulative probability curve of turbidite represents threestage and the frequency histogram is bimodal. The lithofacies succession of Changpu Formation is a rock association indicating the transgressiveregressive processes with the thickening upward of sandstone layers. The transgressive regressive succession indicates that two eustatic sea level change occurred during development of Changpu Formation. The shallow muddy and turbidite deposits constitute a flysch succession. Markov chain analysis shows that it is a significant coarseningupward succession. Geochemical data reveal that sediments of Changpu Formation have features of both passive continental margin and active continental margin. The sediments were from the recycled orogen related to the magmatic arc orogen and subduction complex after analysis of the Dickinson Graphic of sandstone composition. Haifeng region was close to the thrust fault zone. The sedimentary basin developed under a tectonic setting of compressional retroarc foreland during the early Jurassic, and the basin provenances were both of recycled orogen zone and continental block.
Changpu Formation of lower Jurassic outcropped in Haifeng, Guangdong province is a set of shallow marine clastic deposits, composed of shoreface sandstones and turbidite deposits in the muddy shelf environment. The particle size analysis of sandstones shows that the probability cumulative curve of shoreface sandstone represents twostage and the frequency histogram is a single peak, and cumulative probability curve of turbidite represents threestage and the frequency histogram is bimodal. The lithofacies succession of Changpu Formation is a rock association indicating the transgressiveregressive processes with the thickening upward of sandstone layers. The transgressive regressive succession indicates that two eustatic sea level change occurred during development of Changpu Formation. The shallow muddy and turbidite deposits constitute a flysch succession. Markov chain analysis shows that it is a significant coarseningupward succession. Geochemical data reveal that sediments of Changpu Formation have features of both passive continental margin and active continental margin. The sediments were from the recycled orogen related to the magmatic arc orogen and subduction complex after analysis of the Dickinson Graphic of sandstone composition. Haifeng region was close to the thrust fault zone. The sedimentary basin developed under a tectonic setting of compressional retroarc foreland during the early Jurassic, and the basin provenances were both of recycled orogen zone and continental block.
2012, 30(2): 264-273.
Abstract:
Braidedstream deposits are the major depositional system of lower Jurassic in the northwestern margin, Junggar Basin. Based on observation and description of cores, thinsection identification, assay and analysis, and well logging of Badaowan Formation, lower Juassic in No.7 area of Xinjiang oil field, the depositional markers' features of braided stream were generalized in which rock types are simple such as; the maturity of rock is low; rock compositions are complicate; plant residue carbides locally concentrate into stratiform; sedimentary structures are plentiful; there is a dual structure that a top layer and a bottom layer vertically overprint and many sandbodies form pan communicated sandbody. This parper further analysed the changes of color, rock, granularity, sedimentary structure and logging responses in vertical depositional associations of braided stream, which is interpreted as a sequence of channel lag deposit, midchannel bar and flood plain. Using the spatial distribution of microfacies, it summarized the facies model of braided stream of Badaowan Formation, lower Juassic in No.7 area. These results have vital significance for progressive exploration and adjusted development of oil field.
Braidedstream deposits are the major depositional system of lower Jurassic in the northwestern margin, Junggar Basin. Based on observation and description of cores, thinsection identification, assay and analysis, and well logging of Badaowan Formation, lower Juassic in No.7 area of Xinjiang oil field, the depositional markers' features of braided stream were generalized in which rock types are simple such as; the maturity of rock is low; rock compositions are complicate; plant residue carbides locally concentrate into stratiform; sedimentary structures are plentiful; there is a dual structure that a top layer and a bottom layer vertically overprint and many sandbodies form pan communicated sandbody. This parper further analysed the changes of color, rock, granularity, sedimentary structure and logging responses in vertical depositional associations of braided stream, which is interpreted as a sequence of channel lag deposit, midchannel bar and flood plain. Using the spatial distribution of microfacies, it summarized the facies model of braided stream of Badaowan Formation, lower Juassic in No.7 area. These results have vital significance for progressive exploration and adjusted development of oil field.
2012, 30(2): 274-282.
Abstract:
The genetic type of sandbodies and sedimentary filling models were controlled by characteristics of sedimentary environment in sedimentary basin. According to the systematic sampling of argillaceous sediments of Es4x of Well Fengshen 2, Guan 112 and Liang 120 in Dongying Depression, whole rock Xray diffraction and macroelements and microelements were analyzed, based on which the paleoclimate indexs and paleosalinity indexs of Es4x of Dongying Depression were studied. It turned out that the paleoclimate index Rb/Sr was direct proportion to content of quartz and feldspar, element Cr and element P and inversely proportional to paleosalinity index content of carbonate and sulphate. The increasing ratio of Rb/Sr reflected relatively damp climate, while the increasing content of carbonate and sulphate reflected relatively arid climate. The characteristics of the climate of the period of Es4x of Dongying Depression were frequent damp climate alternate with arid climate. At the period of damp climate, the relative lake level rise and the salinity of lake water decline, while the relative lake level decline and the salinity of lake water rise at the period of arid climate. The characteristics of climate made the lake of Es4x of Dongying Depression have the character of high frequency oscillatory salt lake. Clastic sediments were the main deposits at the period of damp climate, including alluvial fan sediments, shallow water delta sediments, lakeshore beachbar sediments and nearshore subaqueous fan sediments, and the sag belt mainly deposited mudstone, lime mudstone, gypseous mudstone and a small quantity of argillaceous gypsum rock. At the period of arid climate, the deposition was mainly developed in sag belt and was characterised by gypsum and salt sediments, which have the evolutive sequence of gypseous mudstone, argillaceous gypsum rock, gypsum rock and salt rock upward and the zonal structure with lime mudstone, gypseous mudstone, argillaceous gypsum rock, gypsum rock and salt rock from the margin to the center of the lake in the plane.
The genetic type of sandbodies and sedimentary filling models were controlled by characteristics of sedimentary environment in sedimentary basin. According to the systematic sampling of argillaceous sediments of Es4x of Well Fengshen 2, Guan 112 and Liang 120 in Dongying Depression, whole rock Xray diffraction and macroelements and microelements were analyzed, based on which the paleoclimate indexs and paleosalinity indexs of Es4x of Dongying Depression were studied. It turned out that the paleoclimate index Rb/Sr was direct proportion to content of quartz and feldspar, element Cr and element P and inversely proportional to paleosalinity index content of carbonate and sulphate. The increasing ratio of Rb/Sr reflected relatively damp climate, while the increasing content of carbonate and sulphate reflected relatively arid climate. The characteristics of the climate of the period of Es4x of Dongying Depression were frequent damp climate alternate with arid climate. At the period of damp climate, the relative lake level rise and the salinity of lake water decline, while the relative lake level decline and the salinity of lake water rise at the period of arid climate. The characteristics of climate made the lake of Es4x of Dongying Depression have the character of high frequency oscillatory salt lake. Clastic sediments were the main deposits at the period of damp climate, including alluvial fan sediments, shallow water delta sediments, lakeshore beachbar sediments and nearshore subaqueous fan sediments, and the sag belt mainly deposited mudstone, lime mudstone, gypseous mudstone and a small quantity of argillaceous gypsum rock. At the period of arid climate, the deposition was mainly developed in sag belt and was characterised by gypsum and salt sediments, which have the evolutive sequence of gypseous mudstone, argillaceous gypsum rock, gypsum rock and salt rock upward and the zonal structure with lime mudstone, gypseous mudstone, argillaceous gypsum rock, gypsum rock and salt rock from the margin to the center of the lake in the plane.
2012, 30(2): 283-290.
Abstract:
Mixed rocks is composed of lacustrine carbonates and terrigenous clastics, which is neither typical carbonate rocks nor classic clastic rocks. As a special type of rock, it develops extensively in the Meber 4 of Shahejie Formation of Paleogene in Leijia area of Western Sag of Liaohe Oilfield. Based on detailed observations of cores and thin sections combined with comprehensive analyses of testing data, the mixed sedimentation of Leijia area is studied carefully, such as geological setting, petrological characteristic and depositional environment, etc. The characteristics of mixed sedimentation are textural mixed and interbedded mixed. The former is between terrigenous fragment constituent and carbonate constituent in one layer. The latter is between terrigenous fragment and carbonate of lacustrine facies in high frequency. Various tectonic settings develop in different mineral matters in textural mixed rocks of Leijia area. Mixed rocks that mostly consist of intrabasinal composition develops in the west gently slope belt, which the lithologies are mainly composed of argillaceous dolomite, argillaceous limestone, dolomitebearing sandstone, limestonebearing sandstone and so on. Mixed rocks mainly composed of terrigenous components develops in the east steep slope belt and the middle part, which the lithologies are mainly composed of dolomitic sandstone, dolomitic mudstone, calcareous mudstone, calcareous sandstone and so on. Carbonated volcanic breccia distributes in local region, which the new type of mixed deposit is discovered for the first time by this paper. Mixed sedimentary action types include blended mixed deposits and complex mixed deposits I, salutatory mixed deposits are developing in the local region. Through the study of dolomite genesis on theory, the penecontemporaneous dolomization is pointed out in this area and the transgression and palaeoclimate have exerted an important effect on the formation of the dolostones. At last, the geological conditions and sedimentary environment for the formation of mixed deposits are discussed.
Mixed rocks is composed of lacustrine carbonates and terrigenous clastics, which is neither typical carbonate rocks nor classic clastic rocks. As a special type of rock, it develops extensively in the Meber 4 of Shahejie Formation of Paleogene in Leijia area of Western Sag of Liaohe Oilfield. Based on detailed observations of cores and thin sections combined with comprehensive analyses of testing data, the mixed sedimentation of Leijia area is studied carefully, such as geological setting, petrological characteristic and depositional environment, etc. The characteristics of mixed sedimentation are textural mixed and interbedded mixed. The former is between terrigenous fragment constituent and carbonate constituent in one layer. The latter is between terrigenous fragment and carbonate of lacustrine facies in high frequency. Various tectonic settings develop in different mineral matters in textural mixed rocks of Leijia area. Mixed rocks that mostly consist of intrabasinal composition develops in the west gently slope belt, which the lithologies are mainly composed of argillaceous dolomite, argillaceous limestone, dolomitebearing sandstone, limestonebearing sandstone and so on. Mixed rocks mainly composed of terrigenous components develops in the east steep slope belt and the middle part, which the lithologies are mainly composed of dolomitic sandstone, dolomitic mudstone, calcareous mudstone, calcareous sandstone and so on. Carbonated volcanic breccia distributes in local region, which the new type of mixed deposit is discovered for the first time by this paper. Mixed sedimentary action types include blended mixed deposits and complex mixed deposits I, salutatory mixed deposits are developing in the local region. Through the study of dolomite genesis on theory, the penecontemporaneous dolomization is pointed out in this area and the transgression and palaeoclimate have exerted an important effect on the formation of the dolostones. At last, the geological conditions and sedimentary environment for the formation of mixed deposits are discussed.
2012, 30(2): 291-300.
Abstract:
On the basis of stratigraphic theory and the analysis of core,thin section, logging, seismic and paleontological data,five sequence boundaries which are similar to type two sequence boundary of Vail sequence and four sequences can be recognized of carbonate of Zhujiang Formation in the eastern Pearl River Mouth Basin.The isochronous formation framework has been established. According to the study of sequence stratigraphy,the temporal and distribution of reservoir of the carbonate rock can be inferred. The relation between reservoir and sequence stratum is determined and the reservoir mainly occurs in the HST of the sequence framework. The results show that platform edge reef and bioclast bank of SQ3HST in liuhua area are the favorable reservoir belt, reef and bioclast bank of platform edge or platform point reef and bioclast bank of internal platform of SQ1HST and SQ2HST in Huizhou area and platform point reef and bioclast bank of internal platform of SQ1HST in lufeng area are the less favorable reservoir.
On the basis of stratigraphic theory and the analysis of core,thin section, logging, seismic and paleontological data,five sequence boundaries which are similar to type two sequence boundary of Vail sequence and four sequences can be recognized of carbonate of Zhujiang Formation in the eastern Pearl River Mouth Basin.The isochronous formation framework has been established. According to the study of sequence stratigraphy,the temporal and distribution of reservoir of the carbonate rock can be inferred. The relation between reservoir and sequence stratum is determined and the reservoir mainly occurs in the HST of the sequence framework. The results show that platform edge reef and bioclast bank of SQ3HST in liuhua area are the favorable reservoir belt, reef and bioclast bank of platform edge or platform point reef and bioclast bank of internal platform of SQ1HST and SQ2HST in Huizhou area and platform point reef and bioclast bank of internal platform of SQ1HST in lufeng area are the less favorable reservoir.
2012, 30(2): 301-309.
Abstract:
Daqing Placanticline was located in the central sag of Songliao Basin. Upper Putaohua oilbearing layer (PI) belongs to a part of the 3rd Member of Qingshankou Formation and 1st Member of Yaojia Formation. According to the data of logging, cores, seismic and highresolution sequence stratigraphy theory, the highprecision sequence stratigraphy framework has been established. The 3rd Member of Qingshankou Formation and the 1st Member of Yaojia Formation are combined to one long base level cycle, which was limited by flooding surfaces. The PI oilbearing layer is judged leaping over the transformation surface, which could be considered as one middle base level cycle and 14 short base level cycles inside. Flooding surfaces are considered as marin surfaces of the middle term cycle in the study area, corresponding to the mudstone of front delta facies in top and bottom of PI oilbearing layer. Because of the stable spreading for this front delta mudstone, it is easy to track the surface of middle base level cycle. The transformation surface in the middle base level cycle corresponds to the unconformity between Qingshankou Formation and Yaojia Formation. The framework of highresolution sequence stratigraphy is established based on the understanding above.Based on the framework of highresolution sequence stratigraphy, several sections are established. Much bigger thickness of stratigrahpy and more shortterm base level cycles are found in southern of study area. According to the analysis of these highdense sections, three kinds of stratigraphy overriding models are proposed, includes active progradation model in low accommodation condition, forcing progradation model in lowest accommodation condition and congruence model of progradation and erosion. The first model formed in lower accommodation space (A/S<1), which reflected relatively stable lake level in the study area (the increasing rate of lakelevel can not meet the abundant supply of source material), the new accommodation space formed by lake level rising was rapidly filled with sediment, leading the location of shoreline migrate to depocenter. The second model formed in much lower accommodation space conditions (A/S<<1), accompaning with relatively decline of lake level in the study area. PI32 and PI31 layers in Lamadian and Saertu area were belong to the this kind of model. Gentle slope of Shallowwater delta will make this deposition hiatus development widely.PI43PI33 layers belong to the third model. With the continuous decline of the midterm base level, PI43, PI42 and PI41 layer showed progradation style, the ratio of sand increase to up. PI43PI33 layers in Saertu and Lamadian area were eroded after the tectonic uplifting in the northern area.These stratigraphy overriding models are the main facts causing the differences in stratigraphic thickness and number of shortterm cycles. The establishment of these deposition models is favor of the highprecision strata correlation in LaSaXing area, northern Daqing Placanticline.
Daqing Placanticline was located in the central sag of Songliao Basin. Upper Putaohua oilbearing layer (PI) belongs to a part of the 3rd Member of Qingshankou Formation and 1st Member of Yaojia Formation. According to the data of logging, cores, seismic and highresolution sequence stratigraphy theory, the highprecision sequence stratigraphy framework has been established. The 3rd Member of Qingshankou Formation and the 1st Member of Yaojia Formation are combined to one long base level cycle, which was limited by flooding surfaces. The PI oilbearing layer is judged leaping over the transformation surface, which could be considered as one middle base level cycle and 14 short base level cycles inside. Flooding surfaces are considered as marin surfaces of the middle term cycle in the study area, corresponding to the mudstone of front delta facies in top and bottom of PI oilbearing layer. Because of the stable spreading for this front delta mudstone, it is easy to track the surface of middle base level cycle. The transformation surface in the middle base level cycle corresponds to the unconformity between Qingshankou Formation and Yaojia Formation. The framework of highresolution sequence stratigraphy is established based on the understanding above.Based on the framework of highresolution sequence stratigraphy, several sections are established. Much bigger thickness of stratigrahpy and more shortterm base level cycles are found in southern of study area. According to the analysis of these highdense sections, three kinds of stratigraphy overriding models are proposed, includes active progradation model in low accommodation condition, forcing progradation model in lowest accommodation condition and congruence model of progradation and erosion. The first model formed in lower accommodation space (A/S<1), which reflected relatively stable lake level in the study area (the increasing rate of lakelevel can not meet the abundant supply of source material), the new accommodation space formed by lake level rising was rapidly filled with sediment, leading the location of shoreline migrate to depocenter. The second model formed in much lower accommodation space conditions (A/S<<1), accompaning with relatively decline of lake level in the study area. PI32 and PI31 layers in Lamadian and Saertu area were belong to the this kind of model. Gentle slope of Shallowwater delta will make this deposition hiatus development widely.PI43PI33 layers belong to the third model. With the continuous decline of the midterm base level, PI43, PI42 and PI41 layer showed progradation style, the ratio of sand increase to up. PI43PI33 layers in Saertu and Lamadian area were eroded after the tectonic uplifting in the northern area.These stratigraphy overriding models are the main facts causing the differences in stratigraphic thickness and number of shortterm cycles. The establishment of these deposition models is favor of the highprecision strata correlation in LaSaXing area, northern Daqing Placanticline.
2012, 30(2): 310-317.
Abstract:
Dickite was detected in carbonate of Xiaohaizi Formation at BachuMarkit area, in Tarim Basin in this study. Identification of dickite was made by XRay diffraction. Through thin section and CL observing, the morphological character and distribution of dickite were studied. Dickite was blocky, and the size of its crystal was 313μm, which distributing widely in the dissolved pores, intercrystalline pores of dolomite, and in the dissolved segment of stylolites. The thin sections in study area were observed under cathode luminescence, and we found that there were some fluorites coexisting with dickite. The mineral association of dickite and fluorite illuminated that there was hydrothermal activity in Xiaohaizi formation in study area. Generally, dickite and fluorite were rich in certain layer, which can be use to trace the depth of hydrothermal fluid. Because of absence of a precursor mineral, and dickite occurring in the formation with temperature less than 100℃, it was proposed that dickite was hydrothermal origin. Hydrothermal fluid not only created the condition of dickite formation, but also led to form many dissolved pores in carbonate of Xiaohaizi Formation. The reaction between hydrothermal fluid and rock led to dolomite was replaced by fluorite, and dolomite recrystallized along the dissolved pore wall. Base on physical properties data of reservoirs, it's obvious that the hydrothermal corrosion can make porosity increase. However, fluorite and dickite filled in pores could destroy porosity. As a result, we suggest that hydrothermal corrosion was the important mechanism of carbonate reservoir formation in Xiaohaizi Formation, which can guide the oil and gas exploration in the future.
Dickite was detected in carbonate of Xiaohaizi Formation at BachuMarkit area, in Tarim Basin in this study. Identification of dickite was made by XRay diffraction. Through thin section and CL observing, the morphological character and distribution of dickite were studied. Dickite was blocky, and the size of its crystal was 313μm, which distributing widely in the dissolved pores, intercrystalline pores of dolomite, and in the dissolved segment of stylolites. The thin sections in study area were observed under cathode luminescence, and we found that there were some fluorites coexisting with dickite. The mineral association of dickite and fluorite illuminated that there was hydrothermal activity in Xiaohaizi formation in study area. Generally, dickite and fluorite were rich in certain layer, which can be use to trace the depth of hydrothermal fluid. Because of absence of a precursor mineral, and dickite occurring in the formation with temperature less than 100℃, it was proposed that dickite was hydrothermal origin. Hydrothermal fluid not only created the condition of dickite formation, but also led to form many dissolved pores in carbonate of Xiaohaizi Formation. The reaction between hydrothermal fluid and rock led to dolomite was replaced by fluorite, and dolomite recrystallized along the dissolved pore wall. Base on physical properties data of reservoirs, it's obvious that the hydrothermal corrosion can make porosity increase. However, fluorite and dickite filled in pores could destroy porosity. As a result, we suggest that hydrothermal corrosion was the important mechanism of carbonate reservoir formation in Xiaohaizi Formation, which can guide the oil and gas exploration in the future.
2012, 30(2): 318-324.
Abstract:
Xray radiograph of sedimentary core contains much information, including sedimentary texture, density, structure, etc. We can quickly extract the information of climate and environment changes from sedimentary core by using digital image processing method, witch may be a powerful research tools to exploring highresolution sedimentary records and palaeoenvironment evolution. Based on the matlab software platform, we obtained the Xray images of the sediment core taken from the subaqueous Yangtze River delta and changed them into digital gray images then for extracting their gray values. Combined with the sediment properties in the core such as grain size parameters, influencing factors of the digital gray values were discussed. The results indicate that the gray values of sediment core are influenced comprehensively by sediment composition, texture and structure, with being dominantly influenced by sediment grainsize. There is a good linear relationship between mean grainsize and gray value. Furthermore, there is a positive correlation between sand, silt and gray value. In contrary, it is of a good negative relationship between clay and gray value. Generally, the Xray image gray value of sediment core may be an ideal proxy of comprehensive sedimentary records.
Xray radiograph of sedimentary core contains much information, including sedimentary texture, density, structure, etc. We can quickly extract the information of climate and environment changes from sedimentary core by using digital image processing method, witch may be a powerful research tools to exploring highresolution sedimentary records and palaeoenvironment evolution. Based on the matlab software platform, we obtained the Xray images of the sediment core taken from the subaqueous Yangtze River delta and changed them into digital gray images then for extracting their gray values. Combined with the sediment properties in the core such as grain size parameters, influencing factors of the digital gray values were discussed. The results indicate that the gray values of sediment core are influenced comprehensively by sediment composition, texture and structure, with being dominantly influenced by sediment grainsize. There is a good linear relationship between mean grainsize and gray value. Furthermore, there is a positive correlation between sand, silt and gray value. In contrary, it is of a good negative relationship between clay and gray value. Generally, the Xray image gray value of sediment core may be an ideal proxy of comprehensive sedimentary records.
2012, 30(2): 325-332.
Abstract:
Six sediment cores were collected during 2007 from the coastal zone of Guangxi province. The temporal evolution of biogenic elements (C, N and P) and metal (Hg, Cu, Pb, Zn, Cd, Cr and As) inputs was clearly recorded by high 210Pbxs-derived sedimentation rates (0.25~1.68 cm y-1), especially in the estuary of Qinjiang river and Nanliu river (1.68 cm·y-1 and 0.70 cm·y-1, respectively), which could be attributed to high rates of river sediment transport. Based on the vertical distributions of enrichment factors and excess fluxes, heavy metals and total phosphorus were obviously enriched in the recent 20 years, but do not exceed the quality standard for marine sediment. The results indicated that the natural inputs prevailed up to the early 1980s except Cu. After this period, the excess metal fluxes could be associated with the intensive use of phosphate fertilizers and the combustion of fossil fuels, which caused a slight enrichment. However, total organic carbon showed decreasing trends toward the surface, which could be associated with the decreases of the mangrove forest derived from tidal flat reclamation recently. According to all indicators, environmental evolution of the Guangxi coast during the recent 100 years can be divided into two stages: (1) before the early 1980s characterized by the relatively low heavy metal pollution and scarce eutrophication; (2) after the early 1980s, the concentrations of heavy metals and total phosphorus are significantly increasing, indicating of the anthropogenic inputs.
Six sediment cores were collected during 2007 from the coastal zone of Guangxi province. The temporal evolution of biogenic elements (C, N and P) and metal (Hg, Cu, Pb, Zn, Cd, Cr and As) inputs was clearly recorded by high 210Pbxs-derived sedimentation rates (0.25~1.68 cm y-1), especially in the estuary of Qinjiang river and Nanliu river (1.68 cm·y-1 and 0.70 cm·y-1, respectively), which could be attributed to high rates of river sediment transport. Based on the vertical distributions of enrichment factors and excess fluxes, heavy metals and total phosphorus were obviously enriched in the recent 20 years, but do not exceed the quality standard for marine sediment. The results indicated that the natural inputs prevailed up to the early 1980s except Cu. After this period, the excess metal fluxes could be associated with the intensive use of phosphate fertilizers and the combustion of fossil fuels, which caused a slight enrichment. However, total organic carbon showed decreasing trends toward the surface, which could be associated with the decreases of the mangrove forest derived from tidal flat reclamation recently. According to all indicators, environmental evolution of the Guangxi coast during the recent 100 years can be divided into two stages: (1) before the early 1980s characterized by the relatively low heavy metal pollution and scarce eutrophication; (2) after the early 1980s, the concentrations of heavy metals and total phosphorus are significantly increasing, indicating of the anthropogenic inputs.
2012, 30(2): 333-339.
Abstract:
The redox potential (Eh) of the surface sediments in the northern waters of Liaodong Bay was directly measured in the autumn of 2007, and the distribution and its main factors including sediments characteristics, the overlying seawater, and river input was studied deeply. The results indicate that: the Eh of the surface sediments ranges between -24.8 mv and -366.7 mv, which means the environment has changed from weak reductive system controlled by O2/H2O, organic matter, MnO2/Mn2+ and Fe(OH)3/Fe2+ in the 1990s to reductive system now mainly controlled by SO24/HS, S/HS and furthermore, there are significant variations in the spatial distribution of Eh, i.e. the value of Eh in the Liaodong Bay tends to become lower from the northeast to the southwest. Although the organic matter is an essential factor of redox reactions, its impact on the distribution of Eh in this region is not obvious due to the higher sedimentation rate and the strong reductive environment. On the contrary, sulfide and temperature have direct impact on the value of Eh, i.e. the higher sulfide and temperature correspond to the lower Eh. Dissolved oxygen of the overlying water is another important factor, and the impact is more obvious especially in the surveyed area with relatively higher dissolved oxygen, where Eh tends to be lower with the decreasing of dissolved oxygen. In addition, the river input is also an important factor affecting the Eh, and the scope is mainly in the Fanshaped region where fresh water can reach with the center of the Shuang Taizi river mouth. In the past two decades, the concentration of organic matter and sulfide keeps increasing due to the intensified human activity, such as landbased pollution and marine aquaculture, which results in the decreasing of Eh and significant change of the environment. In addition, the distribution and change of Eh in the surface sediments of this area should be the results of the combined effects of the longterm emissions of organic matter and sulfur, the temperature, dissolved oxygen in the overlying water and the mixing of the river input and the tide. To a certain extent, it reflects the pollution of this area. So it is necessary to take appropriate measures to strengthen environment protection in order to keep the sustainable development of the regional economy.
The redox potential (Eh) of the surface sediments in the northern waters of Liaodong Bay was directly measured in the autumn of 2007, and the distribution and its main factors including sediments characteristics, the overlying seawater, and river input was studied deeply. The results indicate that: the Eh of the surface sediments ranges between -24.8 mv and -366.7 mv, which means the environment has changed from weak reductive system controlled by O2/H2O, organic matter, MnO2/Mn2+ and Fe(OH)3/Fe2+ in the 1990s to reductive system now mainly controlled by SO24/HS, S/HS and furthermore, there are significant variations in the spatial distribution of Eh, i.e. the value of Eh in the Liaodong Bay tends to become lower from the northeast to the southwest. Although the organic matter is an essential factor of redox reactions, its impact on the distribution of Eh in this region is not obvious due to the higher sedimentation rate and the strong reductive environment. On the contrary, sulfide and temperature have direct impact on the value of Eh, i.e. the higher sulfide and temperature correspond to the lower Eh. Dissolved oxygen of the overlying water is another important factor, and the impact is more obvious especially in the surveyed area with relatively higher dissolved oxygen, where Eh tends to be lower with the decreasing of dissolved oxygen. In addition, the river input is also an important factor affecting the Eh, and the scope is mainly in the Fanshaped region where fresh water can reach with the center of the Shuang Taizi river mouth. In the past two decades, the concentration of organic matter and sulfide keeps increasing due to the intensified human activity, such as landbased pollution and marine aquaculture, which results in the decreasing of Eh and significant change of the environment. In addition, the distribution and change of Eh in the surface sediments of this area should be the results of the combined effects of the longterm emissions of organic matter and sulfur, the temperature, dissolved oxygen in the overlying water and the mixing of the river input and the tide. To a certain extent, it reflects the pollution of this area. So it is necessary to take appropriate measures to strengthen environment protection in order to keep the sustainable development of the regional economy.
2012, 30(2): 340-345.
Abstract:
It has been observed that the Suess effect has influenced the isotopic composition of dissolved inorganic carbon in the sea. However, investigations for the Suess effect on the isotopic composition of organic carbon in the sea are rare. The South China Sea is one of the most important marginal sea in the world and the most crucial area in carbon budget in China Sea. Therefore, understanding the Suess effect occurring in the organic carbon is important for the carbon budget in the South China Sea. Here, the δ13Corg in surficial sediments and sinking particulate matter in South China Sea are reported to study the contribution for the surficial sediment organic material from terrestrial and marine. For marine sediments, the effect from selective degradation for the older sediments is larger than that for the younger one resulting in isotopic compostion of the former organic carbon lighter than the latter. However, the δ13Corg in surficial sediments is higher than that in particulate matter in our results, suggesting that Suess effect is innegligible for the modern process in South China Sea. The reason for this pattern might be that extensive burning of fossil fuels in recent years result in δ13C of atmospheric CO2 and dissolved inorganic carbon in seawater lighter, and then causing the δ13Corg in particulate matter lighter than that in surficial sediments. The difference in δ13Corg between surficial sediments and sinking particulate matter can show the effect that Suess effect exert to the modern progress in South China Sea. After using the difference in δ13Corg between surficial sediments and sinking particulate matter to amend the δ13Corg of terrestrial and marine, the contribution for the surficial sediment organic material from terrestrial is estimated to 48%, and from marine 52% on the adjacent inner shelf of South China Sea. In contrast, the contribution is estimated to 14% from terrestrial and 86% from marine beyond the inner shelf. This suggests the effects on the material input from rivers increase in the marginal sea with increasing human activities recently. This work expands our understanding of carbon isotope as biogeochemical tools for the Suess effect on the isotopic composition of organic carbon in the sea, emphasizing the role that the Suess effect may play in altering the isotopic composition of organic carbon in the sea.
It has been observed that the Suess effect has influenced the isotopic composition of dissolved inorganic carbon in the sea. However, investigations for the Suess effect on the isotopic composition of organic carbon in the sea are rare. The South China Sea is one of the most important marginal sea in the world and the most crucial area in carbon budget in China Sea. Therefore, understanding the Suess effect occurring in the organic carbon is important for the carbon budget in the South China Sea. Here, the δ13Corg in surficial sediments and sinking particulate matter in South China Sea are reported to study the contribution for the surficial sediment organic material from terrestrial and marine. For marine sediments, the effect from selective degradation for the older sediments is larger than that for the younger one resulting in isotopic compostion of the former organic carbon lighter than the latter. However, the δ13Corg in surficial sediments is higher than that in particulate matter in our results, suggesting that Suess effect is innegligible for the modern process in South China Sea. The reason for this pattern might be that extensive burning of fossil fuels in recent years result in δ13C of atmospheric CO2 and dissolved inorganic carbon in seawater lighter, and then causing the δ13Corg in particulate matter lighter than that in surficial sediments. The difference in δ13Corg between surficial sediments and sinking particulate matter can show the effect that Suess effect exert to the modern progress in South China Sea. After using the difference in δ13Corg between surficial sediments and sinking particulate matter to amend the δ13Corg of terrestrial and marine, the contribution for the surficial sediment organic material from terrestrial is estimated to 48%, and from marine 52% on the adjacent inner shelf of South China Sea. In contrast, the contribution is estimated to 14% from terrestrial and 86% from marine beyond the inner shelf. This suggests the effects on the material input from rivers increase in the marginal sea with increasing human activities recently. This work expands our understanding of carbon isotope as biogeochemical tools for the Suess effect on the isotopic composition of organic carbon in the sea, emphasizing the role that the Suess effect may play in altering the isotopic composition of organic carbon in the sea.
2012, 30(2): 346-355.
Abstract:
Through deeply field survey,a Holocene loesssoil profile with interbedded flood slackwater deposits (SWD) was found in Xianyang of the middle reaches of the Weihe River,which recorded the information of palaeoflood events. In order to achieve OSL ages,9 luminescence samples were collected and postIR OSL measurements were used with singlealiquot regenerativedose (SAR) protocol. Grainsize distribution and magnetic susceptibility were also analysed so as to research the occurrence and cause of palaeoflood.The result shows that the fast component is dominant in OSL signals of quartz grains(40~63 μm),which is suitale for postIR OSL measurements. For all dating measurements, preheat temperature of each natural or regenerated dose of young samples and older samples were 260℃ and 240℃,respectively；and the cutheat was set to 220℃. OSL ages increases with depth and conform to layer where were collected except individual ages underestimated.At the NSC site, the layer of flood slackwater deposits (SWD) with horizontal bedding、silty claylike and sallow colour, was in the depth of 95~110 cm,which has typical characteristic of SWD. This flood deposit involve 3 flood depositional layers, indicate of at least 3 palaeoflood evevts occured. The average of lowfrequency magnetic susceptibility of paleosoil was 133.62 108 m3.kg1,was the highest in this profile,while the value of SWD layer was 113.68 108m3.kg1 which was much higher than Malan loess,but lower in paleosoil layer. Grainsize distribution of SWD layer was dominated by silt, the content of silt was 59.43% and clay was 38.107%,the content of sand (>0.05 mm)was the least that was 3.32%. The curve of sand (>0.05 mm) in the SWD layer present a small peak. The dating results show that the extreme palaeofloods occurred 3.0~3.2 ka. According to the analysis of all the result, extraordinary floods occurred 3 200～3 000 a B. P. in the Weihe river ,the period of flood occurred frequently. Three flood depositional layers indicates that each of the slackwater deposit beds has recorded one individual flood event. So the Weihe river chronological framework of palaeoflood were established. This study shows that the Weihe river in transform period from rainy to dry; the highly variable, unstable and catastrophic climate was the cause of extreme palaeofloods occurrence.
Through deeply field survey,a Holocene loesssoil profile with interbedded flood slackwater deposits (SWD) was found in Xianyang of the middle reaches of the Weihe River,which recorded the information of palaeoflood events. In order to achieve OSL ages,9 luminescence samples were collected and postIR OSL measurements were used with singlealiquot regenerativedose (SAR) protocol. Grainsize distribution and magnetic susceptibility were also analysed so as to research the occurrence and cause of palaeoflood.The result shows that the fast component is dominant in OSL signals of quartz grains(40~63 μm),which is suitale for postIR OSL measurements. For all dating measurements, preheat temperature of each natural or regenerated dose of young samples and older samples were 260℃ and 240℃,respectively；and the cutheat was set to 220℃. OSL ages increases with depth and conform to layer where were collected except individual ages underestimated.At the NSC site, the layer of flood slackwater deposits (SWD) with horizontal bedding、silty claylike and sallow colour, was in the depth of 95~110 cm,which has typical characteristic of SWD. This flood deposit involve 3 flood depositional layers, indicate of at least 3 palaeoflood evevts occured. The average of lowfrequency magnetic susceptibility of paleosoil was 133.62 108 m3.kg1,was the highest in this profile,while the value of SWD layer was 113.68 108m3.kg1 which was much higher than Malan loess,but lower in paleosoil layer. Grainsize distribution of SWD layer was dominated by silt, the content of silt was 59.43% and clay was 38.107%,the content of sand (>0.05 mm)was the least that was 3.32%. The curve of sand (>0.05 mm) in the SWD layer present a small peak. The dating results show that the extreme palaeofloods occurred 3.0~3.2 ka. According to the analysis of all the result, extraordinary floods occurred 3 200～3 000 a B. P. in the Weihe river ,the period of flood occurred frequently. Three flood depositional layers indicates that each of the slackwater deposit beds has recorded one individual flood event. So the Weihe river chronological framework of palaeoflood were established. This study shows that the Weihe river in transform period from rainy to dry; the highly variable, unstable and catastrophic climate was the cause of extreme palaeofloods occurrence.
2012, 30(2): 356-365.
Abstract:
The loess deposition at desert margin holds a good archive of climatic change as such area is sensitive to variations of Asian Monsoon. However, due to the complexity of magnetic enhancement mechanism in loess at desert margin, magnetic susceptibility is not suitable for summer monsoon reconstruction. In this paper, we investigated the geochemical characteristics of loess deposition since last interglacial at desert margin and try to screen good geochemical indicators of weathering and sorting of loess deposition at desert margin. In doing so, we investigated a loess site at Baiya which is located 50 km south to Tengger Desert. The Baiya loess section in this study consists of S0, L1 and S1, corresponding to the Holocene, the last glacial, and the last interglacial respectively. 730 samples were collected from this section. All of them were subjected to magnetic measurement using Bartington MS2B and grain size analysis using Malvern Mastersizer 2000. 183 samples were subjected to chemical elements determination using Xray fluorescence (XRF) analysis on Panalytical Magix PW2403 spectroscope. All the lab works were carried out at the Key Laboratory of Western China's Environmental Systems (Ministry of Education), Lanzhou University. The geochemical results from the whole section show that the content of SiO2, Al2O3 is close to that of UCC, the content of CaO, MgO, TiO2, Fe2O3 was enriched relative to that of UCC; the content of Na2O, K2O was depleted relative to that of UCC. As the chemical weathering strengthened, the striking phenomenon of elements behavior of this section is the depletion of sodium and the enrichment of iron and magnesium. However, the behavior of calcium was equivocal, which is probably caused by weak leaching in deposition area and strong evaporatinginduced ascending of Ca in source area. Generally, the chemical weathering in the study area is weak and on its initial weathering stage as expressed by the low chemical index of alteration (CIA) which spanned from 50 to 60. Four frequentlyused geochemical indicators were tested in current study, e.g., CIA, the ratio of Rb to Sr (Rb/Sr), the molar ratio of SiO2 to TiO2 (SiO2/TiO2), and the ratio of Zr to Rb (Zr/Rb). CIA is sensitive to reflect the weathering and the pedogenesis, and thus can be used as a proxy of Asian Summer Monsoon strength. The Rb/Sr is a good indicator of chemical weathering when it was applied in the main body of the Chinese loess Plateau. However, it didn't work well at Baiya section. We assumed that the problem is mainly caused by the behavior of Sr. That is, under warmer and wetter climate, more Sr was washed into source area, strong evaporation induced ascending of Sr to surface soil with the capillary force, leading to the decrease of Rb/Sr. When such source material was transported to the deposition area, the postdepositional Rb/Sr didn't increase significantly because of relatively weaker leaching at desert margin. In short, the ultimate Rb/Sr at Baiya section contained both weathering signal and source material signal, and it was not suitable for reconstructing summer monsoon variations. The other two geochemical indicators, SiO2/TiO2 and Zr/Rb closely follow the variation of grain sizes, and they are positively correlated to the median grain size (the coefficient r is 0.907, 0.824, respectively), thus, they can be used as indicators of winter monsoon intensity. In addition, SiO2/TiO2 and Zr/Rb are negatively correlated to CIA (the coefficient r is 0.657, 0.575 respectively), suggesting summer monsoon is also an important factor affecting the grain size variation through modulating the expansion and contracti on of desert. In current study, we also aimed to examine the provenance of loess material at different climatic stages. Al, Ti, Zr is the most stable element during chemical weathering. Their individual content might change in response to the chemical weathering; however, the ratios of AlTiZr can be inherited from the source area as they are very stable. We thus used the ternary diagram of 15Al2O3, Zr, and 300TiO2 to trace the potential change of provenance (source material and/or source region). The AlTiZr ternary diagrams showed that loess deposition during the the Holocene and the Last Interglacial period (So and S1) was well mixed while the loess deposition during the Last Glacial (L1) was not homogeneously mixed. We suggested that the dust has experienced long distance transport and more thorough mixing processes during interglacial period while the source material didn't undergo thorough mixing processes during glacial period as the source was probably getting closer.
The loess deposition at desert margin holds a good archive of climatic change as such area is sensitive to variations of Asian Monsoon. However, due to the complexity of magnetic enhancement mechanism in loess at desert margin, magnetic susceptibility is not suitable for summer monsoon reconstruction. In this paper, we investigated the geochemical characteristics of loess deposition since last interglacial at desert margin and try to screen good geochemical indicators of weathering and sorting of loess deposition at desert margin. In doing so, we investigated a loess site at Baiya which is located 50 km south to Tengger Desert. The Baiya loess section in this study consists of S0, L1 and S1, corresponding to the Holocene, the last glacial, and the last interglacial respectively. 730 samples were collected from this section. All of them were subjected to magnetic measurement using Bartington MS2B and grain size analysis using Malvern Mastersizer 2000. 183 samples were subjected to chemical elements determination using Xray fluorescence (XRF) analysis on Panalytical Magix PW2403 spectroscope. All the lab works were carried out at the Key Laboratory of Western China's Environmental Systems (Ministry of Education), Lanzhou University. The geochemical results from the whole section show that the content of SiO2, Al2O3 is close to that of UCC, the content of CaO, MgO, TiO2, Fe2O3 was enriched relative to that of UCC; the content of Na2O, K2O was depleted relative to that of UCC. As the chemical weathering strengthened, the striking phenomenon of elements behavior of this section is the depletion of sodium and the enrichment of iron and magnesium. However, the behavior of calcium was equivocal, which is probably caused by weak leaching in deposition area and strong evaporatinginduced ascending of Ca in source area. Generally, the chemical weathering in the study area is weak and on its initial weathering stage as expressed by the low chemical index of alteration (CIA) which spanned from 50 to 60. Four frequentlyused geochemical indicators were tested in current study, e.g., CIA, the ratio of Rb to Sr (Rb/Sr), the molar ratio of SiO2 to TiO2 (SiO2/TiO2), and the ratio of Zr to Rb (Zr/Rb). CIA is sensitive to reflect the weathering and the pedogenesis, and thus can be used as a proxy of Asian Summer Monsoon strength. The Rb/Sr is a good indicator of chemical weathering when it was applied in the main body of the Chinese loess Plateau. However, it didn't work well at Baiya section. We assumed that the problem is mainly caused by the behavior of Sr. That is, under warmer and wetter climate, more Sr was washed into source area, strong evaporation induced ascending of Sr to surface soil with the capillary force, leading to the decrease of Rb/Sr. When such source material was transported to the deposition area, the postdepositional Rb/Sr didn't increase significantly because of relatively weaker leaching at desert margin. In short, the ultimate Rb/Sr at Baiya section contained both weathering signal and source material signal, and it was not suitable for reconstructing summer monsoon variations. The other two geochemical indicators, SiO2/TiO2 and Zr/Rb closely follow the variation of grain sizes, and they are positively correlated to the median grain size (the coefficient r is 0.907, 0.824, respectively), thus, they can be used as indicators of winter monsoon intensity. In addition, SiO2/TiO2 and Zr/Rb are negatively correlated to CIA (the coefficient r is 0.657, 0.575 respectively), suggesting summer monsoon is also an important factor affecting the grain size variation through modulating the expansion and contracti on of desert. In current study, we also aimed to examine the provenance of loess material at different climatic stages. Al, Ti, Zr is the most stable element during chemical weathering. Their individual content might change in response to the chemical weathering; however, the ratios of AlTiZr can be inherited from the source area as they are very stable. We thus used the ternary diagram of 15Al2O3, Zr, and 300TiO2 to trace the potential change of provenance (source material and/or source region). The AlTiZr ternary diagrams showed that loess deposition during the the Holocene and the Last Interglacial period (So and S1) was well mixed while the loess deposition during the Last Glacial (L1) was not homogeneously mixed. We suggested that the dust has experienced long distance transport and more thorough mixing processes during interglacial period while the source material didn't undergo thorough mixing processes during glacial period as the source was probably getting closer.
2012, 30(2): 366-374.
Abstract:
Element content can be affected by the grain size of sediments. Previous studies revealed that elements, content of which can be easily affected the grain size distribution are usually concentrated in finegrain fractions. The grain size effect makes it more complicated to decipher useful information on provenance via the elemental compositions of sediments. Provenance of the late Cenozoic sediments in the Jianghan Basin has been highlighted for a long time. Many provenance indictors have been taken to decipher information on the provenance of the sediments of the Jianghan Basin. Provenance study of the sediments in the Jianghan Basin plays an important role in reconstructing the evolutionary history of the Yangtze River and has been highlighted for a long time. Among these researches, geochemical methods have been largely adopted, e.g. the elemental compositions of the sediments. Unfortunately, it is still controversial that how the grain size affect the elemental compositions of the sediments. In this study, we presented the elemental compositions of the late Cenozoic sediments of the Jianghan Basin and tried to decipher some information on the correlation between the elemental compositions and the grainsize effect and the sedimentary environment of the Jianghan Basin.The correlation between the 23 elements and the grainsize effect revealed that only 6% of the 23 elements show correlation higher than 0.3, while 13%, 35% and 46% of the 23 elements show correlation of 0.2~0.3, 0.1~0.2 and <0.1, respectively. The elements of V,Sc,Cr,Zr,Co,Sr,Ba,Nb,Hf,Ta,Hf,Th,U are relatively concentrated in the grain size fraction of 5~7, in contrast the elements of Li,Rb,Cu,Cs are concentrated in the grain size fraction of 10~12. The content of Be, Y and Pb are not obviously affected by the grainsize effect. It means that the grainsize effect is not the main factor that affects the elemental compositions of the late Cenozoic sediments of the Jianghan Basin. Based on that, we conclude that the elemental compositions can be effective provenance indicators. The grainsize effect can be ignored when the elemental compositions are used to trace the source of the late Cenozoic sediments of the Jianghan Basin.The average variation coefficient of the 23 elements is 0.23, of which the Sr, Zr, Ba and Hf are the most fluctuant elements while the Y has the lowest variation coefficient. Curiously, the elements with higher variation coefficients are also enriched compared with the UCC.The lacustrine sediments with lowest Sr content in the core sediments around the depth of 287 m indicate the weak chemical weathering conditions. The lowest V/Ni ratio indicates the weak oxidizing or reduction conditions. Meanwhile content of the lithophile elements are low throughout the core sediments, indicating less terrigenous input. Besides the color of these sediments is steel gray, which accords well with the elemental characteristics. We propose that around 2.6~2.43 Ma BP, the Jianghan Basin was controlled by arid climate. Rivers around the basin were with small water discharge inducing the development of salt lake. All of these factors could result in less terrigenous input. Sediments around the depth of 214 m are characterized by highest Sr content. The Sr/Ba ratios are relatively low while the V/Ni ratios are generally high and fluctuant. Most lithophile elements are with peak values of content. All of the evidence indicates that during this period the Jianghan Basin was controlled by humid climate. The water discharge of the rivers was sufficient especially the upper reaches. Under this condition the basin received large amounts of terrigenous input. As a result of this weather condition and the river hydrodynamic conditions, the lake in the Jianghan Basin was under oxidizing environment. Based on those evidence, we made a reasonable assumption that large lake developed under the control of the Yangtze River during this period.Trace elemental compositions of the sediments revealed that most of the lithophile and chalcophile elements are relatively enriched compared to the Upper Continental Crust (UCC). The siderophile elements are depleted compared with the UCC. It probably indicates that the most of the sediments of the Jianghan Basin derived from the upper Yangtze rather than the materials from the deep earth in the Yangtze block. The lacustrine sediments of the Core Zhoulao around 287m show lowSr, and V/Ni ratios and high Zr/Sr and Rb/Sr ratios, which indicate that salt lake largely developed in the Jianghan Basin under the cold and dry weather between 2.6 ~ 2.43 Ma B.P.. In contrast, freshwater lake developed around 2.1 Ma B.P.. It is consistent with the late Cenozoic pollen assemblages in the Jianghan Basin, and the sedimentary records in the Subei Basin and Yangtze delta. We conclude that the elemental compositions in the Jianghan Basin might record the global cooling around 2.5 Ma B.P. and the intense uplift of the Tibetan Plateau around 1.4~1.2 Ma B.P.
Element content can be affected by the grain size of sediments. Previous studies revealed that elements, content of which can be easily affected the grain size distribution are usually concentrated in finegrain fractions. The grain size effect makes it more complicated to decipher useful information on provenance via the elemental compositions of sediments. Provenance of the late Cenozoic sediments in the Jianghan Basin has been highlighted for a long time. Many provenance indictors have been taken to decipher information on the provenance of the sediments of the Jianghan Basin. Provenance study of the sediments in the Jianghan Basin plays an important role in reconstructing the evolutionary history of the Yangtze River and has been highlighted for a long time. Among these researches, geochemical methods have been largely adopted, e.g. the elemental compositions of the sediments. Unfortunately, it is still controversial that how the grain size affect the elemental compositions of the sediments. In this study, we presented the elemental compositions of the late Cenozoic sediments of the Jianghan Basin and tried to decipher some information on the correlation between the elemental compositions and the grainsize effect and the sedimentary environment of the Jianghan Basin.The correlation between the 23 elements and the grainsize effect revealed that only 6% of the 23 elements show correlation higher than 0.3, while 13%, 35% and 46% of the 23 elements show correlation of 0.2~0.3, 0.1~0.2 and <0.1, respectively. The elements of V,Sc,Cr,Zr,Co,Sr,Ba,Nb,Hf,Ta,Hf,Th,U are relatively concentrated in the grain size fraction of 5~7, in contrast the elements of Li,Rb,Cu,Cs are concentrated in the grain size fraction of 10~12. The content of Be, Y and Pb are not obviously affected by the grainsize effect. It means that the grainsize effect is not the main factor that affects the elemental compositions of the late Cenozoic sediments of the Jianghan Basin. Based on that, we conclude that the elemental compositions can be effective provenance indicators. The grainsize effect can be ignored when the elemental compositions are used to trace the source of the late Cenozoic sediments of the Jianghan Basin.The average variation coefficient of the 23 elements is 0.23, of which the Sr, Zr, Ba and Hf are the most fluctuant elements while the Y has the lowest variation coefficient. Curiously, the elements with higher variation coefficients are also enriched compared with the UCC.The lacustrine sediments with lowest Sr content in the core sediments around the depth of 287 m indicate the weak chemical weathering conditions. The lowest V/Ni ratio indicates the weak oxidizing or reduction conditions. Meanwhile content of the lithophile elements are low throughout the core sediments, indicating less terrigenous input. Besides the color of these sediments is steel gray, which accords well with the elemental characteristics. We propose that around 2.6~2.43 Ma BP, the Jianghan Basin was controlled by arid climate. Rivers around the basin were with small water discharge inducing the development of salt lake. All of these factors could result in less terrigenous input. Sediments around the depth of 214 m are characterized by highest Sr content. The Sr/Ba ratios are relatively low while the V/Ni ratios are generally high and fluctuant. Most lithophile elements are with peak values of content. All of the evidence indicates that during this period the Jianghan Basin was controlled by humid climate. The water discharge of the rivers was sufficient especially the upper reaches. Under this condition the basin received large amounts of terrigenous input. As a result of this weather condition and the river hydrodynamic conditions, the lake in the Jianghan Basin was under oxidizing environment. Based on those evidence, we made a reasonable assumption that large lake developed under the control of the Yangtze River during this period.Trace elemental compositions of the sediments revealed that most of the lithophile and chalcophile elements are relatively enriched compared to the Upper Continental Crust (UCC). The siderophile elements are depleted compared with the UCC. It probably indicates that the most of the sediments of the Jianghan Basin derived from the upper Yangtze rather than the materials from the deep earth in the Yangtze block. The lacustrine sediments of the Core Zhoulao around 287m show lowSr, and V/Ni ratios and high Zr/Sr and Rb/Sr ratios, which indicate that salt lake largely developed in the Jianghan Basin under the cold and dry weather between 2.6 ~ 2.43 Ma B.P.. In contrast, freshwater lake developed around 2.1 Ma B.P.. It is consistent with the late Cenozoic pollen assemblages in the Jianghan Basin, and the sedimentary records in the Subei Basin and Yangtze delta. We conclude that the elemental compositions in the Jianghan Basin might record the global cooling around 2.5 Ma B.P. and the intense uplift of the Tibetan Plateau around 1.4~1.2 Ma B.P.
2012, 30(2): 375-384.
Abstract:
Based on the information about reservoir bitumen, such as occurrences, types, group composition, the characteristic of saturated hydrocarbon' gas chromatogram and biomarkers, as well as the reservoir bitumen reflectivity, this paper thoroughly analyze the geochemical characteristic of reservoir bitumen from Feixianguan Formation in Well Puguang 2 and its possible cause of formation. It is concluded that the reservoir bitumen which is classified to thermal pyrobitumen is the residue formed after ancient reservoir cracked. nalkane in reservoir bitumen distribute integrally with the carbon number range from C14 to C30, without obvious trace of biodegradation. Pr/Ph、Pr/nC17 and Ph/nC18 are all smaller than 1.0, OEP varies from 1.25 to 1.43 and CPI varies from 0.98 to 1.19, without odd even predominance of normal alkanes. Among regular silane series, C27 plays a dominant role with the appearance of "V" shape of the distribution of C27C29. Isomerization of sterane in initial stage, the ratio is obviously below average value. It is believed that "S" configuration crack faster than "R" configuration is the reason. The content of pregnane and litres of progesterone silane steroid in Fei1 Formation and Fei2 Formation is apparently higher than the counterpart of Fei3 Formation as the result of the difference of environment of sedimentation or source rock. Among terpene series, pentacyclic triterpenoids dominate, tricyclic ones develope well, especially ,C23 is the base peak, the content of gammacerane is relatively high. All of these characteristics mentioned above demonstrate that reservoir bitumen in Puguang2 Well mainly derived from lower level hydrobiont, thermal evolution stayed at middlehigher stage. Parent materials formed in marine sedimentary environment with high salinity. The high content of C25norhopane is associated with high thermal evolutional stage rather than biodegradation.
Based on the information about reservoir bitumen, such as occurrences, types, group composition, the characteristic of saturated hydrocarbon' gas chromatogram and biomarkers, as well as the reservoir bitumen reflectivity, this paper thoroughly analyze the geochemical characteristic of reservoir bitumen from Feixianguan Formation in Well Puguang 2 and its possible cause of formation. It is concluded that the reservoir bitumen which is classified to thermal pyrobitumen is the residue formed after ancient reservoir cracked. nalkane in reservoir bitumen distribute integrally with the carbon number range from C14 to C30, without obvious trace of biodegradation. Pr/Ph、Pr/nC17 and Ph/nC18 are all smaller than 1.0, OEP varies from 1.25 to 1.43 and CPI varies from 0.98 to 1.19, without odd even predominance of normal alkanes. Among regular silane series, C27 plays a dominant role with the appearance of "V" shape of the distribution of C27C29. Isomerization of sterane in initial stage, the ratio is obviously below average value. It is believed that "S" configuration crack faster than "R" configuration is the reason. The content of pregnane and litres of progesterone silane steroid in Fei1 Formation and Fei2 Formation is apparently higher than the counterpart of Fei3 Formation as the result of the difference of environment of sedimentation or source rock. Among terpene series, pentacyclic triterpenoids dominate, tricyclic ones develope well, especially ,C23 is the base peak, the content of gammacerane is relatively high. All of these characteristics mentioned above demonstrate that reservoir bitumen in Puguang2 Well mainly derived from lower level hydrobiont, thermal evolution stayed at middlehigher stage. Parent materials formed in marine sedimentary environment with high salinity. The high content of C25norhopane is associated with high thermal evolutional stage rather than biodegradation.
2012, 30(2): 385-391.
Abstract:
There are a number of sets of source rocks ,a number of hydrocarbon source area,multistage hydrocarbon generation and multistage hydrocarbon accumulation in the middle part of the West Sichuan Depression and it also experienced a number of tectonic stages adjustment and havoc. On it's vertical, multiple sets of sourcereservoircap assemblages gave birth to multilayer gasbearing series. According to the results of gas carbon isotopic analyses, part of upper Triassicseries Xujiahe Formation's gas ethane carbon isotopic have obvious negative skewness characteristics in this area.Relative photos' discrimination show that the gas has the feature of oil cracking gas. Meanwhile, a large amount of reservoir asphalt fillings have been discovered in upper Triassicseries Xujiahe formation in this area. Through the analysis of core observation, micrograph, elements, pyrolysis and so on,we can see reservoir asphalt fillings have many characteristics such as multitude types, several shapes of distribution, a more clear boundary and so on. Reservoir asphalt fillings also have a characteristic that these reservoir asphalt fillings have a higher reflecting especially in the second member of Xujiahe Formation's reservoir bitumen. This characteristic shows residue's characteristic which is similar to the coal tar pitch's basic characteristic after oil reservoir cracking. The discovery of oil cracking gas and the coal tar pitch confirms the existence of paleooil pools of Xujiahe Formation in middle part of the West Sichuan Depression. On this basis, through the generalized analysis of genetic oil and cracking condition and so on, we carried out the preliminary discussion on the forming pattern of paleooil pools cracking gas of the Xujiahe Formation.We can divide this process into three consecutive phases: Late Indosinian paleooil pools's formation, Middle Yanshan paleooil pools's cracking and Late YanshanHimalayan period's gas reservoir adjustment. It is of certain significance to deepening recognition on the formation mechanism and distribution of gas of the middle part of the West Sichuan Depression.
There are a number of sets of source rocks ,a number of hydrocarbon source area,multistage hydrocarbon generation and multistage hydrocarbon accumulation in the middle part of the West Sichuan Depression and it also experienced a number of tectonic stages adjustment and havoc. On it's vertical, multiple sets of sourcereservoircap assemblages gave birth to multilayer gasbearing series. According to the results of gas carbon isotopic analyses, part of upper Triassicseries Xujiahe Formation's gas ethane carbon isotopic have obvious negative skewness characteristics in this area.Relative photos' discrimination show that the gas has the feature of oil cracking gas. Meanwhile, a large amount of reservoir asphalt fillings have been discovered in upper Triassicseries Xujiahe formation in this area. Through the analysis of core observation, micrograph, elements, pyrolysis and so on,we can see reservoir asphalt fillings have many characteristics such as multitude types, several shapes of distribution, a more clear boundary and so on. Reservoir asphalt fillings also have a characteristic that these reservoir asphalt fillings have a higher reflecting especially in the second member of Xujiahe Formation's reservoir bitumen. This characteristic shows residue's characteristic which is similar to the coal tar pitch's basic characteristic after oil reservoir cracking. The discovery of oil cracking gas and the coal tar pitch confirms the existence of paleooil pools of Xujiahe Formation in middle part of the West Sichuan Depression. On this basis, through the generalized analysis of genetic oil and cracking condition and so on, we carried out the preliminary discussion on the forming pattern of paleooil pools cracking gas of the Xujiahe Formation.We can divide this process into three consecutive phases: Late Indosinian paleooil pools's formation, Middle Yanshan paleooil pools's cracking and Late YanshanHimalayan period's gas reservoir adjustment. It is of certain significance to deepening recognition on the formation mechanism and distribution of gas of the middle part of the West Sichuan Depression.
2012, 30(2): 392-398.
Abstract:
Based on the research of the organic geochemistry characteristics of source rocks, the hydrocarbongenerating conditions of the Lower Cretaceous source rocks in Jiuquan Basin are evaluated systematically by means of being classified by sag and formation.Moreover, the hydrocarbongenerating conditions of the Lower Cretaceous source rocks from the Jiuxi Depression and those of Jiudong Depression are compared. The research results show that the hydrocarbongenerating conditions of the Lower Cretaceous source rocks from the Jiuxi Depression have a tendency of growing better from the Zhonggou Formation to the Xiagou Formation and to the Chijinbu Formation, however, in the Jiudong Depression, there have an opposite tendency showing that the hydrocarbongenerating conditions grow worse gradually from up to down, which reflects the characteristics that the better source rock is immature but the mature source rock is not good. The Xiagou Formation and the Chijinbu formation from the Jiuxi Depression are the main contributors to the hydrocarbongeneration of the Lower Cretaceous source rocks from the Jiuquan Basin. The research results will be of great significance on the exploration of oil and gas in Jiuquan Basin.
Based on the research of the organic geochemistry characteristics of source rocks, the hydrocarbongenerating conditions of the Lower Cretaceous source rocks in Jiuquan Basin are evaluated systematically by means of being classified by sag and formation.Moreover, the hydrocarbongenerating conditions of the Lower Cretaceous source rocks from the Jiuxi Depression and those of Jiudong Depression are compared. The research results show that the hydrocarbongenerating conditions of the Lower Cretaceous source rocks from the Jiuxi Depression have a tendency of growing better from the Zhonggou Formation to the Xiagou Formation and to the Chijinbu Formation, however, in the Jiudong Depression, there have an opposite tendency showing that the hydrocarbongenerating conditions grow worse gradually from up to down, which reflects the characteristics that the better source rock is immature but the mature source rock is not good. The Xiagou Formation and the Chijinbu formation from the Jiuxi Depression are the main contributors to the hydrocarbongeneration of the Lower Cretaceous source rocks from the Jiuquan Basin. The research results will be of great significance on the exploration of oil and gas in Jiuquan Basin.
2012, 30(2): 399-404.
Abstract:
The basin fluid is the very active factor in the sedimentary basins. The hydrogeochemistry is mainly controlled by fluid rock interaction. The source and genesis of the formation water are very complex. It is difficult to determine the genesis and source just according to the general component ions concentration and the interrelationship of ions. In this case, it is necessary to combine the trace elements and isotopic components to explain the genesis and source of the formation water. Applying isotopic chemistry method to research the formation water, in order to find the source, carry out the intensity of waterrock interaction, trace fluid flow direction, and compute the paleotemperature, age and residence time of the basin fluid. Based on hydrogeochemical characters of formation water and analysis of SrDO isotope data, this article researches on the northern area of Songliao Basin, discusses the relationship of waterrock interaction and SrDO isotope. It is of great theoretical significance for the isotope tracers in the enrichment of waterrock interaction. The result of the hydrogenoxygen isotope testing suggests that formation water in the western area is evidently influenced by the ancient precipitation, and the positive excursion of the δ18O in the central depression is probably caused by the strengthing of waterrock interaction. The formation water is a mixture of meteoric water and primary sedimentary water, the slight value of the δD reflects the original sediment belongs to the continent depositional water. In the groundwater, the concentration of Sr2+ increases with TDS, Sr comes from the dissolution of rock dissolved by groundwater. The groundwater from Quantou Group (K2q) and Yingcheng Group (K1yc) has same character as the continent depositional water. Meanwhile, the groundwater from Qingkoushan Group shows the character of the sea depositional water obviously. The groundwater from Quantou Group and Yingcheng Group shows the character of the continent depositional water obviously. The distribution range of 87Sr/86Sr values from different formation water is concentrated, and has homologue. In all salt rocks, except those from Quantou Group, the distribution range of 87Sr/86Sr values from different formation rock is also concentrated, and has the same type of source. The salt rocks from Quantou Group are from distinct source and the higher value of 87Sr/86Sr should be inflected by the siliconaluminium rock from the crust source. The 87Sr/86Sr value of formation water is slightly lower but the concentration of Sr2+ is higher, the formation water is a mixture of high 87Sr/86Sr value fluid end member and low 87Sr/86Sr value fluid end membera mixture of surface source water and deep formation water, which is also obtained from mantle deep water like high Sr2+ value and low 87Sr/86Sr value volcanic geothermal water.
The basin fluid is the very active factor in the sedimentary basins. The hydrogeochemistry is mainly controlled by fluid rock interaction. The source and genesis of the formation water are very complex. It is difficult to determine the genesis and source just according to the general component ions concentration and the interrelationship of ions. In this case, it is necessary to combine the trace elements and isotopic components to explain the genesis and source of the formation water. Applying isotopic chemistry method to research the formation water, in order to find the source, carry out the intensity of waterrock interaction, trace fluid flow direction, and compute the paleotemperature, age and residence time of the basin fluid. Based on hydrogeochemical characters of formation water and analysis of SrDO isotope data, this article researches on the northern area of Songliao Basin, discusses the relationship of waterrock interaction and SrDO isotope. It is of great theoretical significance for the isotope tracers in the enrichment of waterrock interaction. The result of the hydrogenoxygen isotope testing suggests that formation water in the western area is evidently influenced by the ancient precipitation, and the positive excursion of the δ18O in the central depression is probably caused by the strengthing of waterrock interaction. The formation water is a mixture of meteoric water and primary sedimentary water, the slight value of the δD reflects the original sediment belongs to the continent depositional water. In the groundwater, the concentration of Sr2+ increases with TDS, Sr comes from the dissolution of rock dissolved by groundwater. The groundwater from Quantou Group (K2q) and Yingcheng Group (K1yc) has same character as the continent depositional water. Meanwhile, the groundwater from Qingkoushan Group shows the character of the sea depositional water obviously. The groundwater from Quantou Group and Yingcheng Group shows the character of the continent depositional water obviously. The distribution range of 87Sr/86Sr values from different formation water is concentrated, and has homologue. In all salt rocks, except those from Quantou Group, the distribution range of 87Sr/86Sr values from different formation rock is also concentrated, and has the same type of source. The salt rocks from Quantou Group are from distinct source and the higher value of 87Sr/86Sr should be inflected by the siliconaluminium rock from the crust source. The 87Sr/86Sr value of formation water is slightly lower but the concentration of Sr2+ is higher, the formation water is a mixture of high 87Sr/86Sr value fluid end member and low 87Sr/86Sr value fluid end membera mixture of surface source water and deep formation water, which is also obtained from mantle deep water like high Sr2+ value and low 87Sr/86Sr value volcanic geothermal water.
