2010 Vol. 28, No. 4
Display Method:
2010, 28(4): 645-658.
Abstract:
Detailed geologic mapping and borehole data was taken to reveal the sedimentary and geomorphic features and risesubsidence process of Chishan uplift and Anxiang sag in the south of the Quaternary Dongting basin. The Chishan uplift is a small faultblock with 18km length and 4~5 km width and was restricted by the eastern and western normal faults. The Anxiang sag is located to the west of the Chishan uplift. There occurred several grades of terraces covered with Early Pleistocene Miluo Formation, Middle Pleistocene Xinkaipu Formation and Baishajin Formation. There occurred 200~300 m thick fluviatile and lacustrine deposits in the Anxiang sag which were composed of Early Pleistocene Huatian Formation and Miluo Formation, Middle Pleistocene Dongtinghu Formation, Late Pleistocene Potou Formation and Holocene alluviallocustrine deposits. Geomorphic and sedimentary characteristics show that Chishan uplift experienced pulsative rises as a whole with rising stage alternating steady stage during Early Pleistocenemiddle Middle Pleistocene, while Anxiang sag experienced episodic subsidence with slow alternating rapid subsidence. Steady and rising period of Chishan uplift corresponded with slow and rapid subsiding period of Anxiang sag, respectively. The Chishan uplift and Anxiang sag rose together and sufferred from denudation during late Middle Pleostocene. There occurred deposits in the Anxiang sag in depressional tectonic setting during Late Pleistocene and Holocene. The corresponding relation between the pulsative rises of Chishan uplift and the episodic subsidence of Anxiang sag provided a constraint for the basinrange coupling processes of Dongting basin and around uplifts, and suggested that the faulting subsidence of Dongting basin were related with that the ductile matter of the middle curst in sags expanded and moved toward periphery caused by the mantle uplift.
Detailed geologic mapping and borehole data was taken to reveal the sedimentary and geomorphic features and risesubsidence process of Chishan uplift and Anxiang sag in the south of the Quaternary Dongting basin. The Chishan uplift is a small faultblock with 18km length and 4~5 km width and was restricted by the eastern and western normal faults. The Anxiang sag is located to the west of the Chishan uplift. There occurred several grades of terraces covered with Early Pleistocene Miluo Formation, Middle Pleistocene Xinkaipu Formation and Baishajin Formation. There occurred 200~300 m thick fluviatile and lacustrine deposits in the Anxiang sag which were composed of Early Pleistocene Huatian Formation and Miluo Formation, Middle Pleistocene Dongtinghu Formation, Late Pleistocene Potou Formation and Holocene alluviallocustrine deposits. Geomorphic and sedimentary characteristics show that Chishan uplift experienced pulsative rises as a whole with rising stage alternating steady stage during Early Pleistocenemiddle Middle Pleistocene, while Anxiang sag experienced episodic subsidence with slow alternating rapid subsidence. Steady and rising period of Chishan uplift corresponded with slow and rapid subsiding period of Anxiang sag, respectively. The Chishan uplift and Anxiang sag rose together and sufferred from denudation during late Middle Pleostocene. There occurred deposits in the Anxiang sag in depressional tectonic setting during Late Pleistocene and Holocene. The corresponding relation between the pulsative rises of Chishan uplift and the episodic subsidence of Anxiang sag provided a constraint for the basinrange coupling processes of Dongting basin and around uplifts, and suggested that the faulting subsidence of Dongting basin were related with that the ductile matter of the middle curst in sags expanded and moved toward periphery caused by the mantle uplift.
2010, 28(4): 671-675.
Abstract:
Glauconite is a kind of hydrous layered aluminium silicate mineral, which is commonly refered to as a marine facies indicative mineral. Numerous studies have demonstrated that glauconites minerals usually form in modern oceans with high depths and slowly sedimentary rates. The Paleoproterozoic Xiong'er Group, widely occurring in the Xiong'erZhongtiao aulacogen in the southern margin of the North China craton, represents the most intensive magmatism after the formation of the crystalline basement of the North China craton. The Xiong'er Group is occupied by volcanic lavas as well as minor sedimentary rocks and volcanic clastic rocks (4.3% in thickness). The sedimentary rocks occur as interbeds in the Dagushi and Majiahe Formations of the Xiong'er Group. Glauconites were discovered in the sandstone from the Majiahe Formation, which gives us a opportunity to elucidate the formation environment of the Xiong'er Group. Sedimentological and petrographic studies indicate that the glauconites have high content of K2O(>8%), showing that these glauconites belong to the highevolved glauconites. The characteristics of glauconites from the Majiahe Formation reflect that they formed in a highenergy shallow sedimentary environment, not in a environment with a slowly sedimentary rate. Shortly afiter the extension of the Xiong'erZhongtiao aulacogen, transgression was northward in the Palaeoproterozoic era. At the early stage of the Xiong'er Group, the southern part of Henan province was in a marine environment, whereas the northern part is still in a continental environment. At the later stage, the southern area of Shanxi province was in the marine environment, as indicated by the discoveries of glauconites in the Majiahe Formation.
Glauconite is a kind of hydrous layered aluminium silicate mineral, which is commonly refered to as a marine facies indicative mineral. Numerous studies have demonstrated that glauconites minerals usually form in modern oceans with high depths and slowly sedimentary rates. The Paleoproterozoic Xiong'er Group, widely occurring in the Xiong'erZhongtiao aulacogen in the southern margin of the North China craton, represents the most intensive magmatism after the formation of the crystalline basement of the North China craton. The Xiong'er Group is occupied by volcanic lavas as well as minor sedimentary rocks and volcanic clastic rocks (4.3% in thickness). The sedimentary rocks occur as interbeds in the Dagushi and Majiahe Formations of the Xiong'er Group. Glauconites were discovered in the sandstone from the Majiahe Formation, which gives us a opportunity to elucidate the formation environment of the Xiong'er Group. Sedimentological and petrographic studies indicate that the glauconites have high content of K2O(>8%), showing that these glauconites belong to the highevolved glauconites. The characteristics of glauconites from the Majiahe Formation reflect that they formed in a highenergy shallow sedimentary environment, not in a environment with a slowly sedimentary rate. Shortly afiter the extension of the Xiong'erZhongtiao aulacogen, transgression was northward in the Palaeoproterozoic era. At the early stage of the Xiong'er Group, the southern part of Henan province was in a marine environment, whereas the northern part is still in a continental environment. At the later stage, the southern area of Shanxi province was in the marine environment, as indicated by the discoveries of glauconites in the Majiahe Formation.
2010, 28(4): 682-687.
Abstract:
Carbonate rock facies model of the upper third member of Shahejie Formation of central uplift belt in Dawangzhuang oilfield of Raoyang depression were studied by core observation, granularity analysis and well log analysis. It can be seen that the aim stratum in the study area develop carbonate rock shoal, and the type of carbonate rock consist of algalsandclastic dolomite, oolitic dolomite , micritic dolomite , clasticbearing sand clasticoolitic dolomite. Carbonate shoal develop four microfacies: algal shoal , oolitic shoal, micritic carbonate bend and terrestrial grain shoal. The alternation of lake level, ancient landform, the strength of tectonic action and the provision of terrestrial material affect the carbonate shoal, and the change of micromilieu in the central uplift belt palaeogeomorphology directly affect the rock type and sedimentary microfacies, high terrain develop algal shoal and oolitic shoal, micritic carbonate bend appear in low terrain with low energy. Algal shoal and oolitic shoal is the best reservoir in the studied area, sedimentary microfacies analysis and facies model establishment can help Dawangzhuang oilfield's reservoir forecast, and can be a useful geologic model for reservoir forecast in other similar areas.
Carbonate rock facies model of the upper third member of Shahejie Formation of central uplift belt in Dawangzhuang oilfield of Raoyang depression were studied by core observation, granularity analysis and well log analysis. It can be seen that the aim stratum in the study area develop carbonate rock shoal, and the type of carbonate rock consist of algalsandclastic dolomite, oolitic dolomite , micritic dolomite , clasticbearing sand clasticoolitic dolomite. Carbonate shoal develop four microfacies: algal shoal , oolitic shoal, micritic carbonate bend and terrestrial grain shoal. The alternation of lake level, ancient landform, the strength of tectonic action and the provision of terrestrial material affect the carbonate shoal, and the change of micromilieu in the central uplift belt palaeogeomorphology directly affect the rock type and sedimentary microfacies, high terrain develop algal shoal and oolitic shoal, micritic carbonate bend appear in low terrain with low energy. Algal shoal and oolitic shoal is the best reservoir in the studied area, sedimentary microfacies analysis and facies model establishment can help Dawangzhuang oilfield's reservoir forecast, and can be a useful geologic model for reservoir forecast in other similar areas.
2010, 28(4): 696-705.
Abstract:
Due to intensive tectonic uplift and denudation affection in early Hercynian, the majority of the study area only keeps unsound Huanglong Formation of Upper Carboniferous in Eastern ChongqingWestern Hubei area. The Huanglong Formation is one of the most important natural gas reservoirs in the eastern Sichuan area and one of the most favourite horizons for exploring new gas sources. Based on core description, measured crosssection and thin section analysis, and combined with sedimentary marks of lithology, palaeontology, logging analysis, and so on., the Huanglong Formation is divided into four main sedimentary facies: sabkha, beachbarrier coast, gulf shelf and open shelf. During the field investigation, passageway of sea water connecting the gulf of the eastern Sichuannorthern Chongqing with open sea of the western Hubei has been found, which has important meaning to furthur understand the regional sedimentary facies. On the basis of sequece stratigraphy, and used the three system tracts: LST, TST and EHST as the maping units, three paleogeographic maps have been mapped and lithofacies paleographic characteristics of each system tract has been described. Combined with the reservoir characteristics of all sorts of sedimentary facies, the barrier grain beach and offshore grain beach are thought to be the most favourite reservoir facies.
Due to intensive tectonic uplift and denudation affection in early Hercynian, the majority of the study area only keeps unsound Huanglong Formation of Upper Carboniferous in Eastern ChongqingWestern Hubei area. The Huanglong Formation is one of the most important natural gas reservoirs in the eastern Sichuan area and one of the most favourite horizons for exploring new gas sources. Based on core description, measured crosssection and thin section analysis, and combined with sedimentary marks of lithology, palaeontology, logging analysis, and so on., the Huanglong Formation is divided into four main sedimentary facies: sabkha, beachbarrier coast, gulf shelf and open shelf. During the field investigation, passageway of sea water connecting the gulf of the eastern Sichuannorthern Chongqing with open sea of the western Hubei has been found, which has important meaning to furthur understand the regional sedimentary facies. On the basis of sequece stratigraphy, and used the three system tracts: LST, TST and EHST as the maping units, three paleogeographic maps have been mapped and lithofacies paleographic characteristics of each system tract has been described. Combined with the reservoir characteristics of all sorts of sedimentary facies, the barrier grain beach and offshore grain beach are thought to be the most favourite reservoir facies.
2010, 28(4): 717-729.
Abstract:
The viewpoint that slope break belt developed both in the marine basin and the nomarine rift basin played important controlling effect on sequence and sediment frameworks has got extensive concern and been widely accepted in recent years. According to the combination characteristic of seismic profiles and sedimentary microfacies，studies on the Triassic Yanchang Formation in the Ordos basin show that sedimentary slope break belts were also developed in the large depression lacustrine basin, and could be clearly recognized either in the deep water or in the shallow water. Deposits of the deepwater gravity flows such as the sandy debris flows and the turbidity flows were mainly controlled by the slope break belt in deep water, whereas deposits of tractive current like subaqueous distributary channels in the deltafront were controlled by that in the shallow water. Further studies suggest that, except for sandbody origin types, the deepwater and shallowwater sedimentary slope breaks also have obvious controlling effect on thickness, plane distribution, and physical properties of the sandstones.
In addition, it is suggested that petroleum distribution was also controlled to a certain extent by the slope break belt. Although oil reservoirs can be found everywhere in the Yanchang Formation, most of the larger lithologic reservoirs are located either below the slope breaks or in the LST(lowstand systems tracts) sandstones neighboring the sequence boundary, or controlled by both of the slop break belt and the sequence boundary.
The viewpoint that slope break belt developed both in the marine basin and the nomarine rift basin played important controlling effect on sequence and sediment frameworks has got extensive concern and been widely accepted in recent years. According to the combination characteristic of seismic profiles and sedimentary microfacies，studies on the Triassic Yanchang Formation in the Ordos basin show that sedimentary slope break belts were also developed in the large depression lacustrine basin, and could be clearly recognized either in the deep water or in the shallow water. Deposits of the deepwater gravity flows such as the sandy debris flows and the turbidity flows were mainly controlled by the slope break belt in deep water, whereas deposits of tractive current like subaqueous distributary channels in the deltafront were controlled by that in the shallow water. Further studies suggest that, except for sandbody origin types, the deepwater and shallowwater sedimentary slope breaks also have obvious controlling effect on thickness, plane distribution, and physical properties of the sandstones.
In addition, it is suggested that petroleum distribution was also controlled to a certain extent by the slope break belt. Although oil reservoirs can be found everywhere in the Yanchang Formation, most of the larger lithologic reservoirs are located either below the slope breaks or in the LST(lowstand systems tracts) sandstones neighboring the sequence boundary, or controlled by both of the slop break belt and the sequence boundary.
2010, 28(4): 735-744.
Abstract:
Based on the research development in international sequence stratigraphy, this paper puts some viewpoints forward as follows: (1) sequence of seismic stratigraphy is different from the depositional sequence of sequence stratigraphy; (2) after 1992 the transformation from threedivided to fourdivided models, the difference between marine and continental depositional sequence makes sequence stratigraphy develop complicatedly; (3) the base level curve correlative to the fourdivided model of current sequence stratigraphy is nonperiodic and is not correlative to the periodicity of shoreline trajectory; (4) this paper introduces LHT sequence stratigraphy including conceptual model, diagrammatizing rules and approach of chronsequence framework, revamped base level curve correlative to systems tracts of LHT sequence stratigraphy. This paper redefines sequence as "a relatively conformable succession of genetically related strata bounded by remnant maximum flooding surfaces (RMFS) and their correlative subaerial unconformities (CSU)".
Based on the research development in international sequence stratigraphy, this paper puts some viewpoints forward as follows: (1) sequence of seismic stratigraphy is different from the depositional sequence of sequence stratigraphy; (2) after 1992 the transformation from threedivided to fourdivided models, the difference between marine and continental depositional sequence makes sequence stratigraphy develop complicatedly; (3) the base level curve correlative to the fourdivided model of current sequence stratigraphy is nonperiodic and is not correlative to the periodicity of shoreline trajectory; (4) this paper introduces LHT sequence stratigraphy including conceptual model, diagrammatizing rules and approach of chronsequence framework, revamped base level curve correlative to systems tracts of LHT sequence stratigraphy. This paper redefines sequence as "a relatively conformable succession of genetically related strata bounded by remnant maximum flooding surfaces (RMFS) and their correlative subaerial unconformities (CSU)".
2010, 28(4): 752-761.
Abstract:
Based on the comprehensive application of properties, oil production test, and mercury injection data, the lower property limit of deep clastic reservoirs of Paleogene in Chezhen depression was determined by applying distribution function curve method, testing method, production test method, irreducible water saturation method, and the lowest effective pore throat radius method, and the influence factors were analyzed. On this basis, regarding the porosity and permeability difference as comparison parameters, the controlling actions of which sedimentation, formation pressure and diagenesis played on the deep effective reservoir were researched. The porosity lower limit and log depth are linear relationship, and the lower permeability limit and depth are exponential relationship. Deltaic front subaqueous distributary channel and mouth bar develop most effective reservoir, and porosity difference and permeability difference are well. while sublacustrine fan, nearshore subaqueous fan, fan delta and alluvial fan sandconglomerate develop less effective reservoir, and porosity difference and permeability difference are worse. The effective reservoir percentage content, porosity difference and permeability difference of middle and strong overpressure reservoirs are better than that of normal pressure and weak overpressure reservoirs. The effective reservoir percentage content, porosity difference and permeability difference of reservoirs on the middle diagenetic stage A1 are better than that of the reservoirs on the middle diagenetic stage A2 and B. In general, sedimentary facies is the main controlling factor on the development of deep effective reservoir, and the controlling action of overpressure on the deep effective reservoirs is stronger than diagenesis. The influence of diagenesis on the deep effective reservoirs is controlled by both sedimentary facies and overpressure. The reservoirs with high primary porosity and permeability protected by overpressure are dissolved easily to be good effective reservoirs.
Based on the comprehensive application of properties, oil production test, and mercury injection data, the lower property limit of deep clastic reservoirs of Paleogene in Chezhen depression was determined by applying distribution function curve method, testing method, production test method, irreducible water saturation method, and the lowest effective pore throat radius method, and the influence factors were analyzed. On this basis, regarding the porosity and permeability difference as comparison parameters, the controlling actions of which sedimentation, formation pressure and diagenesis played on the deep effective reservoir were researched. The porosity lower limit and log depth are linear relationship, and the lower permeability limit and depth are exponential relationship. Deltaic front subaqueous distributary channel and mouth bar develop most effective reservoir, and porosity difference and permeability difference are well. while sublacustrine fan, nearshore subaqueous fan, fan delta and alluvial fan sandconglomerate develop less effective reservoir, and porosity difference and permeability difference are worse. The effective reservoir percentage content, porosity difference and permeability difference of middle and strong overpressure reservoirs are better than that of normal pressure and weak overpressure reservoirs. The effective reservoir percentage content, porosity difference and permeability difference of reservoirs on the middle diagenetic stage A1 are better than that of the reservoirs on the middle diagenetic stage A2 and B. In general, sedimentary facies is the main controlling factor on the development of deep effective reservoir, and the controlling action of overpressure on the deep effective reservoirs is stronger than diagenesis. The influence of diagenesis on the deep effective reservoirs is controlled by both sedimentary facies and overpressure. The reservoirs with high primary porosity and permeability protected by overpressure are dissolved easily to be good effective reservoirs.
2010, 28(4): 768-775.
Abstract:
This paper used multibiomarkers to study the R12a core' s top 40 cm samples' phytoplankton and community sampled during the Second Chinese Arctic expedition from the Chukchi Sea in summer, 2003, and to abtain the information of the phytoplankton production and community change since 500 a.The results indicate the total and individual primary productivity increased over the last 500 a. The phytoplankton community structure mostly show the contributions of coccolithforids decreased, the contribution of diatoms increased, and the relative abundances of dinoflagellates not have obvious changes. This may be related with the Chukchi Sea's nutrients structure which is determined by the waters from the north Pacific Ocean and the summer ice cover change in the Chukchi Sea.
This paper used multibiomarkers to study the R12a core' s top 40 cm samples' phytoplankton and community sampled during the Second Chinese Arctic expedition from the Chukchi Sea in summer, 2003, and to abtain the information of the phytoplankton production and community change since 500 a.The results indicate the total and individual primary productivity increased over the last 500 a. The phytoplankton community structure mostly show the contributions of coccolithforids decreased, the contribution of diatoms increased, and the relative abundances of dinoflagellates not have obvious changes. This may be related with the Chukchi Sea's nutrients structure which is determined by the waters from the north Pacific Ocean and the summer ice cover change in the Chukchi Sea.
2010, 28(4): 783-789.
Abstract:
Dongping lake is located in the southwest of Shandong Province, it is the second lake in size in Shandong Province and is also an important flood control reservoir at the lower reaches of the Yellow River. Based on the modern sedimentary age sequence of the Dongping Lake which was established according to 210Pb and 137Cs methods, the sedimentary flux changes since 1889 were estimated and the reasons were analyzed and discussed. By using 137Cs method, three obvious peaks were observed in the core and the sedimentary flux was 0.145
g·cm2·a1 by 137Cs time marker(1963). The CRS model of 210Pb dating was used to caculate the sedimentary flux at different time intervals since 1989, the results showed that the sedimentary flux changed greatly, indicating that the sedimentary environment of Dongping Lake was unstable more than a century: from 1989 to 1938, the average sedimentary flux was high and stable, which was about 0.292 g·cm2·a1; decreased year by year during 1938 to 1965, with an average of 0.213 g·cm2·a1; was low and stable and showed a good agreement with the 137Cs method from 1965 to 2000; and started increasing year by year since 2000, with an average of 0.167 g·cm2·a1. The early high depostion flux maybe relevant to the fact that Dongping Lake has acted as a natural flood storage basin of the Yellow River, and the latter as a result of human activities (lake governance, water conservancy construction of the Yellow River, and so on) which controled the natural flooding of the Yellow River and led to a decline in sedimentary flux and tend to be stable, while the recent rise is a reflect of the increased economic activity. In this paper, the spatial distribution regularity of sedimentary flux and the relationship between the sedimentary flux and nature and human activities were explored so as to reveal the evolutionary history of the sedimentory environment of Dongping Lake more than a century and offer valuable basic information for protection and sustainable exploration of the Dongping Lake.
Dongping lake is located in the southwest of Shandong Province, it is the second lake in size in Shandong Province and is also an important flood control reservoir at the lower reaches of the Yellow River. Based on the modern sedimentary age sequence of the Dongping Lake which was established according to 210Pb and 137Cs methods, the sedimentary flux changes since 1889 were estimated and the reasons were analyzed and discussed. By using 137Cs method, three obvious peaks were observed in the core and the sedimentary flux was 0.145
g·cm2·a1 by 137Cs time marker(1963). The CRS model of 210Pb dating was used to caculate the sedimentary flux at different time intervals since 1989, the results showed that the sedimentary flux changed greatly, indicating that the sedimentary environment of Dongping Lake was unstable more than a century: from 1989 to 1938, the average sedimentary flux was high and stable, which was about 0.292 g·cm2·a1; decreased year by year during 1938 to 1965, with an average of 0.213 g·cm2·a1; was low and stable and showed a good agreement with the 137Cs method from 1965 to 2000; and started increasing year by year since 2000, with an average of 0.167 g·cm2·a1. The early high depostion flux maybe relevant to the fact that Dongping Lake has acted as a natural flood storage basin of the Yellow River, and the latter as a result of human activities (lake governance, water conservancy construction of the Yellow River, and so on) which controled the natural flooding of the Yellow River and led to a decline in sedimentary flux and tend to be stable, while the recent rise is a reflect of the increased economic activity. In this paper, the spatial distribution regularity of sedimentary flux and the relationship between the sedimentary flux and nature and human activities were explored so as to reveal the evolutionary history of the sedimentory environment of Dongping Lake more than a century and offer valuable basic information for protection and sustainable exploration of the Dongping Lake.
2010, 28(4): 798-807.
Abstract:
Ordos Basin is the famous petroliferous basin of Mesozoic in China. Yanchang Formation of Upper Triassic and Yan'an Formation of Jurassic are the main oilbearing strata. The oilbearing strata got through IndoChina movement, Yanshanian movement and Himalayan movement. Based on the analyses of the tectonic stress field of Mesozoic and Cenozoic and the research of the tectonic heat events, combined with fracture property, fracture azimuth and characteristic of inclusion in fracture, the relationship between the petroleum accumulation of Mesozoic and tectonic movement was discussed. It is suggested that EW, NNE and NE striking fractures were developed in the basin. Among them, the NE striking shear fractures with thin filled were developed in the SN compression environment in IndoChina period, or the NE striking fractures induced tensional fracture formed by basement fault. The EW shear striking fractures with thin filled were developed in the NWSE compression environment in Yanshanian period.The NNE tensional striking fractures with strong filled were developed in the NNWSSE extensional environment in Himalayan period. Each tectonic movements occured in Mesozoic and Cenozoic controlled the migration and accumulation of the petroleum.Because of the IndoChina movement, Ordos Basin deposited the important hydrocarbon source rock in Mesozoic. The hydrocarbon source rock reached the peak of hydrocarbon generation and expulsion because of the tectonic heat event which was producted by Yanshanian movement, resulting in the petroleum accumulation during Yanshanian period. The petroleum undergone largescale migration and adjustment because of the Himalayan movement led to the petroleum distribution of upper Mesozoic consistent with the trend of basement fracture belt. These three Mesozoic and Cenozoic tectonic movements have signicantly influenced the development of Ordos Basin and hydrocarbon accumulation within it.
Ordos Basin is the famous petroliferous basin of Mesozoic in China. Yanchang Formation of Upper Triassic and Yan'an Formation of Jurassic are the main oilbearing strata. The oilbearing strata got through IndoChina movement, Yanshanian movement and Himalayan movement. Based on the analyses of the tectonic stress field of Mesozoic and Cenozoic and the research of the tectonic heat events, combined with fracture property, fracture azimuth and characteristic of inclusion in fracture, the relationship between the petroleum accumulation of Mesozoic and tectonic movement was discussed. It is suggested that EW, NNE and NE striking fractures were developed in the basin. Among them, the NE striking shear fractures with thin filled were developed in the SN compression environment in IndoChina period, or the NE striking fractures induced tensional fracture formed by basement fault. The EW shear striking fractures with thin filled were developed in the NWSE compression environment in Yanshanian period.The NNE tensional striking fractures with strong filled were developed in the NNWSSE extensional environment in Himalayan period. Each tectonic movements occured in Mesozoic and Cenozoic controlled the migration and accumulation of the petroleum.Because of the IndoChina movement, Ordos Basin deposited the important hydrocarbon source rock in Mesozoic. The hydrocarbon source rock reached the peak of hydrocarbon generation and expulsion because of the tectonic heat event which was producted by Yanshanian movement, resulting in the petroleum accumulation during Yanshanian period. The petroleum undergone largescale migration and adjustment because of the Himalayan movement led to the petroleum distribution of upper Mesozoic consistent with the trend of basement fracture belt. These three Mesozoic and Cenozoic tectonic movements have signicantly influenced the development of Ordos Basin and hydrocarbon accumulation within it.
2010, 28(4): 815-820.
Abstract:
Aryl isoprenoids have been detected in late Cretaceous shale in Qn1,Songliao basin. It range from C13 to C23,and these compounds have a high concentration in some samples, the highest concentration can be above 30% of aromatic hydrocarbons. These samples are distributed in Chaochang area in southeast Songliao Basin. Aryl isoprenoids and some saturated hydrocarbon biomarkers suggested that the source rocks were deposited under a brackish and reducing and sulphate or sulphied rich water .The algae and Chlorobiaceae are the main source of organic matter in source rocks.The distribution of Aryl isoprenoids indicated that there was a marine transgressional event in Songliao Lake during the late Cretaceous and its direction may be from the southeast to northwest.
Aryl isoprenoids have been detected in late Cretaceous shale in Qn1,Songliao basin. It range from C13 to C23,and these compounds have a high concentration in some samples, the highest concentration can be above 30% of aromatic hydrocarbons. These samples are distributed in Chaochang area in southeast Songliao Basin. Aryl isoprenoids and some saturated hydrocarbon biomarkers suggested that the source rocks were deposited under a brackish and reducing and sulphate or sulphied rich water .The algae and Chlorobiaceae are the main source of organic matter in source rocks.The distribution of Aryl isoprenoids indicated that there was a marine transgressional event in Songliao Lake during the late Cretaceous and its direction may be from the southeast to northwest.
2010, 28(4): 832-848.
Abstract:
The Chipu leadzinc deposit has closely associated with the bitumen. There have a large number of bitumen grown up with leadzinc sulfide hosted by carbonate rocks. Through ethnic separation, quantitative and saturated hydrocarbons chromatogrammass spectrum analysis, we researched on the ethnic composition and biomarker of bitumen and discussed their geological significance. The conclusions are shown as follows: (1) Organic matter in leadzinc deposits mainly came from carbonate rocks, minor came from the shale, and no continental organic matter added in it. Characteristics of this kind of mixed origin could be affected by different sources of oreforming fluid. (2) Organic matter in deposit implies that the hydrothermal fluids suffered from the physical and chemical processes of high reduction and high salinity. (3) Organic matter, which hosted by leadzinc ore and dolostone, with high maturity, belongs to carbon bitumen, which reflect the evolution of higher levels of organic matter. Organic matters in ore and host rock have a similar maturity, and reflect a similar geological process. (4) Organic matter reduced the sulfate in carbonate rocks, and resulted in reduced sulfur to create the conditions for lead and zinc sulfide precipitation. (5) oreforming fluids in the hydrocarbon content is relatively high, it inferred that high mature stage of evolution of organic matter may be the formation of the ancient reservoir involved in the mineralization. The organic matter plays a role of reducing agent during mixing with orebearing fluid.
The Chipu leadzinc deposit has closely associated with the bitumen. There have a large number of bitumen grown up with leadzinc sulfide hosted by carbonate rocks. Through ethnic separation, quantitative and saturated hydrocarbons chromatogrammass spectrum analysis, we researched on the ethnic composition and biomarker of bitumen and discussed their geological significance. The conclusions are shown as follows: (1) Organic matter in leadzinc deposits mainly came from carbonate rocks, minor came from the shale, and no continental organic matter added in it. Characteristics of this kind of mixed origin could be affected by different sources of oreforming fluid. (2) Organic matter in deposit implies that the hydrothermal fluids suffered from the physical and chemical processes of high reduction and high salinity. (3) Organic matter, which hosted by leadzinc ore and dolostone, with high maturity, belongs to carbon bitumen, which reflect the evolution of higher levels of organic matter. Organic matters in ore and host rock have a similar maturity, and reflect a similar geological process. (4) Organic matter reduced the sulfate in carbonate rocks, and resulted in reduced sulfur to create the conditions for lead and zinc sulfide precipitation. (5) oreforming fluids in the hydrocarbon content is relatively high, it inferred that high mature stage of evolution of organic matter may be the formation of the ancient reservoir involved in the mineralization. The organic matter plays a role of reducing agent during mixing with orebearing fluid.
2010, 28(4): 659-670.
Abstract:
To reconstruct the evolution process of tectonics and paleoenvironment during the lateCenozoic time in West Kunlun area, clay mineralogy of the molasse sediments of the foreland basin of West Kunlun mountains were investigated using Xray diffraction (XRD) and scanning electron microscopy (SEM) methods. The results show that clay minerals in sediments of 81.8Ma B.P. are mainly illite and smectite, with minor chlorite and kaolinite, while their relative contents and illite crystallinity change apparently along the profile. Illite content and its crystallinity are both notably high, and the content of smectite is low, with minor kaolinite occurring throughout the sediments of 8~3.5 Ma B.P. The content of smectite increases sharply while the content of illite, as well as the illite crystallinity, decreases, and no kaolinite is present in the period of 3.5~3.3Ma B.P. Clay mineral indices of the period of 3.3~2.8 Ma B.P. are similar to those of 8~3.5 Ma B.P., and which of the period of 2.8~1.8 Ma B.P. are similar to those of 3.5~3.3 Ma B.P. It is concluded that changes in clay mineralogy of the Yecheng sediments was dominantly controlled by the changes of source rocks and, to some extent, by changes in climate around the area. The uplift of the West Kunlun is uneven and stepwise according to clay mineralogy of sediments.
There were three times structural uplift events in the west Kunlun area, which had occurred around 3.5 Ma B.P., 3.3 Ma B.P. and 2.8 Ma B.P., respectively.
In addition, an arid episode occurred around 2.5 Ma B.P. in the region.
To reconstruct the evolution process of tectonics and paleoenvironment during the lateCenozoic time in West Kunlun area, clay mineralogy of the molasse sediments of the foreland basin of West Kunlun mountains were investigated using Xray diffraction (XRD) and scanning electron microscopy (SEM) methods. The results show that clay minerals in sediments of 81.8Ma B.P. are mainly illite and smectite, with minor chlorite and kaolinite, while their relative contents and illite crystallinity change apparently along the profile. Illite content and its crystallinity are both notably high, and the content of smectite is low, with minor kaolinite occurring throughout the sediments of 8~3.5 Ma B.P. The content of smectite increases sharply while the content of illite, as well as the illite crystallinity, decreases, and no kaolinite is present in the period of 3.5~3.3Ma B.P. Clay mineral indices of the period of 3.3~2.8 Ma B.P. are similar to those of 8~3.5 Ma B.P., and which of the period of 2.8~1.8 Ma B.P. are similar to those of 3.5~3.3 Ma B.P. It is concluded that changes in clay mineralogy of the Yecheng sediments was dominantly controlled by the changes of source rocks and, to some extent, by changes in climate around the area. The uplift of the West Kunlun is uneven and stepwise according to clay mineralogy of sediments.
There were three times structural uplift events in the west Kunlun area, which had occurred around 3.5 Ma B.P., 3.3 Ma B.P. and 2.8 Ma B.P., respectively.
In addition, an arid episode occurred around 2.5 Ma B.P. in the region.
2010, 28(4): 676-681.
Abstract:
This paper reports siliceousphosphatic nodules from the Yanjiahe Formation, Terreneuvian in Three Gores area, Hubei province, South China. The results of XRD show phosphatic contents are higher in interior and siliceous contents are higher in exterior of the nodules. The nodules' interior shows loose texture, and abundant Cyanobacteria and diverse Small Shelly Fossils are found in siliceousphosphatic nodules. It indicates Cyanobacteria and SSFs play an important part in formation process of nodules. Under the regulating action of microorganisms, siliceousphosphatic nodules were formed gradually along with the mediums' change of physicchemical condition.
This paper reports siliceousphosphatic nodules from the Yanjiahe Formation, Terreneuvian in Three Gores area, Hubei province, South China. The results of XRD show phosphatic contents are higher in interior and siliceous contents are higher in exterior of the nodules. The nodules' interior shows loose texture, and abundant Cyanobacteria and diverse Small Shelly Fossils are found in siliceousphosphatic nodules. It indicates Cyanobacteria and SSFs play an important part in formation process of nodules. Under the regulating action of microorganisms, siliceousphosphatic nodules were formed gradually along with the mediums' change of physicchemical condition.
2010, 28(4): 688-695.
Abstract:
In order to interpret continental responses to globally climatic cooling in the EoceneOligocene, we have studied the paleolake features of Fushun Basin, an Eocene faultdepression basin in NE China, through measuring actual strata profiles in the fields and indoor sample testing. The analysis of rock facies, facies indicators and rock thinsections suggests the evolution history of sedimentary facies in Eocene, Fushun Basin. Sedimentary subfacies vary as: lake and marshlandshallow lacustrinehalf deep lacustrinedeep lacustrine half deep lacustrineshallow lacustrine, with the water depth varying as: shallowdeepshallow. On the basis of contents of trace elements (B, Mn, Ti, Co, Cr, Ni, V), element contents ratios (Sr/Ba, V/（V+Ni）, Ni/ Co, ωFe2O3/ωFeO) and ratios of oxides, we point out that there was an abrupt climatic change from early Eocene to late Eocene in Fushun Basin. In the early Eocene, climate was moisture and good for coral forming. While, in the middlelate Eocene, climate changed into drier and made contribution into the interbedding between marlite forming in saline and halfsaline water and clay shale. In general, our study shows that the climate changed from moisture to dry in EoceneOligocene.
In order to interpret continental responses to globally climatic cooling in the EoceneOligocene, we have studied the paleolake features of Fushun Basin, an Eocene faultdepression basin in NE China, through measuring actual strata profiles in the fields and indoor sample testing. The analysis of rock facies, facies indicators and rock thinsections suggests the evolution history of sedimentary facies in Eocene, Fushun Basin. Sedimentary subfacies vary as: lake and marshlandshallow lacustrinehalf deep lacustrinedeep lacustrine half deep lacustrineshallow lacustrine, with the water depth varying as: shallowdeepshallow. On the basis of contents of trace elements (B, Mn, Ti, Co, Cr, Ni, V), element contents ratios (Sr/Ba, V/（V+Ni）, Ni/ Co, ωFe2O3/ωFeO) and ratios of oxides, we point out that there was an abrupt climatic change from early Eocene to late Eocene in Fushun Basin. In the early Eocene, climate was moisture and good for coral forming. While, in the middlelate Eocene, climate changed into drier and made contribution into the interbedding between marlite forming in saline and halfsaline water and clay shale. In general, our study shows that the climate changed from moisture to dry in EoceneOligocene.
2010, 28(4): 706-716.
Abstract:
Based on a comprehensive analysis of core, logging data and seismic survey, the sedimentary facies types of Paleogene Dainan Formation, Gaoyou Sag, Subei Basin were studied systematically, as well as their distribution and evolution. The research showed that fan delta, delta, nearshore subaqueous fan and lacustrine facies deposited in the formation, of which fan delta and nearshore subaqueous fan located along the steep south border, delta in the gently north slope and lacustrine in the central zone of the deep area and the flank of the fan delta, delta and nearshore subaqueous fan. From the margin to the depocenter of the sag, the sedimentary environments gradually changed from fan delta, delta or nearshore subaqueous fan to shoreshallow sediments and middle depth lacustrine. The palaeogeography of the Dainan Formation displayed a clear southnorth zonation. The sedimentary envolution of Dainan Formation was divided into two stages, in which the sedimentary characteristics and the sedimentary facies distribution were correspondingly different. As a whole, the depth of water changed from shallow to deep, and then to shallow, sedimentary area gradually enlarged, and fan delta, delta and nearshore subaqueous fan frist retrogradated, then progradated.
Based on a comprehensive analysis of core, logging data and seismic survey, the sedimentary facies types of Paleogene Dainan Formation, Gaoyou Sag, Subei Basin were studied systematically, as well as their distribution and evolution. The research showed that fan delta, delta, nearshore subaqueous fan and lacustrine facies deposited in the formation, of which fan delta and nearshore subaqueous fan located along the steep south border, delta in the gently north slope and lacustrine in the central zone of the deep area and the flank of the fan delta, delta and nearshore subaqueous fan. From the margin to the depocenter of the sag, the sedimentary environments gradually changed from fan delta, delta or nearshore subaqueous fan to shoreshallow sediments and middle depth lacustrine. The palaeogeography of the Dainan Formation displayed a clear southnorth zonation. The sedimentary envolution of Dainan Formation was divided into two stages, in which the sedimentary characteristics and the sedimentary facies distribution were correspondingly different. As a whole, the depth of water changed from shallow to deep, and then to shallow, sedimentary area gradually enlarged, and fan delta, delta and nearshore subaqueous fan frist retrogradated, then progradated.
2010, 28(4): 730-734.
Abstract:
In the ways of recovering eroding strata's thickness, the problem of extracompensation and lesscompensation of eroding strata is the essential factor that always restricts the selection of the ways and the result that is whether right or not. Example for Dongpu Depression, the rationality of recovering the Dongying Formation thickness by the method of mudstone compaction is analyzed. By this, the new cognition for compensation sediment of eroding strata is acquired. The study shows that when using the methods of recovering eroding strata's thickness that relates to the tendency of the pore's variation with depth, the compensation sediment of eroding strata should be understood by weight compensation. When using the methods of recovering eroding strata's thickness that relates to the temperature index, the compensation sediment of eroding strata should be understood by temperature compensation. And it shouldn't be understood by thickness compensation simply.
In the ways of recovering eroding strata's thickness, the problem of extracompensation and lesscompensation of eroding strata is the essential factor that always restricts the selection of the ways and the result that is whether right or not. Example for Dongpu Depression, the rationality of recovering the Dongying Formation thickness by the method of mudstone compaction is analyzed. By this, the new cognition for compensation sediment of eroding strata is acquired. The study shows that when using the methods of recovering eroding strata's thickness that relates to the tendency of the pore's variation with depth, the compensation sediment of eroding strata should be understood by weight compensation. When using the methods of recovering eroding strata's thickness that relates to the temperature index, the compensation sediment of eroding strata should be understood by temperature compensation. And it shouldn't be understood by thickness compensation simply.
2010, 28(4): 745-751.
Abstract:
There exist some faults about the factor controlling sequence and the system tract partition in the former fluvial sequence stratigraphic models. The author finds that there are some terrace staircases in the fluvial valley during the fluvial parasequence correlation of He 8th in Sulige gas field. Studies about modern valleyform show that the secondary intermittent tectonic uplifts during the first tectonic uplift led to the alternation of vertical erosion and lateral erosiondeposition, which forms the terrace staircases. And the first tectonic fall led to base level uplift and the change of new space added, which will control the sandbody distribution. According to the role of tectonic during forming fluvial sequence and the contact relationship between terrace staircases and their surrounding formations, the author modifies Wright, et al (1993) fluvial sequence stratigraphic model, and he thinks that the tectonic movement controls the fluvial sequence. The hemicycle of tectonic uplift forms the regressive systems tract that is made of a series of relative isochronous terraces staircases. And the hemicycle of tectonic fall forms the lowstand systems tract, transgressive systems tract and highstand systems tract. The lowstand systems tract includes some filling sedimentary compound in the fluvial valley. The transgressive systems tract and the highstand systems tract are the same as the corresponding systems tract in the Wright, et al (1993) model.
There exist some faults about the factor controlling sequence and the system tract partition in the former fluvial sequence stratigraphic models. The author finds that there are some terrace staircases in the fluvial valley during the fluvial parasequence correlation of He 8th in Sulige gas field. Studies about modern valleyform show that the secondary intermittent tectonic uplifts during the first tectonic uplift led to the alternation of vertical erosion and lateral erosiondeposition, which forms the terrace staircases. And the first tectonic fall led to base level uplift and the change of new space added, which will control the sandbody distribution. According to the role of tectonic during forming fluvial sequence and the contact relationship between terrace staircases and their surrounding formations, the author modifies Wright, et al (1993) fluvial sequence stratigraphic model, and he thinks that the tectonic movement controls the fluvial sequence. The hemicycle of tectonic uplift forms the regressive systems tract that is made of a series of relative isochronous terraces staircases. And the hemicycle of tectonic fall forms the lowstand systems tract, transgressive systems tract and highstand systems tract. The lowstand systems tract includes some filling sedimentary compound in the fluvial valley. The transgressive systems tract and the highstand systems tract are the same as the corresponding systems tract in the Wright, et al (1993) model.
2010, 28(4): 762-767.
Abstract:
The Luoping Biota is contained in the Member Ⅱ of the Ainsian Guanling Formation at Dawazi Village, Luoping County, Yunnan Province, China. It is characterized by abundant wellpreserved marine ichthyofauna , associated with marine reptiles, echinoderms, crustaceans, bivalves and plant fossils. The strata bearing the Luoping Biota are dominated by gray black thin bedded micrite as well as a large number of sedimentary structrues, such as horizontal laminae, wavy bedding, deformation structures (slump structures, convolute bedding) and trace fossils and so on. This paper aims to study the sedimentary environment and taphonomy of the Luoping Biota. The result shows that the sedimentary environment of Luoping Biota is a deep water basin with distally steepened ramp on the platform. The sea water in this basin was relatively quiet with intermittent reducing condition which effectively prevented the degradation of organisms. The sedimentary deformation structures on distally steepened ramp indicate that the environment was changed suddenly, which led to the demise and the rapid burial of the biota.
The Luoping Biota is contained in the Member Ⅱ of the Ainsian Guanling Formation at Dawazi Village, Luoping County, Yunnan Province, China. It is characterized by abundant wellpreserved marine ichthyofauna , associated with marine reptiles, echinoderms, crustaceans, bivalves and plant fossils. The strata bearing the Luoping Biota are dominated by gray black thin bedded micrite as well as a large number of sedimentary structrues, such as horizontal laminae, wavy bedding, deformation structures (slump structures, convolute bedding) and trace fossils and so on. This paper aims to study the sedimentary environment and taphonomy of the Luoping Biota. The result shows that the sedimentary environment of Luoping Biota is a deep water basin with distally steepened ramp on the platform. The sea water in this basin was relatively quiet with intermittent reducing condition which effectively prevented the degradation of organisms. The sedimentary deformation structures on distally steepened ramp indicate that the environment was changed suddenly, which led to the demise and the rapid burial of the biota.
2010, 28(4): 776-782.
Abstract:
210Pb and 137Cs were used to analyze for the Fuxian Lake sediment core. 210Pb (CRS) dating result showed a little deviation from 137Cs dating, and two reasons were investigated. According to the feature of Fuxian Lake, we analyzed the grain size characteristics and obtained the content of the core, which contained 36% of clay, 44% of fine sand and 18% of coarse sand. By calculation, the different grainsize parameters were also obtained, the mean grain diameter () was between 6.48 and 7.92, the standard deviation (So) was between 1.27 and 1.42, and the skewness (SKD) was between 0.18 and 0.04. Based on radionuclide dating and grainsize distribution characteristics in the sediment core, we concluded a sedimentary environment in Fuxian Lake had been greatly changed since 1878, which can be marked off four stages: natural evolution stage, manmade disturbances stage, manmade transformation stage, and recent treatment stage. Human activities of historical period had played a very important role in changing the environment of the Lake.
210Pb and 137Cs were used to analyze for the Fuxian Lake sediment core. 210Pb (CRS) dating result showed a little deviation from 137Cs dating, and two reasons were investigated. According to the feature of Fuxian Lake, we analyzed the grain size characteristics and obtained the content of the core, which contained 36% of clay, 44% of fine sand and 18% of coarse sand. By calculation, the different grainsize parameters were also obtained, the mean grain diameter () was between 6.48 and 7.92, the standard deviation (So) was between 1.27 and 1.42, and the skewness (SKD) was between 0.18 and 0.04. Based on radionuclide dating and grainsize distribution characteristics in the sediment core, we concluded a sedimentary environment in Fuxian Lake had been greatly changed since 1878, which can be marked off four stages: natural evolution stage, manmade disturbances stage, manmade transformation stage, and recent treatment stage. Human activities of historical period had played a very important role in changing the environment of the Lake.
2010, 28(4): 790-797.
Abstract:
By analyzing lithology, magnetic features, the highfrequency and the lowfrequency quality magnetic susceptibility, frequency magnetic susceptibility and total organic matter (TOC) of the sediments of the 523m CH0310 core in Qarhan paleolake, Qaidam Basin, the conclusion shows that magnetite is the main contributor to the magnetic susceptibility in the CH0310 core. Due to the impact and control of the climate and environment, magnetic susceptibility is positively correlated with coarse sand content and negatively correlated with the clay content in sediments from the weak oxidation environmentdominated CH0310 core. Based on the further analysis on the relevance of magnetic susceptibility and TOC, the results present that the relevance of magnetic susceptibility and TOC in the different sediment layers show the positive and negative differences, reflecting the different corresponding model of magnetic susceptibility to climate and environment in CH0310 different layers, revealing the complexity of the factors as well as the uncertainty of the lake magnetic susceptibility as a proxy indicator of climate. Therefore, for the lake which is located in the plateau and arid area and has the rapid sedimentation rate and thicker sediment layers, special care should be taken if using magnetic susceptibility as a single indicator to reflect and reconstruct the paleoclimatic and paleoenvironmental changes.
By analyzing lithology, magnetic features, the highfrequency and the lowfrequency quality magnetic susceptibility, frequency magnetic susceptibility and total organic matter (TOC) of the sediments of the 523m CH0310 core in Qarhan paleolake, Qaidam Basin, the conclusion shows that magnetite is the main contributor to the magnetic susceptibility in the CH0310 core. Due to the impact and control of the climate and environment, magnetic susceptibility is positively correlated with coarse sand content and negatively correlated with the clay content in sediments from the weak oxidation environmentdominated CH0310 core. Based on the further analysis on the relevance of magnetic susceptibility and TOC, the results present that the relevance of magnetic susceptibility and TOC in the different sediment layers show the positive and negative differences, reflecting the different corresponding model of magnetic susceptibility to climate and environment in CH0310 different layers, revealing the complexity of the factors as well as the uncertainty of the lake magnetic susceptibility as a proxy indicator of climate. Therefore, for the lake which is located in the plateau and arid area and has the rapid sedimentation rate and thicker sediment layers, special care should be taken if using magnetic susceptibility as a single indicator to reflect and reconstruct the paleoclimatic and paleoenvironmental changes.
2010, 28(4): 808-814.
Abstract:
The pyrolysis simulation of the asphaltenes in marine crude oil in Tarim Basin was carried out in an anhydrous closed system under a constant pressure of 50 MPa. The gasgeneration mechanism of asphaltene in marine crude oil was discussed on the basis of the yields and carbon isotopic composition of gaseous hydrocarbons and the yields of pyrobitumen. Kinetic parameters of gaseous hydrocarbons generation generated from asphaltene was obtained by kinetic calculation and extrapolated to geological conditions. Gaseous hydrocarbon begin to generate from asphaltene around Easy%Ro 0.8, and the conversion rate of gaseous hydrocarbon reach to 1 at Easy%Ro 2.65. The main gasgeneration period of asphaltene pyrolysis range from Easy%Ro 0.9 (conversion rate 0.1) to Easy% Ro 2.3 (conversion rate 0.9). The application result can provide a theoretical basis for identification and assessment of oil cracking gas and exploration decision of marine carbonate area in China.
The pyrolysis simulation of the asphaltenes in marine crude oil in Tarim Basin was carried out in an anhydrous closed system under a constant pressure of 50 MPa. The gasgeneration mechanism of asphaltene in marine crude oil was discussed on the basis of the yields and carbon isotopic composition of gaseous hydrocarbons and the yields of pyrobitumen. Kinetic parameters of gaseous hydrocarbons generation generated from asphaltene was obtained by kinetic calculation and extrapolated to geological conditions. Gaseous hydrocarbon begin to generate from asphaltene around Easy%Ro 0.8, and the conversion rate of gaseous hydrocarbon reach to 1 at Easy%Ro 2.65. The main gasgeneration period of asphaltene pyrolysis range from Easy%Ro 0.9 (conversion rate 0.1) to Easy% Ro 2.3 (conversion rate 0.9). The application result can provide a theoretical basis for identification and assessment of oil cracking gas and exploration decision of marine carbonate area in China.
2010, 28(4): 821-831.
Abstract:
Geochemistry of fluorite deposits and its ore rocks in Sickl area, Tarim Basin is applied to investigate the ingenesis. The study shows that: relative LREE concentration and positive Eu anomaly are resulted from REE distribution pattern diagrams of fluorite; Eu, Sr and Ba are related closely in trace element analysis; the isotope ratio of Sr in fluorite is close to that in surrounding rocks. Conclusions are: oreforming fluids of the fluorite mainly are from the infiltration of heated basin brine ; trace elements(including REE) are from underlying strata and surrounding rocks; and elementsF, Ba, Eu are from Lower Cambrian siliceous rocks and phosphorite.
Geochemistry of fluorite deposits and its ore rocks in Sickl area, Tarim Basin is applied to investigate the ingenesis. The study shows that: relative LREE concentration and positive Eu anomaly are resulted from REE distribution pattern diagrams of fluorite; Eu, Sr and Ba are related closely in trace element analysis; the isotope ratio of Sr in fluorite is close to that in surrounding rocks. Conclusions are: oreforming fluids of the fluorite mainly are from the infiltration of heated basin brine ; trace elements(including REE) are from underlying strata and surrounding rocks; and elementsF, Ba, Eu are from Lower Cambrian siliceous rocks and phosphorite.
