APPOACH OF TECTONIC BACKGROUND FOR MID PROTEROZOIC MESOZOIC SANDSTONES IN JINXI，LIAONING
摘要: 砂岩的碎屑组成特征与所处的大地构造位置关系密切.利用砂岩的构造属性,可对区域构造的演化过程、性质及延续和转折时间等进行有效的分析.砂岩的QFL和QmFLt碎屑组合分析表明,从中元古代至中生代,辽宁锦西地区经历了基底隆起、克拉通化、再旋回沉积、活动大陆边缘深挖拗陷和强烈断陷活动等几次性质不同的沉积-构造发展阶段.Abstract: In factors of controlling sedimentation，effect of regional tectonic is the most important. On the one hand tectonic action opens up terrigenous fragmental materials，and the other hand it offers sediroental places .Fragmental composition and its time-space changes.therefore. in a certain degree. can reflect effectively in- tensity，nature, and continued -turned times of regional tectonic action.In the case of continental cratons that stages of ebolution is unclear it is specially significance.Based on the research of regional petrology，thespaper ，taking Jinzi area in Liaoning as a point of architectonic pattern of Sino-Korean Platform, place emphasis on studing of sandstones in relation to tectics from Mid Protcrozoic to Mesozoic. Probenance terranes corre- sponding to plate tectonic units subdibided recently by Dickinson and others are adopted in the paper Fragmental composition of sandstones in this area shows the following changes:feldspar一quartz (Mid-Late Proterozoic) deribed mainly from crystal rocks of continental basement: lithec fragment-quartz (Late Paleozoic)，from continental basement and pre-sediments getting into recycles; and fdld-spar-lithec fragment (Mespzoic)，from mother rocks around basin and products of bolcanic cycles.K20/Na20rate of sandstones is lower and its maturity reduces with changing of times. The threekinds of fragmental ebolution present basically the two facts:l.non-stability of fagmental composition is increasing;2.probenances of sedimentary materialtend to dibersity. Analysis of tectonic setting of sandstones with QFL and QmFLt diagrams shows that fragmental points were distributed over bsement uplift and transition area of continental blocks due to high conten of feldspar in early Changchengian of Mid Proterozoic in Jinxi, It displays that settlement of Yanliao Basin during Mid Proterozoic was accompanide uplift action of the shanhaiguan ancient Iand.Feldspar-riched sands from base- ment accumulated mainly to the Xingcheng一Huludao yoked basin near uplift area. Quartz content of sand- stones generally tends to increase from Changchengian to Qingbeikouan of Late Proteozoic，which tectonic ac- tion of sedimental area develops towards stabilfty.In the area high mature quartz sands formde mat shape were widely distributed over the western liaoning, Bohai Gulf，and the eastern Liaoning.This is resuly that strand line is slowly moved Forward in stable condition and quartz sands belong to products of continental cratonization. Because chert and other lithic Cragments increawe, the points of Permian sandstones Fall mainly to field of recycled orogens. According to analysis of regional stratigraphy and tectonics，this kind of sub-stable Crag- ments deribed closing of Inner Mongolia geosyneline in Late Paleozoic. Based on the analysis of focal folds， volcan actibity，and intrusion of neutral-acid magma, Permian sandston fragments distrubuted on recucled orogens hint that possessed one kind of“orogenic” character in evolution of“sino- Korean Plat- form” in sometime.Affected by plate collision of neighbour areas，probenance of the foreland uplift lay under the doub- 1e controls of continental blocks and orogenie bewlts during late period of Late Paleozoic in the western Liaon- ing.In this problem.it is not quite definite to classify on Dickinson′s probenances. In Early-Mid Triassic time，fragments were mainly distributed between continents and magmatic arcs， which show tectonic property of intense basin depression.To compare Triassic fragmental composition wigh Late Paleozoic one、associations of mother rock are different; but with Jurassic one，similar.It shows that the regional tectonec property of controlling probenances habe changed in initial stage of Mesozoec and tha Triassic time was a transitional time from eratonec enbironment to actibe continental margin in this area.From Jurassis to Cretaceousm，Volcanic debris came repeadly into sedimental cycles and increase gradually，It rebealed that this area hs been completely inbolbed in the field of actibe continental matgin，and eben more in- tenser. In summary，Jinxi area underwent two large-scale ebolutional stages of sedimentary-tectonic cycle from sub- stable craton to actibe continental margins，including basement uplift，cratonization, recycled sedimentation, and intense depression and fault subsidence. Both Q/F+L and F/L balues indicate that periodic interval of sedimentary reformational history was shortened and reformational intensity became reduced on the evolution of times. It eomfirrns that tectonic actibity of the crust in the area tectonics on sedimentation proceed from the insied to the outside Among the， the F/Lratios of two times in the early proterozoic and the early Mid Mesozoic re larger tha others.The both predict beginning of two large-scale sedimentary-tectonee cycles belong to the types of sub-stable craton and active continental margin.
(10)Dickinson，W.R.1983, Geol. Soc. Amer. Bull.,V94, N.2. P.222-235
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