辽宁锦西地区中元古代-中生代砂岩构造背景的探讨

APPOACH OF TECTONIC BACKGROUND FOR MID PROTEROZOIC MESOZOIC SANDSTONES IN JINXI, LIAONING

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.

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 sedimental places .Fragmental composition and its time-space changes .therefore, in a certain degree, can reflect effectively intensity , 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 , thes paper , taking Jinxi 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 corresponding 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 - 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 threekmds of fragmental ebolution present basically the two facts : 1. non-stability of fagmental composition is increasing ; 2.probenances of sedimentary material tend 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 land.Feldspar-riched sands from basement accumulated mainly to the Xingcheng - Huludao yoked basin near uplift area. Quartz content of sandstones generally tends to increase from Changchengian to Qingbeikouan of Late Proteozoic , which tectonic action of sedimental area develops towards stability.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 fragments 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 fragments deribed closing of Inner Mongolia geosyncline in Late Paleozoic. Based on the analysis of local 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 double controls of continental blocks and orogenic bewlts during late period of Late Paleozoic in the western Liaoning .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 cratonec 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 cont