高校地质学报2018，Vol.24Issue(3)：390-400,11.DOI:10.16108/j.issn1006-7493.2017109
四川盆地川中地区须家河组古盐度特征及其地质意义
Paleosalinity of the Xujiahe Formation in Central Sichuan Basin and Its Geological Significance
摘要
Abstract
On the basis of sedimentological research, we study clay minerals by X-ray diffraction and trace element analysis to infer paleosalinity of the lacustrine environment in which the Xujiahe Formation was deposited in Sichuan Basin. Paleosalinity was determined using the Couch formula and the paleosalinity values range from 4.8 to 19.7 per thousand, with an average value of 12.8 per thousand. The paleosalinity of different layers in the Xujiahe Formation changed regularly, and there is a gradual decrease trend from the second to the sixth member, i.e., from saline to brackish water. The increase in salinity is favorable for the conversion of montmorillonite to illite, suggesting that clay mineral of the second member of the Xujiahe Formation is mainly illite. The illite content decreases gradually from the fourth member to the sixth member, indicating thatclay mineral in fourth member and sixth member is mainly chlorites. Palaeosalinity also has a certain effect on the chlorite composition. with the increase of salinity, Si4+, Fe2+/Mg2++Fe2+content decreases and AlIVcontent increases in the chlorite composition. Combined with tectonic movement, the change in paleosalinity of the Xujiahe Formation was probably caused by the Indosinian tectonism, the southern section of Longmen mountain uplift during the third member period, the Sichuan Basin and the sea lost contact and became a separate deposition system. The sedimentary facies of the second and the third member of the Xujiahe formation should be deposited in a terrestrial environment. However, it was superimposed by tide. The fourth, fifth and sixth member of the Xujiahe Formation should belong to the normal continental sedimentary environment.关键词
四川盆地/上三叠统须家河组/古盐度/粘土矿物/Couch公式Key words
Sichuan Basin/Upper Triassic Xujiahe Formation/paleosalinity/clay mineral/Couch formula分类
天文与地球科学引用本文复制引用
戴朝成,任军平,饶强,张怀胜..四川盆地川中地区须家河组古盐度特征及其地质意义[J].高校地质学报,2018,24(3):390-400,11.基金项目
国家自然科学青年基金(41402085) （41402085）
核资源与环境重点实验室开放基金(NRE1403)联合资助 （NRE1403）
