Geochemistry of Jurassic Detrital Rocks and Geological Significance in Ningwu——Jingle Basin
详细信息
- 责任者：Li Zhenhong (Institute of Geomechanics ; Chinese Academy of Geological Sciences ; Beijing 100081 ; China) ; Dong Shuwen
- 刊名：Geological Review
- 出版年：2013
- 卷期：59(4)
- 关键词：碎屑岩 ; clastic rocks ; 岩石地球化学 ; lithogeochemistry ; 华北地台 ; North China Platform
- 页码：p.637-655
- 图表：illus., 4 tables, 73 refs.
- 分类号：0803
- issnNo：ISSN0371-5736
- isbnNo：CN11-1952/P
摘要
The Jurassic strata of the Ningwu—Jingle Basin, the Yongdingzhuang Formation of Lower Jurassic, the Datong, Yungang and Tianchihe Formation of Middle Jurassic, are primarily composed of siltstone and mudstone. Provenance area is mainly point to the central Yinshan—Yanshan Orogen according to former Jurassic Palaeogeomorphology and Paleocurrent. Based on the geochemical signatures of major elements, trace elements, and rare earth elements from 24 samples, which picked from Chenjiabangou profile on the Ningwu—Jingle Basin, three conclusions have been obtained. Firstly, in these samples, CO2 vs. CaO have a good correlation, δCe vs. δEu , δCe vs. ∑REE、CIA vs. Th/U、CIA vs. Th/Sc have no correlation, those imply that the Jurassic detrital rocks are mainly controlled by source characteristics, were not impacted by chemical weathering and oxidation — reduction conditions. Secondly, the distribution patterns of rare earth elements are basically the same, LREE/HREE ratios are high, Eu negative anomalies are evident, which show that provenance are the same during the Early—Middle Jurassic, and the rocks are the main pro-granite and felsic, and the parent rock debris come mainly from the upper crust,have no mantle material, those discrimination diagrams about REE—La/Yb,La/Th—Hf,Co/Th—La/Sc,Th—Hf—Co,SiO2/Al2O3—∑REE,K2O/Na2O—∑REE prove the same viewpoint. Thirdly, during Yungang and Tianchihe of Middle Jurassic, a sudden rise on CaO content, CO2 content, Gd content, ICV,(Gd/Yb)n ratio, which show that the Provenance area is in rapid uplift and erosion stage, with a large number of ancient sedimentary material being added, the starting time of the Yanshan movement may be the early Yungang term of Middle Jurassic.
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