K-Bentonites from the Jinsushan Formation of Late Ordovician, Southern Ordos Basin: SHRIMP Dating and Tectonic Environment

详细信息   

• 责任者：Chen Cheng (School of Earth Sciences and Resources ; China University of Geosciences ; Beijing 100083 ; China) ; Shi Xiaoying
• 刊名：Geoscience
• 出版年：2012
• 卷期：26(2)
• 关键词：膨润土 ; bentonite ; SHRIMP定年 ; SHRIMP dating ; 鄂尔多斯盆地 ; Ordos Basin
• 页码：p.205-219
• 图表：7 illus., 3 tables, 73 refs.
• 分类号：0803
• issnNo：ISSN1000-8527
• isbnNo：CN11-2035/P

摘要

 
    

The Late Ordovician Jinsushan Formation in southern Ordos Basin is characterized by carbonate of deep marine facies, and contains several marked tuffaceous clay beds of orange color. Mineral and geochemical analysis show that the clay beds mainly consist of illite and mixed illite-montmorillonite in composition, with some quartz, feldspar and zircon minerals that derived from intermediate to acidic magma, rich in K₂O, and are of typical K-bentonites. Analysis on trace elements and geochemical composition of the bentonites suggests that their source rock is likely derived from syn-collision island-arc volcanism. SHRIMP U-Pb dating on zircons from the bentonites has yielded three sets of ages: (451.5±4.9) to (452.1±5.1) Ma, (457.5±5.1) Ma and (465.8±8.3) Ma, with the former two identical to those of the well-known Millbrig-Kinnekulle and Dicke bentonites in Laurentia and Baltica.