摘要
沉积岩物源分析对揭示盆地物质组成、储集岩性质及古环境恢复等研究具有重要指示意义。文中对藏北羌塘盆地角木日地区中二叠统龙格组的钙质泥岩样品进行了微量元素地球化学测试分析,系统地研究了微量元素含量、特征比值及稀土元素配分方式。结果表明研究区龙格组钙质泥岩样品具有中等轻稀土元素分异（（La/Sm）N=2.50-5.41）,重稀土元素比较平坦（（Gd/Yb）N=1.32-2.47）,具有微弱的Eu负异常;Sr/Ba,V/Cr,Ni/Co,Ceanom及δEu等相关参数综合显示,研究区中二叠纪时期整体表现为海相氧化环境;样品Rb/Sr比值及La/Th-Hf,La/Sc-Co/Th,Th/Sc-Zr/Sc关系图解综合说明龙格组钙质泥岩物源区风化作用较弱,源岩主要为安山岩;通过对沉积岩La/Sc-Ti/Zr,La-Th-Sc和Th-Sc-Zr/10等构造环境判别图解分析,综合表明区钙质泥岩物源区的构造背景主要为大洋岛弧型。
Provenance analysis of sedimentary rocks has an important significance on revealing the composition of basins, qualities ofreservoirs and sedimentary environment. Trace elements of Middle Permian carbonaceous mudstone samples in Jiaomuri area,Qiangtang Basin were analyzed and discussed. The study of trace element content,characteristic ratios and REE distribution indicatesthat the samples are moderately differentiated in LREE（（La/Sm）N=2.50-5.41）, while the HREE shows flat pattern（（Gd/Yb）N=1.32-2.47）and all samples have slight Eu abnormity. The ratios of Sr/Ba, V/Cr, Ni/Co, Ceanomand δEu values are used to reveal the redox ofpaleo-ocean. Our data show that the Middle Permian sedimentary environment where mudstones deposited was mainly oxidizing marineconditions. Ratio of Rb/Sr and La/Th-Hf, La/Sc-Co/Th, Th/Sc-Zr/Sc diagrams show that the provenance area underwent weakweathering and the source rocks are probably mainly andesitic rocks. La/Sc-Ti/Zr,La-Th-Sc and Th-Sc-Zr/10 discriminationdiagrams suggesting that the carbonaceous mudstone of the Longge Formation formed probably in an oceanic island arc tectonic setting.
出处
《高校地质学报》
CAS
CSCD
北大核心
2015年第1期59-67,共9页
Geological Journal of China Universities
基金
中国地质调查局<羌塘盆地油气地球化学实验技术及应用研究>(1212011221112)
关键词
羌塘盆地
中二叠统
龙格组
钙质泥岩
地球化学
构造背景
Qiangtang Basin
Middle Permian
Longge Formation
carbonaceous mudstone
element geochemistry
tectonic setting
