青海柴达木盆地马海凹陷冷湖地区古—新近系泥岩地球化学特征及物源区性质

Geochemical Characteristics and Its Provenance Nature of Paleogene—Neogene Mudstone in Lenghu Area in Mahai Sag of Qaidam Basin in Qinghai Province

摘要:

为了明确柴达木盆地马海凹陷沉积物物源的演化过程，以古—新近系泥岩的主要元素、微量元素和稀土元素测试数据为基础，采用数值对比及判别图解等方法对研究区物源性质、构造背景和古气候特征进行了深入研究。稀土元素分布配分形式显示轻稀土元素富集，重稀土元素则较平稳，Eu出现负异常的特征。V/（V+Ni）,Ce/La比值及Ceanom表明古环境处于缺氧环境；构造背景图解La/Yb∑REE,La/ScCo/Th,K2O/Na2OSiO2/Al2O3,LaThSc,ThScZr/10表明马海凹陷冷湖地区泥岩处于活动大陆边缘和大陆岛弧环境;母岩物源复杂，岩性为长英质火山岩和铁镁质岩均可见；古气候指标CAI及Sr/Cu比值反映了源区古气候主要为干热气候或构造活动区，风化程度较弱。

Abstract:

In order to reveal the evolution process of Mahai sag in Qaidam basin, taking data of major elements, trace elements and rare elements of Paleogene Neogene mudstone in study area, using the numerical value comparison and the chart identification, the provenance attitude, tectonic setting and palaeoclimate have been studied in this paper. The REE distributions of mudstones show LREE enrichment, have a flat HREE pattern and a week Eu anomaly. As showed by the numerical of V/（V+Ni），Ce/La and Ceanom, the palaeoclimate in anaerobic environment. From the discrimination diagram of La/Yb∑REE, La/ScCo/Th, K2O/Na2OSiO2/Al2O3, LaThSc、ThScZr/10, Paleogene Neogene mudstone in Mahai sag in the area are in active continent magin and continental island arc environment. Felsic volcanic rock and femic rock could be seen, provenance parent rock composition is quite complicated. Chemical Index alteration (CAI) and the ratio of Sr/Cu indicate that the intensity of chemical weathering is relatively hot and week, and tectonic setting belongs to an active tectonic zone.