黔北地区下寒武统底部黑色页岩沉积环境条件与源区构造背景分析

为了深入探讨黔北地区下寒武统底部黑色页岩的沉积环境条件和源区构造背景，对黔北地区下寒武统牛蹄塘组黑色页岩进行系统采样,对其微量元素和稀土元素地球化学特征进行了系统分析。研究表明，微量元素中高的WV/(WNi+WV)和U/Th比值等反映该区黑色页岩形成于海域开阔的还原环境。区内黑色页岩样品中Mo、Sb、U、Cd、 V、Ba、Tl、Ni、W、 Cr、Cs、Cu、Zn、Bi等元素的高富集以及正Eu异常和较低的Co/Zn比值均反映了黔北下寒武统底部黑色页岩受到深部热液活动的影响。根据主、微量和稀土元素组合及比值特征可以看出黔北地区下寒武统底部黑色页岩的源岩具有花岗岩、沉积岩和玄武岩等多成因性质。源区构造背景以被动大陆边缘为主，由于受深部热液活动的影响，也显示大陆岛弧构造背景的特征。

Depositional Setting and Tectonic Background Analysis on Lower Cambrian Black Shales in the North of Guizhou Province

In order to discuss depositional setting and its tectonic background of the black shale and on the base of the researched 20 profiles, we chose 20 samples collected from bottom of lower Cambrian in the north of Guizhou Province to test and analyze clay minerals, X ray diffraction of the rock minerals and trace elements (including REE). Current study shows that the main minerals are quartz whose average content are 55.75%, and clay minerals whose average content are 28.35%, Among which, the average content of illite is 59%,and the main aeceasory mineral is pyrite in the bottom of lower Cambrian in the north of Guizhou Province; ΣREE is very high and the differentiation between LREE and HREE is distinct which LREE is enriched and Eu is postive anomaly and Ce is negative anomaly; the average ratio of WV/(WNi+WV)and U/Th is respectively 0.78 and 3.76 and the depleted Ce together reflect that Black shale in the north of Guizhou Province forms in reduction environment with stable crust, transgression sea climax and open sea area；the enrichment of trace elements Mo,Sb,U,Cd, V,Ba,Tl,Ni,W,Cr,Cs,Cu,Zn,Bi，strongly depleted Sr,Re , positive Eu anomaly and the lower Co/Zn ratio of the Black shale in the north of Guizhou Province are most likely due to a hydrothermal input;. By the contrast of major elements, trace elements and REE parameters , a conclusion can drawn that in research areas source rocks are mainly sedimentary rocks and granitic rocks with a few locally involved basalt components , the tectonic setting is mainly passive continental margin and partly continental island arc because of hydrothermal input.