安徽石台地区下寒武统黑色岩系微量元素地球化学特征

TRACE ELEMENT GEOCHEMICAL FEATURES OF LOWER CAMBRIAN BLACK ROCK SEQUENCE IN THE SHITAI AREA,ANHUI

黑色岩系成因复杂,且与多金属元素成矿密切相关。对安徽石台地区下寒武统黑色岩系微量元素地球化学研究表明,其富集Ag、V、U、Mo、As、Sb等多种金属元素。且在这套黑色岩系地层剖面中,其中部碳质页岩的金属元素富集程度比其它岩性的富集程度明显偏高。微量元素组成及相关元素比值显示这套黑色岩系形成于海相热水沉积作用,代表了一种非正常海水沉积。沉积环境由早期缺氧的还原环境逐渐向后期的半还原-氧化环境演化,反映早寒武世安徽下扬子海由海侵向海退的逐渐过渡。

Black rock sequence has complicated genesis and is usually closely related to polymetallic elements ore formation. Geochemical study of trace element geochemical features of lower Cambrian black rock sequence in the Shitai area, Anhui indicates that it is rich in many metallic elements as Ag, V, U, Mo, As and Sb. As shown in the stratigraphic section of the black rock sequence, the middle part of carbonaceous shale is much more abundant in metallic elements than other lithology. Trace elements composition and relevant element ratios suggest that this black rock sequence is resulted from marine thermal water sedimentation, typical of abnormal seawater deposition. Sedimentary environment evolved gradually from the early oxygen-deficiency reduction to late semi-reduction-oxidation, reflecting the transition from transgression to regression in the Anhui Lower Yangtze Sea in Early Cambrian.