关键词: 下扬子地区, 黑色岩系, 地球化学, 构造背景, 物源分析, 沉积环境

Abstract:

Three sets of the Early Paleozoic deep-water black shales, respectively named of  ∈₁h and ∈₁ht, O₃w, S₁g and S₁x,  are mainly developed in Anhui Province, the Lower Yangtze subcontinent.  Total of 27 samples sampled from the three sets of black shale series for ICP-MS measurement were used to analyze their geological settings of tectonic and sources. Results show that within these shale samples, elements Li, Be, Rb, Ba, Cs, W, Th, U, Cd, Bi, Pb are enriched, Sc、Sr，Cr、Cu、Ga、Co、Ni are poor, contents of rare earth elements are high, Eu is obviously  negative, and the fractionation between light and heavy REE is being pronounced. Trace inactive element content and the ratio of characteristics of the tectonic setting discrimination diagrams indicate that the black shales could have been deposited in a deep-water and lag sedimentary environment within the continental island arc and active continental margin in early stage, fllowing a passive continental margin in late stage. The parent rocks could be mainly derived from the recycled sediments of the upper crust and the Post-Archean strata as well as  the undifferentiated Archaean crust and  basalts. According to the  devolpment of the ancient Jiangnan island and the geochemistry comparison of the Lower Paleozoic black shales from other place of the Yangtze continent, it is proposed that the black shales in Anhui Province could have been southwardly sourced from the ancient Jiangnan island.

Key words: Lower Yangtze area, black rock series, geochemistry, tectonic setting, provenance analysis, sedimentary environment