Re-Os isotopes and PGE geochemistry of black shales and intercalated Ni-Mo polymetallic su

Re-Os isotopes and PGE geochemistry of black shales and intercalated Ni-Mo polymetallic sulfide bed from the Lower Cambrian Niutitang Formation,

South China

JIANG

Shaoyong;YANG

Jinghong;LING

Hongzhen;CHEN

Hongfei;FENG

Yongquan;CHEN Jianhua

【期刊名称】《自然科学进展（英文版）》 【年(卷),期】2003(013)010

【摘要】The Lower Cambrian Niutitang Formation consists of a thick black shale sequence with a regionally distributed conformable Ni-Mo polymetallic sulfide horizon and a chert bed at its basal strata on theYangtze Platform, South China. In this paper, we discuss all available data on Re-Os isotopes and Platinum Group Element (PGE) distribution pattern of the Ni-Mo polymetallic sulfide ore and its host rocks (black shales, cherts, and phosphorites) from Guizhou and Hunan provinces. Our results show that the black shales and the Ni-Mo sulfide ore have a high initial 187Os/188Os ratio of 0.78～0.86, indicating that the Early Cambrian ocean across the Yangtze Platform had a highly radiogenic Os value. This ratio is slightly lower than but still similar to present-day seawater, possibly as a result of high continental weathering at that time. The Ni-Mo sulfide ore yields a Re-Os isochron of 537±10 Ma (MSWD=11.9), possibly representing the depositional age of the