摘要
华南寒武纪早期牛蹄塘组黑色岩系底部赋存有一层富Ni-Mo多金属元素的硫化物矿层。Lehmann等(2007)报道Ni-Mo矿石的Mo同位素组成十分均一,δ98/95MoMOMO值为-1.24‰±0.10‰;而赋矿围岩黑色页岩的Mo同位素组成变化较大,δ98/95MoMOMO值为-1.82‰^-0.40‰,并认为Mo全部来源于海水。笔者发现,含Mo低的黑色页岩具有Mo含量与Mo同位素组成的正相关关系,可能反映了海水来源Mo(以富重Mo同位素为特征)与页岩中碎屑组分来源Mo(以富轻Mo同位素为特征)两者的混合。Ni-Mo矿石非常均一的Mo同位素组成可能反映了它们的Mo来源既不是海水,也不是碎屑组分,而很可能是第3种来源,即以海底热液占主导。有必要对含矿与不含矿的该套黑色岩系开展更详细的Mo同位素研究,以便进一步确定寒武纪早期海水的Mo同位素组成和Ni-Mo矿层的成因。
A Ni-Mo sulfide bed occurs in the lower portion of the lower Cambrian Niutitang Formation in south China. Lehmann et al.（2007） reported data of Mo-isotopic compositions of the Ni-Mo sulfide ores and host black shales, and suggested a seawater origin for the Mo. The Ni-Mo sulfide ores show very limited Mo-isotopic variation with δ^98/95 MoMOMO values of -1.24‰± 0.10‰, whereas the host black shales show larger Mo-isotopic variations with δ^98/95MoMOMO values from -1.82‰ to-0.40‰. Those with low-Mo content black shales show a linear relationship between Mo contents and Mo-isotopic compositions. We suggest that this correlation may reflect a two end-member mixing of seawater Mo and clastic sediment Mo. The sources of Mo in the Ni-Mo sulfide ores were probably from submarine hydrothermal fluids. Further work is needed both on the Ni-Mo ore bed bearing and the barren black shales of the Niutitang Formation in south China, in order to better estimate the Mo-isotopic compositions of the early Cambrian seawater, and to better constrain the ore genesis.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2008年第4期341-345,共5页
Acta Petrologica et Mineralogica
基金
国家自然科学基金资助项目(40221301)
