湖南桃江响涛源锰矿地球化学特征及其成因意义

Geochemical Characteristics and Genetic Significance of the Xiangtaoyuan Manganese Deposit in Taojiang County,Hunan Province

湖南响涛源锰矿位于湘中桃江成锰盆地。盆地内发育一组NNW向同沉积断裂,形成了一系列断陷槽,控制了沉积岩相的分布,其中黑色页岩、含锰灰岩、碳酸锰矿为成矿最佳岩性组合。矿石的化学组分多样,Co、Ni、Pb、Mo和Ba等丰度较高,Co/Ni、SiO2/Al2O3、(Fe+Mn)/Ti、Al/(Fe+Mn+Al)、Fe/Ti比值以及Co/Zn-(Cu+Ni+Co)和Fe-Mn-(Cu+Ni+Co)图解揭示锰矿成矿过程中有海底热水的参与;稀土元素配分模式、Ce、Eu异常表示锰矿形成于被动大陆边缘环境,并具有热水沉积特征;碳同位素结果显示出富集碳的轻同位素特征,反映了响涛源锰矿成矿过程中深部热水沉积及生物作用的特征;氧同位素计算古温度为湘中响涛源锰矿床的低温热水沉积成因提供了有利的佐证。

The Xiangtaoyuan manganese deposit is located in the Taojiang manganese-forming basin in central Hunan Province. A group of NNW-trending synsedimentary faults developed in the basin,forming a series of fault troughs,which control the distribution of sedimentary facies. Black shale,manganese-bearing limestone and manganese carbonate are the best lithologic assemblages. The chemical compositions of ores are various,and the abundance of Co,Ni,Pb,Mo and Ba is relatively high. Co/Ni,SiO2 /Al2O3 ,(Fe+Mn)/Ti,Al/(Fe+Mn+Al)ratios and Co/Zn-(Cu+Ni+Co)and Fe-Mn-(Cu+Ni+Co)diagrams reveal the participation of seafloor hot water in the mineralization process of manganese deposits. Rare earth element distribution patterns,Ce and Eu anomalies indicate that manganese deposits were formed in a passive continental margin environment and have the characteristics of hydrothermal deposition. It shows the characteristics of light isotope enriched with carbon and reflects the characteristics of deep hydrothermal deposition and biological processes during the mineralization of the Xiangtaoyuan manganese deposit. The calculation of paleotemperature by oxygen isotope provides favorable evidence for the genesis of low-temperature hydrothermal deposition of the Xiangtaoyuan manganese deposit in central Hunan.