贵州松桃白石溪锰矿地球化学特征及其地质意义

Geochemical Character of the Songtao Baishixi Manganese Deposit in Guizhou and Its Geological Significance

白石溪锰矿床位于江南造山带西南段,上扬子陆块的南东缘.矿床主要赋存在南华系下统大塘坡组第一段的炭质砂页岩中.含锰岩系Ca O+Mg O值表明在成因上与海相碎屑沉积有关;n(Si O2)/n(Al2O3)值表明锰矿床的形成与热水活动和生物活动有关.微量元素Sr/Ba值表明锰矿床沉积环境为滞留浅海环境,n(V)/n(V+Ni)比值进一步表明其形成环境为还原环境,Co/Zn-(Cu+Co+Ni)相关性图显示其形成过程受到了热液活动的影响.区内含锰岩系形成过程中轻、重稀土元素分异明显,呈现富集轻稀土元素的特征.北美页岩标准化稀土元素配分图上曲线呈近水平分布,具有弱的正Eu异常和弱的正Ce异常,反映还原的沉积环境.δCe值和La/Yb-ΣREE图解进一步确认了其沉积环境为受热水影响的大陆边缘区.因此白石溪锰矿床系在大陆边缘还原环境沉积并受热水活动影响形成的矿床.

The Baishixi Manganese deposit located in the southwest section of Jiangnan orogen, on the south eastern edge of the Shangyangzi landmass. The mineral deposit mainly occurs in the carbonaceous sandstone and shale of the first section of Datangpo Group under Nanhua System. CaO ＋ MgO values of the Mn - bearing rocks suggest that it should be associated with Marine clastic sediment; the values of n （SiO2 ）/n（ A12 03 ）reflect that the ore formation related to hydrothermal activity and biological effects. Sr/Ba values suggest that the Mn - bearing rocks should be deposited from backwater of shallow ma- rine. The Co/Zn - （ Cu ＋ Co ＋ Ni） diagram of Mn - bearing rocks also present that manganese forming was affected by the hydrothermal activity, and the ratio of n（ V）/n（ V ＋ Ni） further expresses that its forming environment is the reduction en- vironment. The region＇ s Mn - bearing rocks have a feature that there is a clear differentiation of light and weight rare earths and light rare earths enrichment of priority. The NASC normalized REE curve is a horizontal line with weak positive Eu a- nomaly and weak positive Ce anomaly, indicating a reduction aggradation environment. The value of characteristic parame- ter 8Ce and the La/Yb - EREE diagram of Mn - bearing rocks indicate that the tectonic environment of the study area is continental margin, mineral deposit formation was affected by hydrothermal activity. So the Baishixi Manganese deposit is the one that is sedimentary in the reducing environment of continental margin and was formed by the affection of hydrother- mal activity.