广西盘龙铅锌矿床赋矿地层有机质特征与成矿作用关系探讨

Discussion on the relationship between organic matter characteristics and mineralization of ore-bearing strata in Panlong lead-zinc deposit,Guangxi

盘龙铅锌矿床赋矿地层为下泥盆统上伦组,有机质发育。采用岩矿石光薄片显微鉴定、有机质含量、有机质抽提、族组分分离及饱和烃色谱-质谱等实验测试分析,研究了赋矿地层及典型矿石的有机质特征及其地质意义,并对有机质与铅锌成矿的关系进行探讨。结果表明,矿石中存在原生有机质和运移有机质,有机碳含量与铅锌矿化呈正相关关系;∑C21-/∑C22+平均为0.544、(nC21+nC22)/(nC28+nC29)平均为1.381、规则甾烷/17α(H)-藿烷平均为0.325,认为赋矿地层有机质以陆相生物为主,少量来自海相菌藻类水生生物输入;OEP和CPI平均值均接近于1、Pr/C17和Ph/C18平均值下降、Ts/Tm值均大于1、C32二升藿烷的22S/(22S+22R)在0.553~0.604、βα-莫烷/αβ-藿烷在0.141~0.247、规则甾烷5α-C2920S/(20R+20S)与ββ/(αα+ββ)平均值分别为0.442、0.460,表明赋矿地层有机质正处于成熟演化阶段;规则甾烷C27~C29呈不对称"V"分布、伽马蜡烷指数和升藿烷指数均偏低,表明在晚古生代沉积成岩时矿区沉积水体较浅、盐度较低,为弱氧化环境。受喷流热液影响,有机质可以促使早期相对开放性成矿环境向还原性状态转变,同时还可与Pb、Zn等金属阳离子发生吸附络合作用,保证了矿质顺利迁移,为铅锌金属的大规模成矿提供了条件。

The ore-bearing strata in Panlong lead-zinc deposit is the Lower Devonian Shanglun Formation and organic matter exists in the strata. By microscopic identification of rock and mineral,organic matter content, organic extraction, family components separation and quantitative, saturated hydrocarbons chromatogram-mass spectrum were analyzed, and the characteristics of the organic matter and its geological significances and relationship between organic matter and lead-zinc mineralization were discussed. Based on the study of organic matter petrography and soluble organic matter characteristics, this paper analyzes the geological significance of organic matter and discusses the relationship between organic matter and lead-zinc mineralization.∑C21-/∑C22+ has an average of 0.544,(nC21+nC22)/(nC28+nC29) has an average of 1.381.The regular decane/17α(H)-hopane is less than 1(average 0.325).These characteristics indicate that the organic matter of the Devonian strata of the mining area is composed of mixed sources. The organic matter was mainly derived from terrestrial organisms, and a small amount is marine algae aquatic organisms. The average values of OEP and CPI are close to 1. The average ratios of Pr/C17 and Ph/C18 decrease, and the ratio of Ts/Tm is greater than 1. The hopane C32 22S/(22S+22R) ranges from 0.553 to 0.604. The average value of βα-molane/αβ-decane ranges from 0.141 to 0.247, and the average values of 20S/(20R+20S) and ββ/(αα+ββ) of regular decane 5α-C29 are 0.442 and 0.460.These characteristics indicate that the organic matter of Panlong mining area is in the stage of midhigh mature evolution. The sample decane C27-C29 shows that asymmetric"V", gamma wax index and the homohopane index C35/∑(C31-C35)are low, which indicates that the sedimentary water of the mining area was shallow water, low salinity and weak oxidation-reduction environment in the Late Paleozoic. Under the influence of hydrothermal fluid, organic matter can promote the transition from an early relatively open ore-forming environment to a reducing state, and can also adsorb and complexate with metal cations, such as lead and zinc, ensuring migration of minerals and providing conditions for large-scale mineralization of lead and zinc metals.