贵州镇宁-紫云泥盆系大型沉积重晶石矿床成矿过程研究

Mineralization Process of the Large Devonian Barite Deposits in the Zhenning-Ziyun Area,Guizhou,China

古生代是全球沉积型重晶石矿床成矿的重要时期,这一时期在全球范围内形成了多个大型和超大型重晶石矿。特别是在扬子陆块西南缘的镇宁-紫云地区,发育一个泥盆系大型沉积重晶石矿床,其资源储量逾6000万吨。本文在已有研究基础上,结合最新的野外调查和研究成果,探讨了重晶石成矿过程、成矿规律和关键控矿要素。研究认为,重晶石矿床成矿与甲烷渗漏活动存在成因上的联系。水城-紫云-南丹裂陷槽内次级盆地对矿体的形态和空间展布有重要控制和影响作用。在含矿岩系出露区,矿体明显呈透镜状赋存于上泥盆统响水洞组硅质建造之中,并且显示出从NW至SE厚度不断减薄的规律性变化。结合Sr、S、C、O同位素组成,推断乐纪一带可能更靠近重晶石成矿的中心。甲烷渗漏强度及其消耗途径变化是不同剖面之间重晶石矿体厚度及其共生灰岩的产出特征和数量在空间上存在差异性的主要控制因素。综合研究,将重晶石成矿过程划分为成矿前、成矿期、成矿后三个阶段,并总结了不同阶段的野外识别标志,初步构建了重晶石成矿的理论模型。

The Paleozoic era was a significant peak period for the mineralization of sedimentary barite deposits,during which a series of large and super-large barite deposits were formed worldwide.The large Devonian barite deposits in the Zhenning-Ziyun area of Guizhou province,on the southwestern margin of the Yangtze platform,are estimated to have a total reserve of more than 60 million tonnes.On the basis of previous research,combined with the latest field investigation and research findings,this paper discussed the metallogenic process,metallogenic regularity,and key ore-controlling factors of barite deposits.The results revealed a genetic connection between barite mineralization and methane leakage.The secondary basin in the Shuicheng-Ziyun-Nandan rifting trough has significant control and influence over the morphology and spatial distribution of the ore bodies.The ore bodies were lenticular and occurred in the siliceous unit of the Upper Devonian Xiangshuidong Formation,and their thickness decreased from Northwest to Southeast.Considering the strontium,sulfur,carbon,and oxygen isotopic compositions,it is speculated that the Leji area may be closer to the center of barite mineralization.The variation in methane leakage intensity and its consumption pathway are important factors governing the thickness changes of the barite ore bodies and the occurrence of coexisting limestones.Finally,the barite mineralization process was divided into pre-metallogenic,mineralization,and post-metallogenic stages.The field identification markers of different stages were summarized,and a metallogenic model for the barite deposits was established.