深穿透地球化学异常源同位素识别研究:以新疆金窝子金矿床、内蒙古拜仁达坝—维拉斯托多金属矿床为例

Research on Isotope Identification for Anomalous Sources of Deep-Penetration Geochemistry: Two Cases of Jinwozi Au Deposit,Xinjiang and Bairendaba-Weilasituo Polymetallic Deposit,Inner Mongolia

通过研究两个已知隐伏矿床(新疆金窝子金矿床、内蒙古拜仁达坝—维拉斯托多金属矿床)不同介质(地气、细粒级土壤、围岩、矿石)中的铅、硫同位素特征,探讨铅、硫同位素对地气、土壤中异常物质来源的示踪,得到以下结论:(1)两矿床的介质从地气、矿石、围岩到土壤,铅同位素比值(208Pb/204Pb、207Pb/204Pb、206Pb/204Pb)一般依次增加;土壤异常区相对土壤背景区,δ34S偏高。但对两个矿床背景区、异常区地气中的铅同位素组成、土壤中的铅、硫同位素组成进行方差分析后发现,数据均没有明显的差异,从统计学的角度初步证明研究区不适宜用铅、硫同位素示踪地气、土壤中异常物质的来源。(2)两个矿床的矿石、围岩中铅同位素组成均有明显差异,即围岩中明显有放射成因铅的积累。但这种差异没有显著地反映到背景区、异常区的地气中,原因有待进一步查证。仅从捕获剂的角度初步探讨了其原因。用土壤全量中铅、硫同位素组成特征来示踪土壤异常源,并没有成功,建议采用偏提取的方法测量其中活动态中的铅、硫同位素组成,在深穿透地球化学研究中更合理。

Through research on lead and sulfur isotopic characteristics of different media（earthgas,fine-grained soil,surrounding rock,ore） in two known concealed deposits（Jinwozi gold deposit in Xinjiang,Bairendaba-Weilasituo polymetallic deposit in Inner Mongolia）,the following conclusions are drawn in this paper.In these two deposits,lead isotopic ratios（208Pb/204Pb,207Pb/204Pb and 206Pb/204Pb） generally increased from the earthgas,ores,surrounding rocks to the soil.The δ34S of anomaly zones was higher than that of soil background areas.The test of variance analysis on the lead isotopic compositions of earthgas,the lead and sulfur isotopic characteristics of soil proved no significant isotopic differences between background and abnormal areas,which preliminarily proved that it is inappropriate to trace the source of abnormal substances by lead,sulfur isotope of earthgas and soil in these two deposits.But the Pb isotopic compositions of ores and surrounding rocks in these two deposits were significantly different.That is,the surrounding rocks obviously have accumulation of radiogenic lead.However,this difference was not significantly reflected in the earthgas of background and abnormal areas.This paper discussed its reasons only from the perspective of the capture fluids.Lead,sulfur isotopic compositions in the soil were analyzed to trace the source of abnormal substances in this paper,which was not successful.Further research will adopt partial extraction method to measure lead,sulfur isotopic compositions in active phase of soil.