桂北376铀矿床烃气地球化学研究

Hydrocarbon Geochemistry of the 376 Uranium Deposit in Northern Guangxi

烃气测量法在锡、金、铜、铅锌等金属矿床找矿中得到了广泛应用,而该技术在花岗岩型铀矿找矿中的应用鲜有报道。本文对桂北376铀矿床已知矿体开展了烃气测量试验,结果显示:相较于其他金属矿,该铀矿区花岗岩和土壤中总烃含量极低,而且花岗岩总烃含量(平均19.42μL/kg)高于上覆土壤(平均6.32μL/kg)。花岗岩中U与多数烃气组分呈负相关,与重烃呈正相关,重烃在U迁移过程中作用强于轻烃;花岗岩烃气标准化配分模式以C_(1)、iC_(4)和C_(2)^(-)正异常为特征;铀矿化程度与iC_(4)/nC_(4)、(C_(1)+iC_(4)+C_(2)^(-))/(C_(2)+C_(3)+nC_(4))及C_(2)^(-)/C_(3)^(-)比值呈正相关,与C_(2+)/∑C比值呈负相关等可为寻找铀矿提供依据。376铀矿床中花岗岩具有不对称对偶双峰烃气异常模式,其低值区域及重烃的高值异常与矿体位置相吻合;土壤中U与烃气均呈正相关,指示吸附作用是导致土壤中U与烃气富集的重要因素,同时土壤具有顶端多峰烃气异常模式,其峰位高值区域指示矿体位置。本研究显示应用烃气测量技术寻找花岗岩型铀矿具有可行性。

Hydrocarbon measurements have been widely used in the exploration of Au,Pb-Zn and Cu deposits,but are little reported in prospecting granite-type uranium deposits.This work conducted hydrocarbon measurements of granite and soil in the 376 uranium deposit of northern Guangxi.Results show that the hydrocarbon content in the 376 uranium deposit is extremely lower than that of other metal deposits,and the average value of total hydrocarbon content in granite is 19.42μL/kg,higher than that in soil(6.32μL/kg).The content of uranium is negatively correlated with most hydrocarbon components in granite,but is positively correlated with heavy hydrocarbons,which indicates that heavy hydrocarbons play a more important role in uranium migration than light hydrocarbons.The normalized hydrocarbon gas patterns of granite are characterized by positive C_(1),iC_(4) and C_(2)^(-)anomalies.The uranium mineralization is positively correlated with the ratios of iC_(4)/nC_(4),(C_(1)+iC_(4)+C_(2)^(-))/(C_(2)+C_(3)+nC_(4))and C_(2)^(-)/C_(3)^(-),and is negatively correlated with the ratios of C_(2)+/ΣC.These features are important indication for prospecting.The hydrocarbon gas in granite belongs to asymmetric dual bimodal anomaly patterns,whose high anomalies of heavy hydrocarbons and low value area between the bimodal anomalies coincide well with the ore bodies.The content of uranium is positively correlated with all hydrocarbon components in soil,showing the adsorption is significant for enrichment of uranium and hydrocarbon in soil,and the hydrocarbon in soil has a top multi-peaked shape anomaly pattern.Its high value peak indicates the position of ore bodies,while the multi-peak anomaly usually indicates the position of ore bodies.It is thus feasible to apply hydrocarbon measurements to prospecting granite-type uranium ore bodies.