柴北缘绿草山上干柴沟组沉积-构造特征及与铀矿化关系

Sedimentary and Structural Characteristics and Uranium Mineralization of Shangganchaigou Formation in Lucaoshan,Northern Margin of Qaidam Basin

通过1∶5万地质填图、钻孔验证,结合单井沉积相分析、古水流测定及地质连井剖面等综合研究,系统总结了绿草山地区上干柴沟组沉积特征及其与构造演化的耦合关系。结果表明绿草山地区紧邻南祁连大柴达木山富铀花岗岩体,具有良好的铀源条件;上干柴沟组沉积期处于晚燕山运动和早喜山运动间的构造静宁期,构造活动表现出较强-较弱-较强的演化趋势,从而由下到上发育有冲积扇-三角洲-冲积扇沉积序列,受周期性湖泊影响上干柴沟组发育有多期三角洲河道沉积,古水流测量方向为南东-南南东;结合钻孔中铀矿化异常段沉积组合特征分析,确定了绿草山上干柴沟组时期三角洲沉积体系为有利找矿目的层位,对绿草山内的铀成矿过程进行了综合分析,并初步评价了该区砂岩型铀成矿潜力。

With 1∶50000 geological mapping,borehole verification,single-well sedimentary analysis,paleocurrent measurement,and cross-well geological profiles,The sedimentary characteristics of Shangganchaigou Formation and its coupling relationship with tectonic evolution are summarized systematically in Lucashan area,Northern Margin of Qaidam Basin.The results showed that the Lucaoshan area has uranium-rich granite which is close to Daqaidam Mountain of southern Qilian.Shangganchaigou Formation was sedimented in the inactive tectonic period between the Late Yanshanian and the Early Himalayan.Therefore a system of alluvial fan-delta-alluvial fan was formed in response to the strong-weak-strong tectonic evolution trend,and multi-phase delta channel sediments were formed.Paleocurrent measurement showed that the stream was running SSE.By analyzing the sedimentary combination feature of uranium mineralization anomalies in the borehole,the favorable prospecting horizon in the delta sedimentary system of the Shangganchaigou Formation was determined for the uranium exploration in Lucaoshan area.