云南白牛厂银多金属矿床成矿作用特征的稀土元素地球化学约束  

The Ore-forming Characteristics of the Bainiuchang Ag-polymetallic deposit in Yunnan:Constrain from REE Geochemistry

作　　者：祝朝辉[1,2] 刘淑霞[1] 张乾[2] 邵树勋[2] 谷德敏[1] 

机构地区：[1]河南省国土资源科学研究院,郑州450053 [2]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵阳550002

出　　处：《矿物岩石地球化学通报》2009年第4期365-376,共12页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国科学院重点方向项目(KZCX3-SW-125);国家自然科学基金项目资助(40172037)

摘　　要：为了研究白牛厂银多金属矿床成矿作用特征,对矿区岩浆岩、围岩和矿石的稀土元素进行了ICP-MS分析测试。花岗岩稀土元素组成表现了较强的Eu负异常和弱的Ce负异常。围岩稀土元素特征表现出一定程度的热水沉积成因。矿石的稀土元素组成大致可分为两组:一组矿石表现为Eu正异常或无异常和Ce负异常,反映喷流沉积稀土元素组成特征,主要是距离花岗岩体较远的白羊矿段,指示成矿热液为温度较高(>250℃)、相对还原的流体,另外,Eu正异常和Ce负异常同时出现,说明矿石沉淀时较高温度的流体与少量的海水发生了对流混合;另一组矿石表现出与岩浆岩一致的球粒陨石标准化稀土配分模式,显示岩浆热液叠加改造成因,主要是距离花岗岩体较近的穿心洞矿段和对门山矿段。两组矿石稀土元素组成特征总体来说随着花岗岩体距离的变化而变化。根据岩浆岩、围岩和矿石的稀土元素组成特征,白牛厂银多金属矿床由喷流沉积形成主矿体,燕山期花岗质岩浆活动对矿体部分叠加改造。This paper investigated the mineralization characteristics of sea-floor exhalative sedimentation and magmatic hydrothermal superimposition on the Bainiuchang ploymetallic deposit by systematically analyzing the REE compositions of granites, host-rocks and ores in the deposit area using ICP-MS. The REE compositions of granites possess obvious negative Eu anomalies and weak negative Ce anomalies; the REE characteristics of host-rocks imply they derived partly from sea-floor exhalative sedimentary. According to their REE compositions, the ores can be separated into two groups： one group, collected in Baiyang segment, a segment locates relatively further from the Bozhushan granite matrix, possesses none to positive Eu anomalies and negative Ce anomalies. This ore group represents that the ore-forming hydrothermal fluid is relatively reductive and its temperature is higher than 250℃. The co-occurrence of positive Eu anomalies and negative Ce anomalies indicates that convective mixing of a small a- mount of seawater with the hydrothermal fluid may have happened during ore depositing on the ancient seafloor. The other group, mainly collected from Chuanxindong and Duimenshan segments, segments locates relatively closer to the Bozhushan granite matrix, has similar chondrite-normalized REE distribution pattern to that of the granite. In addition to above differences, the REE characteristics of both groups of ores vary gradually by the distances of the collecting locations to the Bozhushan granite matrix. Based on REE characteristics of the Bainiuchang A-polymetallic deposit, we believe that the main ore body was formed by exhalative sedimentations and was partially superimposed by the Yanshanian granitic magma activites.

关 键 词：白牛厂银多金属矿床 喷流沉积 岩浆热液叠加改造 稀土元素 

分 类 号：P618.7[天文地球—矿床学]