隐伏斑岩铜矿区微细粒土壤地球化学特征及其找矿指示意义——以福建罗卜岭铜钼矿为例  

Geochemical Characteristics of Fine-Grained Soils in Weathering Crust Over Concealed Porphyry Deposits and Their Prospecting Significance:A Case Study of the Luoboling Cu-Mo Deposit in Fujian Province

作　　者：李建亭 韩志轩[1,3] 张必敏 柳青青[1] 刘汉粮[1] 吴慧[1] LI Jianting;HAN Zhixuan;ZHANG Bimin;LIU Qingqing;LIU Hanliang;WU Hui(Key Laboratory of Geochemical Exploration,Ministry of Natural Resources,Institute of Geophysical and Geochemical Exploration,Langfang,Hebei 065000;Chengdu University of Technology,Chengdu,Sichuan 610059;Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources By the Province and Ministry,Guilin University of Technology,Guilin,Guangxi 541004)

机构地区：[1]自然资源部地球化学探测重点实验室,中国地质科学院地球物理地球化学勘查研究所,河北廊坊065000 [2]成都理工大学,四川成都610059 [3]桂林理工大学,有色金属矿产勘查与资源高效利用省部共建协同创新中心,广西桂林541004

出　　处：《地质与勘探》2022年第4期836-845,共10页Geology and Exploration

基　　金：国家重点研发计划项目(编号:2016YFC0600608);中央级公益性科研院所基本科研业务费项目(编号:AS2019P03)联合资助。

摘　　要：在风化壳覆盖区应用传统化探方法和矿物地球化学找矿方法开展斑岩型矿床深部找矿存在一定制约。土壤微细粒分离测量技术是一种可应用于覆盖区找矿的穿透性地球化学勘查技术,在干旱地区已取得良好的应用效果,亟需开展多景观、多矿种应用试验。基于此,本文选择红土风化壳覆盖的福建省罗卜岭斑岩铜钼矿为研究区,开展风化壳土壤微细粒分离测量技术有效性实验。结果显示,与不含矿酸性岩体风化壳相比,研究区明显富集铜钼矿成矿及伴生元素,尤其是Mo、Cu、Au显著富集,与此同时,含矿岩体风化壳中元素变异系数较低,符合斑岩型矿床元素含量富集系数高、变异系数低的典型特征。元素空间分布特征与矿化蚀变、断裂构造、地形演化密切相关。Cu-Mo异常可以圈定矿化中心蚀变带,V、Hg则在外蚀变带富集。Cu与Mo在研究区西北部的分异指示了紫金山矿田由SE向NW主成矿作用由Cu-Mo演变为Cu-Au。元素剖面分布特征进一步验证了成矿蚀变、地形演化对元素分布的控制作用。地形演化决定了蚀变带在地表的分布,进而控制元素的分布。罗卜岭铜钼矿体呈马鞍状分布于古背斜两翼,在后期风化剥蚀作用下,背斜核部演化为负地形,使得中心蚀变带接近出露地表,表现为Cu的正异常;古背斜两翼现今为正地形,矿体埋深较大,前缘晕元素Hg表现为正异常。因子分析结果很好地展示了元素的组合与分异特征。总体上,可以根据Cu-Mo异常判断矿体中心位置,根据Hg判断矿体埋深,根据Sn、V、Cr等识别花岗闪长斑岩体边界。本研究系统证明微细粒土壤测量在风化壳覆盖区探测隐伏斑岩铜钼矿的有效性。In weathering crust coverage area,traditional geochemical and mineral geochemical prospecting methods cannot be well used to prospect deep-seated porphyry deposits.Fine-grained soil survey is a penetrating geochemical exploration technique applicable to ore prospecting in coverage area,which has been well utilized in arid area and requires further multi-landscape and multi-mineral application experiments.Taking the Luoboling porphyry Cu-Mo deposit in Fujian Province as an example,this work conducted experiments on the validity of fine-grained soil survey in this weathering crust coverage area.Results show that,compared with the weathering crust of non-ore acid rock,this deposit is significantly enriched in metallogenic and associated elements of copper-molybdenum ores,especially Mo,Cu and Au,and the element variation coefficient is small in the weathering crust of ore-bearing rock mass.The high enrichment coefficient and low variation coefficient agree well with those of typical porphyry deposits.The spatial distribution of elements is closely related to mineralized alteration,fractures and topographic evolution.The Cu and Mo anomalies can delineate inner alteration zone,while V and Hg elements are enriched in the outer alteration zone.The differentiation of Cu and Mo in the northwest of this deposit indicates that the main mineralization of Zijinshan ore field changed from Cu-Mo to Cu-Au from SE to NW.The element distribution from a geological profile further confirms the controlling effect of tectonic and topographic evolution on element distribution.Topographic evolution determines the distribution of altered zones on the surface and then controls the element distribution.The Luoboling Cu-Mo ore bodies were hosted in ancient anticlinal limbs with a saddle shape.Under the action of weathering and denudation,the core of the anticline evolved into negative topography,and the central alteration zone was exposed on the surface to display positive Cu anomaly.The two wings of the ancient anticline are now in a positi

关 键 词：风化壳覆盖区 斑岩铜钼矿 微细粒土壤 蚀变带 地形演化 罗卜岭斑岩铜钼矿 福建省 

分 类 号：P632[天文地球—地质矿产勘探]