摘要
温屋矿区位于紫金山矿田的北部,区内发育良好的火山机构.深部的温屋斑岩体具有钾化、青磐岩化等蚀变,并具有网脉状矿化特征,但目前没有发现富矿体.尝试对比贫矿的温屋斑岩体和区内与之同期的富矿罗卜岭斑岩体的岩石地球化学特征,探究影响其成矿的相关因素.研究显示温屋斑岩体与罗卜岭斑岩体主量元素成分相似,并均具有亏损Nb,Ta,Ti等高场强元素和Eu异常不明显的特征.但是温屋斑岩体具有显著的Sr亏损和较大的MREE/HREE特征,而罗卜岭斑岩体基本无Sr异常,MREE与HREE配分较小.地球化学特征的差异可能反映了两者经历了不同的分离结晶过程.温屋斑岩以斜长石的分离结晶为主;罗卜岭斑岩体斜长石的分离结晶被抑制并可能经历了角闪石的分离结晶,相对富水.温屋斑岩体的相对贫水导致成矿元素难以在热液中富集,可能制约了温屋地区的成矿潜力.但是,在火山机构附近裂隙发育,有利于富矿流体的集中,因此火山机构附近可以成为有利的成矿物质富集区域.
Zijinshan ore district is a famous porphyry and epithermal mineralization system in China, which consists of Zijinshan high-sulfidation epithermal deposit, Luoboling porphyry deposit and Yueyang intermediate-sulfidation epithermal deposit. Wenwu prospective area is located in the north of Zijinshan ore district. The surface of this area is predominateiy covered by the early Cretaceous volcanic rock and volcanic edifice is well-developed. In deep, Wenwu porphyry shows characteristics of porphyry type mineralization,as indicated by propylitic alternation,potassic alter nation and stockwork veins. According to the zircon U-Pb dating,the diagenetic age of Wenwu porphyry is similar to that of Luoboling porphyry, but Wenwu porphyry only exhibits weak mineralization compared to Luoboling porphyry. In this study,we try to compare the characteristics of the geochemistry of these two porphyries to reveal diagenetic process and controlling factor of mineralization. These two porphyries show similar characteristic of major elements. On the trace element and REE diagram,these two porphyries exhibit characteristics of depletion in high field strength elements and weak Eu anomaly. However, compared with the Luoboling porphyry,Wenwu porphyry exhibits obvious depletion of strontium and flat to concave-upward MREE-HREE pattern,which indicates different processes of fractional crystallization caused by different volatile contents. As suggested by their geochemical charac- teristics,the volatile content of Wenwu porphyry is relatively low indicated by plagioelase fractionation and that of Luoboling porphyry is rich suggested by abundant hornblende fractionation, respectively. The low mineralization grade in Wenwu may be caused by low volatile content of the porphyry, which limits the enrichment of metals. Nevertheless, the formation of stockwork, breccia pipes or vent structures near the volcanic edifice may benefits the accumulation and convertion ore-forming fluid,which could promote mineralization potential in this area.
作者
迟哲
倪培
廖剑锋
范明森
刘政
张鑫
Chi Zhe1 , Ni Pei1 , Liao Jianfeng2 , Fan Mingsen1 , Liu Zheng1 , Zhang Xin1(1.State Key Laboratory for Mineral Deposits Research, Institute of Geo-Fluids, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China ; 2.Fujian Institute of Geological Survey, Fuzhou, 350013, Chin)
出处
《南京大学学报(自然科学版)》
CAS
CSCD
北大核心
2018年第2期398-412,共15页
Journal of Nanjing University(Natural Science)
基金
国家重点研发计划(2016YFC0600206),中国地质调查项目(12120114028601)
关键词
岩石地球化学
分离结晶
温
屋
罗卜岭
紫金山
geochemistry,fractional crystallization, Wenwu, Luoboling, Zijinshan