云南马厂箐富碱斑岩中黑云母的地球化学特征及其地质意义  

Geochemistry and Geological Significance of Biotite in the Machangqing Cu-Mo-Au Deposit in the Yunnan Alkali-rich Porphyry Belt

作　　者：刘志荣[1] 王蝶[1] 薛传东[1] LIU Zhirong;WANG Die;XUE Chuandong(Faculty of Land Resource Engineering,Kunming University of Science and Technology,Kunming 650093,Yunnan,China)

机构地区：[1]昆明理工大学国土资源工程学院,云南昆明650093

出　　处：《大地构造与成矿学》2025年第2期454-466,I0026-I0032,共20页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(41963003);第二次青藏高原综合科学考察研究项目(2021QZKK0301);云南省“兴滇青年人才”项目联合资助。

摘　　要：黑云母是中酸性岩浆岩中常见的暗色矿物,其地球化学特征对揭示岩浆岩的形成环境、成因机制及成矿潜力具有重要的指示意义。本研究以云南三江成矿带马厂箐斑岩‒矽卡岩型铜(钼、金)多金属矿床为研究对象,对与成矿具有时空关联的富碱斑岩体中的黑云母开展了系统的矿物学和元素地球化学研究。研究结果表明,马厂箐花岗斑岩和正长斑岩中的黑云母具有相似的地球化学特征,均属于高硅、贫铁的富镁黑云母,且偏向金云母端员,指示其为壳幔混合作用的产物。黑云母的化学成分特征显示其结晶温度为698~762℃,logƒO_(2)为−15.93~−14.31,压力范围为36~118 MPa,表明岩体形成于相对浅成高温的环境,且体系具有较高的氧逸度,这有利于Cu、Mo和Au的成矿作用。此外,花岗斑岩和正长斑岩中黑云母的微量和稀土元素特征存在差异。其中花岗斑岩中黑云母的稀土元素配分模式与三江富碱斑岩成矿带内的含矿斑岩相似,受到的热液蚀变作用更强烈,暗示马厂箐花岗斑岩与成矿作用具有更为密切的成因联系。Biotite,as a ubiquitous mineral in igneous rocks,plays a crucial role in elucidating the petrogenetic environment,magmatic evolution,and mineralization potential of igneous systems.This study focused on the geochemical characteristics of biotite from alkaline porphyry intrusions associated with the Machangqing porphyry-skarn type Cu-Mo-Au polymetallic deposit within the Sanjiang metallogenic belt,Yunnan province.The analytical results demonstrate that biotite in granite and syenite porphyries exhibits comparable geochemical signatures.The biotite is characterized by high-silica,low-iron,and magnesium-rich,exhibiting a compositional trend toward the phlogopite endmember,indicative of a crust-mantle mixing origin.Geothermobarometric calculations based on biotite chemistry revealed that the biotite was crystallized at temperatures ranging from 698℃ to 762℃,oxygen fugacities(logƒO_(2))between−15.93 and−14.31,and pressures of 36 MPa to 118 MPa.These physicochemical conditions suggest that the porphyries were emplaced in a relatively shallow depth and low-temperature environment with elevated oxygen fugacity,which is particularly favorable for the formation of Cu-Mo-Au deposits.However,distinct differences were observed in the trace and rare earth element(REE)characteristics between granite and syenite porphyry biotites.The REE patterns of biotite from the granite porphyry exhibit remarkable similarity to those of mineralized porphyries within the Sanjiang alkaline porphyry metallogenic belt,suggesting more intense hydrothermal alteration and implying a stronger genetic relationship between the granite porphyry and mineralization processes.

关 键 词：黑云母 富碱斑岩 氧逸度 马厂箐 

分 类 号：P595[天文地球—地球化学] P571[天文地球—地质学]