安徽铜陵地区晚中生代中基性侵入岩成因与成矿:来自磷灰石矿物学和地球化学证据  

Petrogenesis and mineralization of intermediate-basic intrusive rocks in the Late Mesozoic in the Tongling area,Anhui:Evidence from apatite mineralogy and geochemistry

作　　者：徐晓春[1] 夏彩莲 金林森 谢巧勤[1] 闫峻[1] 谢建成[1] Xu Xiaochun;Xia Cailian;Jin Linsen;Xie Qiaoqin;Yan Jun;Xie Jiancheng(School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009)

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009

出　　处：《地质科学》2024年第5期1391-1411,共21页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:42030801,41472066);国家重点研发计划项目(编号:2016YFC0600209)资助。

摘　　要：辉石闪长岩是安徽铜陵地区晚中生代侵入岩的重要类型,与铜金多金属成矿密切相关。本文以白芒山岩体和舒家店岩体辉石闪长岩为研究对象,着重开展磷灰石矿物学和地球化学研究,探索中基性侵入岩成因及与成矿关系。结果显示:磷灰石强烈富集稀土元素,轻重稀土元素分异明显,弱—中等Eu负异常,富集Th、U等高场强元素,亏损Ta、Nb、Ti、Zr、Hf等高场强元素和Rb、Ba、Sr等大离子亲石元素,稀土—微量元素组成特征指示其寄主岩石成岩物质具有壳幔混源特征。岩相学特征显示磷灰石具有两种不同的晶体形态、产出状态和显微结构,即长柱状、包裹体相、均质结构和短柱状、晶间相、核—边/环带结构,其元素地球化学特征有显著差异,指示其寄主岩石成岩作用经历过壳源长英质岩浆冷凝结晶→高温幔源镁铁质岩浆注入和长英质岩浆早期结晶矿物熔蚀→混合岩浆侵位和结晶的复杂过程。核—边/环带结构磷灰石从核部到边部SO_(3)和Cl含量波动式变化特征,指示镁铁质岩浆幕式注入,并触发混合岩浆上升侵位,有利于流体出溶和热液成矿。磷灰石卤族元素(F、Cl)和SO_(3)高含量则提供板块俯冲环境证据,指示基性端元的镁铁质弧岩浆来自俯冲板片析出流体交代富集岩石圈地幔,镁铁质岩浆幕式注入有利于流体出溶和热液成矿。Pyroxene diorite is an important type of Late Mesozoic intrusive rock in the Tongling area of Anhui,closely associated with copper and polymetallic mineralization.This study focuses on the pyroxene diorite of the Baimangshan and Shujiadian plutons as research subjects,emphasizing the mineralogical and geochemical studies of apatite,to explore the genesis of intermediate-basic intrusive rocks and their relationship with mineralization.The results show that the apatite particles are highly enriched in REE,with a clear differentiation between LREE and HREE,a weak to moderate Eu negative anomaly,enrichment in HFSE such as Th and U,and depletion in Ta,Nb,Ti,Zr,Hf,and LILE like Rb,Ba,Sr.The characteristics of REE and trace elements indicate that the materials of their host rocks are mixed source of crust and mantle.Petrographic features show that the apatite particles have two categories with different crystal morphologies,occurrences and microstructures:one is long columnar,inclusion phase,homogeneous structure,and another is short columnar,intercrystalline phase,core-rim/banded structure.Their elemental geochemical characteristics show significant differences,these features indicate that the host rocks have undergone a complex process consisting of crustal-derived felsic magma condensation and crystallization→high-temperature mantle-derived mafic magma injection and dissolution of already crystallized minerals→mixed magma emplacement and crystallization.The core-rim/zonal structure of apatite shows fluctuating SO_(3) and Cl contents from the core to the rim,indicating the curtain-style injection of mafic magma,which triggers the rise and emplacement of mixed magmas conducive to fluid exsolution and hydrothermal mineralization.The high content of halogen elements(F,Cl)and SO_(3) in apatite provides evidence of a subduction zone environment,indicating that the mafic end-member arc magmas originate from the mantle wedge metasomatized by fluids released from the subducting slab,the curtain-style injection of mafic ma

关 键 词：辉石闪长岩 中基性侵入岩 磷灰石矿物学和地球化学 晚中生代 安徽铜陵地区 

分 类 号：P588.1[天文地球—岩石学]