岩石矿物学杂志2017，Vol.36Issue(3)：329-342,14.
江西金鸡窝铜矿床花岗闪长斑岩黑云母矿物学特征及其对岩石成因与成矿的指示
Mineral chemistry of biotites from the granodiorite porphyry around the Jinjiwo copper deposit in the Jiurui ore district: Implications for petrogenesis and mineralization
摘要
Abstract
Based on detailed petrographical and mineralogical compositional features of biotite from the granodiorite porphyry around the Jinjiwo deposit in the Jiurui ore district,the authors not only established the physicochemical conditions of the mineral formation but also explored its significance for rock and ore formation.Major element composition of the biotite phenocrysts of the samples was measured by the electron probe micro-analyzer (EPMA).The Ti content and the Mg/(Mg + Fe) ratios of the biotite from the Jinjiwo granodiorite porphyry are 0.44～0.47 apfu (atoms per formula unit) and 0.58～0.62,respectively,and the compositions of these biotite are plotted in both the domain of the primary magmatic biotite and that of the Mg-rich biotite.These features suggest that the biotite phenocrysts of the samples are all eastonite,and that these analyzed biotites display the Mg-rich and Fe-poor characteristics.The oxidation coefficient and the MF values of biotites are 0.31～0.67 and 0.38～0.41,respectively.Biotite has 13.27％～14.28％ MgO,3.59％～8.93％ K2O,0.26％～3.28％Na2O,15.74％～17.30％ FeO,3.93％～4.19％ TiO2,and 13.52％～14.19％ Al2O3,respectively.It contains about 2.00～2.24 apfu of tetrahedral AlⅣ and 0.15～0.41 apfu of octahedral AlⅥ.The TAl content of biotite can be used to figure out the solidification pressure of the granitoid.Considering the composition of biotites together with experimental results of the former research,which falls on or above Fe2O3-Fe3O4 buffer in the Fe3 +-Fe2 +-Mg diagram,the authors consider that the biotites from granodiorite porphyry in the study region were crystallized under the condition of temperatures 734～748℃ and pressures 71～89 MPa,corresponding to solidification depth 2.7～3.3 km.The above characteristics suggest that the Jinjiwo granodiorite porphyry belongs to high potassium Ca-alkaline series,showing the typical syntexis type (or Ⅰ-type) granitoid derived from a crust-mantle mixing source,and that the pluton was formed in a relatively high oxygen fugacity environment,which was beneficial to copper mineralization.关键词
花岗闪长斑岩/黑云母地球化学/氧逸度/成岩成矿作用/壳幔混合Key words
granodiorite porphyry/geochemistry of biotite/oxygen fugacity/petrogenesis and mineralization/crust-mantle interaction分类
天文与地球科学引用本文复制引用
杜后发,赖天功,江媛媛,范鹏飞,龚维强..江西金鸡窝铜矿床花岗闪长斑岩黑云母矿物学特征及其对岩石成因与成矿的指示[J].岩石矿物学杂志,2017,36(3):329-342,14.基金项目
核资源与环境重点实验室开放基金项目(NRE1309) （NRE1309）
中国地质调查局研究项目(ZR2013000018) （ZR2013000018）
创新创业项目(2310400136)Open Foundation of Key Laboratory of Nuclear Resources and Environment(NRE1309) （2310400136）
Research Project of China Geological Survey (ZR2013000018) （ZR2013000018）
Innovation and Entrepreneurship Item (2310400136) （2310400136）
