地质与勘探2024，Vol.60Issue(6)：1129-1141,13.DOI:10.12134/j.dzykt.2024.06.004
西秦岭洛大式菱铁矿矿床的成矿年龄及其成因
Metallogenic Age and Genesis of the Luoda-Type Siderite Deposits in West Qinling
摘要
Abstract
Iron ores are critical ore resources in our country.Taking the Luoda-type siderite deposits in West Qinling as examples,this work analyzed the metallogenic stages and determined the metallogenic age using Re-Os isochrons of pyrite.Combined with sulfur isotopic composition of pyrite,regional geological background,and deposit geology,the material sources of the deposits were discussed,and their genesis was determined.In addition,this work explored the reasons for overspread points of Re-Os isotopes of pyrite by the exclusion method and also associated with ore characteristics.Results show that the Luoda-type deposits were formed at about 130±20 Ma(2σ),corresponding to the transitional period from the Middle-Late Jurassic to early Early Cretaceous continental convergence to Late Cretaceous continental extension.The initial osmium isotopic composition of 0.04±0.22(MSWD=1.11)was indicative of a mantle source of ore-forming materials.The sulfur isotope was characterized by a mixed source of magmatic sulfur with sedimentary sulfur as well as by inorganic reduction sulfur.Iron may be derived from mantle fluid and its leaching of late Indonesian granitoids.The fissures in pyrite along ore fracture were filled by impurities that caused the overspread points of pyrite Re-Os isotopes.It is inferred that the Luoda-type siderite deposits should be attributed to meso-epithermal deposits related to mantle fluids,and the prospecting of this type of deposits should focus on the metallogenic regularities of coupling tectonism and fluids.For sampling and preparing pyrite samples for testing Re-Os isotopic tests,the pyrites with high proportion of iron oxides along late fissures should be removed.关键词
黄铁矿/Re-Os同位素/过度散布点/早白垩世/幔源流体/浅成中-低温热液型矿床/洛大式菱铁矿/西秦岭Key words
pyrite/Re-Os isotope/overspread points/Early Cretaceous/mantle fluid/meso-epithermal ore deposit/Luoda-type siderite deposit/west Qinling分类
天文与地球科学引用本文复制引用
何进忠,刘涛,何甘地,余君鹏,牛鹏飞,吴义布..西秦岭洛大式菱铁矿矿床的成矿年龄及其成因[J].地质与勘探,2024,60(6):1129-1141,13.基金项目
中国地质调查局地质调查项目(编号:121201004000150017-35)和甘肃省自然资源厅科技创新项目(编号:202231)联合资助. （编号:121201004000150017-35）
