云南大红山铁铜矿床石榴子石特征与地质意义  被引量:6

Characteristics and geological significances of the garnets in the Dahongshan iron-copper deposit,Yunnan, China

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作  者:叶紫枫 杨光树[1] 覃龙江 陈爱兵[1] 郑晓军 王明均 YE Zi-feng;YANG Guang-shu;QIN Long-jiang;CHEN Ai-bing;ZHENG Xiao-jun;WANG Ming-jun(Faculty of Land Resources Engineering Kunming University of Science and Technology,Kunming 650093,China;Guangzhou Huali Science and Technology Vocational Colloge,Guangzhou 510000,China;Yuxi Dahongshan Mining Co.,Ltd.,Xinping 653405,China;Yunnan Nonferrous Geological Bureau,Kunming 650051,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 [2]广州华立科技职业学院,广东广州510000 [3]玉溪大红山矿业有限公司,云南新平653405 [4]云南省有色地质局,云南昆明650051

出  处:《矿物学报》2022年第4期461-477,共17页Acta Mineralogica Sinica

基  金:国家自然科学基金项目(编号:42162012,42072094,41762008);云南省应用基础研究计划项目(编号:2018FB080)。

摘  要:大红山矿床位于扬子板块西南缘康滇成矿带南部,是我国重要的超大型铁铜多金属矿床之一。矿床中主要发育3类石榴子石,分别产于块状细粒磁铁矿石、赋矿围岩片岩和变质火山岩中。矿石中石榴子石晶体完整,裂纹少,与石英共生;片岩和变质火山岩中石榴子石晶体破碎,裂纹多,常被磁铁矿、石英等充填交代。本文利用电子探针(EPMA)和LA-ICP-MS分析了3类石榴子石的成分,探讨了其成因和地质意义。结果表明,3类石榴子石均以富铝为特征,端元组成以铁铝榴石为主。矿石与围岩石榴子石均具有重稀土富集、轻稀土亏损的左倾型配分模式和明显的Eu正异常,Ce异常不明显;矿石中石榴子石的稀土元素含量,特别是重稀土元素含量明显高于围岩石榴子石,且Eu正异常也更显著。微量元素组成特征表明,矿石与围岩石榴子石均为变质成因,围岩中石榴子石的端元组分从核部到边缘呈规律性变化,稀土元素含量逐渐降低,Eu正异常升高,表明其受到了后期热液作用的改造,后期热液流体的淋滤作用可能是导致矿石与围岩石榴子石Eu和HREE含量差异的主要原因。The Dahongshan deposit is located in the southern Kangdian metallogenic belt at the southwestern margin of the Yangtze plate. It is one of the most important super large iron-copper polymetallic deposits in China. Three kinds of garnets were respectively developed in massive fine-grained magnetite ore, ore-hosted schists and meta-volcanic rocks in the deposit. Garnets in ores are generally intergrown with quartz with complete crystal and little fissure. Garnets in schists and meta-volcanic rocks are commonly infilled and replaced by magnetite and quartz with broken crystal and many fissures. In this paper, in order to understand the genesis and geological significance of the garnets, the chemical compositions of different types of garnets were analyzed by EPMA and LA-ICPMS. The results show that all three kinds of garnets are characterized by rich aluminum, and they mainly belong to iron-aluminum garnet series. Garnets in ores and wallrocks are characterized by HREE-enriched and LREE-depleted left-declined REE distribution patterns, with obviously positive Eu anomalies and unobvious Ce anomalies. Total REE(especially HREE) contents of ores are obviously higher than those of wallrocks and the positive Eu anomalies of ores are more significant than those of wallrocks. Characteristics of trace elements of garnets show that all garnets in ores and wallrocks are of metamorphic origin. From the core to the edge of garnets in the wallrocks, the end-member compositions are regularly changed, the total REE contents are gradually decreased, and the positive δEu values are increased, indicating that garnets in wallrocks were partly reworked by later hydrothermal fluid. The leaching and reworking of later hydrothermal fluid may lead to the difference of Eu and HREE contents in garnet between ores and wallrocks.

关 键 词:石榴子石 电子探针 LA-ICP-MS 大红山铁铜矿床 云南 

分 类 号:P578.94[天文地球—矿物学] P579[天文地球—地质学] P618.4101

 

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