湖南金船塘锡铋矿床石榴子石原位LA-ICP-MS稀土元素分析及其意义  

In situ LA-ICP-MS REE analyses of the skarn garnets from the Jinchuantang tin-bismuth deposit in Hunan Province,and their significance

作　　者：刘晓菲[1] 袁顺达[2] 双燕[3] 原垭斌[1] 弥佳茹 轩一撒 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所,国土资源部成矿作用与矿产资源评价重点实验室 [3]重庆地质矿产研究院,外生成矿与矿山环境重庆市重点实验室

出　　处：《岩石学报》2014年第1期163-177,共15页Acta Petrologica Sinica

基　　金：中央级公益性科研院所基本业务费专项资金(K1204);国家重点基础研究课题(2012CB416704);国家自然科学基金项目(41173052;41373047;41003024);公益性行业基金(200911007-11)联合资助

摘　　要：金船塘锡铋矿床是东坡矿田内一以锡铋为主的大型矽卡岩型多金属矿床。本文在详细野外地质考察、镜下观察以及电子探针分析的基础上,利用高精度LA-ICP-MS对该矿床的矽卡岩内石榴子石原位的微量元素进行了系统的分析。结果表明,金船塘锡铋矿床的钙铝榴石(Gro)大体上具重稀土(HREE)富集、轻稀土(LREE)亏损,负Eu异常的特征;而钙铁榴石(And)不同样品之间存在一定差异性,有的样品显示HREE富集、LREE亏损的特征,有的则轻重稀土分异不明显,除了多数呈Eu负异常外,还有部分表现为弱的正Eu异常,这可能是受钙铝-钙铁榴石混合物中的静电作用所导致。并且,上述不同石榴子石REE分配的差异还进一步指示,钙铝榴石(Gro)矿物生长速率较低,与孔隙流体之间基本保持动态平衡,水/岩(W/R)比值较低,其REE的化学行为主要受到晶体化学等机制的影响;钙铁榴石(And)矿物生长速率较高,具有较高的水/岩(W/R)比值,吸附作用在REE配分模式中起到重要作用。总体上,矽卡岩内的石榴子石的REE的分配呈HREE富集、LREE亏损,负Eu异常的特征,与千里山花岗岩REE分配模式一致,指示了金船塘锡铋矿床的成矿作用可能与千里山花岗岩体具有密切的成因联系。The Jinchuantang deposit is a large-sized skarn-type tin-bismuth deposit in the Dongpo ore field. In the present contribution,the in situ trace element concentrations in garnet collected from the Jinchuantang deposit are performed by LA-ICP-MS. The results show that the grossularites are HREE-enriched,LREE-depleted patterns with negative Eu anomalies. Some andradites are HREE-enriched,LREE-depleted patterns,while the REE patterns of others are not obvious between the LREE and HREE. Most andradites are negative Eu anomalies with a small part of positive anomalies. The reason for those may be the electrostatic interactions in the mixture of grossularite-andradite. For the environment,the grossularites grow slowly and in near equilibrium with local pore fluids,indicating the low W / R ratios,during diffusive metasomatism. Under such conditions incorporation and fractionation of REE is basically controlled by crystal chemistry and extrinsic mechanisms. The andradites grow rapidly,from externally derived fluids,with high W / R ratios,and where adsorption must have had a major control on the observed REE patterns. Moreover,the results show that the REE patterns between Jinchuantang deposit and Qianlishan granite are the same,which fully proves that the mineralization of Jinchuantang tin-bismuth deposit is related to the Qianlishan granite.

关 键 词：石榴子石 主量元素 微量元素 湖南金船塘 

分 类 号：P575[天文地球—矿物学] P578.947[天文地球—地质学]