投稿时间：2024-05-22
修订日期：2024-11-07
网络发布日期：2025-01-07
中文摘要:四川德昌大陆槽矿床是中国目前唯一确认的与隐爆作用有关的稀土矿床，具有埋藏浅、品位高、规模大等特征。氟碳铈矿是目前矿区内查明的唯一稀土工业矿物，主要分布在角砾状矿石的细粒至微细粒胶结物中。文章在大陆槽稀土矿床角砾状矿石中发现了粗粒至伟晶状氟碳铈矿，分布在含氟碳铈矿的萤石-重晶石-霓辉石角砾、含氟碳铈矿的萤石-重晶石-方解石角砾、含氟碳铈矿的方解石碳酸岩角砾中，亦呈氟碳铈矿矿物角砾。角砾中的氟碳铈矿多呈中粗粒乃至伟晶状，为板柱状自形-半自形晶体，碎裂结构发育。角砾被细粒至微细粒的石英-天青石-萤石胶结。胶结物中的氟碳铈矿呈针状、细板状或放射状集合体产出，粒度多小于100 μm。粗粒状氟碳铈矿的稀土元素氧化物含量（REO）在65%~71%之间，富铈和镧（占稀土元素总量的82%~95%），镨和钕含量相对偏低（占稀土元素总量的4%~17%）；LA-ICP-MS分析获得206Pb/238U加权平均年龄为（14.78±0.27）Ma（MSWD=1.1，n=21）。大陆槽稀土矿床中粗粒氟碳铈矿的存在增加了矿石的稀土品位，提升了矿床的经济价值（易于回收）。同时，说明大陆槽稀土矿在隐爆作用发生之前已形成一定规模的稀土矿化，暗示矿区深部可能存在一定规模的粗粒至伟晶状脉状矿体。
Abstract:The Dalucao deposit in Sichuan Province, China, is the only confirmed rare earth deposit associated with cryptoexplosion. It is characterized by shallow burial, high-grade ore and large tonnage. Bastnaesite, the primary rare earth industrial mineral identified in this deposit, is mainly found in the fine-to-micro cements of breccia ore and is not easy observable with the naked eye. In this study, we discovered coarse-grained to pegmatitic bastnaesite in the breccia ore of the deposit. These coarse-grained bastnaesite distribute in bastnaesite-bearing aegirine augite-fluorite-barite breccia, bastnaesite-bearing fluorite-barite-calcite breccia and bastnaesite-bearing calcite carbonate breccia, they also appear as the bastnaesite mineral breccia. The bastnaesite grains in breccia usually exhibit plate columnar and granular morphology, occur as euhedral or subhedral crystals with varying size of medium-coarse or even pegmatitic, and mostly have cataclastic texture. The breccias are cemented by fine-to-micro-grained quartz-fluorite-cerite, and the cements also contain bastnaesites in the form of acicular crystal, tabular crystal or radiate-columnar aggregate, with grain size mostly smaller than 100um. The content of rare earth oxides (REO) in coarse-grained bastnaesite ranges between 65% and 71%, with a higher abundance of cerium and lanthanum (accounting for 82%~95% of the total rare earth content), and relatively lower proportions of praseodymium and neodymium (accounting for 4%~17% of the total rare earth content); the 206Pb/238U weighted average age obtained by LA-ICP-MS is (14.78±0.27) Ma (MSWD=1.1, n=21). The occurrence of coarse-grained bastnaesite in the Dalucao deposit makes the ore having higher grade, and also enhances its economic value (higher recoverability). Furthermore, it suggests the possible occurrence of a certain scale of rare earth mineralization in the area prior to the formation of the cryptoexplosive brecciation, this indicates the possible presence of coarse grained or pegmatitic veins containing bastnaesite at depth in the deposit.
keywords:coarse-grained bastnaesites breccia REE ore U-Pb age Dalucao rare earth element deposit Sichuan Province
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基金项目:本文得到中国稀土集团有限公司科技项目“四川省牦牛坪、大陆槽稀土矿成矿规律与找矿预测”（HE2310）、中国地质调查局“战略新兴产业矿产地质调查工程”（DD20230034）、“四川康定-云南个旧稀有稀土矿产地质调查”项目（DD20230290）和中国矿产地质志续编与产品服务项目（DD20221695）共同资助
引用文本：
赵芝,王登红,王伟,刘善宝,吕秉廷,何斌,班西雨.2024.四川大陆槽稀土矿床粗粒氟碳铈矿的发现及对找矿的指示意义[J].矿床地质,43(6):1380~1389ZHAO Zhi,WANG DengHong,WANG Wei,LIU ShanBao,Lü BingTing,HE Bin,BAN XiYu.2024.Discovery of coarse-grained bastnaesite in Dalucao rare earth element deposit, Sichuan Province, and its prospecting significance[J].Mineral Deposits43(6):1380~1389
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