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首页> 外文期刊>Brazilian Journal of Geology >Diamonds from the Coromandel Area, West Minas Gerais State, Brazil: an update and new data on surface sources and origin
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Diamonds from the Coromandel Area, West Minas Gerais State, Brazil: an update and new data on surface sources and origin

机译：巴西西米纳斯吉拉斯州科罗曼德地区的钻石：地表来源和来源的最新数据

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Important diamond deposits southeast of Coromandel and the local geology have been studied in an attempt to understand what surface source provided the stones. River gravels of Pleistocene to Recent age from this region have supplied most of Brazil's large diamonds over 100 ct. The upper cretaceous Capacete Formation of the Mata da Corda Group, composed of mafic volcanoclastic, pyroclastic and epiclastic material, has been worked locally for diamonds, nevertheless considered non-economic. The authors present results of their study of a deactivated small mine, representing the first report with description and analyses of two gem diamonds washed from this material. Hundreds of kimberlites, discovered in the last half century in the region, are sterile or non-economic. We propose that the surface source of the diamonds is the Capacete "conglomerado". The volume of this material is enormous representing a potential resource for large-scale mining. The authors suggest detailed studies of the volcanic facies of this unit focusing on the genesis, distribution and diamond content. As to the question concerning the origin of these diamondiferous pyroclastic rocks, the authors exclude the kimberlites and point towards the large Serra Negra and Salitre alkaline complexes which are considered the primary source for the pyroclastic units of the Mata da Corda Group. They propose that early eruptive phases of this alkaline complex brought diamonds from a mantle source to the surface, much as happens with traditional kimberlites, to explain the association of such huge carbonatite complexes and diamonds.
机译：对科罗曼德（Coromandel）东南部的重要钻石矿床和当地地质情况进行了研究，以试图了解提供这些宝石的地表来源。来自该地区的更新世至最近时代的河砾提供了巴西超过100克拉的大部分大型钻石。 Mata da Corda组的上白垩统Capacete地层由镁铁质火山碎屑，火山碎屑和表层碎屑材料组成，目前已在当地加工钻石，但仍被认为不经济。作者介绍了他们对一个失活的小矿山的研究结果，这是第一个报告，描述和分析了从这种材料中洗出的两颗宝石。在过去的半个世纪中在该地区发现的数百个金伯利岩是不育的或不经济的。我们建议钻石的表面来源是Capacete“团聚体”。这种材料的数量巨大，代表着大规模采矿的潜在资源。作者建议对这个单元的火山岩相进行详细研究，重点是成因，分布和钻石含量。关于这些含钻石的火山碎屑岩的起源的问题，作者排除了金伯利岩，而是指向大型的Serra Negra和Salitre碱性复合物，它们被认为是马塔达科尔达集团火碎屑单元的主要来源。他们提出，这种碱性复合物的早期喷发阶段将钻石从地幔来源带到地表，这与传统的金伯利岩很相似，以解释这种巨大的碳酸盐复合物与钻石的联系。

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