湖南砂矿金刚石成分及结构特征研究综述

Composition and Structural Characteristics of Alluvial Diamond from Hunan Province, China

  • 摘要: 目前关于我国重要金刚石产地之一的湖南砂矿金刚石的研究较少有系统总结性报道。在本文,笔者梳理了有关湖南砂矿金刚石成分和结构特征。研究显示,湖南金刚石以ⅠaAB型为主,Ⅰb和Ⅱa型的比例较高,含氮量以及氮聚集程度分布明显不均一;湖南金刚石晶面花纹和颜色丰富,晶体形态变化大,大多呈现曲面外观,说明金刚石上升到地壳的过程中经历过复杂环境;生长结构有简单生长结构,也有复杂的斑杂生长结构和似玛瑙状生长结构;碳同位素组成分布范围较广,其范围与榴辉岩型金刚石更为一致,可能相对富集轻碳同位素,与华北克拉通所产金刚石有不同碳源和形成机制;包裹体种类有橄榄岩系列和榴辉岩系列组合,深部包裹体来源值得进一步探索。综上,湖南金刚石多来源,多期次,复杂度高。不同金刚石具有一定来源个性,无法简单地通过单一金刚石特征来确认其“整体”产地来源特征,需要通过不断挖掘现有金刚石中所携带的信息,完善对湖南金刚石产地来源的认识。

     

    Abstract: At present, there are few systematic summary reports on the researches about alluvial diamond from Hunan Province, which is one of the important diamond producing region in China. In this paper, the composition and structural characteristics of alluvial diamond from Hunan Province were summarized. The researches show that alluvial diamonds from Hunan Province are mainly ⅠaAB type with the notably higher proportion of Ⅰb and Ⅱa types, and the distribution of nitrogen content and the degree of nitrogen aggregation exhibit significant unevenness. The surface patterns and colours of diamond crystals from Hunan Province are rich, significant variations in morphology; most of them being curved crystal surfaces, which indicate the complex environment in the process of rising to the crust.The growth structures of alluvial diamonds are different, including simple growth structure or complex mottled and "agate-like" structure. The carbon isotope composition of diamonds from Hunan Province exhibit a broad distribution range, which is more closely to that of eclogite-type diamonds. It may be relatively enriched in light carbon isotopes, and has different carbon sources and formation mechanisms of diamond from North China Craton. The inclusion types include peridotite and eclogite series, and the origin of inclusions from deep mantle is worthy of further exploration. In summary, diamonds from Hunan Province possess multiple sources, multiple stages and complexity. Due to the unique source characteristics of the diamond, it is unfeasible to determine the whole origin of diamonds from Hunan Province simply by individual diamond characteristics. It is necessary to continuously explore the information carried in the existing diamonds to improve the its producing region in Hunan Province.

     

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