沅江辰溪地区河流碎屑石榴子石地球化学特征及其对湖南原生金刚石找矿的启示
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P619.24+1;P578.94+7

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国家自然科学基金项目(42073008,41473030)


Geochemical characteristics of fluvial detrital garnet in Chenxi area of Yuanjiang River and its inspiration for diamond prospecting, Hunan Province
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    摘要:

    湖南沅江是我国砂矿金刚石的重要产地,石榴子石和金刚石是砂矿中常见的重矿物,与金刚石相关的石榴子石特征研究,对揭示湖南砂矿金刚石的来源与形成条件有重要意义。本文随机选取湖南沅江辰溪地区金刚石砂矿中160粒碎屑石榴子石和5粒金刚石包裹体中的石榴子石,采用矿物学、地球化学并借鉴统计学方法对它们进行了分析比较。结果显示,碎屑石榴子石主要为铁铝-锰铝榴石系列,其中个别石榴子石含有金刚石包裹体。聚类分析、线性判别、逻辑回归分析计算显示,部分G3榴辉岩型石榴子石与金刚石可能具有成生联系。同时,两个采集地点的石榴子石类型、主微量元素具有一定的差异,其中一个地点的石榴子石样品DJZ-7-1具有与金刚石更强的亲缘性。基于本文碎屑石榴子石Si值大于3.02以及前人对湖南金刚石限定的温压条件进行分析,认为湖南金刚石可能形成于深度小于220 km的橄榄岩-榴辉岩混杂区,该区域系钾镁煌斑岩型金刚石来源的优势区域。据此,建议可在辰溪赤岩村河段上游区域进一步寻找幔源G3型石榴子石以及钾镁煌斑岩,以期发现原生金刚石矿床。

    Abstract:

    Yuanjiang River is an important source of diamond placer in Hunan Province, where the garnet and diamond are common heavy minerals in placer. It is of great significance for revealing the source and formation conditions of diamond placer in Hunan Province to analyze and screen garnets related to diamond. In this paper, detrital garnets (160 grains, 80 grains of DJZ-7-1 sample and 80 grains of DJZ-10-1 sample) in Chenxi area of Yuanjiang River, and inclusion garnets in diamond (5 grains) in Hunan Province were selected and analyzed by mineralogical, geochemical and statistical methods. The results show that the fluvial detrital garnets are mainly Fe-Al and Mn-Al garnet series, a few of them contain diamond inclusions. Cluster analysis, linear discriminant analysis and logistic regression analysis indicate that some G3 eclogite garnets may have genetic relationship with diamonds. Major and trace elements are certain differences between the two sites; analysis result shows that the garnets of DJZ-7-1 samples are more closely related to diamond. Based on the analysis of the Si value of detrital garnets (>3.02) and the limited temperature and pressure conditions of Hunan diamond in previous study, it is considered that Hunan diamond may be formed in the mixing area of peridotite and eclogite with a depth of less than 220 km, which is the dominant source area of lamproite-type diamond. Therefore, it is suggested that G3 garnet and lamproite should be further searched in the upper part of Chenxi, Yuanjiang River, in order to prospect the primary diamond deposits in Hunan Province.

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马瑛,丘志力,邓小芹,陆太进,杨瀚,庄郁晴,2021,沅江辰溪地区河流碎屑石榴子石地球化学特征及其对湖南原生金刚石找矿的启示[J].岩石矿物学杂志,40(6):1116~1130.

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  • 收稿日期:2021-03-22
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  • 在线发布日期: 2021-11-15
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