福建“华安玉”中石榴石的矿物学特征及地质意义

Mineralogical Characteristic and Geological Significance of Garnet in "Hua'an Jade" from Fujian Province

  • 摘要: “华安玉”是福建省的优势矿产资源,前人对“华安玉”进行了系统的地质学、岩石学和矿物学等研究,但“华安玉”形成机制一直存在争议。本次以“华安玉”中新发现的石榴石矿物为研究对象,通过系统薄片观察、利用扫描电子显微镜和电子探针测试方法对“华安玉”中石榴石进行了矿物学特征分析。通过野外调查研究及光薄片分析认为,“华安玉”中石榴石可分为两期,早期呈微细粒状集合体面型产出,晚期呈微细脉状或线脉状产出;电子探针分析表明,“华安玉”中石榴石主要为钙铁榴石,其次为钙铝榴石和铁铝榴石。“华安玉”中的石榴石证实了“华安玉”成因应为矽卡岩型,并且为多期次形成;红色品种“华安玉”(含石榴石)的成玉背景与区域花岗岩的分布关系密切,主要分布于岩基状花岗岩体中(如绵治、九曲等地),呈残留的顶盖状产出;而远离岩体部分少见或未见有石榴石矿物。

     

    Abstract: "Hua'an jade" is an advantageous mineral resource in Fujian Province. Previous studies on "Hua'an jade" have been carried out systematically in terms of geology, petrology and mineralogy, but its formation mechanism has been controversial. In this study, the newly discovered garnet minerals in "Hua'an jade" were studied by means of systematic microscopic observation, SEM and EMPA technology. Through the field investigation and microscopic observation, garnet minerals in "Hua'an jade" can be divided into two stages. The early stage is micro-grained aggregate and the late stage is micro-vein or linear vein. Electron microprobe analysis showed that garnet minerals are mainly andradite, followed by grossular and almandite. The study of garnet minerals confirmed that the origin of "Hua'an jade" should be skarn type and multi-stage formation. The formation of red "Hua'an jade" (garnet-bearing minerals) is closely related to the distribution of regional granites, mainly distributed in the basement granite body as residual caps (such as Mianzhi county and Jiuqu county), but garnet minerals are rare or not found far away from the granite body.

     

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