粤北贵东岩体及外围花岗岩地质特征对比及其意义

    Comparison of geological characteristics between the Guidong pluton and its peripheral granite in northern Guangdong Province and its significance

    • 摘要: 前人对贵东复式岩体的研究多集中在单个岩体上,而未能对整个岩体地质特征、成矿因素等进行全面对比分析。本文为进一步研究粤北贵东岩体及其外围花岗岩体的铀成矿差异的原因,通过对贵东岩体及其外围花岗岩体的地质特征、岩浆演化期次、矿物学特征及地球化学特征等方面进行系统研究分析。研究结果表明:在岩浆演化过程中,岩浆结晶粒度的变化,反映在矿物成分上含量上,主要表现为石英含量逐渐增加,斜长石含量逐渐减少,并且中长石逐渐被钠长石取代,黑云母被白云母替换而含量降低;贵东岩体中西部与东部花岗岩相比,角闪石、斜长石的含量偏大,自变质和交代蚀变较弱,东部花岗岩的矿物组成中基本不含角闪石,斜长石的含量总体上偏低,自变质和交代蚀变较强;地球化学特征表明西-中部岩体属亚碱弱过铝质的花岗岩体,东部及外围属亚碱弱过铝质-过铝质的花岗岩体,说明西-中部岩体在形成过程中可能有少量幔源组分的加入,认为其并非同源物质不同程度部分熔融产物,而是不同源区物质经部分熔融形成。

       

      Abstract: Previous studies on the Guidong complex pluton have mostly focused on a single rock mass, and the geological characteristics and mineralization factors of the entire rock mass have not been comprehensively compared and analyzed. This paper aims to further investigate the reasons for the differences in uranium mineralization between the Guidong pluton and its peripheral granite bodies in northern Guangdong. It systematically analyzes the geological characteristics, magmatic evolution stages, mineralogical characteristics, and geochemical characteristics of the Guidong pluton and its surrounding granite bodies. The results indicate that during the evolution of magma, the changes in crystal size of magma are reflected in the content of mineral components, mainly manifested as a gradual increase in quartz content, a gradual decrease in plagioclase content, and the gradual replacement of feldspar by albite, and a decrease in biotite content replaced by muscovite. Compared with the eastern granite in the central and western parts of the Guidong pluton, the content of hornblende and plagioclase is relatively high, and self metamorphism and metasomatic alteration are weaker. The mineral composition of the eastern granite basically does not contain hornblende, and the content of plagioclase is generally low, with strong self metamorphism and metasomatic alteration. The geochemical characteristics indicate that the western central rock mass belongs to subalkaline weakly peraluminous granite bodies, while the eastern and peripheral parts belong to subalkaline weakly peraluminous peraluminous granite bodies. This indicates that there may be a small amount of mantle derived components added during the formation process of the western central rock mass, and it is believed that they are not products of partial melting of homologous materials to varying degrees, but rather formed by partial melting of materials from different homologous regions.

       

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