桂西红泥坡酸性岩群岩石地球化学特征及成矿作用

Petrogeochemical characteristics and mineralization of the Hongnipo acidic rock group in western Guangxi

广西西部德保县红泥坡酸性岩群岩性以中细粒、细粒(含)黑云二长花岗岩、二长花岗岩、花岗岩、花岗斑岩、石英斑岩为主,呈小岩株、岩脉、岩枝产出,本文报道了其与下泥盆郁江组侵入接触关系的发现。通过岩石地球化学研究,红泥坡酸性岩群具有酸度大、碱质高、钾大于钠、铝过饱和的特点,属于强过铝质高钾钙碱性花岗岩类。稀土元素表现为轻稀土富集,负Eu异常明显,轻重稀土分馏较强。岩浆源区以成熟的泥质岩为主,其中并可能具弱Ce正异常的沉积物参与部分熔融,形成于中浅成相的大陆碰撞挤压构造环境,形成时代晚于早泥盆世,具有较大的Sn成矿潜力。

The Hongnipo acidic rock group in Debao County,western Guangxi is composed of medium-fine-grained、fine-grained biotite monzonitic granite、monzonitic granite、granite、granite porphyry and quartz porphyry,and made up of rock stock、vein and apophysis.This paper reports the discovery of its intrusive contact with the Lower Devonian Yujiang Formation.The acidic rock group has the characteristics of high acidity、high alkalinity、higher potassium than sodium、aluminium supersaturation,and belongs to peraluminous high-potassium calc-alkaline granitoids.Rare earth element index shows the enrichment of light rare earth,obvious anomaly of negative uranium,strong fractionation of the light and heavy rare earth.Sediments with weak positive Ce anomalies in the magma may participate in partial melting,and the magma is formed in the mid-shallow facies of continental collision and compression tectonic environment.The Hongnipo acid rock group is judged to be formed later than the Early Devonian,it has great metallogenic potential of Sn.