广西苍梧社洞钨钼矿床花岗岩类岩石的地球化学特征及其与成矿关系

广西苍梧社洞钨钼矿是与花岗岩类有关的矿床。矿区主要花岗岩类包括加里东期花岗闪长岩、花岗闪长斑岩和燕山晚期花岗斑岩。加里东期花岗闪长岩、花岗闪长斑岩具有低Si、K,富Na、Al和基性组分特征,属于强过铝质的正常钙碱性系列岩石;稀土总量低,轻重稀土分馏明显,弱负Eu异常(δEu=0.62~0.70);Ti、Nb、Ta亏损,Th、U、Pb、Zr、Hf富集,Rb/Sr平均值为0.78,明显富集W、Cu、Mo,属于I型花岗岩,为陆内造山带碰撞早期挤压背景下岩浆活动的产物,表现为对钨、钼、铜的成矿专属性。燕山晚期花岗斑岩具有高Si、K,贫Na、Ca和基性组分,属于强过铝质的高钾-中钾钙碱性系列岩石;稀土总量高,轻重稀土分馏不明显,强负Eu异常(δEu=0.03~0.06);Ti、Ba、K、Eu亏损,Th、U、Sm、Dy、Y、Ho、Yb、Lu富集程度更高,Rb/Sr平均值为7.56,明显富集Sn、Bi,属于燕山晚期岩浆演化程度较高的S型花岗岩,为碰撞后伸展环境的板内花岗岩,表现为对锡、金的成矿专属性。

Geochemistry of granitoid rocks of Shedong W-Mo deposit district in Cangwu County, Guangxi and its relation to mineralization

The Shedong tungsten and molybdenum deposit in Cangwu County,Guangxi is a quartz-skarn type deposit related to granitoids.Major granitoids are comprised of Caledonian granodiorite,granodiorite-porphyry and Late Yanshanian granite porphyry in mineral district.Caledonian granodiorite and granodiorite-porphyry dominantly exhibit low Si,K,high Na,Al and basic components, thus can be classified to the normal calc-alkaline granite with strongly peraluminous.The rocks are characterized by low REE contents, high LREE/HREE ratios,weakly Eu depletion(δEu=0.62～0.70),depletion of Ti,Nb,Ta,enrichment of Th,U,Pb,Zr,Hf, low Rb/Sr ratio(0.78),obviously enrichment of W,Mo,Cu.Geochemical evidences indicate that early Caledonian granodiorite (-porphyry)are I-type granite,and formed in compression tectonic setting of early collision stage in intra-continent orogenic belt,and associated with W,Mo,Cu mineralization.Late Yanshanian granite porphyry dominantly exhibit high Si,K,low Na,Ca and basic contents,can be defined as the high-moderate potassium calc-alkaline granite with strong peraluminous.The rock is characterized by relative high REE contents,low LREE/HREE ratios,strong Eu depletion(δEu=0.03～0.06),depletion of Ti,Ba,K,Eu,more enrichment of Th,U,Sm,Dy,Y,Ho,Yb,Lu,high Rb/Sr ratio(7.56),clearly enrichment of Sn,Bi,thus it is assigned to Late Yanshanian S-type granite evolved well,and formed in intraplate extension tectonic setting of post-collision,and is related to Sn,Au mineralization.