陕西金堆城钼矿区花岗岩Sr、Nd、Pb同位素特征及其地质意义  

Sr,Nd,Pb isotopic characteristics of granite in Jinduicheng area and their geological significance

作　　者：李洪英[1] 毛景文[1] 王晓霞[1] 叶会寿[1] 杨磊 

机构地区：[1]中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中海油研究总院,北京100027

出　　处：《中国地质》2011年第6期1536-1550,共15页Geology in China

基　　金：中央级公益性科研院所基本业务费资助项目(K1019);国土资源部公益性行业科研专项(200911007-6);全国危机矿山接替资源找矿项目(20089949)资助

摘　　要：通过对陕西金堆城钼矿区花岗斑岩体和八里坡斑岩体进行地球化学测试,测得金堆城斑岩体的SiO2含量为72.89%～74.06%,MgO为0.07%～0.3%,稀土总量为43.29×10-6～93.94×10-6,稀土元素配分曲线呈右倾型,具有明显的铕负异常和弱的负铈异常(δEu为0.43～0.78,δCe为0.74～0.86),富集大离子亲石元素K、Rb、U、Th和Sr等元素,亏损Ba、P和Ti等元素。八里坡斑岩体的SiO2含量为69.87%～70.80%,Al2O3 14.93%～15.46%,MgO 0.28%～0.48%,Sr/Y比值大于60,稀土总量为125.23×10-6～139.63×10-6,铕为无异常或微弱的正异常(δEu为0.98～1.04),铈为微弱的负异常(δCe为0.92～0.96),富集Ba、U、K等大离子亲石元素,而亏损P、Ta和Ti等元素。金堆城斑岩体和八里坡斑岩体的岩石类型为I型花岗岩,Pb同位素显示金堆城斑岩体的Pb主要来自下地壳,但有地幔物质的加入,八里坡斑岩体的Pb主要来自下地壳。金堆城斑岩体的ε(Nd,t)值为较低负值(-13.8～-15.2),但ε(Sr,t)变化较大,为-46.4～13.6,八里坡斑岩体具有负低ε(Nd,t)值(-20.4)和正高ε(Sr,t)值(64.5～65.2)。金堆城花岗斑岩和八里坡花岗斑岩的Sr、Nd、Pb同位素与华北地块相似,这两个岩体的源区为华北地块组成部分。A study of petrology and element geochemistry shows that Jinduicheng granite porphyry and Balipo granite porphyry are I–type granites in the Jinduicheng ore concentration area.SiO2 values of Jinduicheng porphyry bodies vary in the range of 72.89%~74.06%（73.48% on average）,MgO values are 0.073%~0.30%,∑REE values are 43.29%~93.94%,REE distribution patterns are of ＂V＂ type,there exists an evident negative Eu anomaly and a weak negative Ce anomaly,δEu values are 0.43~0.78,and δCe are 0.74~0.86.They are enriched with K,Rb,U,Th and Sr,and strongly depleted in Ba,P and Ti.SiO2 of Balipo granites range from 69.87 to 70.80%,Al2O3 values are 14.93%~15.46%,MgO are 0.28%~0.48%,the total rare earth element concentrations（∑REE） of the rocks are 125.23~139.63×10-6,the ratios of Sr/Y are generally higher than 60,Eu has no anomaly or weak positive anomaly,Ce shows weak negative anomaly,and there exists the enrichment of HFSE（such as Ba,U and K） and the depletion of P,Ta and Sr.Plotting of lead isotopes of granite porphyry on the 207Pb/204Pb diagrams and 208Pb/204Pb versus 206Pb/204Pb evolution curves show that lead of Balipo granite porphyry might have come from crust source area,and lead of Jinduicheng granite porphyry was probably derived from the crust-mantle mixing source area.Jinduicheng has low Nd（ε（Nd,t）=-20.8^-18.3） and high Sr（ε（Sr,t）= 63.0~74.3）,Balipo rocks have extremely low ε（Nd,t） of-20.8^-18.3 and relatively high ε（Sr,t） of 63.0~74.3.Sr.Nd and Pb plots show that the Jinduicheng rocks originated from the lower crust,but were contaminated by mantle-derived materials,and the source rock of Balipo is the lower crust,which has considerable ore-forming potential.the values of Sr,Nd and Pb isotopes are similar to the data of the North China plate,suggesting that these intrusives constitute a component part of the North China plate.

关 键 词：Sr、Nd、Pb同位素 花岗斑岩 岩石地球化学 金堆城 

分 类 号：P618.65[天文地球—矿床学] P597[天文地球—地质学]