豫西银家沟杂岩体年代学、地球化学和岩石成因  

Geochronology, geochemistry and petrogenesis of the Yinjiagou complex in western Henan Province, China

作　　者：李铁刚[1] 武广[2] 陈毓川[3] 李宗彦 杨鑫生 乔翠杰 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]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开放实验室,北京100037 [3]中国地质科学院,北京100037 [4]河南省灵宝市金源矿业有限责任公司,灵宝472500

出　　处：《岩石学报》2013年第1期46-66,共21页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41172081);河南省灵宝市金源矿业有限责任公司博士后科研项目(200906001)联合资助

摘　　要：银家沟杂岩体位于河南省灵宝市,主要岩石类型为二长花岗斑岩、钾长花岗斑岩和石英闪长斑岩,并有少量呈脉状产出的花岗闪长斑岩及闪长玢岩。该杂岩体是银家沟硫铁多金属矿床的成矿母岩。杂岩体的元素地球化学和锆石SHRIMPU-Pb年代学研究结果表明,银家沟杂岩体二长花岗斑岩、钾长花岗斑岩和花岗闪长斑岩的侵位年龄分别为147.5±2.1Ma、147.8±1.6Ma和142.0±2.0Ma,为晚侏罗世-早白垩世的产物。二长花岗斑岩和钾长花岗斑岩具有高的SiO2(65.17%～73.94%)和Al2O3含量(13.53%～15.96%)、非常高的K2O含量(5.03%～9.89%,多数大于6.0%),但具有低的Na2O(0.24%～1.86%,多数小于1.0%)、Fe2O3(0.82%～3.71%)、FeO(0.02%～1.62%)、MgO(0.23%～1.47%,多数小于1.0%)和CaO含量(0.08%～1.98%,多数小于0.4%),铝指数(ASI)为1.18～2.04,全部大于1.1,应为热液蚀变引起。杂岩体的稀土元素总量介于71.38×10-6～276.4×10-6,具有中等-微弱的Eu负异常(δEu介于0.57～0.88),稀土元素分馏强烈,其(La/Yb)N介于6.93～30.1之间,为轻稀土富集型。岩石具有低Sr(104×10-6～461×10-6,多数<300×10-6)和Yb含量(0.90×10-6～2.10×10-6,绝大多数<1.9×10-6)。在原始地幔标准化的微量元素蜘蛛网图中,银家沟杂岩体富集Rb、Ba、Th、U、K、La、Ce、Nd、Hf、Zr等,强烈亏损Sr、P、Ti等,具有中等Nb、Ta亏损。主量、稀土和微量元素特征表明,岩石具后碰撞花岗岩类的地球化学特征,属后碰撞花岗岩。杂岩体的锶初始比值(ISr)为0.7069～0.7091,多数<0.7085,εNd(t)值为-14.99～-10.57,亏损地幔单阶段Nd模式年龄为1.41～1.76Ga,两阶段Nd模式年龄为1.51～1.81Ga;钾长石206Pb/204Pb、207Pb/204Pb和208Pb/204Pb比值变化范围分别为17.376～17.628、15.455～15.502和37.867～38.090,Nd、Sr和Pb同位素组成指示银家沟杂岩体最可能源自宽坪群、二郎坪群和太华群的混合物。银家沟杂岩体形成于晚侏罗世-早白垩世期间的EW向�The Yinjiagou complex, located in Lingbao City, western Henan Province, is mainly composed of monzogranite porphyry, K-feldspar granite porphyry and quartz diorite porphyry, with minor granodiorite and diorite porphyry dykes, which is closely related to the Yinjiagou porphyry-skarn pyrite-polymetallic deposit. The monzogranite porphyry, K-feldspar granite porphyry and granodiorite porphyry yiled zircon SHRIMP U-Pb ages of 147.5±2.1Ma, 147.8±1.6Ma and 142.0±2.0Ma, respectively, indicating that the Yinjiagou complex formed during the transition from Jurassic to Cretaceous. Both the monzogranite porphyry and K-feldspar granite porphyry have high contents of SiO2（65.17%-73.94%）, Al2O3 （13.53%-15.96%） and K2O （5.03%-9.89%, mostly 〉6.0%）, but low contents of Na2O （0.24%-1.86%, mostly 〈1.0%）, Fe2O3 （0.82%-3.71%）, FeO （0.02%-1.62%）, MgO （0.23%-1.47%, mostly 〈1.0%） and CaO （0.08%-1.98%, mostly 〈0.4%）. They have high aluminum saturation index （1.18-2.04, all 〉1.1） and have been altered. The REE contents range from 71.38×10^-6 to 276.4×10^-6, with mediately negative Eu anomalies （δEu=0.57-0.88） and strong REE fractionation （（La/Yb）N=6.93-30.09）. The Yinjiagou complex is characterized by low Sr （104×10^-6-461×10^-6, generally 〈300×10^-6） and Yb contents （0.90×10^-6-2.10×10^-6, mostly 〈1.9×10^-6）. The complex is enriched in Rb, Ba, Th, U, K, La, Ce, Nd, Hf and Zr, but strongly depleted in Sr, P and Ti, with moderate depletion of Nb and Ta. The geochemical signatures above are similar to those of post-collisional granitoids, suggesting that the Yinjiagou complex can be classified into the group of post-collisional granites. The complex has initial 87Sr/86Sr ratios of 0.7069-0.7091 （mostly 〈0.7085）, εNd（t） values of -14.99 to -10.57, tDM1（Nd） of 1.41-1.76Ga and tDM2（Nd） of 1.51-1.81Ga, respectively. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of K-feldspar range 17.376-17.628, 15.455-15.502 and 37.867-38.090, respectivel

关 键 词：锆石SHRIMP U-Pb年龄 元素地球化学 SR-ND-PB同位素 岩石成因 银家沟杂岩体 东秦岭钼矿带 

分 类 号：P588.13[天文地球—岩石学] P597.3[天文地球—地质学]