东昆仑卡尔却卡矿区似斑状二长花岗岩成因：锆石U-Pb年龄及Sr-Nd同位素制约  

THE GENESIS OF PORPHYRITIC MONZOGRANITIE OF THE KAERQUEKA DEPOSIT IN THE EAST KUNLUN:EVIDENCE FROM ZIRCON U-Pb DATING AND Sr-Nd ISOTOPIC COMPOSITIONS

作　　者：李积清[1] 陈静[1] 史青瑞[1] 李彬 王进寿[1] 舒树兰[1] 

机构地区：[1]青海省地质调查院,青藏高原北部地质过程与矿产资源重点实验室,青海西宁810012 [2]青海省电力设计院,青海西宁810008

出　　处：《矿物岩石》2016年第3期87-95,共9页Mineralogy and Petrology

基　　金：青海省应用基础研究(2015-ZJ-762;2016-ZJ-719);青海省重点实验室专项资金计划(2014-Z-Y06)

摘　　要：卡尔却卡铜多金属矿区似斑状二长花岗岩体与成矿关系密切。LA-ICP-MS锆石U-Pb结果表明岩体形成时代为220.4 Ma±0.79Ma(MSWD=0.30)。岩石地球化学特征显示其属于准铝质(ACNK=0.93~1.04)、高钾钙碱性-钾玄岩系列,具有大离子亲石元素富集、高场强元素亏损、轻稀土富集、负Eu异常中等(σEu介于0.47~0.70之间)等特征。岩体(^(87)Sr/^(86)Sr)_ⅰ值为0.710 71~0.713 66,平均0.711 52,εNd(t)值为-3.6^-5.4,平均-4.1,T_(2DM)=1.29-1.44Ga,平均1.36Ga。考虑到本区中晚三叠是花岗岩类普遍含大量暗色镁铁质包体,具有明显的岩浆底侵和混合的证据,且样品Sr-Nd同位素显示富集地幔源区特征,认为似斑状二长花岗岩形成于晚三叠世后碰撞阶段,岩浆起源于富集地幔的基性岩浆底侵并与古老陆壳发生混合,幔源岩浆活动与成矿作用关系密切,解释了东昆仑地区成矿作用主要与中晚三叠世岩浆活动有关。Porphyritic monzogranite in Kaerqueka is closely related to minerahzatlon ot copper polymetallic deposit. LA-MC-ICP-MS U-Pb zircon dating yields emplacement age of 220.4 Ma＋ 0.79 Ma and represents the Late Triassic magmatism. Geochemical characteristics of the rock show that it belongs to aluminum, high potassium ealc-alkali to shoshonite series, enriched with large ion lithophile and light rare earth elements, depleted of high field strength elements,with medium negative Eu anomaly （-Eu= 0.47 -0.70）. Geochemical study also shows that （87 St/ 86Sr） i --0. 710 71-0. 713 66 with an average of 0. 711 52, -Nd（t） value is 3.6-5.4,with an av- erage of 4. 1, T2D- = 1.29-1.44 Ga, with an average of 1.36 Ga. Dark mafic inciusions widely oc- cur in the middle-late Triassic granitoids indicate the magma invasion and mixture of crust with the mantle. Meanwhile,Sr and Nd isotopes analysis also show that the samples are characteristic of magma source of enrichment mantle. Therefore,it is proposed that the porphyritic monzogran- ire in the Kaerqueka deposit formed in late Triassic collision stage,originated from the enrichment mantle,in which the mafic magma invaded and mixed with the ancient continental crust.

关 键 词：锆石U-PB年龄 SR-ND同位素 似斑状二长花岗岩 卡尔却卡矿床 东昆仑 

分 类 号：P588.12[天文地球—岩石学]