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.
出处
《矿物岩石》
CAS
CSCD
北大核心
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)
