内蒙古敖包吐铅锌矿床花岗岩类年代学及其地球化学特征  

Geochronology and geochemistry of granite in Aobaotu Pb-Zn deposit, Inner Mongolia

作　　者：董旭舟[1] 周振华[2] 王润和 李进文[2] 何姝 

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实验室,北京100037 [3]内蒙古地质矿产勘查院,内蒙古呼和浩特010010

出　　处：《矿床地质》2014年第2期323-338,共16页Mineral Deposits

基　　金：中国地质调查局地质调查项目(12120113093600、1212011085260)联合资助成果

摘　　要：内蒙古敖包吐铅锌矿是大兴安岭南段成矿带上新发现的矿床，成矿与花岗闪长斑岩关系密切。对矿区内花岗闪长斑岩和花岗岩的LA—ICP—MS锆石U_Pb测年结果表明，形成年龄分别为（140．0±0．5）]Ma（MSWD=1．3）和（151．6±0．4）Ma（MSWD=1．2），为晚侏罗世一早白垩世岩浆活动的产物。岩石地球化学测试结果显示，花岗闪长斑岩具有高硅（w（SiO2）=65．51％～67．85％），富碱（w（Na2O＋K2O）=6．86％～7．81％），贫P2O5的特征，A／CNK在0．95～1．02之间，富集微量元素K、Rb、Nd，亏损Ta、Nb、P、Ti，为I型花岗岩。花岗岩的A／CNK值为1．58，属强过铝质岩石。Rb／Sr比值大于0．9，为S型花岗岩。敖包吐花岗岩的全岩Pb同位素组成显示，其206 Pb／204Pb为18．398-18．755，207pb／204Pb为15．53415．541，208pb／204Pb为38．386--38．542，铅具有混合来源特征。岩浆很可能来源于岩石圈地幔，并受到一定程度的混染。敖包吐花岗岩类可能与兴蒙造山带东段的后碰撞环境有关，并受到与古太平洋板块俯冲有关的弧后伸展影响。The Aobaotu ore deposit, located in the southern part of the Da Hinggan Mountains metallogenic belt, is a newly discovered lead-zinc deposit. The results of zircon LA-ICP-MS U-Pb dating for granodiorite-porphyries and granites in the study area show that granodiorite-porphyries were formed at （ 140.0± 0.5 ） Ma（MSWD = 1.3）, meanwhile, the age of granites is （151.6 ± 0.4） Ma （MSWD= 1.2）, which indicates that they are the products of magma movement during Late Jurassic-Early Cretaceous period. An analysis of major elements, trace elements and REE has revealed that the granodiorite-porphyries from the Aobaotu deposit are characterized by high silica （65.51%--67.85%） and alkali （w（Na2O＋K2O） = 6.86%--7.81%）, low P205, with the A/CNK being 0.95-- 1.02, enrichment of K, Rb and Nd, and depletion of Ta, Nb, P and Ti, suggesting I-type granitoids. Characteristics of Aobaotu granites are similar to those of S-type granitoids. The Pb isotope values show crust-mantle mixing characteristics, with the 206pb/204pb values ranging from 18.398 to 18. 755, 207pb/ 204pb values between 15.534 and 15.541, and 208 pb/204 pb values between 38. 386 and 38.542. The magma source might have mostly originated from the lithospheric mantle components which were transformed or affec- ted by the subduction components, and its formation was probably closely related to the post-collision of the Xing＇ an-Mongolia belt and the subduction of the Palm-Pacific Ocean.

关 键 词：地球化学 花岗岩 LA-ICP—MS锆石U-Pb定年 敖包吐铅锌矿床 大兴安岭 内蒙古 

分 类 号：P618.42[天文地球—矿床学] P618.43[天文地球—地质学]