内蒙古乌奴格吐山斑岩铜钼矿床低Sr-Yb型成矿斑岩地球化学特征及地质意义  

Geochemistry and geological significances of ore-forming porphyry with low Sr and Yb value in Wunugetushan copper-molybdenum deposit,Inner Mongolia.

作　　者：陈志广[1,3] 张连昌[1] 万博[1,3] 张玉涛[2,3] 吴华英[1,3] 

机构地区：[1]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [2]岩石圈演化国家重点实验室,中国科学院地质与地球物理研究所,北京100029 [3]中国科学院研究生院,北京100039

出　　处：《岩石学报》2008年第1期115-128,共14页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2006CB403506)资助

摘　　要：内蒙古满洲里乌奴格吐山大型斑岩铜-钼矿床位于大兴安岭北段西侧的满洲里新右旗。成矿岩体类型为二长花岗斑岩,年代学研究表明该斑岩形成于早侏罗世。元素地球化学表明,斑岩呈钙碱性、具高Si、富Al和Na、高A/CNK值,低Ca、Mg和Fe_2O_3~T特征;稀土元素Eu无异常,微量元素表现出富集大离子亲石元素,亏损高场强元素,Sr(16.51×10^(-6)～95.58×10^(-6))和Yb(0.39×10^(-6)～0.82×10^(-6))含量低的特点,总体上成矿斑岩为低Sr低Yb特征的Ⅰ型花岗岩。斑岩初始锶比值为0.70522～0.70690,ε_(Nd)(t)值为0.3～1.0,Pb同位素组成较均匀,其中^(206)Pb/^(204)Pb比值为18.563～18.926,^(207)Pb/^(204)Pb为15.568～15.598,^(208)Pb/^(204)Pb为38.255～38.529。上述地球化学特征反映成矿斑岩岩浆起源于加厚的下地壳底部,来自岩石圈地幔热源诱发下地壳底部发生减压熔融。同时乌奴格吐山这套低Sr低Yb的Ⅰ型花岗斑岩的出现,指示了早侏罗世蒙古-鄂霍次克海闭合、华北板块与西伯利亚板块碰撞后引张的构造环境。通过对乌山斑岩铜矿与全国其它斑岩型铜-钼矿床对比发现,其成矿斑岩地球化学具有许多相似性。结合区域地质和地球化学,我们认为本地区Cu和Mo具有很大的成矿潜力。Wunugetu porphyry copper-molybdenum deposit is located in the western area of northern Da Hinggan Ranges. Based on isotopic dating, it is indicated that the ore-forming porphyry was formed in early Jurassic. The major elements of the ore-forming porphyries show high SiOz, AlzO3, NaO contents and A./CNK value, and low CaO, MgO and Fe2O3T contents, belonging to the calc- alkaline series and I-type granites. The REE and trace elements data of the porphyry are characterized by unconspicuous positive and negative Eu anomalies, LILE enrichment and HFSE depletion, especially for a significantly negative Nb-Ta and Sr-Yb anomaly. The rocks also exhibit positive end （t） values （ ＋ 0. 3 - 1. 0） and relatively high initial 87 Sr/86 Sr values （0. 705222 - 0. 706901 ）. The above features indicate that the ore-forming porphyry shows some characteristics of the mantle sources. The ranges of 206Pb/204Pb （ 18. 5631 - 19. 0192）, 207Pb/204Pb （ 15. 5684 - 15. 5981 ） and 208Pb/204Pb （ 38. 2554 - 38. 5285 ） of the porphyry show components of lower continental crust. Base on studies on the geology and geochemistry, we suggest that the porphyry was formed in the transition stage of collision to post-collision orogeny. Through contrasting with other porphyry copper-molybdenum deposits in China, it is indicated the geochemical characters of the Wunugetushan ore-forming porphyry are similar with other deposits. Combining with geological background, we consider that the Wunugetushan porphyry copper-molybdenum deposit has definite ore-forming conditions and prodigious metallogenic potential.

关 键 词：Ⅰ型花岗岩 低Sr低Yb花岗岩 斑岩铜-钼矿 碰撞期后 早侏罗世 乌奴格吐山 

分 类 号：P597.3[天文地球—地球化学] P618.41[天文地球—地质学]