青海都兰县阿斯哈金矿区花岗斑岩岩石地球化学、锆石U-Pb年代学与Hf同位素研究  

Geochemistry, Zircon U-Pb Dating and Hf Isotopic Compositions of the Granite-porphyry in Asiha Gold Ore District, Dulan County, Qinghai Province

作　　者：岳维好 周家喜[2] 高建国[3] 黄艳华[4] 贾福聚[3] YUE Weihao;ZHOU Jiaxi;GAO Jianguo;HUANG Yanhua;JIA Fuju(Yunnan Geological Prospecting Institute, China Chemical Geology and Mine Bureau, Kunming 650206,Yunnan, China;School of Resource Environment and Earth Science, Yunnan University, Kunming 650050,Yunnan, China;College of Land Resource Engineering, Kunming University of Science and Technology,Kunming 650093, Yunnan, China;Division of Assets Administration, Kunming University of Science and Technology, Kunming 650504, Yunnan, China)

机构地区：[1]中化地质矿山总局云南地质勘查院,云南昆明650206 [2]云南大学资源环境与地球科学学院,云南昆明650050 [3]昆明理工大学国土资源工程学院,云南昆明650093 [4]昆明理工大学资产管理处,云南昆明650504

出　　处：《大地构造与成矿学》2017年第4期785-798,共14页Geotectonica et Metallogenia

基　　金：国家自然科学基金(41272111);山东黄金集团基本科研业务费专项基金(201122010100)联合资助

摘　　要：阿斯哈金矿区钻孔中新发现的花岗斑岩,呈岩脉、岩株或舌状分布。岩石呈灰-灰白色,细-中粒斑状结构,块状构造。主要矿物为石英、斜长石、钾长石、黑云母及少量角闪石,副矿物有磁铁矿、钛铁矿、锆石、磷灰石和榍石等。全岩高硅(SiO_2=70.03%~72.83%),高钾(K_2O=3.96%~5.21%),低P_2O_5(0.09%~0.10%),低FeO^T/MgO(1.76~3.91),A/CNK值(1.04~1.29)多数小于1.1,为高钾钙碱性系列弱过铝质-过铝质花岗岩类岩石,具有I型花岗岩特征。样品具有轻稀土富集和中等负Eu异常(δEu=0.71~0.78)特征,且富集大离子亲石元素(LILE:K、Rb、Th、U等)、亏损高场强元素(HFSE:Nb、Ta、Ti等)。LA-ICP-MS锆石U-Pb定年结果显示,其结晶年龄为222.1±3.9 Ma(MSWD=5.4,n=15),形成于晚三叠世。锆石Hf同位素组成(ε_(Hf)(t)=-4.3^-1.4)和二阶段Hf模式年龄(t_(DM2)=1.34~1.53 Ga),表明新发现的花岗斑岩源于古老地壳物质的深熔或重熔,并可能有幔源物质的加入。上述特征表明,阿斯哈金矿区花岗斑岩形成于东昆仑晚古生代-早中生代构造-岩浆旋回的碰撞晚期-后碰撞阶段,可能是晚三叠世幔源岩浆底侵下地壳岩石部分熔融的产物,并在形成过程中有幔源物质的加入。此外,研究区花岗斑岩的侵位与沟里地区(包括阿斯哈)金多金属矿床的形成具有内在的联系。The newly discovered granite-porphyry dike in the Asiha Au ore district consist mainly of quartz,plagioclase,K-feldspar,biotite and a small quantity of hornblende,with magnetite,ilmenite,zircon,apatite and titanite as accessoryminerals.This granite-porphyry is characterized by high SiO2(SiO2=70.03%-72.83%),high K2O(K2O=3.96%-5.21%),low P2O5(0.09%-0.10%)and low FeOT/MgO(1.76-3.91).Most A/CNK(1.04-1.29)values are less than1.1,withI-type granite features.This indicates that it belongs to high-K calc-alkaline and weak peraluminous-peraluminousgranite.The rocks are enriched in large ion lithophile elements(LILE;e.g.,K,Rb,Th and U)and LREE with moderatenegative Eu anomalies(δEu=0.71-0.78),but depleted in high field strength elements(HFSE;e.g.,Nb,Ta,and Ti).LA-ICP-MS zircon U-Pb dating yielded an age of222.1±3.9Ma(MSWD=5.4,n=15).εHf(t)(from?4.3to?1.4)and tDM2(1.34-1.53Ga)values of zircons indicate that the porphyry was derived from ancient crust sources and mixed probably withjuvenile mantle material.Therefore,we propose that the newly discovered porphyry formed during the collision topost-collision stage of Late Paleozoic to Early Mesozoic tectonic-magmatic cycle in the East Kunlun region.It is a productionof partial melting of crustal rocks intrigued by mantle underplating in Late Triassic.In addition,there is a close geneticrelationship between the porphyry and Au polymetallic deposits in the Gouli area(includes Asiha).

关 键 词：花岗斑岩 岩石地球化学 LA-ICP-MS锆石U-Pb年代学 岩石成因 构造环境 阿斯哈金矿区 东昆仑 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]