义敦岛弧晚白垩世斑岩成矿系统  

Late Cretaceous porphyry metallogenic system of the Yidun arc,SW China

作　　者：杨立强[1] 高雪[1] 和文言[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083

出　　处：《岩石学报》2015年第11期3155-3170,共16页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划(2015CB452605;2015CB452606);中国地质调查局地质调查项目(12120114013501);北京市优秀博士学位论文指导老师科研项目(20111141501);高等学校学科创新引智计划(B07011)联合资助

摘　　要：义敦岛弧晚白垩世花岗(斑)岩及其相关成矿系统发育,呈南北向展布,且由北向南呈规律性变化,形成北段昌台弧、中段乡城弧和南段中甸弧3个子系统:(1)北段昌台弧发育97~93Ma的斑状二长花岗岩岩基和矽卡岩型锡矿床,岩体侵位于乡城-格咱断裂与甘孜-理塘断裂的交汇地带,表现了较宽的主量元素变化范围,属于高钾钙碱性-钾玄质的过铝质系列,稀土配分模式较平坦、具有负Eu异常,锡矿化多发育于岩体与上三叠统图姆沟组碳酸盐岩的接触带上;(2)中段乡城弧乡城-格咱断裂两侧发育大量85~77Ma的花岗(斑)岩及斑岩-矽卡岩型Sn-Pb-Zn-Ag多金属矿床,主体岩相为斑状黑云二长花岗岩,是碱性、分异程度高的酸性岩,具典型钾质演化系列,多金属矿化主要发生在岩体与上三叠统图姆沟组碳酸盐岩和变质碎屑岩接触带中,从花岗岩向外为Sn→Pb-Zn,垂向上由深部到浅部依次为含Sn磁铁矿→Sn→Sn-Pb-Zn-Ag;(3)南段中甸弧发育呈岩株出露的88~78Ma的二长花岗斑岩及斑岩-矽卡岩型Cu-Mo-W多金属矿床,休瓦促和热林花岗斑岩体侵入上三叠统喇嘛亚组、拉纳山组砂板岩中,主要发育蚀变花岗岩型和热液石英脉型矿体;红山花岗斑岩体侵入上三叠统图姆沟组碳酸盐岩和变质碎屑岩中,主要发育矽卡岩型矿体。斑岩体中发育角闪石斑晶,铝饱和指数小于1.1,Zr、P与SiO 2呈显著负相关,具有I型花岗岩特征。与晚三叠世同俯冲的弧花岗岩相比,晚白垩世花岗(斑)岩明显偏酸性(SiO 2含量范围为65.06%~76.30%)、富碱质(K2O+Na2O含量范围为6.55%~10.77%)和铝饱和(A/CNK=0.72~1.13);岩浆源区深度变浅,且花岗(斑)岩源区从昌台弧(Eu/Eu*=0.20~0.66,εNd(t)=-6.90^-5.30,εHf(t)=-0.6~1.9)→乡城弧(Eu/Eu*=0.04~0.18,(87Sr/86Sr)i=0.7110~0.7250,εNd(t)=-8.40^-5.54)→中甸弧(Eu/Eu*=0.14~0.88,(87Sr/86Sr)i=0.7075~0.7092,εNd(t)=-8.50^-5.76,εHf(t)=-9.5^-2.2)呈现由中-酸性变沉积地壳到The Late Cretaceous granite porphyry and associated metallogenic system developed in the Yidun arc are distributed along NS-trending,showing regular pattern from north to south. As a result,it can be divided into three sub-systems named the Changtai arc,the Xiangcheng arc and the Zhongdian arc;（ 1） The Changtai arc which is located in the northern section of the Yidun arc develop porphyritic monzonitic granite batholith and skarn tin deposits of 97 ~ 93 Ma. The batholith emplaced in the intersection between the Xiangcheng-Geza fault and the Ganzi-Litang fault,and they have a wide range of major elements,belonging to high-K calc-alkaline to shoshonitic peraluminous series. These rocks display flat REE patterns with negative Eu anomaly. Tin mineralization occurred in the contact of the monzonitic granites and the Tumugou Formation;（ 2） The Xiangcheng arc which is located in the middle of the Yidun arc develop abundant granitic porphyries and skarn Sn-Pb-Zn-Ag polymetallic deposits of 85 ~ 77 Ma along the Xiangcheng-Geza fault. The main facies of the rock are biotite monzonitic granites,which are alkaline,highly fractionated,with a typical potassium evolution.Polymetal mineralization mainly occurred in the contact between granite and carbonates,meta-clastic rocks of the Tumugou Formation.Horizontally,the mineralization varies from Pb-Zn to Sn outward from granite; Vertically,from the deep to shallow followed by magnetite-containing Sn,through Sn,to Sn-Pb-Zn-Ag;（ 3） The Zhongdian arc which is located in the southern section develop monzonite porphyry rock and porphyry-skarn Cu-Mo-W polymetal deposits of 88 ~ 78 Ma. The Xiuwacu and the Relin plutons intruded into the sandstone and slate of the Lamaya Formation,developing alter-granite and hydrothermal quartz vein type ores. While the Hongshan pluton intruded into carbonates and clastic rocks of the Tumugou Formation,developing skarn ore bodies. These plutons contain hornblende phenocrysts,with aluminum saturation index of less than 1. 1,and their Zr,P are

关 键 词：晚白垩世花岗(斑)岩 岩浆源区 氧逸度 成矿系统多样性 义敦岛弧 

分 类 号：P588.121[天文地球—岩石学] P611[天文地球—地质学]