东昆仑尕林格铁矿床成因年代学及Hf同位素制约

尕林格矿床发育大量与铁多金属成矿关系密切的花岗闪长岩、石英二长岩、石英二长闪长岩和石英闪长岩体.LA-ICP-MS锆石U-Pb年代学表明石英二长闪长岩的年龄为228.3土0.5 Ma,石英二长岩的年龄为234.4±0.6 Ma.地球化学特征也较为相似,SiO2质量分数中等(58.4％～64.3％),w(FeOT)/w(MgO)偏低(0.62～1.38),A/CNK值(0.52～0.86)＜1,轻稀土富集,轻重稀土分馏明显,中等—强烈的负Eu异常(δEu为0.33～0.82),富集Rb,Th等大离子亲石元素,明显亏损高场强元素(Sr,P,Nb,Ta,Ti等),w(Rb)/w(Sr)为0.12～0.39,具有壳幔混合Ⅰ型花岗岩的特征.锆石Hf同位素组成表明,石英二长闪长岩的εHf(t)为-4.15～3.44,T2DM为1042～1523 Ma;石英二长岩εHf(t)为-5.06～1.7,T2DM为1157～1587 Ma,二者具有相同的岩浆来源,可能为壳幔混合岩浆作用的结果.综合研究认为尕林格铁矿床中三叠世岩体为东昆仑218～242 Ma俯冲—碰撞转换阶段,地幔底侵古老陆壳,幔源基性岩浆与壳源花岗质岩浆发生不同程度混合作用的产物,中高温岩浆流体与围岩发生水—岩反应是矽卡岩型矿体形成的主要因素.

Genesis,geochronology and Hf isotopic compositions of the magmatic rocks in Galinge iron deposit,eastern Kunlun

The granodiorites,adamellites,quartz monzodiorites and quartz diorites in Galinge deposit are closely related with Fe mineralization.The results of LA-ICP-MS U-Pb isotope dating showed that quartz monzodiorite formed in 228.3±0.5 Ma,and the quartz diorite formed in 234.4±0.6 Ma.Major and trace element data of quartz monzodiorites and quartz diorites showed similar characteristics,with SiO₂ 58.4%～64.3%, w（FeO^T）/w（MgO） 0.62～1.38,A/CNK（0.52～0.86）<1,LREE enrichment,medium to strong negative Eu anomalies （δEu 0.33～0.82）,rich LILEs such as Rb and Th,depleted HFSEs such as Sr,P,Nb,Ta and Ti,w（Rb）/w（Sr） 0.12～0.39,all of which imply that the quartz monzodiorites and quartz diorites might be the crust-mantle mixedⅠ-type granites.TheεHf（t） values of quartz monzodiorite vary from—4.15 to 3.44,and the value of T2DM varies from 1042 to 1523 Ma.TheεHf（t） values of quartz diorite vary from-5.06 to 1.7,and the value of T2DM varies from 1157 to 1 587 Ma.The similar Hf isotopic composition indicates that their parental magmas were consistent,which might be a mixture with a mantle source and ancient crust.It is suggested that the middle Triassic magmatic rocks in Galinge deposit might have been formed by underplating and magma mixing,and emplaced at the same time with subduction-collision stage from 218 to 242 Ma in east Kunlun.The water-rock interaction between middle-high temperature magmatic fluid and wall rocks could be closely related with the formation of Skarn type ore bodies.