西藏雄村斑岩铜金矿集区火山-岩浆岩锆石Hf同位素组成  

Zircon Hf Isotopic Composition of Volcanic-Magmatic Rocks at Xiongcun Porphyry Copper-Gold Deposit,Tibet

作　　者：黄勇[1] 唐菊兴[2] 张丽[1] 郎兴海[3] 

机构地区：[1]中国地质调查局成都地质调查中心,成都610081 [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]成都理工大学,成都610059

出　　处：《地质学报》2014年第8期1528-1538,共11页Acta Geologica Sinica

基　　金：国家自然科学基金(编号:41172077);西藏大型矿床成矿专属性研究(编号:1212011221073)共同资助成果

摘　　要：通过对西藏雄村斑岩铜金矿集区内各期次火山—岩浆岩开展锆石Hf同位素研究,结合岩浆锆石U-Pb年龄,可将矿集区内火山—岩浆岩划分为两组。第一组为早—中侏罗世火山—岩浆岩:包括富矿安山质凝灰岩、成矿早期角闪石英闪长玢岩、成矿期石英闪长斑岩、含粗粒石英斑晶的石英闪长斑岩、以及穿插矿体的安山岩脉。第二组为始新世黑云母花岗闪长岩。第一组火山—岩浆岩锆石Hf同位素具有高度亏损的Hf同位素组成以及年轻的单阶段模式年龄,初始εHf(t)值分别为+13.76^+17.50、+12.24^+18.79、+14.39^+17.64、+12.50^+16.26、+10.66^+15.44之间,高度亏损的铪同位素组成表明该组火山-岩浆岩起源于亏损地幔的部分熔融。同时相对均一的Hf同位素组成暗示该组火山-岩浆岩并未经历过壳源物质的混染,即该组火山岩浆岩形成于洋壳之中的岛弧环境,火山-岩浆岩可能受控于深部同一岩浆房。第二组始新世黑云母花岗闪长岩初始εHf(t)值介于+5.75^+9.42之间,与冈底斯南缘同期岩体εHf(t)组成类似,起源于新生下地壳的部分熔融。This paper report the Hf isotope compositions of volcanic-magmatic rocks from Xiongcun Porphyry copper-gold deposit,Tibet.Volcanic-magmatic rocks are divided into two groups based on U-Pb dating and Hf isotope.The first group is early to middle Jurassic volcanic-magmatic rocks：ore-bearing andesitic tuff,pre-mineralization hornblende quartz diorite porphyry,syn-mineralization quartz diorite porphyry, quartz diorite porphyry with bigger quartz eyes,and andesite dyke crosscutting ore-body.The second group is Eocene biotite granodiorite.The first group volcanic-magmatic rocks are characterized by similar depleted Hf isotope composition and young model age.The initial value ofεHf（t）are ＋13. 76-＋17. 50、＋12. 24-＋18. 79、＋14. 39-＋17. 64、＋12. 50-＋16. 26、＋10. 66-＋15. 44 respectively.The depleted Hf isotope compositions of first group indicate that magmas are derived by partly melting of depleted mantle.At other hand,relatively homogeneous Hf isotope compositions also indicated that the first group magmatisms did not mixed with older continent crust,and are belong to island arc magmas.The initial value ofεHf（t）of second group Eocene biotite granodiorite are ＋5. 75-＋9. 42,which are similar to the same period magma of south Gangdisi belt,which are derived by partly melting of juvenile lower continental crust.

关 键 词：Hf同位数 火山-岩浆岩 斑岩铜金矿床 雄村 冈底斯 西藏 

分 类 号：P618.41[天文地球—矿床学] P618.51[天文地球—地质学] P597