摘要
选择西藏念青唐古拉地区的工布江达—墨竹工卡县亚贵拉-沙让-洞中拉铅锌钼铜银矿集区典型的中新生代岩浆岩作为研究对象,详细研究了岩体中锆石的Hf同位素组成。亚贵拉燕山期石英斑岩(λπ53)锆石的176Hf/177Hf比值为0.282090～0.282480,εHf(t)为-7.750～-21.449,TDM2为1679～2543Ma;亚贵拉喜马拉雅期石英斑岩(λπ16)锆石的176Hf/177Hf为0.282413～0.282805,εHf(t)为-11.463～2.460,TDM2为980～1864Ma;亚贵拉喜马拉雅期花岗岩(γ35)锆石的176Hf/177Hf比值为0.282601～0.282800,εHf(t)值在-2.279～2.182之间,TDM2为996～1279Ma;亚贵拉喜马拉雅晚期花岗斑岩(γπ63)锆石的176Hf/177Hf比值为0.282600～0.282830之间,εHf(t)为-5.676～3.128之间,TDM2为900～1461Ma;沙让喜马拉雅期角闪闪长岩(δψk)锆石的176Hf/177Hf比值为0.282700～0.282790,εHf(t)值为-1.536～1.618,TDM2为1019～1219Ma;洞中拉燕山期花岗斑岩锆石的176Hf/177Hf比值为0.282142～0.282396,εHf(t)为-19.744～-10.620,TDM2为1857～2430Ma。通过与驱龙铜矿含矿斑岩、林子宗火山岩Hf同位素特征对比研究,认为:①亚贵拉两期次侵入的石英斑岩体(λπ53、λπ61)具有不同的Hf同位素地球化学特征。②亚贵拉燕马拉雅期石英斑岩(λπ35)与洞中拉燕山期石英斑岩的锆石Hf同位素特征相似,176Hf/177Hf比值、εHf(t)值、两阶段Hf模式年龄(TDM2)暗示其源区为古老地壳物质;亚贵拉喜山期石英斑岩(λπ61)(66Ma)、亚贵拉花岗岩(γ61)(62Ma)、亚贵拉花岗斑岩(γπ63)(17Ma)、沙让角闪闪长岩(δψk)(53Ma)、林子宗火山岩和驱龙含矿岩体的Hf同位素组成暗示其形成于古老地壳与亏损地幔的混染,不同地质体锆石Hf同位素组成的差异可能与幔源岩浆中混入古老地壳物质的不同比例有关。
In this paper,the Mesozoic-Cenozoic magmatic rocks in Yaguila-Sharang-Dongzhongla ore-forming area serve as the object for zircon Hf isotope study by means of LA-MC-ICP-MS.Hf isotopic compositions of the zircons from Yanshanian Yaguila quartz porphyry（λπ35）show that the ratio of 176Hf/177Hf is 0.282 090 ～0.282 480,the εHf（t）value is-7.750～-21.449,and the TDM2 value is 1 679～2 543 Ma;Hf isotopic compositions of the zircons from Himalayan Yaguila quartz porphyry（λπ16）show that the ratio of 176Hf/177Hf is 0.282 413～0.282 805,the εHf（t）value is-11.463～2.46,and the TDM2 value is 980～1 864 Ma;Hf isotopic compositions of the zircons from Himalayan Yaguila granite（γ35）show that the ratio of 176Hf/177Hf is 0.282 601～0.282 800,the εHf（t）value is-2.279～2.182,and the TDM2 value is 996～1 279 Ma;Hf isotopic compositions of the zircons from late Himalayan Yaguila granite-porphyry show that the ratio of 176Hf/177Hf is 0.282 600～0.282 830,the εHf（t）value is-5.676～3.128,and the TDM2 value is 900～1 461 Ma;Hf isotopic compositions of the zircons from Himalayan Sharang hornblende diorite show that the ratio of 176Hf/177Hf is 0.282 700～0.282 790,the εHf（t）value is-1.536～1.618,and the TDM2 value is 1 019～1 219 Ma;Hf isotopic compositions of the zircons from Yanshanian Dongzhongla quartz porphyry show that the ratio of 176Hf/177Hf is 0.282 142～0.282 396,the εHf（t）value is-19.744～-10.620,and the TDM2 value is 1 857～2 430 Ma.Based on a comparison with the Hf isotopic compositions of the zircons from porphyry of the Qulong ore deposit and Linzizong volcanic rock,the authors have reached some conclusions：① The characteristics of Hf isotope of two intrusion stages of Yaguila quartz porphyry（λπ35）（λπ16）are different from each other.The characteristics of Hf isotope of Yanshanian Yaguila（λπ35）and Dongzhongla quartz porphyries are similar to each other,suggesting that the rocks were formed by the crust base materials.② The Hf isotope of Ya
出处
《矿床地质》
CAS
CSCD
北大核心
2011年第2期279-291,共13页
Mineral Deposits
基金
国家973项目(编号:2011CB403103)
青藏专项项目(编号:1212010012005)资助的成果
