高级检索

    西藏亚贵拉含钼岩体锆石LA-ICP-MS年龄和地质意义

    U-Pb zircon LA-ICP-MS age of the Yaguila molybdenum-bearing intrusion in Tibet and its geological significance

    • 摘要: 提要:冈底斯带东段的念青唐古拉地区除了发育许多大中型铅锌矿床外,还发育大型钼矿床,前者被认为是始新世成矿作用的产物,后者则被认为是古新世斑岩型钼矿床。在该区规模最大的亚贵拉铅锌矿床评价过程中,不仅发现铅锌矿化与石英斑岩体关系密切,而且在岩体内发现了规模较大的辉钼矿脉。应用LA-ICP-MS对石英斑岩锆石微区U-Pb年龄和微量元素进行了测定,90%的测点Th/U比值较高,阴极发光图像显示锆石内部发育明显的环带构造,具岩浆成因特点。2件石英斑岩样品的锆石206Pb/238U加权平均年龄分别为(65.8±1.3)Ma(MSWD=3.0)、(68.6±1.7)Ma(MSWD=1.8),表明岩体形成于晚白垩世。在野外实地调研的基础上,结合石英斑岩体微量元素含量以及前人对钼矿体的辉钼矿Re-Os年龄测定,认为辉钼矿化、铅锌矿化均与石英斑岩岩浆热液密切相关,但亚贵拉钼矿化与沙让斑岩钼矿化有别。念青唐古拉地区在晚白垩世可能发生铅锌成矿作用以及钼成矿作用。

       

      Abstract: Abstract:There exist a large number of large and medium-sized lead-zinc deposits as well as a large-sized molybdenum deposit in Nyainqentanglha region of eastern Gangdise. The former deposits are considered to be products of Eocene mineralization,whereas the latter deposit is regarded as a Paleocene porphyry deposit. In the process of the evaluation of the Yaguila ore deposit, which is the largest lead-zinc deposit in the Gangdise metallogenic belt,the authors found that lead-zinc mineralization is closely related to the quartz porphyry body, and that a large-sized molybdenum vein occurs inside the intrusion body. U-Pb isotopic ages and trace element content of zircon crystals from the intrusion were measured by using LA-ICP-MS techniques. About 90% of the zircons have relatively high Th/U ratios and clear oscillatory zoning,indicating that they are of igneous origin. The acquired 206Pb/238U weighed average ages of LA-ICP-MS zircon U-Pb isotopes are 65.8±1.3 Ma (MSWD =3.0) and 68.6±1.7 Ma(MSWD=1.8), indicating that the quartz porphyry body was formed in the late Cretaceous period. Based on field investigation and an analysis of trace elements content of the quartz porphyry in combination with the Re-Os ages of the molybdenum vein obtained by previous researchers, the authors point out that both molybdenum and lead-zinc mineralizations are associated with the quartz porphyry, but Yaguila′s molybdenum was formed earlier than Sharang′s. It is concluded that not only lead-zinc mineralization but also molybdenum mineralization occurred in late Cretaceous in Nyainqentanglha region.

       

    /

    返回文章
    返回