蒙古国Oyu Tolgoi外围碱长花岗岩LA-ICP-MS锆石U-Pb定年及其地质意义

LA-ICP-MS zircon U-Pb dating of alkali-feldspar granite on the periphery of the Oyu Tolgoi deposit, Mongolia, and its geological significan

摘要: 位于蒙古国Oyu Tolgoi超大型斑岩型铜-金矿床南20km的碱长花岗岩区, 构造上处于西伯利亚板块南缘近东西向和北东向深大断裂所挟持的戈壁-天山古生代岛弧带内。利用LA-ICP-MS U-Pb同位素测年法对研究区碱长花岗岩中的锆石进行高精度的年代学测试, 获得²⁰⁶Pb/²³⁸U年龄加权平均值为286.00± 0.91Ma, 为早二叠世。研究区具有多期次成岩、成矿特征, 本次定年不仅为该区多期次岩浆活动提供了直接的年龄证据, 也为该区找矿指明了方向。

Abstract: The alkali-feldspar granite of the study area located 20km south of the superlarge Oyu Tolgoi Cu-Au deposit. The tecton-ic setting of the study area belongs to Paleozoic island arc zone of Gobi-Tianshan controlled by intersection of the near-latitudinal fault and an oblique transverse fault on the south margin of Siberian plate. A sample was collected from Onealkali-feldspar granite, and CL characteristics of zircons suggest magmatic origin. LA-ICP-MS U-Pb dating of zircon from the sample shows that the em-placing age is 286.0± 0.91Ma (MSWD=1.4), belonging to Permian period. The study area is characterized by multiperiodic diagenesis and mineralization. The isotope age provides not only the direct evidence for the multiperiodic magmatic activities but also the pros-pecting direction for the study area.