扬子陆核古元古代变质事件——来自孔兹岩系变质锆石U-Pb同位素年龄的证据

    Paleoproterozoic metamorphic event in the nucleus of the Yangtze craton:Evidence from U-Pb geochronology of the metamorphic zircons from the khondalite

    • 摘要: 崆岭杂岩除太古宙结晶基底外,还出露一套以含石墨和富铝矿物为特征的孔兹岩系。相对于结晶基底,目前对于该套表壳岩系的同位素年代学研究有限。对该套孔兹岩系中代表性岩石类型榴线英岩开展了变质锆石U-Pb同位素年龄测定。研究结果表明,榴线英岩变质年龄为1964±12Ma。结合前人在相近地层岩石组合中报道的锆石U-Pb年龄数据,推测崆岭杂岩孔兹岩系原岩可能沉积于2.1~2.0Ga。扬子陆核的古元古代变质-岩浆作用可能与全球广泛存在的同时期(2.1~1.8Ga)碰撞造山事件有关,暗示其很可能是Columbia超大陆的重要组成部分。

       

      Abstract: Apart from the Archean metamorphic crystal basement, a series of khondalite-bearing graphites and Al-rich minerals are exposed in the Kongling Complex.However, relative to the study of metamorphic crystal basement, geochronological studies of the supracrustal rocks are still very insufficient.In this study, the LA-ICP-MS zircon U-Pb study was carried out for the typical samples of garnet-sillimanite quartzite in the khondalite series.The result shows that the garnet-sillimanite-quartzite was metamorphosed at 1964±12Ma.Combined with the documented zircon U-Pb geochronologic data, the authors hold that the khondalite-series in the Kongling Complex was deposited at 2.1~2.0Ga.The Paleoproterozoic metamorphism and magmatism recognized in the interior of the Yangtze craton are consistent with the worldwide coeval collision-related orogenic event during 2.1~1.8Ga, indicating that this event may have been an important component in the Columbia supercontinent.

       

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