摘要:甘肃阿克塞县安南坝地区镁铁质麻粒岩呈脉状或透镜状赋存于新太古代米兰岩群和TTG片麻岩中。岩石主要由斜方辉石（Opx）+单斜辉石（Cpx）+角闪石（Amp）+斜长石（Pl）+磁铁矿（Mt）等组成，具有典型中-低压麻粒岩相岩石的矿物组合特征。LA-ICP-MS锆石U-Pb测年结果显示镁铁质麻粒岩原岩形成时代可能为2 561±29 Ma，与塔里木东南缘2.6～2.5 Ga岩浆作用时代基本一致，说明新太古代晚期是塔里木东南缘重要的陆壳增生期。此外，通过测年还获得了～1.95 Ga、～1.86 Ga两期变质年龄。其中，～1.95 Ga的峰期变质年龄是塔里木克拉通东南缘古元古代晚期强烈构造—热事件的地质记录。～1.86 Ga的变质年龄可能与该地区古元古代末期构造—岩浆事件密切相关。镁铁质麻粒锆石176Hf/177Hf比值均＜0.281 621，εHf(t) 值为-14.08～3.12，两阶段模式年龄（TDM2）主要集中在～2.65 Ga，指示其原岩岩浆起源于新太古代富集岩石圈地幔。
关键词: 镁铁质麻粒岩/
锆石U-Pb年龄/
Hf同位素/
安南坝地区/
塔里木东南缘
Abstract:Mafic granulite as vein or len is commonly identified within Milan rock group and TTG gneiss formed in the Neoarchean in Annanba area of Aksai County，Gansu Province. The granulite is composed of orthopyroxene （Opx），clinopyroxene （Cpx），amphibole （Amp），plagioclase （Pl） and magnetite （Mt），which is the typical mineral assemblage of the medium-low pressure granulite facies rocks. The LA-ICP-MS zircon U-Pb dating of the granulite from Annanba area of Aksai，indicates that the formation age of the protolith of the mafic granulite is possibly 2 561±29 Ma，basically consistent with the age of magmatism of the southeastern Tarim （2.6～2.5 Ga），showing the significant continental crust accretion in Late Neoarchean. Two episodes of metamorphic ages are recognized in zircons of the mafic granulite. The older one has ages of ca.1.95 Ga，representing intense tectonothermal event of Late Paleoproterozoic age in the southeastern Tarim. In the meanwhile，the younger one with ages of ca.1.86 Ga might be closely related to the Late Paleoproterozoic tectonic-magmatic event in this area. The εHf(t)? of all analyses of zircons from the mafic granulite change from -14.08～3.12，176Hf/177Hf＜0.281 621，and the two stage Hf model ages are mainly concentrated in ca.2.65 Ga，which demonstrates that the mafic magmas of the granulite were derived from the Neoarchean enriched-type lithospheric mantle.
Key words:Mafic granulite/
Zircon U-Pb dating/
Hf isotopes/
Annanba area/
Southeastern Tarim
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