【摘要】 中国东北地区佳木斯地块南部麻山杂岩正、副片麻岩 7个样品的锆石 SHRIMP年龄数据首次明确地表明 ,东北地区存在 500 Ma的晚泛非期高级变质作用事件。峰期麻粒岩相变质导致柳毛地区 (502± 10)Ma (2σ )深熔花岗岩的形成。正、副片麻岩变质年龄的一致性表明它们已在变质前发生了构造叠置。西麻山副片麻岩中含有在后期麻粒岩相变质过程中未重结晶的碎屑锆石，由此形成从协和一致的 550 Ma到弱不一致 1 900 Ma的较大 207Pb/206Pb年龄变化范围，表明其原岩具有从新元古代到中元古代-古元古代的年龄。柳毛地区变质的片麻状闪长岩中所含的古老锆石的 207Pb/206Pb年龄为 546～ 1 460 Ma表明，该闪长岩大约在 1 400 Ma就位，并受到 500 Ma变质事件的影响，从而说明柳毛地区存在中元古代基底。然而，与以前的认识相反，麻山杂岩不存在具有太古宙基底的同位素证据。晚泛非期变质事件年龄的确定对重塑晚前寒武纪-显生宙早期麻山杂岩和佳木斯地块的古地理位置具有重要意义。根据目前获得的有关证据，认为佳木斯地块可能曾经位于冈瓦纳大陆北缘的华北克拉通附近。更多还原

【Abstract】 SHRIMP U- Pb zircon dating of seven samples of ortho- and paragneisses obtained from the southern outcrop of the Mashan Complex provides the first conclusive evidence for a～ 500 Ma Late Pan- African high- grade metamorphic event in northeastern China. Peak granulite facies metamorphism resulted in the production of local anatectic granite at Liumao and this gives a 206Pb/238U age of (502± 10) Ma (2σ ). There is no distinction between the metamorphic age of the ortho- and paragneisses, indicating that they were tectonically interleaved prior to metamorphism. Paragneisses from Ximashan contain evidence of detrital zircons that were not recrystallised during the granulite facies metamorphism. These show a spectrum of concordant to weakly discordant 207Pb/206Pb ages from～ 550 Ma to 1 900 Ma, indicating source rocks of Neoproterozoic, Mesoproterozoic and Palaeoproterozoic age. A metamorphosed gneissic diorite from Liumao also contains older zircons, with 207Pb/206Pb ages from 546 Ma to 1 460 Ma. These are interpreted to represent an igneous source rock, emplaced～ 1 400 Ma ago and variously affected by the 500 Ma metamorphic event. This indicates the presence of Mesoproterozoic basement in the Liumao area. However, contrary to previous views, there is no isotopic evidence that Archaean rocks are present in the Mashan Complex. The Late Pan- African age of metamorphism is important when considering the location of the Mashan Complex and Jiamusi Massif during the late Precambrian to early Phanerozoic. On the available evidence, it is argued that the Jiamusi Massif was most likely located close to the North China Craton, on the northern margin of Gondwanaland.更多还原