CAJ | 학술논문

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500Ma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550Ma到弱不一致1900Ma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546～1460Ma表明，该闪长岩大约在1400Ma就位，并受到500Ma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。
중국동북지구가목사지괴남부마산잡암정、부편마암7개양품적고석SHRIMP년령수거수차명학지표명，동북지구존재500Ma적만범비기고급변질작용사건。봉기마립암상변질도치류모지구(502±10)Ma(2σ)심용화강암적형성。정、부편마암변질년령적일치성표명타문이재변질전발생료구조첩치。서마산부편마암중함유재후기마립암상변질과정중미중결정적쇄설고석，유차형성종협화일치적550Ma도약불일치1900Ma적교대207Pb／206Pb년령변화범위，표명기원암구유종신원고대도중원고대-고원고대적년령。류모지구변질적편마상섬장암중소함적고로고석적207Pb／206Pb년령위546～1460Ma표명，해섬장암대약재1400Ma취위，병수도500Ma변질사건적영향，종이설명류모지구존재중원고대기저。연이，여이전적인식상반，마산잡암불존재구유태고주기저적동위소증거。만범비기변질사건년령적학정대중소만전한무기-현생주조기마산잡암화가목사지괴적고지리위치구유중요의의。근거목전획득적유관증거，인위가목사지괴가능증경위우강와납대륙북연적화북극랍통부근。
SHRIMP U-Pb zircon dating of seven samples of ortho- andparagneisses 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 460Ma. 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.