Zircon and monazite U-Pb ages of the Mashan Complex of the Jiamusi Block of NE China: a link to Gondwana?
Zircon and monazite U-Pb ages of the Mashan Complex of the Jiamusi Block of NE China: a link to Gondwana?
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中国东北佳木斯地块马山杂岩的锆石和独居石 U-Pb 年龄：与冈瓦纳古陆的联系？
DOI：
10.1080/00206814.2021.1940321
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发表时间：
2021-08
影响因子：
2.6
通讯作者：
Kai Liu
中科院分区：
文献类型：
--
作者：
Maohui Ge;Zhuang Li;Long Li;Jinjiang Zhang;Kai Liu
近十年来，中国东北中亚造山带东部，特别是佳木斯地块的各微大陆的构造亲缘性一直备受争议。马山杂岩是佳木斯地块最古老的出露基底，由长英质麻粒岩、大理岩、石墨片岩和正长石组成，是研究佳木斯地块构造亲和性的关键地质单元。本文对马山杂岩花岗质片麻岩中的锆石和独辉石矿物进行LA-ICP-MS U-Pb定年，以约束佳木斯地块的亲和力。两个花岗质片麻岩的岩浆锆石加权平均206Pb/238U年龄分别为517±7 Ma和527±4 Ma，解释为原岩年龄。这些年龄资料证实了佳木斯地块的一次晚期泛非岩浆活动。某花岗质片麻岩变质锆石的加权平均206Pb/238U年龄为510±3 Ma，限制了马山杂岩体的变质时间。这一变质年龄进一步得到了独居石定年结果的支持——3个花岗质片麻岩样品的独居石加权平均206Pb/238U年龄分别为489±3 Ma、498±3 Ma和500±3 Ma，代表了这些独居石的变质再结晶年龄。这些资料一致表明，佳木斯地块在泛非晚期岩浆活动之后立即发生了区域性变质事件。我们的新数据，结合先前发表的佳木斯地块晚期泛非地质年代学数据，支持佳木斯地块与冈瓦纳的亲缘关系。
ABSTRACT The tectonic affinities of the microcontinents in the eastern Central Asian Orogenic Belt of NE China, particularly the Jiamusi Block, have been hotly debated in the last decade. The Mashan Complex, which is the oldest exposed basement of the Jiamusi Block and consists of khondalitic rocks (felsic granulite, marble, and graphite schist) and orthogneisses, is the key geological unit to look into the tectonic affinity of the Jiamusi Block. In this study, we carried out LA-ICP-MS U-Pb dating on zircon and monazite minerals from the granitic gneisses in the Mashan Complex, to constrain the affinity of the Jiamusi Block. Magmatic zircons from two granitic gneisses yielded weighted mean 206Pb/238U ages of 517 ± 7 Ma and 527 ± 4 Ma, respectively, which are interpreted as the protolith ages. These age data verify a late Pan-African magmatic event in the Jiamusi Block. Metamorphic zircons from one granitic gneiss gave a weighted mean 206Pb/238U age of 510 ± 3 Ma, which constrained the metamorphic time of the Mashan Complex. This metamorphic age is further supported by monazite dating results – the monazites from three granitic gneiss samples yielded weighted mean 206Pb/238U ages of 489 ± 3 Ma, 498 ± 3 Ma, and 500 ± 3 Ma, respectively, which represented the metamorphic recrystallization ages of these monazites. These data consistently indicate a regional metamorphic event immediately after the late Pan-African magmatism in the Jiamusi Block. Our new data, combined with previously published late Pan-African geochronological data from the Jiamusi Block, support that the Jiamusi Block has an affinity to the Gondwana.
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