Mesoproterozoic magmatism redefines the tectonics and paleogeography of the SW Yangtze Block, China
Mesoproterozoic magmatism redefines the tectonics and paleogeography of the SW Yangtze Block, China
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DOI：
10.1016/j.precamres.2022.106558
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发表时间：
2022-03
影响因子：
3.8
通讯作者：
Guimei Lu;C. Spencer;Xin Deng;Yang Tian;Bin-Shu Huang;Yingyan Jiang;Wei Wang
中科院分区：
文献类型：
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作者：
Guimei Lu;C. Spencer;Xin Deng;Yang Tian;Bin-Shu Huang;Yingyan Jiang;Wei Wang
由于文献资料有限，对重建的罗迪尼亚超大陆中元古代晚期扬子地块的地球动力学背景及其古地理的界定较为松散。在此贡献中，我们在扬子西南部发现了一套新的角闪岩，其就位年龄为1175±5 Ma。地球化学模拟表明，它们来源于尖晶石-辉橄榄岩地幔的低程度（3.5% ~ 6.5%）部分熔融。此外，通过提供新的锆石U-Pb-Hf-O同位素和全岩地球化学数据，对扬子西南地块3套晚中元古代花岗岩进行了重新研究。花岗岩的侵位时间为1060 ~ 1042 Ma， Zr + Nb + Y + Ce和tzr值分别在304 ~ 576 ppm和831 ~ 886℃，与a型花岗岩相似。锆石Hf-O同位素数据显示出两个花岗岩亚群，其中一组超球粒体εHf(t)值为+ 2.4 ~ + 11.4，δ18O值为6.5‰~ 7.4‰；另一组εHf(t)值为- 3.9 ~ +1.5，δ18O值为10.0‰~ 11.6‰。第一类花岗岩主要来源于基性拉斑岩的部分熔融作用，第二类花岗岩主要来源于变质沉积岩的部分熔融作用。结合已发表的研究成果，我们认为在~ 1.2 ~ 1.04 Ga期间，西南扬子地块发育了一个陆内裂谷盆地，这与西南扬子地块晚中元古代造山事件相矛盾。对Laurentia、Yangzte和Amazonia的锆石U-Pb-Hf同位素进行统计分析表明，扬子与西努纳具有同位素亲和力。在从努纳/哥伦比亚到罗迪纳的过渡过程中，这些大陆可能沿着罗迪纳超大陆的西部边缘保持统一。
The geodynamic setting of the Yangtze Block and its paleogeography in the reconstructed Rodinia supercontinent during the late Mesoproterozoic is loosely constrained due to the limited geological information reported. In this contribution, we identify a new suite of amphibolites in the SW Yangtze with an 1175 ± 5 Ma emplacement age. Geochemical modeling demonstrates they were derived from low-degree (3.5%–6.5%) partial melting of spinel lherzolite mantle. Additionally, three suites of late Mesoproterozoic granites in the SW Yangtze Block are revisited by providing new zircon U-Pb-Hf-O isotopes and whole-rock geochemical data. The granites have been dated to emplace during 1060–1042 Ma and have Zr + Nb + Y + Ce and Tzrvalues mostly at 304–576 ppm and 831–886 ℃, respectively, similar to A-type granites. Zircon Hf-O isotopic data indicate two subgroups of granites, in which one group has suprachondritic εHf(t) values of + 2.4 to + 11.4 with δ18O values of 6.5‰ to 7.4‰ while the other group has εHf(t) values of −3.9 to +1.5 with δ18O values of 10.0‰–11.6‰. The first group of granites was mainly derived from partial melting of mafic tholeiitic rocks while the second group of granites was mainly formed by partial melting of metasedimentary rocks. Integrated with published work, we propose that an intra-continental rift basin was developed in the SW Yangtze Block during ∼ 1.2–1.04 Ga, arguing against a late Mesoproterozoic orogenic event in the SW Yangtze Block. Statistical analyses based on compiled zircon U-Pb-Hf isotopes from Laurentia, Yangzte, and Amazonia show that the Yangtze has an isotopic affinity with west Nuna. These continents likely remained united during the transition from Nuna/Columbia to Rodina along the western periphery of the Rodinia supercontinent.