New Early Neoproterozoic Paleomagnetic Constraints of the Northwestern China Blocks on the Periphery of Rodinia
New Early Neoproterozoic Paleomagnetic Constraints of the Northwestern China Blocks on the Periphery of Rodinia
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DOI：
10.1029/2022jb024821
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发表时间：
2023-01
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影响因子：
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通讯作者：
Yan Xu;Shihong Zhang;Chuanlin Zhang;Xiantao Ye;Q. Ren;Yang Gao;Haiyan Li;Tianshui Yang;Huaichun Wu
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文献类型：
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作者：
Yan Xu;Shihong Zhang;Chuanlin Zhang;Xiantao Ye;Q. Ren;Yang Gao;Haiyan Li;Tianshui Yang;Huaichun Wu
近年来的研究表明，中国西北地区的板块，如塔北、塔南、阿尔金、柴达木-祁连等，在Rodinia的形成过程中的作用存在争议。本文对北方ATB的16条基性岩脉进行了古地磁、年代学和地球化学研究。在去除最近的粘性剩磁后，分离出三个特征剩磁分量（CH）。在8个北西向的闪长岩脉中识别出CH 1，其中一个通过SHRIMP斜锆石U-Pb方法测得的年龄为895.3 ± 7.7 Ma。它的平均方向（D/I）为123.3°/−42.2°（α95 = 12.1°）。通过对每个岩脉的8个虚拟地磁极（VGPs）进行平均，计算出古地磁极（40.9°S/184.6°E，A95 = 11.7°）。部分烘烤接触试验支持CH 1的主要来源。CH 2从三个东西向的展布岩脉中分离出来，指向西北方向，向下倾斜相当浅。CH 3是从5个层状岩脉中获得的，这些岩脉朝向东南方向，向上倾斜度从中等到浅。然而，CH 2或CH 3的VGP不足以平均精确的平均极点。地球化学分析也揭示了不同类型的脉岩的成因差异。结合全球古地磁数据库和CH 1新的1895 Ma极，结合地质证据，我们提出STB-ATB-QQB和华北克拉通在1895 Ma时位于沿着Rodinia Laurentia西北侧，并认为这种联系可能在1780 Ma之前一直保持完整。
Recent studies highlight the debates about the role of the northwestern China blocks, for example, north Tarim block, south Tarim block (STB), Altyn Tagh block (ATB) and Qaidam‐Qilian block (QQB) during the assembly of Rodinia. We herein present a combined paleomagnetic, geochronological, and geochemical study on 16 mafic dikes in the northern ATB. After removing a recent viscous remanent magnetization, three characteristic remanent magnetization components (CHs) were isolated. CH1 was identified in eight NW‐trending diabase dikes, one of which was newly dated at 895.3 ± 7.7 Ma through use of SHRIMP baddeleyite U‐Pb methodology. It yields a mean direction (D/I) of 123.3°/−42.2° (α95 = 12.1°). The paleopole (40.9°S/184.6°E, A95 = 11.7°) was calculated by averaging eight virtual geomagnetic poles (VGPs) from each dike. A partial baked‐contact test supports the primary origin of CH1. CH2 was isolated from three E‐W trending diabase dikes, pointing northwest with considerably shallower downward inclinations. CH3 was obtained from five lamprophyre dikes, directing southeast with moderate to shallow upward inclinations. However, the VGPs of either CH2 or CH3 are insufficient to average a precise mean pole. Geochemical analyses also reveal petrogenetic discrepancy among the dikes with distinct CHs. Combining the new ∼895 Ma pole of CH1 with the global paleomagnetic database and being aided by geological evidence, we propose that the STB‐ATB‐QQB and the north China craton were located along the northwestern side of Laurentia in Rodinia at ∼895 Ma, and suggest the connection might have been intact until ∼780 Ma.