Pre-Rodinia supercontinent Nuna shaping up: A global synthesis with new paleomagnetic results from North China
Pre-Rodinia supercontinent Nuna shaping up: A global synthesis with new paleomagnetic results from North China
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DOI：
10.1016/j.epsl.2012.07.034
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发表时间：
2012-11
影响因子：
5.3
通讯作者：
Shihong Zhang;Zheng‐Xiang Li;D. Evans;Huaichun Wu;Haiyan Li;Jin Dong
中科院分区：
文献类型：
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作者：
Shihong Zhang;Zheng‐Xiang Li;D. Evans;Huaichun Wu;Haiyan Li;Jin Dong
在过去的十年里，人们普遍推测存在一个前罗迪尼亚前寒武纪超大陆，称为努纳或哥伦比亚，但由于缺乏明确的古地磁和地质约束，其存在的确切时间和结构一直不确定。本文报道了华北陆块南部熊耳群1780年的高质量古地磁结果。共采集了14个站点的110个古地磁样品，并进行了分步热退磁。在去除了近代地磁场中获得的粘滞剩磁的低温分量（CL）后，分离出了红层和火山岩样品中的赤铁矿和磁铁矿所携带的高温分量（CH）。经层理校正后，其平均方向为（D=18.4°，I=−3.7°，α95=7.6°，N=14），对应的古磁极为50.2°N，263.0°E（A95=4.5°）。CH通过了反向测试，并被解释为一次剩磁。这一新的极和另外三个NCB高质量的极（1769± 3 Ma、1560- 1440 Ma和1437± 21 Ma）确定了NCB的1780- 1440 Ma视极移轨迹（APWP）。这与全球高质量古地磁数据集的更新一起，使我们能够证明前Rodinia超大陆Nuna可能至少存在于1780 Ma和1400 Ma之间。我们的基于古地磁学的全球重建，第一次定量地将所有主要的古地磁子聚集在一起;它包括以前提出的区域连接，包括波罗的海、亚马逊河和西非之间的桑巴舞连接（Johansson，2009），劳伦蒂亚，波罗的海和西伯利亚之间的连接在努纳的核心（Evans和Mitchell，2011年），劳伦蒂亚、东南极洲和澳大利亚地块之间的原始SWEAT连接（Payne等人，2009年）和国家协调局与印度的联系（Zhao等人，2011年）。
The existence of a pre-Rodinia Precambrian supercontinent, variously called Nuna or Columbia, has been widely speculated in the past decade, but the precise timing of its existence and its configuration have been uncertain due to the lack of unequivocal paleomagnetic and geological constraints. Here we report high-quality paleomagnetic results from the well dated ∼1780Ma Xiong'er Group in southern North China Block (NCB). A total of 110 paleomagnetic samples from 14 sites were collected and subjected to stepwise thermal demagnetization. After removing a low temperature component (CL) of viscous magnetic remanence acquired in recent geomagnetic field, a high temperature component (CH), carried by hematite and magnetite in redbeds and volcanic samples, has been isolated. It gives a mean direction of (D=18.4°, I=−3.7°, α95=7.6°, N=14) after bedding correction, and a corresponding paleomagnetic pole at 50.2°N, 263.0°E (A95=4.5°). The CH passed a reversal test and was interpreted as a primary remanence. This new pole plus three other high-quality poles from the NCB that have been more precisely dated at 1769±3Ma, 1560–1440Ma and 1437±21Ma define a 1780–1440Ma apparent polar wander path (APWP) for the NCB. This, together with an update of global high quality paleomagnetic dataset, allows us to demonstrate that the pre-Rodinia supercontinent Nuna likely existed at least between ∼1780Ma and ∼1400Ma. Our paleomagnetism-based global reconstruction, for the first time, quantitatively assembles all major cratons together; it encompasses previously proposed regional links including the SAMBA connection between Baltica, Amazonia and Western Africa (Johansson, 2009), connections between Laurentia, Baltica and Siberia at the core of Nuna (Evans and Mitchell, 2011), the proto-SWEAT connection between Laurentia, East Antarctica and Australian blocks (Payne et al., 2009), and the NCB–India connection (Zhao et al., 2011).