The northern Qiangtang Block rapid drift during the Triassic Period: Paleomagnetic evidence
The northern Qiangtang Block rapid drift during the Triassic Period: Paleomagnetic evidence
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DOI：
10.1016/j.gsf.2019.05.003
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发表时间：
2019-11
影响因子：
8.9
通讯作者：
Yanan Zhou;Xin-Yuan Cheng;Yiying Wu;V. Kravchinsky;R. Shao;Weijie Zhang;Bitian Wei;Ruiyao Zhang-Ruiya
中科院分区：
文献类型：
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作者：
Yanan Zhou;Xin-Yuan Cheng;Yiying Wu;V. Kravchinsky;R. Shao;Weijie Zhang;Bitian Wei;Ruiyao Zhang-Ruiya
青藏高原北方羌塘地块作为冈瓦纳大陆的重要派生地块之一，其运动学历史至今仍不清楚，主要原因是缺乏定量的古地磁资料来确定其古位置。为此，我们在北方羌塘地块（NQB）的拉焦查卡和沱沱河地区的三叠纪沉积岩中采集了226个样品（17个点）。逐步退磁隔离高温/场分量从样品。早三叠世和晚三叠世的数据集都以99%的置信水平通过了野外测试，并被证明是原生的。结合已发表的火山岩资料，计算出早三叠世古极点位于24.9°N，216.5°E，A95 = 8.2°（N= 8），晚三叠世古极点位于68.1°N，179.9°E，A95 = 5.6°（N= 37）。这些古极点分别对应于14.3°S±8.2°和29.9°N±5.6°的古纬度。结合以前发表的结果，我们重建了一个三阶段的北漂移过程的NQB。(1)早三叠世前，北方羌塘地块位于南半球的亚热带地区;（2）晚三叠世，该地块从南半球向北方半球迅速漂移;（3）晚三叠世，该地块与欧亚大陆汇合。早三叠世至晚三叠世向北运动了约4800 km，平均运动速率为11.85 cm/a。早三叠世之后，NQB的快速漂移导致了特提斯洋的快速转变。
As one of the pivotal Gondwana–derived blocks, the kinematic history of the northern Qiangtang Block (in the Tibetan Plateau) remains unclear, mainly because quantitative paleomagnetic data to determine the paleoposition are sparse. Thus, for this study, we collected 226 samples (17 sites) from Triassic sedimentary rocks in the Raggyorcaka and Tuotuohe areas of the northern Qiangtang Block (NQB). Stepwise demagnetization isolated high temperature/field components from the samples. Both Early and Late Triassic datasets passed field tests at a 99% confidence level and were proved to be primary origins. Paleopoles were calculated to be at 24.9°N and 216.5°E withA95= 8.2°(N= 8) for the Early Triassic dataset, and at 68.1°N, 179.9°E withA95= 5.6° (N= 37) for the Late Triassic, the latter being combined with a coeval volcanic dataset published previously. These paleopoles correspond to paleolatitudes of 14.3°S±8.2° and 29.9°N±5.6°, respectively. Combining previously published results, we reconstructed a three-stage northward drift process for the NQB. (1) The northern Qiangtang Block was located in the subtropical part of the southern hemisphere until the Early Triassic; (2) thereafter, the block rapidly drifted northward from southern to northern hemispheres during the Triassic; and (3) the block converged with the Eurasian continent in the Late Triassic. The ∼4800 km northward movement from the Early to Late Triassic corresponded to an average motion rate of ∼11.85 cm/yr. The rapid drift of the NQB after the Early Triassic led to a rapid transformation of the Tethys Ocean.