Paleomagnetic results from Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane, Tibet, China, and their tectonic implications
Paleomagnetic results from Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane, Tibet, China, and their tectonic implications
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西藏羌塘地体北部晚石炭世—早二叠世岩石的古地磁结果及其构造意义
DOI：
10.1007/s11430-015-5462-7
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
WU HanNing
中科院分区：
文献类型：
--
作者：
YANG XingFeng;CHENG Xin;ZHOU YaNan;MA Lun;ZHANG XiaoDong;YAN ZhaoSheng;PENG XiMing;SU HaiLun;WU HanNing
本文报道了西藏北方羌塘地区唐古拉山北坡晚石炭世-早二叠世沉积岩的系统古地磁研究结果。资料显示，扎日根组（CP^z）石灰岩样品中的磁性矿物主要为磁铁矿，而诺日巴格日堡组（Pnr）砂岩样品中的磁性矿物主要为赤铁矿或赤铁矿与磁铁矿的混合物。渐进的热，或交变场，退磁使我们能够隔离一个稳定的高温组件（HTC）在127个标本从16个网站成功地通过了砾岩测试，符合初级残留。北方羌塘盆地晚石炭世-早二叠世岩石倾斜校正后的平均方向为Ds =30.2°，Is=-40.9 °，ks=269.0，α95=2.3°，N=16，对应的古磁极为25.7°N，241.5°E（dp/dm=2.8°/1.7°），古纬度为23.4°S。结合已有的古地磁资料，我们认为：（1）西藏北青藏高原位于南半球低纬度地区，在晚石炭世-早二叠世可能属于冈瓦纳北方边缘;（2）晚石炭世-早二叠世古特提斯洋规模较大;（3）NQT随后迅速向北移动，这可能与古特提斯洋在晚二叠世至晚三叠世快速收缩，而新特提斯洋北方分支班公湖-怒江洋在这一时期快速扩张有关。
Results of a systematic paleomagnetic study are reported based on Late Carboniferous to Early Permian sedimentary rocks on the north slope of the Tanggula Mountains, in the northern Qiangtang terrane (NQT), Tibet, China. Data revealed that magnetic minerals in limestone samples from the Zarigen Formation (CP^z)are primarily composed of magnetite, while those in sandstone samples from the Nuoribagaribao Formation (Pnr) are dominated by hematite alone, or hematite and magnetite in combination. Progressive thermal, or alternating field, demagnetization allowed us to isolate a stable high temperature component (HTC) in 127 specimens from 16 sites which successfully passed the conglomerate test, consistent with primary remnance. The tilt-corrected mean direction for Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane isDs=30.2°,Is=- 40.9°,ks=269.0,α95=2.3°,N=16, which yields a corresponding paleomagnetic pole at 25.7°N, 241.5°E (dp/dm=2.8°/1.7°), and a paleolatitude of 23.4°S. Our results, together with previously reported paleomagnetic data, indicate that: (1) the NQT in Tibet, China, was located at a low latitude in the southern hemisphere, and may have belonged to the northern margin of Gondwana during the Late Carboniferous to Early Permian; (2) the Paleo-Tethys Ocean was large during the Late Carboniferous to Early Permian, and (3) the NQT subsequently moved rapidly northwards, perhaps related to the fact that the Paleo-Tethys Ocean was rapidly contracting from the Late Permian to Late Triassic while the Bangong Lake-Nujiang Ocean, the northern branch of the Neo-Tethys Ocean, expanded rapidly during this time.
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