Geochemistry of the subduction-related magmatic rocks in the Dahong Mountains, northern Hubei Province——Constraint on the existence and subduction of the eastern Mianle oceanic basin
Geochemistry of the subduction-related magmatic rocks in the Dahong Mountains, northern Hubei Province——Constraint on the existence and subduction of the eastern Mianle oceanic basin
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DOI：
10.1360/02yd0486
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发表时间：
2004-04
影响因子：
5.7
通讯作者：
Dong Yunpeng;Zhang Guowei;Zhaojun Xia;Y. Anping;L. Xiaoming
中科院分区：
文献类型：
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作者：
Dong Yunpeng;Zhang Guowei;Zhaojun Xia;Y. Anping;L. Xiaoming
南秦岭东部勉略洋盆的存在和俯冲是认识秦岭造山带的关键。在地质填图的基础上，在图们、周家湾、孝浮和元潭地区发现了若干火山岩片，它们分布在大红山北缘，并向三里岗-三阳断裂中逆冲。这些岩片主要由辉绿岩、玄武岩-安山岩、火山碎屑岩和少量凝灰岩组成。玄武岩、安山岩和辉绿岩的地球化学特征是亏损Nb和Ta，富含Th和LILE(如K、Rb、Ba)，在HFSE中未分异。这些地球化学特征表明，这些岩石的原始岩浆起源于俯冲带上方的地幔楔体，形成于石炭纪-早三叠世的岛弧环境。通过与勉县-略阳地区以西蛇绿岩和岛弧火山岩的对比，认为该区存在沿桐柏-大别地块南缘向西与勉略古洋相连的洋盆。根据华山地区的蛇绿岩和大洪山以北的岛弧火山岩，认为该区曾经历过洋盆裂谷俯冲的板块构造演化史。
The existence and subduction of the eastern Mianlue oceanic basin in the south Qinling belt are keys to understand the Qinling orogen. Based on geological mapping, several volcanic slices have been identified in Tumen, Zhoujiawan, Xiaofu and Yuantan areas, which distribute in the northern margin of the Dahong Mountains (DHM), and thrust into the Sanligang-Sanyang fault. These slices consist mainly of diabases, basaltic-andesitic lavas, pyroclastic rocks and a minor tuff. The geochemistry of the basalts, andesites，and diabases is characterized by depleting in Nb and Ta, enriching in Th and LILE (e.g.K, Rb, Ba), and undifferentiating in HFSE. These geochemical characteristics suggest that the original magma of these rocks was derived from a mantle wedge above a subduction zone, and formed in an island-arc setting in Carboniferous-early Triassic. Comparing with the ophiolites and island-arc volcanic rocks in Mianxian-Lueyang area to the west, it is reasonable to consider that there had been an oceanic basin connecting with the Mianlue ancient ocean to the westward, distributing along the south edge of the Tongbai-Dabie block. In view of the ophiolite in Huashan area and these island-arc volcanic rocks along the north of the Dahong Mountains, it is suggested that there had been a plate tectonic evolutionary history with oceanic basin rifting and subduction in this region.