Geochronology, petrogenesis and tectonic implications of the Jurassic Namco–Renco ophiolites, Tibet
Geochronology, petrogenesis and tectonic implications of the Jurassic Namco–Renco ophiolites, Tibet
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DOI：
10.1080/00206814.2015.1017776
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发表时间：
2015-03
影响因子：
2.6
通讯作者：
Yun Zhong;B. Xia;Weiliang Liu;Zheng-xin Yin;Xi-chong Hu;Wei Huang
中科院分区：
文献类型：
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作者：
Yun Zhong;B. Xia;Weiliang Liu;Zheng-xin Yin;Xi-chong Hu;Wei Huang
拉萨郊区北方纳木错-仁科蛇群的性质存在广泛争议。为了研究它们的形成时代、岩石成因和构造环境，选择纳木错蛇绿岩的方辉橄榄岩、玄武岩和变辉长岩以及仁科蛇绿岩的方辉橄榄岩、二辉橄榄岩、辉长岩和辉绿岩脉进行全岩地球化学和锆石U-Pb定年和原位Lu-Hf同位素分析。地球化学和年代学资料表明，纳木错变辉长岩形成于178.0 ± 2.9 Ma，沿着纳木错-伦科橄榄岩形成于大陆边缘盆地的初始阶段;伦科辉长岩形成于149.7 ± 1.6 Ma，沿着伦科闪长岩脉和纳木错玄武岩形成于成熟的弧后盆地。纳木错-伦科蛇绿岩是由亏损地幔源区和少量较老地壳物质共同形成的。结合区域地质背景，纳木错-仁科蛇绿岩的形成可能主要与班公湖-怒江洋壳向南俯冲到拉萨盆地之下有关。该研究为纳木错-伦科蛇绿岩的形成时代和纳木错-伦科洋的构造演化提供了新的制约。
The nature of the Namco–Renco ophiolites in the northern Lhasa subterrane is widely disputed. To investigate their formation age, petrogenesis, and tectonic setting, the harzburgites, basalts, and metagabbros of the Namco ophiolite and the harzburgites, lherzolites, gabbros, and diabasic dikes of the Renco ophiolite were selected for whole-rock geochemical and zircon U-Pb dating and in situ Lu-Hf isotopic analyses. The geochemical and geochronological data indicate that the Namco metagabbros were generated at 178.0 ± 2.9 Ma, along with the Namco–Renco peridotites formed in the initial stage of a continental margin basin; whereas the Renco gabbros were developed at 149.7 ± 1.6 Ma, along with the Renco diabasic dikes and Namco basalts formed later in a mature back-arc basin. The Namco–Renco ophiolites were derived from a depleted mantle source with involvement of minor older crustal materials. Combined with the regional geological background, the Namco–Renco ophiolites were likely formed mainly associated with the southward subduction of the Bangong–Nujiang oceanic lithosphere beneath the Lhasa terrane. This study provides new constraints on the formation ages of the Namco–Renco ophiolites and the tectonic evolution of the Namco–Renco Ocean.