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| Compositional Variation and Mineral Chemistry of the Jinshajiang and Lancangjiang Serpentinites, Yunnan Province, SW China | |
| 作者姓名： | Ahmed E.I. MASOUD YANG Jingsui and LIU Fei |
| 作者单位： | 1 State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China；2 Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China；3 Geology Department, Faculty of Science, Tanta University, Tanta, Egypt |
| 摘 要： | We present the whole rock and the mineral chemical data for upper mantle peridotites from the San-Jiang region in Yunnan, SW China. These peridotites are a part of a Paleo-Tethyan ophiolite belt occurring along the Jinshajiang and Lancangjiang suture zones. All samples of the Jinshajiang and Lancangjiang ultramafic rocks are completely serpentinized. The Jinshajiang serpentinites are characterized by no relict of olivine and pyroxene, and the Cr# content of spinels is 0.32–0.49. The Lancangjiang serpentinites were collected from two different locations; the northern location which has some relict of Opx(Al2O3 is 0.13–2.2 wt%, TiO 2 is 0.004–0.057 wt% and Mg# content is 0.895–0.933) and the Cr# content of spinel is 0.26-0.55; the southern location, which has some relict of Olivine(Fo = 90–92.5 and NiO = 0.12–0.26 wt%), and spinel Cr# ranging from 0.41 to 0.57. The whole rock geochemical and the mineral chemistry data imply that the Jinshajiang and Lancangjiang serpentinites represent abyssal peridotites residues after ~15–20% partial melting for the Jinshajiang and Lancangjiang serpentinites(south location), and ~11–19% partial melting for the Lancangjiang serpentinites(north location). In addition, the compositional trends of the spinel analyses of the Lancangjiang serpentinites imply that the MORB melt-peridotite interaction process played a significant role during their evolution. These processes are evidenced by an increase in Cr# with an increase in TiO 2, whereas the spinel analyses of the Jinshajiang serpentinites display an increase in Cr# with a decrease in Ti O2, indicating that the Jinshajiang serpentinites were subjected to a simple partial melting process. |
| 关 键 词： | Key words: chromite Jinshajiang ophiolite Lancangjiang ophiolite |
| 收稿时间： | 2014/2/25 0:00:00 |
| 修稿时间： | 2014/8/12 0:00:00 |
Compositional Variation and Mineral Chemistry of the Jinshajiang and Lancangjiang Serpentinites,Yunnan Province,SW China |
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| Authors: | Ahmed EIMASOUD YANG Jingsui LIU Fei |
| Institution: | 1. State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China;Geology Department, Faculty of Science, Tanta University, Tanta, Egypt 2. State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China 3. State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
| Abstract: | We present the whole rock and the mineral chemical data for upper mantle peridotites from the San‐Jiang region in Yunnan, SW China. These peridotites are a part of a Paleo‐Tethyan ophiolite belt occurring along the Jinshajiang and Lancangjiang suture zones. All samples of the Jinshajiang and Lancangjiang ultramafic rocks are completely serpentinized. The Jinshajiang serpentinites are characterized by no relict of olivine and pyroxene, and the Cr# content of spinels is 0.32–0.49. The Lancangjiang serpentinites were collected from two different locations; the northern location which has some relict of Opx (Al2O3 is 0.13–2.2 wt%, TiO2 is 0.004–0.057 wt% and Mg# content is 0.895–0.933) and the Cr# content of spinel is 0.26–0.55; the southern location, which has some relict of Olivine (Fo = 90–92.5 and NiO = 0.12–0.26 wt%), and spinel Cr# ranging from 0.41 to 0.57. The whole rock geochemical and the mineral chemistry data imply that the Jinshajiang and Lancangjiang serpentinites represent abyssal peridotites residues after ～15–20% partial melting for the Jinshajiang and Lancangjiang serpentinites (south location), and ～11–19% partial melting for the Lancangjiang serpentinites (north location). In addition, the compositional trends of the spinel analyses of the Lancangjiang serpentinites imply that the MORB melt‐peridotite interaction process played a significant role during their evolution. These processes are evidenced by an increase in Cr# with an increase in TiO2, whereas the spinel analyses of the Jinshajiang serpentinites display an increase in Cr# with a decrease in TiO2, indicating that the Jinshajiang serpentinites were subjected to a simple partial melting process. |
| Keywords: | chromite Jinshajiang ophiolite Lancangjiang ophiolite |
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