| Fluid-Rock Interaction of Shear Zones in Continental Crust:as Evidenced by Xincheng-Xishui and Hetai Shear Zones |
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| 作者姓名： | Zhong Zengqiu You Zhendong Xu QidongFaculty oj Earth Sciences China University of Geosciences Wuhan |
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| 作者单位： | Zhong Zengqiu You Zhendong Xu QidongFaculty oj Earth Sciences，China University of Geosciences，Wuhan 430074 |
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| 基金项目： | The study is sponsored by the National Natural Science Foundation of China (No.49172090 ) and supported by the Open Laboratory of Crust- Mantle Constitution, Recycling and Dynamics of Ministry of Geology and Mineral Resources |
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| 摘 要： | There is a coupling of thermal, mechanical, chemical and fluidal processes in a continental shear zone. Both Xincheng-Xishui and Hetai shear zones are typical continental crust shear zones of greenschist facies environment. The representative mylonite zones of the shear zones are studied with whole rock major and trace element analyses. The chemical compositional variation tendencies in both shear zones are very similar and the gain-loss ratios of various components in the mylonitic rocks are reflected in the mass balance equations. The enrichment of those immobile high-field-strengh elements is considered to he related to the volume loss of the myionitic rocks in a shear zone. Based on the volume loss expression C_s/C_o=1/(1-V),the fractional volume losses (V)are 37.5％ and 36.5％-42.3％ respectively for mylonites and ultramylonites in the Xincheng-Xishui shear zone and 11％ and 28％ respectively for mylonites and phyllonites in the Hetai shear zone. The high volume loss and large removal of SiO_2 from
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Fluid-Rock Interaction of Shear Zones in Continental Crust: as Evidenced by Xincheng-Xishui and Hetai Shear Zones |
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| Zhong Zengqiu You Zhendong Xu QidongFaculty oj Earth Sciences,China University of Geosciences,Wuhan .Fluid-Rock Interaction of Shear Zones in Continental Crust:as Evidenced by Xincheng-Xishui and Hetai Shear Zones[J].Journal of China University of Geosciences,1995(2). |
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| Authors: | Zhong Zengqiu You Zhendong Xu QidongFaculty oj Earth Sciences China University of Geosciences Wuhan |
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| Institution: | Zhong Zengqiu You Zhendong Xu QidongFaculty oj Earth Sciences,China University of Geosciences,Wuhan 430074 |
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| Abstract: | There is a coupling of thermal, mechanical, chemical and fluidal processes in a continental shear zone. Both Xincheng - Xishui and Hetai shear zones are typical continental crust shear zones of greenschist facies environment. The representative mylonite zones of the shear zones are studied with whole rock major and trace element analyses. The chemical compositional variation tendencies in both shear zones are very similar and the gain - loss ratios of various components in the mylonitic rocks are reflected in the mass balance equations. The enrichment of those immobile high - field- strengh elements is considered to be related to the volume loss of the mylonitic rocks in a shear zone. Based on the volume loss expression Cs /Co = 1/(1- V), the fractional volume losses (V) are 37.5% and 36.5%-42.3% respectively for mylonites and ultramylonites in the Xincheng-Xishui shear zone and 11 % and 28% respectively for mylonites and phyllonites in the Hetai shear zone. The high volume loss and large removal of SiO2 from the system imply that there is a large amount of percolating fluids in the shear zones. From the SiO2 loss, the fluid/rock ratios (N) are calculated as Nmyl = 113 - 563, Nultramyl= 133-664 for the Xincheng-Xishui shear zone and Nmyl=42-208, Nphyl=110-550 for the Hetai shear zone. Such a large amount of percolating fluid must have profoundly affected the rheological behavior, chemical behavior and metallogenesis of the shear zones. |
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| Keywords: | continental shear zone chemical compositional variation volume loss flu-id/rock ratio |
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