| Thermal Structure and Rheology of the Upper Mantle Derived from Mantle Xenoliths from Gansu Province, Western China |
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| 作者姓名： | Shi Lanbin |
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| 作者单位： | InstituteofGeology,ChinaEarthquakeAdministration,Beijing100029,China |
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| 基金项目： | TheprojectwassponsoredbytheNationalKeyFundamentalResearchPrograms ,Itemnumber:G19980 4 0 74 0 1.Contributionnumber:2 0 0 3B0 0 4 3,InstituteofGeology ,ChinaEarthquakeAdministration |
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| 摘 要： | Mantle xenoliths brought up by Cenozoic volcanic rocks onto the earth‘s surface may provide direct information about the upper mantle beneath the volcanic region. This paper presents the study on mantle xenoliths collected from Haoti village, Dangchang County, Gansu Province, western China. The main purpose of the study is to gain an insight into the thermal structure and rbeology of the upper mantle beneath the region. The results show that the upper mantle of the region is composed mainly of spinel lherzolite at shallower depth (52-75km), and garnet iberzolite at greater depth (greater than 75km), instead of harzburgite and dunite as proposed by some previous studies. The upper mantle geotherm derived from the equilibrium temperatures and pressures of xenoliths from the region is lower than that of North China, and is somewhat closer to the Oceanic geotherm. The crust-mantle boundary is determined from the geotherm to be at about 52km, and the Moho seems to be the transition zone of lower crust material with spinel iberzolite. If we take 1280℃ as the temperature of the top of asthenosphere, then the fithospbere-asthenosphere boundary should be at about 120km depth. The differential stress of the upper mantle is determined by using recrystallized grain size piezometry, while the strain rate and equivalent viscosity are determined by using the high temperature flow law of peridotite. The differential stress, strain rate and viscosity profiles constructed on the basis of the obtained values indicate that asthenospberic diapir occurred in this region during the Cenozoic time, resulting in the corresponding thinning of the lithosphere. However, the scale and intensity of the diapir was significantly less than that occurring in the North China region. Moreover, numerous small-scale shear zones with localized deformation might occur in the iithospberic mantle, as evidenced by the extensive occurrence of xenoliths with tabular equigranular texture.
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| 关 键 词： | 捕虏岩 上包体 热结构 甘肃 流变学 岩石层位学 |
Thermal Structure and Rheology of the Upper Mantle Derived from Mantle Xenoliths from Gansu Province, Western China |
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| Shi Lanbin.Thermal Structure and Rheology of the Upper Mantle Derived from Mantle Xenoliths from Gansu Province, Western China[J].Earthquake Research in China,2004,18(3):281-299. |
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| Authors: | Shi Lanbin |
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| Institution: | Shi Lanbin,Lin Chuanyong and Chen XiaodeInstitute of Geology,China Earthquake Administration,Beijing 100029,China |
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| Abstract: | |
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| Keywords: | Mantle xenoliths Upper mantle Thermal structure Rheology Gansu Province Western China |
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