The mineral thermobarometry proposed in literature is used to calculate the equilibrium temperature and pressure of garnet Iherzolite and websterite xenoliths within the Cenozoic kama-fugite from west Qinling, Gansu P...The mineral thermobarometry proposed in literature is used to calculate the equilibrium temperature and pressure of garnet Iherzolite and websterite xenoliths within the Cenozoic kama-fugite from west Qinling, Gansu Province, China. The results show that the equilibrium temperature and pressure of garnet Iherzolites and websterite and 1127-1266℃, 2.9-3.6 Gpa and 1169 -1248℃, 2.8-3.2 Gpa respectively. The equilibrium peressures reach or exceed the equilibrium peressure of spinel Iherzolites (2.0-3.0 GPa), and fall into the stability range of garnet peridotite. The equilibrium temperature of the xenoliths reach or exceed the ocean geotherm, identical with the melting temperature of kamafugite magma determined by experiments under the conditions of post-orogenic lithosphere extension. So the thermal state of Cenozoic mantle of the west Qinling may be fit to generate the kamafugite magmatism. The research on petrology-mineralogy and geobarothermometry of the xenoliths shows that both garnet Iherzolite展开更多
THE determination of contents of trace (10<sup>-12</sup>—10<sup>-9</sup>) siderophile elements, Re and Os, and osmium isotopic compositions in mantle-derived rocks is very useful. It has been ...THE determination of contents of trace (10<sup>-12</sup>—10<sup>-9</sup>) siderophile elements, Re and Os, and osmium isotopic compositions in mantle-derived rocks is very useful. It has been a new approach to exploring interactions between the mantle and the crust, and the chemical structure of the mantle. This can be done by combination with isotopic dating and tracing展开更多
Xenoliths of garnet and spinel-garnet 1herzolite from Mingxi, Eastern China have been studied in terms of comprehensive methods of mineralogy, petrology, fabrics, mierostructures and infrared spectrum. The temperature...Xenoliths of garnet and spinel-garnet 1herzolite from Mingxi, Eastern China have been studied in terms of comprehensive methods of mineralogy, petrology, fabrics, mierostructures and infrared spectrum. The temperature and pressure equilibration of the xenolith have been calculated using the TEMPEST program with the two-pyroxene geothermometer of Bertrand and Mercier (1985) combined with the geobarometer of Nickel and Green (1985). The temperature and pressure of xenoliths range from^1300 K at 1. 9 GPa (60 km) to ~1500 K at 2. 6 GPa (80 km). The geotherm inferred from xenolith is excellently consistent with the measured surface heat flow (70 mW/m2) in Mingxi. A character of geothermal curve and conductive type suggest that these xenoliths are from the lithosphere, not from the asthenosphere. The geotherm and mierostructures and preferred orientations of minerals in the xenolith are consistent with tecon-ic thinning of the lithosphere in the present-day extensional back-arc environment.展开更多
基金the Major State Basic Research Development Program(G1998040800), the National Natural Science Foundation of China (Grant No. 49973014) and Qinghai-Xizhang Plateau Special Project of Ministry of Land and Resources (200101020404).
文摘The mineral thermobarometry proposed in literature is used to calculate the equilibrium temperature and pressure of garnet Iherzolite and websterite xenoliths within the Cenozoic kama-fugite from west Qinling, Gansu Province, China. The results show that the equilibrium temperature and pressure of garnet Iherzolites and websterite and 1127-1266℃, 2.9-3.6 Gpa and 1169 -1248℃, 2.8-3.2 Gpa respectively. The equilibrium peressures reach or exceed the equilibrium peressure of spinel Iherzolites (2.0-3.0 GPa), and fall into the stability range of garnet peridotite. The equilibrium temperature of the xenoliths reach or exceed the ocean geotherm, identical with the melting temperature of kamafugite magma determined by experiments under the conditions of post-orogenic lithosphere extension. So the thermal state of Cenozoic mantle of the west Qinling may be fit to generate the kamafugite magmatism. The research on petrology-mineralogy and geobarothermometry of the xenoliths shows that both garnet Iherzolite
文摘THE determination of contents of trace (10<sup>-12</sup>—10<sup>-9</sup>) siderophile elements, Re and Os, and osmium isotopic compositions in mantle-derived rocks is very useful. It has been a new approach to exploring interactions between the mantle and the crust, and the chemical structure of the mantle. This can be done by combination with isotopic dating and tracing
文摘Xenoliths of garnet and spinel-garnet 1herzolite from Mingxi, Eastern China have been studied in terms of comprehensive methods of mineralogy, petrology, fabrics, mierostructures and infrared spectrum. The temperature and pressure equilibration of the xenolith have been calculated using the TEMPEST program with the two-pyroxene geothermometer of Bertrand and Mercier (1985) combined with the geobarometer of Nickel and Green (1985). The temperature and pressure of xenoliths range from^1300 K at 1. 9 GPa (60 km) to ~1500 K at 2. 6 GPa (80 km). The geotherm inferred from xenolith is excellently consistent with the measured surface heat flow (70 mW/m2) in Mingxi. A character of geothermal curve and conductive type suggest that these xenoliths are from the lithosphere, not from the asthenosphere. The geotherm and mierostructures and preferred orientations of minerals in the xenolith are consistent with tecon-ic thinning of the lithosphere in the present-day extensional back-arc environment.
