The shock metamorphism of 47 H group chondrites （H-chondrites） from the Grove Mountains including undulatory extinction, planar fractures, mosaic extinction, shock veins and pockets, and dendritic eutectic metal-sul...The shock metamorphism of 47 H group chondrites （H-chondrites） from the Grove Mountains including undulatory extinction, planar fractures, mosaic extinction, shock veins and pockets, and dendritic eutectic metal-sulfide, is observed through optical microscope. The textures and assemblages of shock veins in these H-chondrites are examined by the scanning electron microscope. Based on observations of the above shock effects, the shock stages of the 47 H-chondrites are classified into S1（5）, S2（19）,S$3（14）, S4（8） and S5（1）. Of these H-chondrites, GRV 022469 has the highest（S5） shock stage. The comparison of shock stages in these H-chondrites with L group chondrites（L-chondrites） indicates that the shock metamorphism of H-chondrites is relatively low （except for GRV 022469, they are all lower than $5）. A scenario for the history of the H-chondrite parent body is proposed that suggests the duration of the shock events in the H-chondrite parent bodies was much shorter than those in L-chondrite parent bodies. Also, the pressure may have been released more quickly, and consequently, the high-pressure phases should be easily preserved. However, the parent bodies of the H-chondrites may have been exposed to high temperatures for a longer time after the shock event, so the high-pressure phases formed by solid transformation might have retro-metamorphosed to low-pressure ones; its peak pressure is estimated to be less than 15 GPa. Wadsleyite was found in a shock vein in GRV022469, as confirmed by the Raman spectrometer. Petrological and mineralogical characteristics support the idea that the wadsleyite was formed by solid-state transformation.展开更多
There are potentially huge amounts of water stored in Earth's mantle, and the water solubilities in the silicate minerals range from tens to thousands of part per minion(ppm, part per million). Exploring water in ...There are potentially huge amounts of water stored in Earth's mantle, and the water solubilities in the silicate minerals range from tens to thousands of part per minion(ppm, part per million). Exploring water in the mantle has attracted much attention from the societies of mineralogy and geophysics in recent years. In the subducting slab, serpentine breaks down at high temperature, generating a series of dense hydrous magnesium silicate(DHMS) phases, such as phase A, chondrodite, clinohumite, etc. These phases may serve as carriers of water as hydroxyl into the upper mantle and the mantle transition zone(MTZ). On the other hand, wadsleyite and ringwoodite, polymorphs of olivine, are most the abundant minerals in the MTZ, and able to absorb significant amount of water(up to about 3 wt.% H_2O). Hence, the MTZ becomes a very important layer for water storage in the mantle, and hydration plays important roles in physics and chemistry of the MTZ. In this paper, we will discuss two aspects of hydrous silicate minerals:(1) crystal structures and(2) equations of state(Eo Ss).展开更多
基金supported by the Pilot Project of Knowledge Innovation of Chinese Academy of Sciences (Grant no.KZCX2-YW-110)the National Natural Science Foundation of China(Grant nos. 40673055 and 40473037)the Open Foundation of Key Laboratory of Geological Engineering Centre of Guangxi Province (Grantno. Gui Ke Neng 07109011-K024)
文摘The shock metamorphism of 47 H group chondrites （H-chondrites） from the Grove Mountains including undulatory extinction, planar fractures, mosaic extinction, shock veins and pockets, and dendritic eutectic metal-sulfide, is observed through optical microscope. The textures and assemblages of shock veins in these H-chondrites are examined by the scanning electron microscope. Based on observations of the above shock effects, the shock stages of the 47 H-chondrites are classified into S1（5）, S2（19）,S$3（14）, S4（8） and S5（1）. Of these H-chondrites, GRV 022469 has the highest（S5） shock stage. The comparison of shock stages in these H-chondrites with L group chondrites（L-chondrites） indicates that the shock metamorphism of H-chondrites is relatively low （except for GRV 022469, they are all lower than $5）. A scenario for the history of the H-chondrite parent body is proposed that suggests the duration of the shock events in the H-chondrite parent bodies was much shorter than those in L-chondrite parent bodies. Also, the pressure may have been released more quickly, and consequently, the high-pressure phases should be easily preserved. However, the parent bodies of the H-chondrites may have been exposed to high temperatures for a longer time after the shock event, so the high-pressure phases formed by solid transformation might have retro-metamorphosed to low-pressure ones; its peak pressure is estimated to be less than 15 GPa. Wadsleyite was found in a shock vein in GRV022469, as confirmed by the Raman spectrometer. Petrological and mineralogical characteristics support the idea that the wadsleyite was formed by solid-state transformation.
基金supported by the National Natural Science Foundation of China(Grant Nos.41590621&41473058)the Fundamental Research Funds for the Central University(Grant No.G1323531512)MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources(Grant No.MSFGPMR07),China University of Geosciences at Wuhan
文摘There are potentially huge amounts of water stored in Earth's mantle, and the water solubilities in the silicate minerals range from tens to thousands of part per minion(ppm, part per million). Exploring water in the mantle has attracted much attention from the societies of mineralogy and geophysics in recent years. In the subducting slab, serpentine breaks down at high temperature, generating a series of dense hydrous magnesium silicate(DHMS) phases, such as phase A, chondrodite, clinohumite, etc. These phases may serve as carriers of water as hydroxyl into the upper mantle and the mantle transition zone(MTZ). On the other hand, wadsleyite and ringwoodite, polymorphs of olivine, are most the abundant minerals in the MTZ, and able to absorb significant amount of water(up to about 3 wt.% H_2O). Hence, the MTZ becomes a very important layer for water storage in the mantle, and hydration plays important roles in physics and chemistry of the MTZ. In this paper, we will discuss two aspects of hydrous silicate minerals:(1) crystal structures and(2) equations of state(Eo Ss).
