HR: 1340h
AN: V43A-1550    [Abstracts]
TI: Nanometer-size P/K-Rich Silica Glass (Former Melt) Inclusions in Microdiamond From the Gneisses of Kokchetav and Erzgebirge Massifs: Diversified Characteristics of the Formation Media of Metamorphic Microdiamond in UHP Rocks due to Host-rock AU: Hwang, S
EM: slhwang@mail.ndhu.edu.tw
AF: Department of Materials Science and Engineering, National Dong Hwa University, Sec.2, Da Hsueh Rd., Shou-Feng, Hualien, 97401 Taiwan
AU: * Chu, H
EM: Chuht@linx.moeacgs.gov.tw
AF: Central Geological Survey, MOEA, 2 Lane 109 Huahsin St., Chungho, Taipei, 235 Taiwan
AU: Yui, T
EM: tfyui@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, 115 Taiwan
AU: Shen, P
EM: pshen@mail.nsysu.edu.tw
AF: Institute of Materials Science and Engineering, National Sun Yat-sen University, 70 Lien-hai Rd., Kaohsiung, 804 Taiwan
AU: Schertl, H
EM: hans-peter.schertl@rub.de
AF: Institut fuer Mineralogie, Geologie und Geophysik, Ruhr-Universitaet Bochum, Bochum, D-44780 Germany
AU: Liou, J
EM: liou@pangea.Stanford.EDU
AF: Department of Geological and Environmental Sciences, Stanford University, Geocorner, Building 320, Room 118 , Stanford, CA 94305 United States
AU: Sobolev, N
V43A-1550 AF: Institute of Mineralogy and Petrography, Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090 Russian Federation
AB: Nanometer-size P/K-rich silica glass (former melt) inclusions were identified within metamorphic microdiamonds from garnets of ultrahigh-pressure (UHP) gneisses of the Kokchetav and the Erzgebirge massifs by analytical electron microscopy. The chemical characteristics of these inclusions within microdiamonds are surprisingly similar among various gneissic rocks from both Kokchetav and Erzgebirge, but are significantly different from the Si-poor ultrapotassic fluid inclusions within microdiamonds from garnets of the Kokchetav UHP marble. These contrasting findings not only provide constraints on the characteristics/compositions of the formation media of metamorphic microdiamonds, but also imply that the formation media must have been buffered by the hosting rocks, resulting in the observed diversities as reported here. In addition, depending on the rock types and thus on the nature of the formation media from which metamorphic microdiamonds were formed, the respective characteristic morphologies of the microdiamonds differs. The P/K-rich silica melt tends to form octahedral or cubo-octahedral microdiamonds within garnet in gneissic rocks, whereas the Si-poor ultrapotassic fluid tends to form spheroids/cuboid microdiamonds with rugged surfaces within garnet in marble. Consequently, the buffered media in hosting rocks played a decisive role in determining the different morphologies and growth rates/mechanisms of metamorphic microdiamonds in general. Keywords: analytical electron microscopy (AEM), diamond, fluid/glass inclusion, Kokchetav/Erzgebirge massifs, UHP metamorphism.
DE: 3654 Ultra-high pressure metamorphism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005