CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

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Paper No. 4
Presentation Time: 9:05 AM

AEM CHARACTERIZATION OF METAMORPHIC MICRODIAMONDS FROM GARNET-CLINOPYROXENE ROCK (KUMDY KOL) AND GNEISS (BARCHI KOL), KOKCHETAV MASSIF


HWANG, Shyh-Lung, Department of Materials Science and Engineering, National Dong Hwa University, Hualien, 970, Taiwan, CHU, Hao-Tsu, Central Geological Survey, MOEA, Taipei, 100, Taiwan, YUI, Tzen-Fu, Institute of Earth Sciences, Academia Sinica, Taipei, 115, Taiwan, SHEN, Pouyan, Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, 804, Taiwan and SOBOLEV, Nikolai V., Institute of Mineralogy and Petrography, Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia, tfyui@earth.sinica.edu.tw

Metamorphic microdiamonds within two Kumdy Kol garnet-clinopyroxene rock samples and two Barchi Kol gneissic samples from the Kokchetav ultrahigh-pressure (UHP) terrane were analyzed by analytical electron microscopy (AEM). Whereas syngenetic nano-meter sized facetted fluid inclusions are highly abundant in microdiamonds from garnet-clinopyroxene rock samples, with chemical characteristics of inclusions closely resembling those in microdiamonds from Kokchetav dolomite marbles (Hwang et al., 2005, 2006), microdiamonds in Barchi Kol gneissic samples surprisingly contain no inclusions whatsoever. These observations, in conjunction with the characteristic rugged, spheroids/cuboid morphology of microdiamond in Kumdy Kol garnet-clinopyroxene rock samples and the {111} facetted octahedral morphology of microdiamond from Barchi Kol gneissic samples, indicate that the diversified characteristics of the formation media of metamorphic microdiamond in UHP rocks due to host-rock buffering must have played a decisive role for the different morphologies and growth rates/mechanisms of metamorphic microdiamonds (Hwang et al., 2005, 2006). The formation media of metamorphic microdiamonds from the Barchi Kol and the Kumdy Kol areas might just represent two extremes of the whole compositional spectrum: one is a highly viscous silica-rich melt leading to slow growth and formation of inclusion-free octahedral microdiamonds, the other is a silica-poor, low viscous, ultrapotassic fluid causing fast growth, entrapment of fluid inclusions at the growth fronts, and formation of rugged spheroids/cuboid microdiamonds.

Hwang, S.L., P., Shen, H.T., Chu, T.F., Yui, J.G.., Liou, N.V., Sobolev, and V.S., Shatsky, 2005. Potassic COH fluid in metamorphic microdiamond. Earth and Planetary Science Letters, 231, 295-306.

Hwang, S.L., P., Shen, H.T., Chu, T.F., Yui, H.-P., Schertl, J.G.., Liou, N.V., Sobolev, 2006. 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 buffering, Earth and Planetary Science Letters, 243, 94-106.

Session No. 12

T34. Ultrahigh-Pressure Metamorphism: Observations from Nano- through Outcrop- to Plate-Tectonic Scales I: In Honor of J.G. Liou, 2011 MSA Roebling Medalist
Sunday, 9 October 2011: 8:00 AM-12:00 PM
Room 102D-F (Minneapolis Convention Center)
Geological Society of America Abstracts with Programs. Vol. 43, No. 5, p.47
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