HR: 0800h
AN: T41D-1246    [Abstracts]
TI: Nanometre sized inclusions in microdiamonds: a new source of information about diamond genesis and fluid composition.
AU: * Wirth, R
EM: wirth@gfz-potsdam.de
AB: Inclusions in diamond provide the unique opportunity investigating the mantle rocks where diamond has formed and the fluids from which they have crystallized. Most of all natural diamonds are microcrystalline diamonds (< 0.5 mm). They contain many submicrometer sized or even nanometre sized inclusions. Spectroscopy was the only method to get information about these inclusions. TEM investigations of inclusions in microdiamond were nearly impossible because of preparation problems. With the availability of the focused ion beam (FIB) technique situation has changed. FIB allows preparing electron transparent foils even from microdiamonds. With TEM it is possible to determine the structure, chemical composition and paragenesis of micro- and nano-inclusions. The excellent electron transparency of diamond allows keeping the FIB prepared foils rather thick (up to 300 nm). Thick foils make it likely to find and investigate such inclusions, which are still closed. With analytical electron microscopy (EDX) or electron energy-loss spectroscopy (EELS) and diffraction analysis the content of the inclusions can be studied. After that, the inclusion is opened drilling a hole with the focused electron beam releasing the fluid and gas content. A second analysis of the remaining material provides an estimate of the fluid and gas composition in the inclusion. The most efficient investigation of inclusions in microdiamonds is the combination of Raman- and IR-spectroscopy and TEM studies of one and the same sample. This is demonstrated on microdiamonds from Udachnaya (Siberia) and from Ukrainia.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 1213 Earth's interior--dynamics (8115, 8120)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting