HR: 0830h
AN: V51A-12    [Abstracts]
TI: Hydrocarbons Encapsulated in Diamonds From China and India
AU: * Leung, I
EM: irene.leung@lehman.cuny.edu
AF: Dept. of Geology, Lehman College, CUNY, 250 Bedford Park Blvd. West, Bronx, NY 10468 United States
AU: Tsao, C
EM: cstsao@juno.com
AF: Linus Pauling Institute of Science and Medicine, 440 Page Mill Road, Palo Alto, CA 94306 United States
AU: Taj-Eddin, I
EM: itaj-Eddin@gc.cuny.edu
AF: Dept. of Mathematics and Computer Science, Graduate Center, CUNY, 365 Fifth Avenue, New York, NY 10016 United States
AB: We examined a large number of diamonds from a kimberlite pipe located in Fuxian, China, and alluvial diamonds from Panna, India. We selected 6-10 diamonds from each locality based on certain characteristics: they are white, brilliant, mostly devoid of mineral inclusions, fracture-free, many contain microscopic bubbles, some display etched circular patterns. These diamonds were examined under ultraviolet (UV) light using a fluorescence microscope, then, investigated using a Nicolet 6700 FT-IR spectrometer. Several diamonds emit blue fluorescence when excited with UV light, while others appear dim because they are not fluorescent. It is the latter that render the included bubbles clearly visible, glowing as yellow and blue spherules within the dim diamond host. These fluorescent bubbles are probably filled with hydrocarbon fluids of variable compositions. FT-IR spectra of diamond typically show absorption due to intrinsic diamond lattice vibrations. We found in most of our diamonds used in this study an additional, outstanding group of absorption bands located just below the wavenumber 3000. Peak positions in this region correlate well with symmetric and asymmetric stretching of methylene and methyl groups, attributable to H bonded to C atoms. Comparing them with standard spectral shapes, we found a good match with an alkane molecule composed of saturated aliphatic hydrocarbons. Our observations provide evidence that hydrocarbons might be important components in the deep mantle, but, to transport them up to Earth's surface would require strong capsules which, perhaps, only diamond could provide.
DE: 1025 Composition of the mantle
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 8124 Earth's interior--composition and state (old 8105)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly