Paper No. 132-0
JAMES, Christina L., Indiana Geol Survey, Bloomington, IN 47405,, BASU, Abhijit, Department of Geological Sciences, Indiana Univ, Bloomington, IN 47405, WENTWORTH, Susan J., Mail Code C23, Lockheed Martin, NASA-Johnson Space Ctr, 2400 NASA Rd 1, Houston, TX 77058, and MCKAY, David S., Mail Code SN, NASA/Johnston Space Ctr, Houston, TX 77058

The areal distribution of submicron sized Fe0, mostly nanophase globules, in lunar agglutinitic glass darkens the Moon's albedo and affects the uv-vis-ir reflectance spectra of lunar soils. No quantitative estimate of the distribution is available. We have imaged Fe0 globules in 436 agglutinate segments from polished grain mounts of the 90-150Ám size fraction of 13 lunar soils of diverse maturity. Backscattered electron (BSE) images were obtained using a JEOL analytical FEG-SEM at magnifications generally ranging from x3,000 to x30,000 using a 15kv beam at 12 nanoamp sample current with a resolution of about 4nm. We report the first results of 2-D grain size distribution of 3505 Fe0 globules in Apollo 17 soil 78421 determined from 90 BSE images of glassy segments of 13 agglutinates. Each image was uploaded using common software and placed under a grid scaled to the magnification for measuring the diameter of the exposed surface of each globule. Numbers of globules within 8 size intervals were counted for plotting a cumulative curve. In soil 78421, their mean size is 12.9F (=129 nm) with a standard deviation of 1.9F, i.e., they are extremely well sorted. A semi-quantitative estimate puts the total area of exposed Fe0 at about 5% of the glassy surface of agglutinates.

GSA Annual Meeting, November 5-8, 2001
General Information for this Meeting
Session No. 132
Planetary Geology (Posters)
Hynes Convention Center: Hall D
1:30 PM-5:30 PM, Wednesday, November 7, 2001

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