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An Evaluation of Quantitative Methods of Determining the Degree of Melting Experienced by a ChondruleMany workers have considered the degree to which partial melting occurred in chondrules they have studied, and this has led to attempts to find reliable methods of determining the degree of melting. At least two quantitative methods have been used in the literature: a convolution index (CVI), which is a ratio of the perimeter of the chondrule as seen in thin section divided by the perimeter of a circle with the same area as the chondrule, and nominal grain size (NGS), which is the inverse square root of the number density of olivines and pyroxenes in a chondrule (again, as seen in thin section). We have evaluated both nominal grain size and convolution index as melting indicators. Nominal grain size was measured on the results of a set of dynamic crystallization experiments previously described, where aliquots of LEW97008(L3.4) were heated to peak temperatures of 1250, 1350, 1370, and 1450 C, representing varying degrees of partial melting of the starting material. Nominal grain size numbers should correlate with peak temperature (and therefore degree of partial melting) if it is a good melting indicator. The convolution index is not directly testable with these experiments because the experiments do not actually create chondrules (and therefore they have no outline on which to measure a CVI). Thus we had no means to directly test how well the CVI predicted different degrees of melting. Therefore, we discuss the use of the CVI measurement and support the discussion with X-ray Computed Tomography (CT) data.
Document ID
Document Type
Conference Paper
Nettles, J. W. (Tennessee Univ. Knoxville, TN, United States)
Lofgren, G. E. (NASA Johnson Space Center Houston, TX, United States)
Carlson, W. D. (Texas Univ. Austin, TX, United States)
McSween, H. Y., Jr. (Tennessee Univ. Knoxville, TN, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Publication Information
Publication: Lunar and Planetary Science XXXV: Chondrules and CAIs
Subject Category
Lunar and Planetary Science and Exploration
Distribution Limits
Public Use Permitted.

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