The bulk mineralogy, elemental composition, and water content of the Winchcombe CM chondrite fall
2023
Bates, Helena C | King, Ashley J | Shirley, Katherine S | Bonsall, Emily | Schroeder, Christian | Wombacher, Frank | Fockenberg, Thomas | Curtis, Rowan J | Bowles, Neil E | The Natural History Museum | The Natural History Museum | University of Oxford | Biological and Environmental Sciences | Biological and Environmental Sciences | University of Cologne | Ruhr-University of Bochum, Germany | University of Oxford | University of Oxford | 0000-0002-7935-6039
On the micro-scale, the Winchcombe CM carbonaceous chondrite contains a number of lithological units with a variety of degrees of aqueous alteration. However, an understanding of the average hydration state is useful when comparing to other meteorites and remote observations of airless bodies. We report correlated bulk analyses on multiple subsamples of the Winchcombe meteorite, determining an average phyllosilicate fraction (PSF) petrologic type of 1.2 and an average water content of 11.9 wt%. We show the elemental composition and distribution of iron and iron oxidation state are consistent with measurements from other CM chondrites, however Winchcombe shows a low Hg concentration of 58.1 ±0.5 ng/g. We demonstrate that infrared reflectance spectra of Winchcombe are consistent with its bulk modal mineralogy, and comparable to other CM chondrites with similar average petrologic types. Finally, we also evaluate whether spectral parameters can estimate H/Si ratios and water abundances, finding generally spectral parameters underestimate water abundance compared to measured values.
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