Mineralogical aspects of terrestrial weathering effects in chondrites from Allan Hills, Antarctica

The work reported here represents a first attempt at comparing the mineralogical aspects of weathering effects in selected Antarctic chondrites with those present in a petrologically similar chondrite which was weathered in the Arizona desert. The methods of analysis employed include X-ray diffractometry, differential thermal analysis, and reflectance spectrophotometry. It is found that the dominant weathering products in the rocks are complex, multiple-phase, hydrous ferric oxides which formed by alteration of Ni-Fe metal and sulfide particles under the influence of liquid water. The Fe-oxide weathering products may comprise approximately 15-20 wt % of the most intensely weathered samples although the same samples contain not more than 5% goethite as the only well-crystallized hydrous ferric oxide.