A weathering index for CK and R chondrites

• Main Authors: Rubin, A. E., Huber, H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Meteoritics & Planetary Science Archives 2005
• Subjects: Composition of meteorites;CK carbonaceous chondrite meteorites;R chondrite Meteorites;Weathering; Antarctic; Antarc*
• Online Access: https://journals.uair.arizona.edu/index.php/maps/article/view/15155

We present a new weathering index (wi) for the metallic-Fe-Ni-poor chondrite groups (CK and R) based mainly on transmitted light observations of the modal abundance of crystalline material that is stained brown in thin sections: wi-0, 5 vol%; wi-1, 525 vol%; wi-2, 2550 vol%; wi-3, 5075 vol%; wi-4, 7595 vol%; wi-5, 95 vol%; wi-6, significant replacement of mafic silicates by phyllosilicates. Brown staining reflects mobilization of oxidized iron derived mainly from terrestrial weathering of Ni-bearing sulfide. With increasing degrees of terrestrial weathering of CK and R chondrites, the sulfide modal abundance decreases, and S, Se, and Ni become increasingly depleted. In addition, bulk Cl increases in Antarctic CK chondrites, probably due to contamination from airborne sea mist.