THE KAIDUN METEORITE - MINERALOGY OF AN UNUSUAL CM1 LITHOLOGY

Kaidun is a breccia of disparate enstatite and carbonaceous chondrite clasts that continues to provide real surprises. Many Kaidun clasts ha ve been intensely altered by aqueous fluids, as evidenced by the wides pread occurrence of ferromagnesian phyllosilicates and by the presence of carbonate- and phyllosilicate-filled veins. In this report, we des cribe an unusual CM lithology containing many mineralogical features n ot previously reported from any meteorite, including pyrrhotite, with exclusive needlelike morphologies and thick mantles of phyllosilicate, and complex aggregates of phyllosilicate, melanite garnet, crosscut b y pentlandite veins. The latter features appear to be due in large par t to extensive hydrothermal alteration at temperatures on the order of 450 degrees C, which is significantly higher than that attained durin g secondary processing from other known CM material.