A UNIQUE AMPHIBOLE- AND MAGNETITE-RICH CARBONACEOUS CHONDRITE FROM ALMAHATA SITTA.

Introduction: Almahata Sitta (AhS) 202 from the UoK collection [1] represents a clast from the polymict breccia asteroid 2008 TC3 [2-4]. AhS 202 was recognized as a unique carbonaceous chondrite (CC) with a high magnetite content [5-7]. Here we report that it also contains a significant amount of amphibole, a mineral that is very rare in chondrites [8,9] and has not previously been reported in significant abundance in a CC [10,11]. We present new petrographic, oxygen isotope, and micro-FTIR [see 12] data. We discuss petrogenesis and possible relationships to known CC. Sample: Almahata Sitta (AhS) 202 had an original mass of 20.057 g [1]. We were allocated <50 mg from which we prepared a polished mount (area ~8.8 mm2) and a small chip for bulk oxygen isotope analyses. Methods: Electron imaging, X-ray mapping, and electron microprobe analyses (EMPA) were conducted at ARES, JSC. Bulk oxygen isotope analyses were obtained at UCLA. Oxygen isotope analyses of minerals were obtained by secondary ion mass spectrometry (SIMS) at WiscSIMS. Micro-FTIR spectroscopy was conducted at SwRI [12].