PATOS DE MINAS: A COMPOSITIONAL STUDY OF SULFIDES, SCHREIBERSITE AND COHENITE

VARELA M.E.; SYLVESTER P,; SOUDERS, K.; SAAVEDRA M.; ZUCOLOTTO M.E.

Houston

Conferencia; Lunar and Planetary Science Conference; 2015

NASA

Patos) is a normal hexahedrite with 5.36 wt% Ni host-ing round nodules of troilite with daubreelite exsolu-tion lamellae [1-2]. The polished sections of Patos (from the MHN, Rio de Janeiro, Brazil) contain sulfide globules that consist of two phases: Cr-bearing troilite and daubreelite each occupying half of it with bars of troilite in daubreelite. These sulfide globules have ~ 5 mm in diameter with round small troilite/daubreelite globules (300 ? 500 μm) attached to them (Fig 1a). Some globules are thinly rimmed (totally or partially) by schreibersite and cohenite. In one globule we found the first silicate phase observed in this meteorite [3]. It consists of a perfectly round silicate inclusion (400 μm in diameter) within an almost perfectly round sulfide inclusion. The REE pattern, with the HREEs depleted with respect to the LREEs showing a weak Tm+ and a strong Eu+ anomaly, is reminiscent of the group II CAI REE abundance pattern. The very high Nb content indicates that the precursor of the silicate could have been a sulfide [3]. In addition to sulfide globules, a subhedral chromite crystal with eight cavities filled with kamacite or sulfides or a combination of both phases was also observed. The chromite is partly en-veloped by troilite and daubreelite. The latter is rimmed by schreibersite (Fig. 1b). Major, minor and trace element analyses were made on the various phas-es in order to understand metal partitioning and origin of the meteorite.