We present a new single-crystal X-ray diffraction (XRD) study performed on a suite of six orthopyroxene grains from the low-shocked H6 Trenzano meteorite. The quenched intracrystalline Fe2+-Mg ordering state in orthopyroxene preserves the memory of the cooling rate near closure temperature T-c, thus yielding useful constraints on the last thermal event undergone by the host rock. The orthopyroxene T-c of 522 +/- 13 degrees C, calculated using a new calibration equation obtained by Stimpfl (2005b), is higher than in previously published H chondrite data. The orthopyroxene cooling rate at this T-c is about 100 degrees C/kyr. This fast rate is inconsistent with the much slower cooling rate expected for H6 in the onion shell structural and thermal model of chondrite parent bodies. A petrographic study carried out at the same time indicated that the Trenzano meteorite is an H5 chondrite and not an H6 chondrite, as it is officially classified. Furthermore, the two-pyroxene equilibrium temperature of Trenzano (824 +/- 24 degrees C), calculated with QUILF95, is similar to the two-pyroxene temperature of 750-840 degrees C obtained for the Carcote (H5) chondrite (Kleinschrot and Okrusch 1999).

Reclassification and thermal history of Trenzano chondrite / A.M. Fioretti, M.C. Domeneghetti, G. Molin, F. Camara, M. Alvaro, L. Agostini. - In: METEORITICS & PLANETARY SCIENCE. - ISSN 1086-9379. - 42:12(2007 Dec), pp. 2055-2066.

Reclassification and thermal history of Trenzano chondrite

F. Camara;
2007

Abstract

We present a new single-crystal X-ray diffraction (XRD) study performed on a suite of six orthopyroxene grains from the low-shocked H6 Trenzano meteorite. The quenched intracrystalline Fe2+-Mg ordering state in orthopyroxene preserves the memory of the cooling rate near closure temperature T-c, thus yielding useful constraints on the last thermal event undergone by the host rock. The orthopyroxene T-c of 522 +/- 13 degrees C, calculated using a new calibration equation obtained by Stimpfl (2005b), is higher than in previously published H chondrite data. The orthopyroxene cooling rate at this T-c is about 100 degrees C/kyr. This fast rate is inconsistent with the much slower cooling rate expected for H6 in the onion shell structural and thermal model of chondrite parent bodies. A petrographic study carried out at the same time indicated that the Trenzano meteorite is an H5 chondrite and not an H6 chondrite, as it is officially classified. Furthermore, the two-pyroxene equilibrium temperature of Trenzano (824 +/- 24 degrees C), calculated with QUILF95, is similar to the two-pyroxene temperature of 750-840 degrees C obtained for the Carcote (H5) chondrite (Kleinschrot and Okrusch 1999).
EQUILIBRATED ORDINARY CHONDRITES; FE2+-MG ORDER-DISORDER; ORTHO-PYROXENE; COOLING RATES; PARENT BODIES; STRUCTURE-REFINEMENT; SHOCK METAMORPHISM; METEORITES; ORTHOPYROXENES; FE
Settore GEO/06 - Mineralogia
dic-2007
Article (author)
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/478910
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