Non-porphyritic chondrules from equilibrated Rumuruti and Ordinary chondrites: Chemical evidences of secondary processing.

VARELA M.E.; SYLVESTER P,; ENGLER A,; KURAT G

METEORITICS & PLANETARY SCIENCE

METEORITICAL SOC

Año: 2012 vol. 47 p. 1537 - 1557

1086-9379

Abstract?Nineteen nonporphyritic pyroxene and pyroxene ⁄ olivine chondrules, chondrule fragments, and irregular objects were studied from two equilibrated chondrites, the ordinary (L ⁄ LL5) Knyahinya chondrite and the Rumuruti type (R4) Ouzina chondrite. Major element contents for almost all objects in the chondrites are disturbed from their chondritic ratios, most probably during metamorphic re-equilibration. However, the volatile elements (Na2O + K2O) in Ouzina scatter around the CI line, probably the result of being generated and ⁄ or processed in different environments as compared with those for Knyahinya. All studied objects from Knyahinya and Ouzina possess systematically fractionated trace element abundances. Depletion of LREE with respect to HREE and ultra-refractory HFSE documents variable degrees of LREE transport into an external mineral sink and restricted mobility of most of the HREE and HFSE. Moderately volatile elements preserve volatilitycontrolled abundances. Strongly fractionated Rb⁄ Cs ratios (up to 10· CI) in all studied objects suggest restricted mobility of the large Cs ion. All studied objects sampled and preserved Y and Ho in solar proportions, a feature that they share with the nonporphyritic chondrules of unequilibrated ordinary chondrites.