Primary crystallization and partial remelting of chondrules in the protoplanetary disk: Petrographic, mineralogical and chemical constraints recorded in zoned type-I chondrules

Chondrules from unequilibrated ordinary chondrites are among the oldest Solar system materials and preserve mineralogical, chemical isotopic signatures that link them to their primary formation mechanisms environments in early System. Some chondrules record features indicating modifications by high- low-temperature processes throughout residence time protoplanetary disk. were partially modified after chemical, textural information on initial conditions subsequent reprocessing essential reconstruct interpret ages recorded individual correctly. The detailed major, minor trace element analyses of two type-I low petrologic type MET 00526 00452 (L/LL3.05) reveal complex systematics bearing testimony multi-stage high temperature evolution, including reheating partial remelting, evolving disk prior accretion into parent bodies. During crystallization chondrule MET00526_Ch43, mineral growth, incipient feldspar outer parts chondrule, led fractionation melt, eventually resulting a gradient mesostasis. later punctuated ultimately remelting mesostasis low-Ca pyroxene remelted partially. This enhanced differences within chemically distinct mesostases inner zone with almost complementary abundances Rb, Na, K, Ba, Sr Eu. calculated bulk composition reveals chondritic relative these elements slight depletion most volatile elements. Chemical observations further indicate this disequilibrium occurred under more reducing than melting event preserved centre, allowing for second generation chondrule. Very similar also MET00452_Ch22 degree being extensive. A previously determined young 26Al-26Mg age ∼3 Ma CAIs dates rather its formation. is evidence late thermal generally indicates multiple, pulses forming region nonconcentric secondary around spherical may directed heat source as cause chondrules.