Procesy wielokrotnego brekcjonowania deformacyjnego i powstawania stopów impaktowych w chondrytach na przykładzie meteorytów z kolekcji Jacka Siemiątkowskiego

Agata Krzesińska, Jacek Siemiątkowski


Evidence for multiple deformational brecciation and impact melting in chondrites from the Jacek Siemiątkowski collection.
A b s t r a c t. Chondrites NWA-869 (L3.9-6 S2), Tsarev (L5 S5), Ghubara (L5 S4), Zag (H3-6 S3) from the Jacek Siemiątkowski Collection show evidence of multiple brecciation. Petrographic and microprobe analyses of thin sections allowed to identify and distinguish syn- and postaccretion impact and thermal transformations which took place on the chondrite parent bodies. The studied meteorites contain clasts of chemically equilibrated and unequilibrated rocks as well as many unusual achondritic-like clasts. The latter are cognate impact-melt rocks. All the clasts provide records of complex metamorphic and deformational histories of the parent bodies. Chondrites displayed numerous metamorphic transformations and deformations caused by many shock or shock-related processes under conditions ranging from impact-related shearing to HP shock-induced shattering and melting. These processes led to the formation of quenched impact melts, metal veins and nodules, darkened clasts and locally cataclasis.

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