Mineralogical study of some brecciated Antarctic eucrites

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In order to obtain better understanding of the entire range of Antarctic brecciated eucrites and impact and thermal history of the HED-parent body, we studied brecciated Antarctic eucrites : Y-82202,Y-82210,Y-793548,and Y-793570 mineralogically and petrographically. Y-793548,Y-82210,and Y-793570 are nearly monomict breccias with clasts components of rapidly cooled materials and minor slowly cooled pyroxenes (e. g., Juvinastype). Y-82202 is a monomict breccia penetrated by glassy shock melt veins. We suggest that the polished thin sections of the five eucrites presently available belong to a single suite which contains mostly quickly cooled varieties of eucrites similar to those in Pasamonte or in the Y-74159-type polymict eucrites, but more slowly cooled varieties such as ordinary eucrites or cumulate eucrites are scarce in these sections. On the basis of geological setting of HED parent body, we envision that these eucrites may have been located in the shallow ejecta blanket of the HED-parent body, judging from the high mixing ratio of unequilibrated clasts and low degree of equilibration of pyroxene.
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