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REPEATED SHOCK AND THERMAL METAMORPHISM OF THE ABERNATHY METEORITE
Author(s) -
Lambert P.,
Lewis C.,
Moore C.B.
Publication year - 1984
Publication title -
meteoritics
Language(s) - English
Resource type - Journals
eISSN - 1945-5100
pISSN - 0026-1114
DOI - 10.1111/j.1945-5100.1984.tb00832.x
Subject(s) - chondrite , plagioclase , petrography , shock metamorphism , geology , meteorite , olivine , parent body , geochemistry , metamorphic rock , metamorphism , pyroxene , chondrule , mineralogy , shock (circulatory) , partial melting , basalt , quartz , physics , astrobiology , paleontology , medicine
Based on the example of Abernathy (L6 chondrite), this study shows how petrographic investigation can be used to unravel the nature, chronology and conditions of superposed metamorphic events in chondrites. Features considered include the texture of the rock, optical characteristics of olivine, pyroxene and plagioclase, refractive index of plagioclase, metallographical characteristics and microhardness of Fe‐Ni alloys. From these data it is deduced that Abernathy has been involved in at least six metamorphic events since the formation of the chondrite. Four distinct shock events and two separate reheating events have been identified. The chronology of these events is established. The conditions for the last four events are reasonably well constrained. These include successively, i) severe reheating (T > 1200°C), ii) severe shock causing complete melting of plagioclase and local melting of the rock (90 < P < 110 GPa, 1250°GC < T < 1350°C), iii) mild shock (10 < P < 25 GPa, T<500°C), and iv) reheating below 800°C.