Two distinct assemblages of high-pressure liquidus phases in shock veins of the Sixiangkou meteorite

Abstract

Shock-produced complex veins, including earlier and later veins, are identified in the Sixiangkou L6 chondrite. The early vein is intersected by the late vein and consists of coarse-grained aggregates of ringwoodite, majorite, and lingunite, and fragments of olivine, pyroxene, plagioclase, metal, and troilite, as well as a fine-grained matrix of garnet, ringwoodite, metal, and troilite. The late vein mainly consists of a fine-grained matrix of garnet, magnesiowstite, metal, and troilite, as well as a small amount of coarse-grained aggregates. The amount of fine-grained matrix suggests that the late vein was nearly completely melted, whereas the early vein underwent partial melting. Both fine-grainedassemblages of garnet plus ringwoodite in the early vein and garnet plus magnesiowstite in the late veinare liquidus phases crystallized from shock-induced melt. Based on our understanding of the liquidus assemblages, the late vein experienced a higher pressure and temperature than the early vein.