“Spherulite-like” jadeite growth in shock-melt veins of the Novosibirsk H5/6 chondrite

• Published in: Russian geology and geophysics Vol. 58; no. 1; pp. 12 - 19
• Main Authors: Bazhan, I.S., Ozawa, Shin, Miyahara, M., Ohtani, E., Litasov, K.D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2017; Allerton Press
• Subjects: chain silicates; Chelyabinsk Meteorite; chemical fractionation; chondrites; clinopyroxene; crystal growth; feldspar group; framework silicates; glasses; H chondrites; impact melts; impacts; jadeite; LL chondrites; melting; melts; metamorphism; meteorites; meteorites and tektites; microstructure; Novosibirsk H5/6 chondrite; Novosibirsk Meteorite; orbicular texture; ordinary chondrites; Petrology; plagioclase; plagioclase melt; pyroxene group; shock metamorphism; silicates; spherulite-like microtexture; spherulites; stony meteorites; textures; veins; jadeite; plagioclase melt; shock metamorphism; Novosibirsk H5/6 chondrite; spherulite-like microtexture
• ISSN: 1068-7971; 1878-030X
• DOI: 10.1016/j.rgg.2016.04.012

The Novosibirsk H5/6 ordinary chondrite has signs of shock metamorphism, such as dark shock-melt veins (SMVs) crossing the chondrite host rock. The plagioclase composition grains (Ab78An14Or7) with jadeite were found in the host-rock fragments inside the SMVs. Jadeite has an unusual radial-concentric spherulite-like microtexture. The spherulite-like jadeite formed from the molten plagioclase grain under high-pressure and high-temperature conditions during an impact event. The crystallization was accompanied by sodium-potassium differentiation between coexisting jadeite and residual melt. The PT-conditions of jadeite formation were estimated to be 3-14 GPa and 1400-2150 °C. Jadeite crystallization, Na-K differentiation, and the pressure-temperature estimates of jadeite formation in the Novosibirsk chondrite are very close to those in the Chelyabinsk LL5 chondrite. The spherulite-like microtexture and jadeite-glass coexistence, most likely, point to a high cooling rate of the SMVs at the pressure release stage of the metamorphic process.