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

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I.S. Bazhan, Shin Ozawa, M. Miyahara, E. Ohtani, K.D. Litasov

Russian Geology and Geophysics
Volume 58, Issue 1, January 2017, Pages 12–19
Received 3 December 2015, Accepted 26 April 2016, Available online 13 February 2017

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“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.”

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