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Jadeite–K-feldspar rocks and jadeitites from northwest Turkey

Published online by Cambridge University Press:  05 July 2018

Aral I. Okay
Aral I. Okay*
Affiliation:
İTÜ, Maden Fakültesi, Jeoloji Bölümü, Ayazağa 80624, İstanbul, Turkey
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Abstract

Blueschist-facies rocks with jadeite-K-feldspar-lawsonite paragenesis occur as exotic blocks in Miocene debris flows in the blueschist belt of northwest Turkey. The jadeite-K-feldspar rocks have a very fine grain size and although recrystallized locally retain a relict porphyritic volcanic texture. The former nepheline microphenocrysts, recognized from their characteristic shapes, are pseudomorphed by jadeite and K-feldspar, while the relict magmatic aegirine has rims of jadeite. The matrix of the rock consists of very fine-grained aggregates of jadeite, K-feldspar and lawsonite. In some blocks, jadeite makes up >60% of the mode. Jadeite, K-feldspar and lawsonite in the blocks are essentially pure end-member in composition. P-T estimates for these rocks are 8 ± 2 kbar and 300 ± 50°C. The preserved volcanic texture, relict aegirine and the bulk rock composition indicate that these rocks represent metamorphosed phonolites. The paragenesis in these rocks shows that jadeite-K-feldspar is a stable mineral pair in blueschist-facies P-T conditions.

Keywords

jadeiteK-feldsparlawsonitejadeititeblueschistTurkey
Type
Mineralogy
Information
Mineralogical Magazine , Volume 61 , Issue 409 , December 1997 , pp. 835 - 843
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1997

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