Mineralogy of jadeitite and related rocks from Myanmar: a review with new data

摘要

The jadeitite from Myanmar is the most important commercial source on Earth, and its mineralogy perhaps the most diverse. More than thirty mineral species, including jadeite, omphacite, kosmochlor, Cr-bearing jadeite-omphacite, albite, celsian, banalsite, hyalophane, nyb?ite, eckermannite, magnesiokatophorite, glaucophane, richterite, winchite, analcime, natrolite, thomsonite-Ca, pectolite, vesuvianite, titanite, grossular, uvarovite, allanite, phlogopite, cymrite, zircon, graphite, quartz, diaspore, kaolinite, pyrite, galena, chromite, and ilmenite have been documented from these jadeitites and related rocks, which we review and update. Phlogopite, natrolite, thomsonite-Sr, titanite and ilmenite are newly reported here. Amphiboles, kosmochlor and omphacite formed closely related to the paragenetic sequence in the presence of jadeite; however, uvarovite is formed by replacement of chromite and does not require the presence of jadeite. At least two stages of jadeitization have been identified for Myanmar jadeitite. Late-stage zeolites, pectolite and hyalophane, banalsite, titanite and some celsian formed at lower P and T. The spectrum of minerals in Myanmar jadeitite indicates that the jadeite-forming fluids were rich in Na, Al, Ba, Sr, and Ca. Moreover, the variety of replacement textures suggests that most rocks in the serpentinite mélanges were subject to infiltration and potential replacement by jadeitite or reaction with jadeitite. Serpentinite was replaced by sodic to sodic-calcic amphibole, chromite in ultramafic rock by kosmochlor and Cr-bearing jadeite, and the clinopyroxene in mafic rock by omphacite. Relict ilmenite replaced by titanite in omphacitite is evidence for metasomatism of mafic rock. Sodium-rich fluids were likely dominant throughout jadeitite crystallization and metasomatic reactions. A general mineralogical comparison of jadeitites world-wide indicates both similarities and distinctions; these could be used for interpreting sources of the jadeite jade, particularly in archaeology.