Chapter 13 Jadeitite and other high-pressure metamorphic rocks from the Jade Mines Belt, Tawmaw area, Kachin State, northern Myanmar by Thet Tin Nyunt, Hans-Joachim Massonne, and Tay Thye Sun Geological Society, London, Memoirs Volume 48(1):295-315 November 15, 2017 © 2017 The Author(s). Published by The Geological Society of London. All rights reserved

Geological map of the Jade Mines Belt (JMB) showing the localities mentioned in the text and the location of the samples described. Geological map of the Jade Mines Belt (JMB) showing the localities mentioned in the text and the location of the samples described. Compiled by Thet Tin Nyunt, modified from Chhibber (1934a), Bender (1983), Than Tun (1997) and Thet Tin Nyunt (2009). Thet Tin Nyunt et al. Geological Society, London, Memoirs 2017;48:295-315 © 2017 The Author(s). Published by The Geological Society of London. All rights reserved

(a) Section through the Uru Boulder Bed exposed in the river bank at Kyettagaung Hill, Kachin State (photograph courtesy of Nyan Thin, 2002). (a) Section through the Uru Boulder Bed exposed in the river bank at Kyettagaung Hill, Kachin State (photograph courtesy of Nyan Thin, 2002). (b) Jadeitite block of the Nant Maw Mine, where the world's largest block of massive jadeitite was discovered (photograph courtesy of George Harlow, 2002). Thet Tin Nyunt et al. Geological Society, London, Memoirs 2017;48:295-315 © 2017 The Author(s). Published by The Geological Society of London. All rights reserved

(a) Outcrop nature of jadeitite in peridotite, Tawmaw (Jade Land worksite). (a) Outcrop nature of jadeitite in peridotite, Tawmaw (Jade Land worksite). (b) Jadeitite which is surrounded by amphibolite at Natmaw. (c) Contact nature of peridotite and amphibolite, intermingled with albitite and jadeitite at Natmaw. (d) Generalized sketch showing the nature of the jadeitite body in the Tawmaw area, showing gradational composition within the peridotite (Bleeck 1908, fig. 3; Harlow et al. 2014, 2015). (e) Long and short prismatic jadeite crystals in jadeitite, showing zoning and twinning (013/05). (f) Granular grains of various sizes of jadeite in jadeitite (MJ12) (crossed-polars). (g) Fan-shaped aggregate of jadeite in jadeitite (SMJD) (crossed-polars). (h) Long prismatic jadeite, bent due to deformation, indicating the shear sense (KT17) (crossed-polars). (i) Long prismatic crystals and aggregates of kosmochlor in jadeitite surrounding relict chromite grains (AS3a) (plane-polarized light). (j) Relict vesuvianite in jadeitite (MJ11) (plane-polarized light). (k) long and short prismatic jadeite crystals and subhedral to anhedral albite in albite–jadeite rock (KT23) (crossed-polars). (l) Parallel alignment of anhedral albite in albitite (008/05) (crossed-polars). (m) Kosmochlor with relict chromite at the core, indicating that kosmochlor was formed due to breakdown at the expense of chromite in Maw-sit-sit (MJ17) (plane-polarized light). (n) Zoning of euhedral amphibole crystals in amphibolite (KT34) (crossed-polars). (o) Parallel alignment of amphibole crystals (richterite and actinolite) along the foliation in actinolite schist (Thein Than) (crossed-polars). (p) Compositional zonation of glaucophane in glaucophane schist (041/05) (plane-polarized light). Words and numbers in parentheses refer to the sample name. Thet Tin Nyunt et al. Geological Society, London, Memoirs 2017;48:295-315 © 2017 The Author(s). Published by The Geological Society of London. All rights reserved

An approximate P–T path (broad dashed line) for jadeitite and related rocks in Myanmar, based on petrogenetic grids, phase equilibria (modified after Shi et al. 2010, 2014) and thermodynamic calculation by Thet Tin Nyunt (2009). An approximate P–T path (broad dashed line) for jadeitite and related rocks in Myanmar, based on petrogenetic grids, phase equilibria (modified after Shi et al. 2010, 2014) and thermodynamic calculation by Thet Tin Nyunt (2009). Estimated P–T condition of Myanmar jadeitite by Oberhänsli et al. (2007). Metamorphic facies boundaries after Maruyama et al. (1996) and Liou et al. (2004). The reaction curves limiting jadeitite-bearing mineral equilibria, the Atg-out reaction and Pg+ Czo assemblage (abbreviations from Whitney & Evans 2010). Thet Tin Nyunt et al. Geological Society, London, Memoirs 2017;48:295-315 © 2017 The Author(s). Published by The Geological Society of London. All rights reserved

Model for the formation of jadeitite. Model for the formation of jadeitite. (i) Fracture in peridotite body. (ii) Shearing movement opens the fracture to permit penetration of fluids, causing serpentinization of the peridotite (light green). Jadeite-saturated fluids intruded along the fracture to deposit jadeite (green). (iii) Successive fracturing in the brittle jadeitite allows the precipitation of additional jadeite (red) (from Harlow & Sorensen 2005). Thet Tin Nyunt et al. Geological Society, London, Memoirs 2017;48:295-315 © 2017 The Author(s). Published by The Geological Society of London. All rights reserved