Table A7.

Isotopic ages and data from the Jade Mines Belt (Fig. A2)

Lithology (sample number) (number of mineral grains analysed)LocationDating methodAge ± error (Ma)MSWDWeighted mean age (Ma)MSWDIsochron age (Ma)MSWDZircon ϵHfReferencesNotes
Jade Mines Belt or ‘Jadeite Uplift’Phengites in eclogites, blueschists, jadeitites and amphibolites40Ar–39Arc. 80Goffé et al. (2002)Eclogite-facies metamorphism
40Ar–39Arc. 30Goffé et al. (2002)Oligocene HP blueschist-facies overprint
SanhkamawGroup-I zircons (n = 17); typical zoning, Na-free Mg-silicate inclusions, highest U and Th values5.8 kg jadeite block from near TawmawSHRIMP U–Pb163.2 ± 3.31.615.5–20.0Shi et al. (2008, 2009)Interpreted as age of igneous (formation of igneous crust) and/or hydrothermal (serpentinization and/or rodingitization of oceanic crust)
Group-II zircons (n = 9); bright zircons with jadeite inclusions, lower U and Th than Group 1SHRIMP U–Pb146.5 ± 3.40.715.6–18.5Shi et al. (2008, 2009)Interpreted as formation age of jadeite
Groups I and II zircons (n = 28)SHRIMP U–Pb157.4 ± 3.83.615.8Shi et al. (2008, 2009)High +ve zircon ϵHf values indicate all zircons derived from rapid reworking of very juvenile crust
Group-III zircon (n = 1); lowest U and Th values, in late veins cutting Group I, II zirconsSHRIMP U–Pb122.2 ± 4.8Shi et al. (2008)Hydrothermal fluids derived from hydration of juvenile oceanic crust plus dehydration of serpentine minerals at greater depths
Guangzhou Jade MarketBean-green coloured jadeite Jz0201 zircons n = 16 (75 analyses)LA-MC-ICP-MS158 ± 21.4Qiu et al. (2009)Metasomatic age of growth of jadeite
Hpakant areaCoarse jadeite BUR Z1 (zircons n = 15, Type I)Hpakant town 25° 36′ N, 96° 18′ ESHRIMP-RG160 ± 13Yui et al. (2013)Zicons with oscillatory zones; inherited igneous zircons
Samples from local minerCoarse jadeite BUR Z1 (zircons n = 3; Type II)SHRIMP-RG77 ± 31.8Yui et al. (2013)Zircons with heterogeneous patchy texture; minimum age of jadeite growth
Jadeitite + omphacite BUR Z2 (zircons n = 8; Type I)SHRIMP-RG159 ± 12.1Yui et al. (2013)Metasomatic/hydrothermal zircons; minimum age of zircon growth
Jadeitite + omphacite BUR Z2 (zircons n = 8; Type III)SHRIMP-RG153–105Yui et al. (2013)Incompletely crystallized zircons gave meaningless ages
MalinhkaawLight green jadeite and black amphibole rock (X8-Jd)4 km NE Tawmaw; 12 km NW Hpakant40Ar–39Ar jadeite123.9 ± 3.41.02123.5 ± 8.6Qi et al. (2013)Initial 40Ar/36Ar age 295.7 ± 5.7 Ma; ridge is between splays of the Sagaing fault
Light green jadeite and black amphibole rock (X8-Amp-I)25° 41′ 13″ N, 96° 15′ 28″ E40Ar–39Ar amphibole134.8 ± 1.40.36134.5 ± 2.3Qi et al. (2013)Initial 40Ar/36Ar age 299 ± 20 Ma
Light green jadeite and black amphibole rock (X8-Amp-II)40Ar–39Ar amphibole92.7 ± 1.20.7995.3 ± 2.6Qi et al. (2013)Initial 40Ar/36Ar age 258 ± 33 Ma. Qi et al. (2013) concluded that the jadeite studied formed during Early Cretaceous (135 Ma) HP metasomatism and also experienced a Late Cretaceous HP metasomatism (93 Ma). The formation of Myanmar jadeite involved multiple stages of metasomatism.
Hpakant townPhengitic-muscovite-rich quartz schist (A4)3 km SW Hpakant40Ar–39Ar phengitic muscovite(293.29 ± 10.96)43.97 ± 1.222.6744.54 ± 2.893.09Shi et al. (2014)Domed plateau (9 steps) caused by >1 recrystalllization; inverse isochron age (same 9 steps) similar
(26° 36.9′ N, 95° 18.2′ E)Phengitic-muscovite-rich quartz schist (A9)3 km SW Hpakant40Ar–39Ar phengitic muscovite(286.91 ± 34.45)44.75 ± 1.1239.4144.97 ± 1.3245.52Shi et al. (2014)Flat plateau (6 steps) indicates minor disturbance; inverse isochron age (same 6 steps) similar age
Glaucophane-barroisite quartz schsit (P4)5 km NW Hpakant40Ar–39Ar glaucophane-barroisite(408.24 ± 200.39)152.44 ± 1.520.64151.64 ± 2.080.03Shi et al. (2014)Upwards staircase spectrum (3 plateau steps used); possible excess Ar so? >1 phase present. 152 Ma represents lower limit age of glaucophane growth and blueschist metamorphism. c. 45 Ma event coeval with India–Eurasia collision.