Eur. J. Mineral. 2012, 24, 345–370 Jadeitite: Published online January 2012 new occurrences, new data, new interpretations

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

1,2, 2 1 1 1 1 3 GUANGHAI SHI *,GEORGE E. HARLOW ,JING WANG ,JUN WANG ,ENOCH NG ,XIA WANG ,SHUMIN CAO 4 and WENYUAN CUI

1 State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, PR China 2 Department of Earth and Planetary Sciences, American Museum of Natural History, New York, NY 10024-5192, USA *Corresponding author, e-mail: [email protected]; [email protected] 3 Guangdong Province Material Testing Center, Guangzhou 510080, PR China 4 School of Earth and Space Sciences, Peking University, Beijing 100871, PR China

Abstract: 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, nybo¨ite, eckermannite, magnesiokatophorite, glaucophane, richterite, winchite, analcime, natrolite, thomso- nite-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 me´langes 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. Key-words: jadeitite, fluid-rock interaction, serpentinite, metasomatism, mineral diversity, subduction, Myanmar.

1. Introduction above. The largest and commercially most important source of jadeitite on the planet is the so-called Jade Mine Tract, Jadeitite is a rock composed almost entirely of jadeite and Kachin State, northern Myanmar (a.k.a. Burma), where related pyroxene, which is found in serpentinite me´lange some classic relationships are preserved. However, it has associated with high-pressure low-temperature (HP/LT) not been as well documented recently as it deserves, largely metamorphosed rock, such as eclogite and blueschist. owing to the difficulty of obtaining access to the deposits. Jadeitite is interpreted as a product of subduction; however, Classic relationships were described over 100 years ago it is rare world-wide and found only at 19 locations (e.g., by Bauer (1895), Noetling (1893, 1896) and Bleeck (1907, Essene, 1967; Chihara, 1971; Harlow, 1994; Shi et al., 1908), but the most important overall review is made by 2001; Tsujimori, 2002; Tsujimori et al., 2005; Harlow Chhibber (1934). These works defined the basic lithologies et al., 2003, 2007, 2012; Harlow & Sorensen, 2005; as jadeitite, albitite, amphibole-rich rocks and serpentinite. Sorensen et al., 2006; Compagnoni et al., 2007; Garcia- More recent studies of Myanmar jadeitite have identified Casco et al., 2009; Schertl et al., 2012; Tsujimori & many minerals, some with unusual chemical compositions Harlow, 2012), and much rarer than either HP/LT eclogite and/or textures (e.g., Me´vel & Kie´nast, 1986; Shi et al., or blueschist. Considerable progress has been made 2005a, 2005b, 2009a, 2010, 2011; Nyunt et al., 2009), as recently in the interpretation of jadeitite petrogenesis and well as six species of amphibole, terrestrial kosmochlor and discovery of new occurrences, as noted in the citations omphacite (Ou Yang, 1984; Harlow & Olds, 1987; Shi et al.,

0935-1221/12/0024-2190 $ 11.70 DOI: 10.1127/0935-1221/2012/0024-2190 # 2012 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart 346 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui

2003, 2005a; Yi et al., 2006). In a comparison of jadeitites Table 1. Mineral formulae and abbreviations used in this paper. world-wide, Sorensen et al. (2006) argued that Myanmar jadeitite is most likely a crystallization product of subduc- Name Abbreviations Formulae tion channel fluids, as with jadeitite from other deposits they Aegirine Aeg NaFeSi O studied. Methane (CH ) bearing fluid inclusions in the 2 6 4 Albite Ab NaAlSi3O8 2þ 3þ Myanmar jadeitite identified by Shi et al. (2005b) support Allanite Aln Ca(REE,Ca)Al2(Fe ,Fe ) a channel origin and suggest a reducing characteristic of the (SiO4)(Si2O7)O(OH) fluid. Research on zircons in jadeitite from Myanmar (Shi Amphibole Amp A B2 C5 T8 O22 W2 et al., 2008), as well as those from Guatemala and Japan (Fu (generalized formula) et al., 2010), indicate that they may be either inherited by Analcime Anl NaAlSi2O6H2O Anorthite An CaAl2Si2O8 rapid reworking of basaltic oceanic crust, based on the Augite Aug (Ca,Na)(Mg,Fe,Al,Ti) highly depleted-mantle e (t) values (Qiu et al., 2009; Shi Hf (Si,Al)2O6 et al., 2009a), or be primary crystallization products from a Banalsite Ban BaNa2Al4Si4O16 fluid as suggested by low Th/U ratios and fluid inclusions Celsian Cls BaAl2Si2O8 (Yui et al., 2010, 2012), or may even have multiple origins Chromite Chr FeCr2O4 (Fu et al., 2010; Mori et al., 2010, 2011). Cymrite Cym BaAl2Si2O8.H2O Our recent work on rocks associated with jadeitite in Diopside Di CaMgSi2O6 Eckermannite Eck NaNa (Mg Al)Si O (OH) Myanmar reveals several occurrences of rare minerals that 2 4 8 22 2 Glaucophane Gln &Na2(Mg3Al2)Si8O22(OH)2 have not been previously reported. In this paper we present Grossular Grs Ca3Al2Si3O12 our new findings within the context of a mineralogical Hyalophane Hy (K,Ba)Al(Si,Al)3O8 review and discuss mineral origins based on paragenetic Ilmenite Ilm FeTiO3 relationships. Relevant mineral formulae and abbrevia- Jadeite Jd NaAlSi2O6 tions are list in Table 1. Kosmochlor Kos NaCrSi2O6 Magnesiokatophorite Mkt Na(CaNa)(Mg4Al)Si7AlO22 (OH)2 Natrolite Ntr Na2(Al2Si3)O102(H2O) Nybo¨ite Nyb NaNa2(Mg3Al2)Si7AlO22 2. Geological setting (OH)2 2þ Omphacite Omp (Ca,Na)(Mg,Fe ,Al)Si2O6 Jadeitite is found along the western boundary of the Orthoclase Or KAlSi3O8 Sagaing fault zone as boulders in drainages and the Uru Pectolite Pct NaCa2Si3O8(OH) Phlogopite Phl KMg3(Si3Al)O10(OH, F)2 conglomerate and as tectonic blocks or veins in serpenti- Richterite Rct Na(CaNa)Mg Si O (OH) nite me´lange at the Jade Mine Tract, near Hpakan, Kachin 5 8 22 2 Thomsonite-Ca Thm NaCa2Al5Si5O206H2O state (Fig. 1a), where basement rocks are exposed through Thomsonite-Sr Thm-Sr Na(Sr,Ca)2Al5Si5O206H2O the sediments of the Chindwin, Irrawaddy and Hukawng Titanite Ttn CaTiSiO5 basins (Mitchell et al., 2007). The Tract is associated with Uvarovite Uv Ca3Cr2(SiO4)3 fragments of an ophiolite or serpentinite me´lange that has Vesuvianite Ves (Ca,Na)19(Al,Mg,Fe)13 been interpreted as a Late Cretaceous (?) collision zone (SiO4)10(Si2O7)4 (OH,F,O) between the West Burma Plate and Shan-Thai block, but 10 Winchite Wnc &(CaNa)(Mg4Al)Si8O22 more recently as an exhumation resulting from transpres- (OH)2 sional deformation of the Shan-Thai block and the trans- Zircon Zrn ZrSiO4 form-like motion along the Indus-Yardang suture adjacent to the Indo-Burman Range (cf. Morley, 2004). This Range Note: Mineral abbreviations mainly according to Whitney & Evans to the west of the Jade Mine Tract covers an area between (2010). the Myanmar Central Basin and the western border with India. The Sagaing fault is a major right-lateral strike-slip free, Mg-rich mineral inclusions, and a mean age of 163.2 continental fault, extending over 1200 km, which reaches 3.3 Ma. Group-II zircons have bright luminescence the Andaman spreading centre at its southern end and is the without oscillatory zoning, jadeite and jadeitic pyroxene modern expression of the transform motion. The rocks in inclusions, lower U and Th contents and a mean age of this range are progressively younger from east to west. 146.5 3.4 Ma. Because of the oscillatory zoning, Mg- Dating of rocks from the Jade Mine Tract has been an rich inclusions typical of a mafic to ultramafic association, important goal for understanding both the evolution of the Group I zircons were interpreted as igneous (oceanic crust) jadeitite and the history of the me´lange. Zircon crystals or hydrothermal (serpentinization and/or rodingitization) occurring in the Jade Tract jadeitites have been studied, in origin from the oceanic crust during the Middle Jurassic. including U-Pb dating by SHRIMP, to elucidate more Group II with inclusions consistent with crystallization about the geochronology (Shi et al., 2008). There are two coeval with jadeitite thus formed during active subduction important groups of zircon grains with different interior in the Late Jurassic. Thus, from this interpretation, some characteristics, cathodoluminescence, mineral inclusions, zircons are inherited while others are primary, crystallized and chemical compositions. Group-I zircons generally during jadeitite crystallization. The average of all Group-I have oscillatory zoning, high U and Th contents, and Na- and II ages of 157.4 3.8 Ma (Shi et al., 2008) is nearly Mineralogy of jadeitite and related rocks from Myanmar 347

Fig. 1. (a) Geological overview of the Myanmar area, showing the Jade Mine Tract. (b) Geological sketch map of the Myanmar Jade Mine Tract (modified after Bender (1983), and Morley (2004)). identical to the ungrouped U-Pb ages of 158 2 Ma for that some veins contain only jadeite and albite, while zircons in jadeitite from the same locality using LA-MC- others have a boundary zone (on one or both sides) of ICPMS techniques by Qiu et al. (2009). amphiboles, such as eckermannite and glaucophane (dark Primary jadeitite deposits occur as massive veins cross- gray to blue-black) or actinolite (dark green). The bound- cutting serpentinized peridotites that belong to the ary with serpentinite is marked by a soft, green border zone Hpakan-Tawmaw serpentinite me´lange (Fig. 1b). that consists of a mixture of the adjacent vein minerals and Country rocks adjacent to the me´lange include phengite- chlorite, with or without calcite, actinolite, talc, and cherty bearing glaucophane schists and stilpnomelane-bearing masses (Chhibber, 1934; Soe Win, 1968), i.e., a blackwall quartzites, as well as amphibolite-facies rocks such as assemblage. Serpentinite conglomerate units in fault con- garnet-bearing amphibolites and diopside-bearing marbles tact with the serpentinite me´langes contain jadeitite (Shi et al., 2001). The primary discontinuous veins of boulders, cobbles and pebbles that are also mined around jadeitite also occur in serpentinized peridotite at several Hpakan and about 60 km west of Hpakan at Nansibon (Ave´ other areas (Chhibber, 1934). At Tawmaw, ‘‘dikes’’ are Lallemant et al., 2000; Goffe´ et al., 2000; Hughes et al., parallel to shear zones following northeasterly strikes with 2000; Harlow & Sorensen, 2005). Jadeitite-bearing con- dips from 18 to 90SE (Hughes et al., 2000, and refer- glomerates also extend from Monhyn (Thin, 1985) to ences therein). Dike thicknesses are poorly reported, prob- Indaw-Tigyaing (United Nations, 1979), 100–230 km ably because of weathering and their irregular swelling, south of Hpakan, along the Sagaing fault. pinching, and faulting-off; however Soe Win (1968) gave a In the classic work by Bleeck (1908) a jadeitite vein width of 1.5–2.5 m for the Khaisumaw dike at Tawmaw. system (described then as a dike) at Tawmaw had a foot- Recently Nyunt (2009) described that jadeitite occurs as wall boundary zone between the serpentinized peridotite vein-like bodies about 15 6 9 m in the Natmaw area body and jadeitite-albitite vein (see fig. 7–2 and Plate 7-2c (Nantmaw #109 mine) and about 3 3 2 m at the Jade in Harlow et al., 2007). Located within or associated with Land worksite at Tawmaw. The second author visited the the amphibole boundary, kosmochlor, chromian jadeite Natmaw mine in 2002 and observed an ellipsoidal body, and some chromian omphacite occur as coronal aggregates like a boudinage, tapering into a centimeters thick vein at with or without a chromite core or as small blocks (Shi one end (source of MJE02-3 samples). Nyunt (2009) et al., 2005a). Small blocks of omphacitite have also been described that jadeitite, albite-jadeite rocks, albitite, chlor- found (Yi et al., 2006). The jadeitite veins are crosscut ite schist, actinolite schist and amphibole felses were found locally by thin late-stage albite veins, which are commonly within the serpentinized peridotite (mainly dunite), and less than 5 mm wide. In addition, accessory minerals such 348 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui as zircon, pyrite and galena also occur in jadeitite (Harlow et al., 2007; Shi et al., 2008). Jadeitite-related rocks in the present investigation refer to rocks adjacent to jadeitite veins or blocks within the serpentinized ultramafic rocks, including amphibole rock, omphacitite, kosmochlor rock, albitite and possible others. Newly studied samples, collected by GHS and by GEH (MJE02 samples are in the petrology collection of the American Museum of Natural History), include a dark green jadeitite (sample No. K068), white jadeitites (sample No. D, 8-4, FC-1), black omphacitites (sample No. YX-1, Rma), kosmochlor rocks (sample No. K13, K15A, WM1), jadeitite-amphibolite (sample No. 012), white-gray albi- tites (sample No. D2, WJ-1, WJ-3), albitite-jadeitite boundary (sample No. Ab-Jd-01), jadeitized rodingite (sample No. 22), and white-grayish zeolite-predominant rocks at the pinching out of a jadeitite vein (sample No. MJE02-3-6 and MJE02-3-9).

3. Lithological features

3.1. Lithological variations of jadeitite and related rocks

Jadeitite occurs as veins and blocks and is associated with Fig. 2. (a) A cluster of euhedral jadeite crystals (Jd-II) formed on omphacitite, kosmochlor rock, jadeitized rodingite, amphi- fine-grained jadeite aggregate (Jd-I, assuming Jd-I precedes Jd-II) bolites (sodic-calcic amphiboles mostly) and albitite, from Myanmar (sample R2, height 10 cm). (b) Comb-like structure either as enclosed selvages or boundary assemblages. of jadeite aggregates (Jd-II) on deformed jadeitite base (Jd-I) from Most jadeitite is white (Fig. 2a), but other colors include Myanmar (Sample 012, width 15 cm). (c) Omphacitite boulder green (Fig. 2b), purple/lavender, and occasionally gray-to- (sample Rma, width 10 cm). (d) Kosmochlor rock and jadeitite (width 16 cm). (e) Crushed jadeitite fragments filled by amphibole black. Ochre to brown coloring is due to staining from matrix (width 20 cm each). (f) Later stage albitite vein cutting surface exposure. Jadeitite consists primarily of jadeite through jadeitite, omphacitite, amphibole rock and/or kosmochlor with minor accessory minerals such as omphacite, amphi- rock (sample Ab-Jd01, width 30 cm). bole, albite, analcime and zircon, etc. Deformation is a common feature, sometimes approaching mylonitic tex- ture, with recrystallization and fluid infiltration crystal- zeolite, chlorite, and barian mineral (Li, 2003; Wang et al., lization responsible for rock cohesion (Sorensen et al., 2012). Its fresh surfaces have green to dark green (pyroxene) 2006). Undeformed jadeitite selvages are occasionally color with areas of light yellow-gray (garnet). This rock is retained even in highly deformed samples (Shi et al., rare and only one piece has been found as a small weathered 2009b). Veining and cavity clusters of jadeite in jadeitite block from eluvium near Hpakan city. Amphibolite appears are a common, late-stage feature (Fig. 2a, b). green to black (Fig. 2b, e, f), consisting principally of sodic Omphacitite is dark green to black and typically occurs as to sodic-calcic amphiboles identified as eckermannite, mag- boulders (Fig. 2c). It is typically composed of omphacite nesiokatophorite, nybo¨ite, glaucophane, richterite and and jadeite with minor titanite, phlogopite, albite, ilmenite, winchite (Shi et al., 2003). Albitite is transparent and color- amphibole, zircon, and vesuvianite, a Ba-Sr-bearing mineral less to opaque and white (Fig. 2f), consisting primarily of and zeolite (e.g., Yi et al., 2006). Most omphacitite is fine- albite with possible thomsonite-Ca, pectolite, vesuvianite, grained and may show a replacement texture of omphacite hyalophane, cymrite, and celsian. by jadeite and may even be cut by jadeite veins. Unfortunately, a direct contact between jadeitite and 3.2. Metasomatic reaction zones and zonations omphacitite has not been observed. Kosmochlor rock is dark green and occurs together with jadeitite (Fig. 2b, d). Primary jadeitite veins occur in serpentinite with albitite It is composed of kosmochlor, jadeite, and Cr-bearing and/or amphibolite boundaries, as illustrated by Bleeck jadeite, with minor chromite, albite, sodic amphibole (1907) and in fig. 2 of Shi et al. (2008). Additionally, uvarovite clinochlore natrolite (Me´vel & Kie´nast, some jadeitite blocks are made up of broken jadeitite frag- 1986; Harlow & Olds, 1987; Colombo et al., 2000; ments in a matrix of amphibole/amphibolite (Fig. 2e), Hughes et al., 2000). Jadeitized rodingite consists of ompha- whereas others consist of foliated jadeite aggregates (Fig. cite, garnet and jadeite, with minor allanite-(La), phlogopite, 2b, f) due to deformation events, both syn- and post- Mineralogy of jadeitite and related rocks from Myanmar 349 crystallization of the jadeitite. Textural observations sug- Table 2. A simplified grouping of minerals in the Myanmar jadei- gest that amphibole forms during fluid infiltration into the tites and related rocks according to chemical composition. contact zone between the jadeitite bodies and the surround- ing ultramafics at high-pressure conditions by means of Group Subgroup Minerals metasomatic reaction (see Shi et al., 2003). Kosmochlor Na-rich Al-dominant Jadeite, albite, analcime, natrolite, aggregates occasionally occur as broad bands outside the omphacite jadeitite vein (Fig. 2d), or mostly as small isolated augen or Mg-dominant Nybo¨ite, eckermannite, glaucophane, zones between amphibolite bands and jadeitite veins (Fig. magnesiokatophorite, richterite, 2b). They also often occur as a string of small rounded winchite, omphacite spherules or elongated aggregates wrapped within jadeitite Cr-dominant Kosmochlor, Cr-bearing jadeite- omphacite, Cr-rich eckermannite, and amphibolite. Between kosmochlor and jadeite zones glaucophane, nybo¨ite, and there usually exists a sharp compositional boundary. The katophorite preservation of relict chromite in the core of kosmochlor Ca-dominant Thomsonite-Ca, pectolite and chromian jadeite indicates a metasomatic origin from a (Ba, Sr)-dominant Banalsite, thomsonite-Sr peridotite protolith, which was infiltrated by an aqueous Na-poor or Ca-dominant Vesuvianite, titanite, grossular, solution rich in Na, Al, and Si (Me´vel & Kie´nast, 1986; absent uvarovite, allanite Harlow & Olds, 1987; Shi et al., 2005b). K-dominant Phlogopite, hyalophane (Ba, Sr)-dominant Hyalophane, cymrite, celsian Others Zircon, quartz, diaspore, kaolinite, ilmenite 3.3. Mineralogical diversity Non- Pyrite, galena, chromite, graphite, silicates iron spherule More than thirty mineral species have been identified in the Myanmar jadeitite and closely related rocks. A few are relict minerals from protoliths (e.g., chromite, ilmenite, capacity to crystallize and/or react with minerals of the and possibly zircon), but most are either vein crystalliza- subduction channel and overlying ultramafic rocks. tion or metasomatic reaction products. The latter include The Na-poor or Na-absent silicate group can be divided pyroxenes (jadeite-omphacite series pyroxenes and Cr- into four subgroups: Ca-, K-, (Ba, Sr)-dominant and alkali- bearing pyroxenes), amphiboles (sodic, sodic-calcic, and or alkali-earth-free (Table 2). In the Ca-dominant sub- calcic amphiboles), phlogopite, vesuvianite, garnet, feld- group, uvarovite, grossular and allanite possibly formed spars, zeolites, sulfide minerals and a few other minerals. before jadeite and may be related to mantle metasomatism Most minerals are Na-dominant to Na-bearing species, or oceanic hydration prior to subduction. Titanite formed at even those that are nominally Na-free, such as vesuvianite the expense of ilmenite (or possibly rutile, although it has and uvarovite, in which small amounts of Na have been not been reported in Myanmar jadeitite) and is texturally measured (e.g., Nyunt et al., 2009). The Na-dominant sili- post-jadeite in Myanmar. Vesuvianite occurs in late-stage cate minerals can be divided into five subgroups which are vein fillings. Thus there are at least two stages of Ca- either Al-, Mg-, Cr-, Ca- or (Ba, Sr)-dominant (Table 2). dominant mineral formation in the Myanmar jadeitite. In Jadeite and albite are the two main and abundant minerals in the (Ba, Sr)-dominant series, celsian in chromian jadeite the Al-dominated subgroup. Albite, together with analcime replaces a precursor Ba mineral (Shi et al., 2005a), so and natrolite in the same subgroup, formed later at lower minerals of this subgroup may have formed before, during, pressure. Six species of amphibole, typically mixed in com- or after the main formation of jadeite, although the most plexly zoned samples, constitute most of the Mg-dominant commonly observed textures suggest late-stage formation. subgroup; they are considered metasomatic reaction pro- Among the silicates without alkalis or alkaline earths, ducts between a fluid rich in Na, Al and serpentinized the only generalizations are for the clay and clay-like ultramafic rocks (e.g., Shi et al., 2003) at HP conditions. species that formed during weathering. Ilmenite is clearly Kosmochlor and Cr-bearing jadeite-omphacite are the inherited; quartz is very rare but potentially inherited, minerals in the Cr-dominant series, which have been inter- primary or secondary, and zircon can be both inherited preted as metasomatic reaction products of chromite with and primary. jadeitic fluids under HP conditions (e.g., Harlow & Olds, Finally, there are the non-silicates which have individual 1987; Ouyang, 2001; Shi et al., 2005a); chromian amphi- characteristics. Sulfides can form at any time but appear to boles are also a part of the group; although they are Mg-rich, be late. Chromite derives from the overlying ultramafics the relevant crystallographic site for Cr is dominantly occu- and the 100 mm iron spherules sheathed in wu¨stite appear pied by it. The chromian amphiboles are also the result of to be inherited from sea-floor sediment (Shi et al., 2011). reactions between fluid and ultramafic (Me´vel & Kie´nast, Small black carbonaceous inclusions have not been studied 1986; Harlow & Olds, 1987). In the Ca- and (Ba, Sr)- sufficiently to know whether it is inherited organic matter dominant series, the minerals formed at low P conditions, or primary graphite crystallized from a fluid. generally after jadeite (omphacite, which may be considered The mineralogical diversity in Myanmar jadeitite- to belong to several groups, may have formed before or after related lithologies reflects the complexity of subduction jadeite). The abundance of Na-dominant silicate minerals channel – me´lange constituents and the fluid-rock interac- clearly reflects the influence of the fluid composition and its tions during the complex dynamic evolution of the rocks, 350 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui from sea floor through subduction and exhumation to weathering.

3.4. Bulk-rock compositions

Unfortunately whole-rock chemical analysis has only been carried out on samples of white jadeitite from Myanmar (Shi et al., 2008). Trace elements display U-shaped REE patterns with pronounced positive Eu anomalies, very low total REE abundances, moderate enrichment of high field strength elements Ti, Zr, and Hf and large ion lithophile elements Pb, Ba, Sr, as well as Li. These features indicate a metaso- matic origin (see Shi et al., 2008) or crystallization from such a metasomatic fluid with a contribution from continen- tally derived sediments (e.g., Sorensen et al., 2006; Simons et al., 2010). In addition, Lu-Hf isotope analyses on zircons in the jadeitite show positive eHf(t) values (eHf(t) ¼ 15.5–20.0). Such highly positive eHf(t) values for the jadei- tite zircons indicate their derivation from prompt reworking of very juvenile crust and support the assumption of the presence of Mesozoic intra-oceanic subduction within the Indo-Burman Range (see Qiu et al., 2009; Shi et al., 2009a).

4. Textures and mineral parageneses of different stages of mineralization

4.1. Formation and recrystallization of jadeitite

Jadeitites manifest both original crystallization and pro- nounced deformation textures. Undeformed jadeitite can be granoblastic to feathery in microtexture and is found in primary veins or as preserved zones in deformed jadeitite. Jadeite crystals are typically euhedral to subhedral and can be very large in size, even reaching more than 5 cm long and 2 cm wide. Jadeite rims display growth zoning, commonly rhythmic in polarized light, back-scattered electron (BSE) or cathodomuminescence (CL) images (Fig. 3a, b; also see Shi et al., 2005b, 2009b). The zoning patterns are similar to those described from other jadeitite localities (Harlow, 1994; Sorensen et al., 2006; Garcia- Casco et al., 2009; Schertl et al., 2012). Two-phase, gas/liquid fluid inclusions are common in undeformed jadeite grains, but rare in the deformed jadei- tite. They are interpreted as being primary because they are Fig. 3. (a) Cathodoluminescence image showing oscillatory zoning elongated parallel to the c-axis of the host jadeite crystals of a coarse-grained jadeite from Myanmar (sample D). (b) Back- and randomly distributed throughout the whole grains, scattered electron (BSE) image showing that the rhythmic zonation of the jadeite crystals is an oscillatory variation in chemical compo- rather than aligned along healed fractures. The inclusions sition. (c) Photomicrograph of fluid inclusions in a jadeite crystal can be classified into two groups, either methane rich or in a coarse-grained jadeitite (plane-polarized light; sample D). poor (Fig. 3c), reflecting the hydrothermal growth medium (d) Photomicrograph of curved mechanical twinning of a jadeite (see Shi et al., 2000m 2005b for details). crystal (crossed polarizers; sample No. 8-4). Deformed jadeitite from Myanmar contains crystals with undulatory extinction in polarized light and has showing variable preferred orientation of crystals, clearly experienced shear stress. Microstructures of the mechanical twinning, shear zones, development of sub- jadeitites from Myanmar suggest that deformation and grains, serrated high-angle sutured grain boundaries, or a recrystallization occurred heterogeneously at the expense ‘‘foam’’ pattern. The microstructure of the Myanmar jadei- of the primary texture (Shi et al., 2009b). Deformed jadeite tite has twofold significance both in gemology and in crystals are smaller than the granoblastic grains, generally rheology. The most precious jadeite jades with high Mineralogy of jadeitite and related rocks from Myanmar 351 translucency, termed as ‘‘icy’’ or ‘‘glassy’’ jades, have formed by decomposition of the surrounding kaolinite (Shi very fine grain size and show pronounced microstructural et al., 2010) and after formation of the jadeitite. alignment, suggesting a close correlation between the deformed microstructure and the appearance of the jadeite 4.3. Formation of later stage veins and hydrothermal jade. Shi et al. (2009b) proposed a ‘‘uniform aggregate alteration of HP minerals model’’ for the transparent jadeite jade: individual jadeite crystals are small in size (so that the inherent cleavage will There are at least two textural settings in the jadeitites; not propagate), all grains have preferred orientation (so jadeitite-II occurs either as a cluster of prismatic crystals that there is no or only infinitesimal variation in refractive (Fig. 2a) or as comb-like aggregates (Fig. 2b) on jadeitite-I, index across the neighboring grains), and grain boundaries which forms massive aggregates. Commonly jadeitite-II are very tight and narrower than the wavelength of visible crystals appear as later-stage veins cutting jadeitite-I, light (letting light transmit through without scattering at reflecting at least two formation stages of the jadeitite. grain boundaries; see fig. 16 in Shi et al. (2009b)). Albitite veins occur either as fine veins of less than 1 cm On the other hand, diverse microstructural characteris- or as broad veins of more than 10 cm (Fig. 2f). The later tics of the Myanmar jadeitite prove themselves to be ideal vein cuts through surrounding rocks of jadeitite, amphibo- samples for understanding HP/LT rheology in subduction lite and kosmochlor rock, and often includes fragments of zones. For example, natural mechanical jadeite twinning these surrounding rocks, suggesting an even later forma- has been found in UHP rocks and is regarded as the result tion relative to these surrounding rocks. of syn-seismic loading below brittle-ductile transition con- Hydrous minerals such as natrolite, analcime, thomso- ¨ ditions (Trepmann & Stockhert, 2001; Orzol et al., 2003). nite-Ca, thomsonite-Sr, pectolite, vesuvianite and cymrite In Myanmar, mechanical twinning has occurred in both often occur as late phases along jadeite grain boundaries, pure jadeitite and in surrounding amphibolite, and some or as later-stage veins adjacent to or cutting the jadeitite. twinned crystals have even been bent (Fig. 3d, also see fig. They represent hydrothermal alteration of previous HP 8 from Shi et al. (2009b)). Although macro- to microtex- minerals, and are inferred to have formed from residual tures appear to be ductile, all our P-T estimates argue for or reworking fluids related to jadeite-forming fluids along brittle-dominant deformation, thus the twinning is possibly cracks of the jadeitite and related rocks. strain induced as is evident from macrotextures and the me´lange source environment. 5. Compositions of primary and metasomatic 4.2. Multi-phase pseudomorphs minerals

Multi-phase pseudomorphs (see fig. 3a of Shi et al. (2010)) 5.1. Analytical techniques occur in chromian clinopyroxene rock composed predomi- nantly of chromian omphacite with minor sodic and sodic- Optical and SEM/BSE petrographic and microprobe ana- calcic amphiboles and small disseminated multi-phase pseu- lysis of thin sections and X-ray diffraction of mineral domorphs. Most multi-phase pseudomorphs with unde- grains were performed in this study. Minerals were ana- formed hexagonal shapes 100–400 mm across formed not lyzed by electron microprobe in thin sections. As various later than the pyroxenes. According to Shi et al. (2010), instruments in different labs were utilized, the specifics of multi-phase pseudomorphs can be classified into two types each are given in the Appendix, freely available online on in terms of celsian content: celsian-rich, and celsian-poor. the GSW website of the journal, http://eurjmin.geoscien- The celsian-rich multi-phase pseudomorphs are composed ceworld.org/. Mineral formulae were normalized either to 2þ of celsian and kaolinite with or without minor graphite and a number of oxygen or silicon atoms. Estimates of Fe 3þ diaspore. Textural relationships indicate that kaolinite and and Fe were made for some species (e.g., pyroxene and graphite were formed subsequent to celsian crystallization. amphibole) using an algorithm similar in concept to that of Diaspore crosscuts kaolinite, and formed as a later stage of Finger (1972); details are given in Harlow et al. (2011). alteration. The celsian-poor multi-phase pseudomorphs are made up of kaolinite, with minor celsian, graphite, diaspore 5.2. Relict minerals and quartz. Celsian is surrounded by kaolinite. Diaspore occurs as fibrous, silky or sheet-like grains crosscutting There are three minerals found in jadeitite and related kaolinite. Graphite is xenomorphic and occurs mainly in rocks that are interpreted as the relics of a protolith from association with kaolinite. Quartz is 5–10 mm in size and the subduction channel–mantle wedge: zircon, ilmenite, found surrounded by kaolinite in one multi-phase pseudo- and chromite. Zircons from Myanmar jadeitite and ompha- morph. A reasonable explanation for the formation of the citite (Fig. 4a; see also fig. 6 in Shi et al. (2008)) provide multi-phase pseudomorphs is the decomposition of a pre- important age and origin constraints (Shi et al., 2008, cursor cymrite. Another possible model is that they represent 2009a). At least two growth periods have been distin- alteration products derived directly from fragments of barite- guished, as discussed above. Zircon-I grains (163.2 3.3 bearing oceanic sediment, but this explanation is not favored Ma average age) were interpreted as being inherited from a (Shi et al., 2010). Quartz and diaspore are more likely to be protolith, whereas zircon-II (146.5 3.4 Ma average age) 352 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui formed contemporaneously with jadeitite crystallization. display a chemical trend such that Mg contents decrease and This interpretation is consistent with the suggestion by Fe contents increase from the core to the rim, suggesting a Mitchell et al. (2004) that high-pressure rocks in the Jade compositional trend towards magnetite (Shi et al., 2005a). Mines Tract uplift were possibly generated in the early On the other hand, Harlow & Olds (1987) noted low Al and Jurassic collision event and finally exhumed within ser- Mg as well as high Cr, Mn, and Zn in chromite, suggesting pentinite diapirs in the Tertiary. preferential reaction of the former during metasomatism and Ilmenite occurs as rounded inclusions in the cores of an increase in the latter elements in residual chromite. titanite grains (Fig. 4b) in omphacitite. Ilmenite is likely a relict igneous mineral from a mafic protolith such as basalt or gabbro rather than eclogite, which would probably con- 5.2. Pyroxenes tain rutile. The grain size was too small to obtain an accurate analysis, although dominant Fe and Ti via 5.2.1. Jadeite-omphacite series pyroxenes EPMA support the phase identification. Jadeite is the main constituent in jadeitite, and a common Chromite occurs in kosmochlor and kosmochlor-amphi- mineral in other related rocks such as omphacitite, kosmo- bole rocks (e.g., Ou Yang, 1984; Me´vel & Kie´nast, 1986; chlor rocks and amphibole rocks, and even in albitite from Harlow & Olds, 1987; Shi et al., 2005a) and is surrounded by the Jade Mine Tract. Jadeite in jadeitite veins is generally kosmochlor (Fig. 4c). The EPMA data show that the relict very pure, with jadeite content (XJd) greater than 98 mol% chromite replaced by kosmochlor is a little higher in Al and (Table 3). Undeformed crystals with rhythmic chemical 3þ lower in Fe than that in the adjacent serpentinized perido- zoning patterns increase in diopside content (XDi) to 8 tite, and that relict chromite grains rimmed by kosmochlor mol% (Shi et al., 2005b). Omphacite and aegirine mainly occur in omphacitite, jadeitized rodingite or as a minor phase in albitite and amphibole-kosmochlor rocks. In omphacitite, replacement of omphacite (Jd26–43Ae29–22 Di22–37) by jadeite or an addition of new jadeite is obvious (Fig. 4a; also see Yi et al., 2006). This texture of omphacite is also obvious in the jadeitized rodingite (Wang et al., 2012). However, Harlow & Olds (1987) described a single cobble containing Cr-bearing omphacite, which appears to be a chromite-bearing omphacitite cut by veins of jadeite with reaction growth of kosmochlor (sample AMNH- 98642). The compositional range of omphacite is Jd30–72Di25–49Kos0–29 Aeg0–34 (for detailed data see Harlow & Olds (1987); Shi et al. (2003, 2005a, 2010); Yi et al. (2006); Nyunt et al. (2009)). Some pyroxenes in the omphacitite contain more Fe3þ than Al and are interpreted as aegirine-augite, e.g., Jd26Di28Aeg42Other4 in Yi et al. (2006), according to the pyroxene nomenclature of Morimoto et al. (1988); a metasomatic origin is indicated.

5.2.2. Cr-bearing pyroxenes Kosmochlor occurs as an accessory mineral in iron meteor- ites (Laspeyres, 1897; Frondel & Klein, 1965; Couper et al., 1981) and in carbonaceous chondrites (Greshake & Bischoff, 1996). Occurrences from UHP metamorphic rocks (Liu et al., 1998), peridotite xenoliths (Sobolev et al., 1997), kimberlites (Sobolev et al., 1975), and meta- sediments (Reznitskii et al., 1999) were reported to contain Cr-bearing jadeite and omphacite, but no kosmochlor. By contrast, kosmochlor and other Cr-bearing pyroxenes are common in rocks from the Myanmar jadeite area (Ou Yang, 1984, 2001; Me´vel & Kie´nast, 1986; Harlow & Olds, 1987; Shi et al., 2005a). Compositions along the Jd-Kos binary are most abundant and offer an opportunity Fig. 4. BSE images of (a) replacement of omphacite by jadeite, new to study their paragenesis as well as the binary itself. jadeite filling fractures, with zircon and titanite (Sample YX-1). (b) The rocks that contain the Cr-bearing jadeite and ompha- Titanite with residual ilmenite core in omphacite-bearing jadeitite and cite are mostly jadeitite, but also omphacitite (Harlow & omphacitite (YX-1). (c) Photomicrograph of kosmochlor aggregates Olds, 1987). Maw-Sit-Sit, a green rock from the mine of with a corona texture surrounding relict chromite (sample WM1). that name consists of Cr-bearing jadeite–kosmochlor þ Table 3. Representative chemical compositions of pyroxenes from the Jade Mine Tract, Myanmar.

K068 22 WJ-3 WJ-1 Ab-Jd-01 Sample Phase Kos Kos Kos Ko-Aug? Cr-Omp Jd Jd Jd Jd Jd Omp Omp Omp Jd Jd Omp Omp Jd Jd Jd No. 5 6 9 10 16 15 38–35 38–38 38–39 38–45 38–40 38–41 38–42 20–1 21–1 40–1 41–2 1–Dec 18–1 20–1 SiO2 51.26 52.55 53.84 52.54 56.73 57.36 58.58 58.50 57.96 57.81 56.98 56.35 57.64 59.87 59.91 57.40 57.15 59.80 59.57 58.85 ieaoyo aett n eae ok rmMyanmar from rocks related and jadeitite of Mineralogy TiO2 bdl bdl bdl bdl 0.02 0.03 0.02 0.09 0.17 0.07 0.01 0.04 0.07 bdl 0.01 0.15 bdl bdl 0.02 0.02 Al2O3 5.49 1.51 6.83 2.67 16.81 21.41 22.59 21.49 21.98 20.60 14.38 11.75 18.21 25.13 25.05 12.86 12.92 24.33 24.93 20.70 Cr2O3 19.47 18.45 19.42 16.04 3.66 1.75 0.29 0.42 0.64 0.12 0.89 1.03 0.75 bdl bdl bdl 0.01 bdl bdl 0.05 Fe2O3 7.64 12.86 0.03 16.14 0.00 0.00 1.00 1.75 1.63 3.21 3.04 4.47 1.66 bdl bdl 3.05 3.01 0.00 bdl 1.51 MgO 0.99 0.18 1.63 0.24 3.94 1.52 0.98 1.62 1.11 1.44 5.66 6.61 2.60 0.10 0.12 7.68 7.29 0.41 0.77 1.85 MnO bdl bdl bdl bdl bdl bdl bdl bdl bdl bdl 0.06 0.07 0.03 bdl 0.05 0.07 0.09 0.02 0.02 bdl FeO 0.00 0.13 1.62 0.00 0.75 0.73 0.29 0.14 0.00 0.00 0.80 0.76 2.06 bdl bdl 0.55 0.40 0.28 bdl 0.98 CaO 3.91 0.50 2.43 0.22 5.62 1.97 1.33 2.41 1.86 2.30 8.82 10.47 4.35 0.15 0.08 10.45 10.37 0.66 0.32 2.39 Na2O 12.14 13.32 12.24 13.69 11.30 13.42 14.30 13.78 14.15 13.90 9.90 8.93 12.22 15.75 15.55 8.86 8.96 14.84 14.55 13.60 K2O bdl bdl bdl bdl bdl bdl 0.01 0.01 bdl bdl bdl bdl 0.01 0.01 0.01 bdl 0.01 0.01 0.02 bdl Total 100.90 99.50 98.04 101.54 98.83 98.19 99.39 100.20 99.50 99.45 100.54 100.49 99.60 101.01 100.78 101.07 100.21 100.35 100.20 99.95 Si 1.906 1.996 2.006 1.959 1.990 1.993 2.002 1.993 1.987 1.993 1.987 1.986 2.005 1.998 2.002 1.991 1.998 2.009 1.998 2.013 Ti n.c. n.c. n.c. n.c. 0.001 0.001 0.001 0.002 0.004 0.002 0.000 0.001 0.002 n.c. 0.000 0.004 n.c. n.c. 0.001 0.001 Al 0.241 0.068 0.300 0.117 0.695 0.877 0.910 0.863 0.888 0.837 0.591 0.488 0.747 0.989 0.987 0.526 0.532 0.963 0.986 0.834 Cr 0.572 0.554 0.572 0.473 0.102 0.048 0.008 0.011 0.017 0.003 0.025 0.029 0.021 n.c. n.c. n.c. 0.000 n.c. n.c. 0.001 Fe3þ 0.214 0.372 0.001 0.453 0.000 0.000 0.026 0.045 0.042 0.083 0.080 0.118 0.043 n.c. n.c. 0.080 0.079 0.000 0.000 0.039 Mg 0.055 0.010 0.091 0.013 0.206 0.079 0.050 0.082 0.057 0.074 0.294 0.347 0.135 0.005 0.006 0.397 0.380 0.021 0.039 0.094 Mn n.c. n.c. n.c. n.c. n.c. n.c. n.c. n.c. n.c. n.c. 0.002 0.002 0.001 n.c. 0.001 0.002 0.003 0.001 0.001 n.c. Fe2þ 0.000 0.004 0.050 0.000 0.022 0.021 0.008 0.008 0.000 0.000 0.023 0.022 0.060 n.c. n.c. 0.016 0.012 0.008 n.c. 0.028 Ca 0.156 0.020 0.097 0.009 0.211 0.073 0.049 0.088 0.068 0.085 0.329 0.395 0.162 0.005 n.c. 0.388 0.388 0.024 0.012 0.088 Na 0.875 0.981 0.884 0.990 0.769 0.904 0.947 0.910 0.941 0.929 0.669 0.610 0.824 1.019 1.008 0.596 0.607 0.967 0.946 0.902 K n.c. n.c. n.c. n.c. n.c. n.c. 0.000 0.000 n.c. n.c. n.c. n.c. 0.000 0.000 0.000 n.c. 0.000 0.000 0.001 n.c. Sum 4.018 4.000 4.000 4.014 3.995 3.996 4.001 3.998 4.004 4.007 4.000 3.999 4.000 4.017 4.008 4.000 4.000 3.993 3.982 4.000 Jd 0.05 0.06 0.30 0.04 0.68 0.86 0.91 0.85 0.86 0.82 0.57 0.46 0.75 0.99 0.99 0.51 0.53 0.96 0.95 0.84 Kos 0.57 0.55 0.57 0.47 0.09 0.04 0.01 0.01 0.02 0.00 0.03 0.03 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ae 0.21 0.37 0.00 0.45 0.00 0.00 0.03 0.04 0.04 0.08 0.08 0.12 0.04 0.00 0.00 0.08 0.08 0.00 0.00 0.04

Note: bdl, below detect limit; n.d., not detected; n.c., not calculated. 353 354 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui albite þ sodic amphibole clinochlore natrolite Olds (1987); Shi et al. (2003) identified a complex amphi- chromite (Me´vel & Kie´nast, 1986; Harlow & Olds, 1987; bole association representing solid solutions involving Colombo et al., 2000; Hughes et al., 2000). There are five compositional variations crossing six distinct amphibole distinct textures and related compositions of kosmochlor species in the amphibolite border zone, according to the and Cr-bearing jadeite in rocks from Myanmar: (1) kosmo- nomenclature of Leake et al. (1997) and Hawthorne & chlor corona aggregates with a corona texture (radiating Oberti (2006): nybo¨ite, richterite and winchite, magnesio- prisms) surrounding relict chromite in amphibole matrix katophorite, eckermannite and glaucophane (Table 4). The (Fig. 4c; e.g., Harlow & Olds, 1987; Shi et al., 2005a); (2) amphiboles are present as fine-grained (,10 mm maximum kosmochlor corona aggregates with a core of low-Cr jadeite dimension) matrix and also as coarse-grained porphyro- containing approximately 10 mol% Kos (Fig. 5a, e.g., Shi blasts (up to 6 mm max. dimension) interspersed within the et al., 2005a); (3) the commonly observed replacement fine-grained matrix. Three amphibole growth episodes texture of kosmochlor penetrating fractured chromite (Fig. were identified: in stage 1, magnesiokatophorite and rich- 5b; also see Ou Yang, 1984; Harlow & Olds, 1987; Shi terite coexist during the earliest stage of amphibole et al., 2005a); (4) granoblastic textures of undeformed growth; nybo¨ite subsequently formed, rimming magnesio- coarse-grained crystals; and (5) recrystallized fine-grained katophorite and also coexisting with eckermannite during aggregates in deformed low-Cr jadeitite. The purest kosmo- stage 2 (Fig. 6; also see Shi et al., 2003). In stage 3, chlor reported from a terrestrial rock (97 mol% NaCrSi2O6) eckermannite rims nybo¨ite and richterite and coexists was found in a coronal growth around chromite (Shi et al., with glaucophane and winchite in the fine groundmass. 2005a). Chemical compositions of kosmochlor and other Jadeite coexists during all of the stages of amphibole Cr-bearing pyroxenes vary greatly (Table 3; also see Ou growth. Me´vel & Kie´nast (1986) found a similar evolution Yang, 1984; Harlow & Olds, 1987; Tsujimori & Liou, in chromian amphiboles from kosmochlor-rich samples, 2004; Shi et al., 2005a). with the zoning evolution starting with katophorite through glaucophane and eckermannite to richterite. This last trend from eckermannite to richterite is not consistent with Shi 5.3. Amphiboles et al. (2003) but might demonstrate a local difference late in the chemical evolution from more sodic (and aluminous) Of all the jadeitite localities worldwide, extensive amphi- to one more calcic (and less aluminous). bole boundaries between jadeitite and serpentinite are only In addition to the compositions being controlled by documented in the Jade Mine Tract. In addition to the reactions involving components such as jadeite þ serpen- ´ ´ observations of Mevel & Kienast (1986) and Harlow & tine þ fluid chromite (Me´vel & Kie´nast, 1986; Harlow & Olds, 1987; Shi et al., 2003), crystallochemically the typical low and decreasing contents of tetrahedral Al but high Na in both A and B sites (using amphibole site label- ing of Hawthorne & Oberti (2006)) are consistent with HP- LT conditions in the presence of a highly sodic fluid, as interpreted for jadeitite formation. In terms of specific trends, Me´vel & Kie´nast (1986) point out that the ecker- mannite evolution from glaucophane represents the C A C A A exchange Mg Na Al –1 & –1 ( & is a vacancy on the A-site) and from katophorite to eckermannite by T B T B Si Na Al–1 Ca–1, which is the most commonly observed zoning among studied samples (also noted by Shi et al. (2003)). Late richterite would evolve from eckermannite through the exchange (or compositional change) C B C B Mg Ca Al–1 Na–1, not unlike the late trend in zoned jadeite compositions toward higher diopside content. However, making quantitative interpretations is impeded by the likely non-equilibrium conditions during transient processes as well as inadequate data on the phase equilibria involved, particularly for amphiboles and fluids. A presen- tation of the amphibole compositions follows.

5.3.1. Sodic amphiboles Glaucophane in Myanmar is generally rare and transitional to eckermannite in individual grains, with some misassign- Fig. 5. Photomicrographs (plane-polarized light) of (a) coronal kos- ments in the literature (including Shi et al. (2003)). It mochlor aggregates with a core of low-Cr jadeite (Sample K15A). differs distinctly in composition from that of blueschists (b) Replacement texture of chromite by kosmochlor (K13). in HP or UHP metamorphic belts, as Mg contents in the C Mineralogy of jadeitite and related rocks from Myanmar 355

Table 4. Chemical compositions of amphiboles from the Jade Mine Tract, Myanmar.

Sample 118Sa Cb 012b 012b 012b 012b 012b 18401c 118Sa 012b 012b 29965c 016b Cb Cb

SiO2 58.75 55.89 53.77 53.90 55.70 58.20 58.31 58.47 57.63 52.17 52.15 52.71 56.18 58.16 57.89 TiO2 0.14 0.07 0.02 bdl bdl bdl bdl 0.04 0.05 bdl bdl bdl bdl 0.04 0.11 Al2O3 10.51 11.04 10.98 9.69 7.03 6.15 7.08 3.55 0.18 10.82 11.18 5.96 4.14 7.99 8.76 Cr2O3 3.56 1.30 bdl bdl bdl 0.08 bdl bdl 10.16 bdl 0.13 0.01 bdl 1.22 0.96 Fe2O3 0.19 0.00 1.89 0.00 4.08 2.07 0.00 2.27 0.00 0.00 0.00 0.00 0.36 0.00 0.00 MgO 13.87 14.05 15.66 15.90 17.81 19.09 18.50 19.77 18.01 15.83 15.82 19.62 19.20 16.14 16.06 FeO 2.47 4.41 3.68 6.82 2.46 1.41 2.76 2.27 1.65 5.52 5.63 3.66 5.53 4.54 5.19 MnO 0.03 0.17 bdl bdl bdl 0.24 0.14 0.06 0.00 bdl bdl 0.10 bdl 0.18 0.12 NiO 0.09 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. CaO 1.04 2.61 1.60 2.45 1.59 0.64 0.22 1.94 0.09 4.11 4.23 9.61 3.56 2.41 2.61 Na2O 7.26 7.24 10.17 8.47 9.79 10.59 9.78 9.24 10.08 8.61 7.66 5.42 8.44 5.70 5.56 K2O 0.06 0.81 bdl 0.21 0.18 0.25 0.32 0.37 0.78 0.17 0.21 n.d. 0.25 1.16 0.93 d H2O 2.24 2.19 2.18 2.16 2.19 2.22 2.20 2.20 2.17 2.15 2.15 2.14 2.16 2.20 2.21 Total 100.21 99.78 99.95 99.60 100.84 100.94 99.32 100.17 100.80 99.38 99.15 99.23 99.82 99.74 100.41 T-site Si 7.870 7.649 7.401 7.499 7.610 7.844 7.933 7.980 7.971 7.292 7.287 7.395 7.808 7.924 7.844 Al 0.130 0.351 0.599 0.501 0.390 0.156 0.067 0.020 0.029 0.708 0.713 0.605 0.192 0.076 0.156 Sum 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 C-site Ti 0.014 0.007 0.002 n.c n.c n.c. n.c. 0.004 0.005 n.c n.c n.c n.c 0.004 0.011 Cr 0.377 0.141 n.c n.c n.c 0.009 n.c. n.c. 1.111 n.c 0.014 0.001 n.c 0.131 0.103 Al 1.530 1.430 1.182 1.088 0.741 0.821 1.068 0.551 0.000 1.075 1.128 0.381 0.486 1.207 1.243 Fe3þ 0.019 0.000 0.196 0.000 0.420 0.209 0.000 0.233 0.000 n.c. 0.000 0.000 0.038 0.000 0.000 Mg 2.770 2.867 3.213 3.298 3.627 3.836 3.752 4.022 3.713 3.299 3.295 4.104 3.978 3.278 3.244 Fe2þ 0.276 0.505 0.408 0.614 0.212 0.122 0.180 0.189 0.171 0.637 0.562 0.430 0.643 0.517 0.398 Mn 0.003 0.020 n.c n.c n.c 0.000 0.000 0.000 0.000 n.c. n.c 0.012 n.c 0.000 0.000 Ni 0.010 n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c Sum 4.999 4.969 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 4.929 5.000 5.000 5.000 B-site Ca 0.149 0.383 0.236 0.365 0.233 0.092 0.032 0.284 0.013 0.616 0.633 1.445 0.530 0.352 0.379 Na 1.851 1.617 1.748 1.455 1.698 1.847 1.818 1.641 1.966 1.365 1.271 0.555 1.325 1.489 1.417 Fe2þ 0.000 n.c 0.016 0.180 0.070 0.034 0.134 0.070 0.020 0.019 0.096 0.000 0.145 0.138 0.190 Mn 0.000 n.c n.c n.c n.c 0.027 0.016 0.006 0.000 n.c n.c 0.000 n.c. 0.021 0.014 Sum 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 A-site Na 0.034 0.304 0.966 0.830 0.896 0.921 0.762 0.804 0.737 0.968 0.804 0.919 0.949 0.016 0.044 K 0.010 0.141 bdl 0.037 0.031 0.043 0.056 0.064 0.138 0.030 0.037 n.c. 0.044 0.202 0.161 Sum 0.054 0.445 0.966 0.867 0.927 0.964 0.817 0.868 0.874 0.998 0.842 0.919 0.993 0.218 0.204 Total 15.043 15.414 15.966 15.867 15.927 15.964 15.817 15.868 15.874 15.998 15.842 15.848 15.993 15.218 15.204 cations OHd 2222 2 22 2 22 2 222 2 Name Gln Gln Nyb Nyb Eck 1 Eck 2 Eck 2 Eck Cr-Eck Mg-Kat Mg-Kat Rich Rich Win-Gl Win

Notes: aanalyses 12 & 7 from table 4 of Me´vel & Kie´nast (1986). bData from Shi et al. (2003) c18401 and 29965 are jadeitite specimens from AMNH mineral collection (see Appendix) dH2O and OH calculated from amphibole stoichiometry assuming only OH in nominally monovalent anion site sites are high, reaching a maximum of 3.0 apfu before Hirajima & Compagnoni, 1993) and from the Myanmar crossing into eckermannite composition space. The values jadeitite area (Me´vel & Kie´nast, 1986; Harlow & Olds, of Mg/(Mg þ Fe2þ þ Mn) are also high, .0.8 (Me´vel & 1987; Htein & Naing, 1994; Shi et al., 2003). Nybo¨ite from Kie´nast, 1986; Shi et al., 2003). The high Mg is most likely Myanmar shows Si contents of 7.31–7.49 apfu, BNa con- related to the reaction with serpentinized peridotite rather tent ranging from 1.64 to 1.84 apfu, CMg ranging from 3.16 than metabasite metamorphism. Of all the coexisting sodic to 3.42 apfu, and ANa from 0.54 to 0.94 Na apfu. In the and sodic-calcic amphiboles of stage 3, glaucophane classification diagram of Leake et al. (1997), the chemical shows the lowest Na contents on the A-site with compositions of nybo¨ite from the inner rims are very close 0.00–0.35 apfu Na (Me´vel & Kie´nast, 1986; Shi et al., to end-member nybo¨ite (Shi et al., 2003). 2003). Eckermannite associated with HP metamorphism has Nybo¨ite is known from HP to UHP metamorphic envir- been described only from jadeitites so far (Bauer, 1895; onments and has been described so far from only three Lacroix, 1930; Chhibber, 1934; Me´vel & Kie´nast, 1986; localities (Ungaretti et al., 1981; Hirajima et al., 1992; Harlow & Olds, 1987; Htein & Naing, 1994; Colombo 356 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui

B such as the Gln-exchange NaAlCa–1 Mg–1 (Shi et al., 2003). Richterite has been described in UHP metapelites from Greece (Mposkos & Kostopoulos, 2001) and a blueschist from the Klamath Mountains in California (Helper, 1986). This amphibole in Myanmar jadeitite has high Si values of 7.72–7.88 apfu, BNa content from 0.50 to 1.48 apfu, Mg contents on C from 3.62 to 4.30 apfu, and lower Al on the tetrahedral sites (TAl ¼ 0.12–0.28 apfu). The composi- tional change from richterite to magnesiokatophorite can be explained by a Tschermak’s substitution. Winchite has been discovered in the manganese ore mine at Kajlidongri, India (where it is violet in color; Leake et al., 1986) and as Mg- and Al-rich winchite from Venezuela (Maresch et al., 1982). However, there is a lack of informa- tion on this species (Sokolova & Hawthorne, 2001). It was reported in the Myanmar jadeitite as a fine-grained amphi- bole matrix or aggregate, and the composition shows slightly elevated Mg contents of 3.26–3.28 apfu and Ca contents ranging from 0.35 to 0.38 apfu (Shi et al., 2003).

5.3.3. Suspected calcic amphiboles Tremolite-actinolite had been mentioned by several authors (Chhibber, 1934; Deer et al., 1963; Soe Win, 1968; Fig. 6. Photomicrographs of an amphibole grain with magnesioka- OuYang, 1993; Hughes et al., (2000) from the Myanmar tophorite core, nybo¨ite mantle and eckermannite rim: (a) plane- jadeitite. It is described as secondary fibrous tremolite polarized light and (b) crossed polarizers (sample 012). which partly replaced some jadeite in the course of late- stage metasomatism, and as part of the blackwall (dark green) boundary between the jadeitite vein and serpentinite. et al., 2000; Shi et al., 2003; Schumacher, 2007; Nyunt However, no chemical compositions were reported, and it et al., 2009). Three parageneses of the eckermannite are has not yet been detected in our mineralogical investiga- distinguished by Si content and texture (Shi et al., 2003). tions, ostensibly for lack of access to blackwall samples. The texturally earliest eckermannite-I (rim of nybo¨ite, Fig. 6) from stage 2 coexisting with nybo¨ite has lower Si content (,7.6 apfu). Texturally later eckermannite-II rimming 5.4. Phlogopite nybo¨ite and richterite has higher Si content (.7.6 apfu). Matrix eckermannite-III shows even higher Si content Whereas phlogopite has been reported from many other (7.9–8.0 Si apfu). These data suggest that there is significant jadeitite occurrences (e.g., Guatemala, Harlow (1994, T C T C Tschermak’s substitution ( Si Mg Al–1 Al–1) from ecker- 1995); Harlow et al. (2011); the Monviso meta-ophiolite, mannite-I, to -II and then to -III (Shi et al., 2003). Piemonte Zone, Italian western Alps, Compagnoni et al. Kosmochlor-bearing jadeitite (Me´vel & Kie´nast, 1986; (2007); the Sierra del Convento, Cuba, Garcia-Casco et al. Harlow & Olds, 1987) and maw-sit-sit (our work) also (2009); and the Nishisonogi metamorphic rocks, Kyushu, contains eckermannite with comparably elevated Si, Cr to Japan, Shigeno et al. (2005)), phlogopite has not been .1 apfu, and typically has slightly lower BNa (,1.95 apfu). previously reported from Myanmar jadeitite. Phlogopite is also rare in Guatemala where phengite and paragonite are common, and even preiswerkite is more common than 5.3.2. Sodic-calcic amphiboles phlogopite. However, phlogopite was found in a late-stage Magnesiokatophorite is very rare in high-P and UHP vein adjacent to jadeitite and as a microcrystalline inter- rocks, known from two localities in the Western Alps growth with cymrite and vesuvianite (Fig. 7a, b), and shows (Reynard & Ballevre, 1988) and the Dabie Shan area variable composition (Tables 5 and 6). Some of this varia- (Dong et al., 1996). However, it is abundant in the reaction tion may be due to submicrometer scale interlayers of boundaries of jadeitite from the Jade Mine Tract (Me´vel & another K-poor phyllosilicate with higher water content, as Kie´nast, 1986; Shi et al., 2003). Chemical compositions of manifested in the analysis 9-11 in Tables 5 and 6. magnesiokatophorite show Si contents of 7.16–7.36 apfu, high Mg content on the C sites ranging from 3.15 to 3.50 apfu, and BNa content from 1.29 to 1.46 apfu and a large 5.5. Allanite variation in the ANa from 0.64 to 0.93 apfu. The composi- tional change from magnesiokatophorite cores to outer Allanite occurs in a jadeitized rodingite as irregularly nybo¨ite zones can be attributed to a coupled substitution shaped grains in association with garnet (Fig. 8a). Mineralogy of jadeitite and related rocks from Myanmar 357

Table 5. Representative chemical compositions of phlogopites in rocks from the Jade Mine Tract, Myanmar.

MJE02-3-6 Sample Anal. 8-2 8-3 9–11

SiO2 41.15 40.42 39.85 TiO2 0.03 0.00 0.06 Al2O3 19.57 17.73 15.61 Cr2O3 0.06 0.09 0.11 Fe2O3 3.62 0.00 6.36 FeO 0.00 4.51 0.00 MnO 0.06 0.14 0.03 MgO 18.26 20.21 19.63 CaO 0.08 0.10 1.54 SrO 0.05 0.00 0.03 BaO 2.14 0.35 0.09 Na2O 0.04 0.09 0.09 K2O 10.04 10.45 9.44 a H2O 4.25 4.18 4.14 Total 99.35 98.26 96.98 Oxygens 22 22 22 Si 5.812 5.801 5.776 Aliv 2.188 2.199 2.224 SUM T 8.000 8.000 8.000 Ti 0.003 0.000 0.007 Al 1.070 0.799 0.442 Cr 0.007 0.011 0.013 Fig. 7. BSE images of (a) later-stage pectolite surrounding cymrite, Fe3þ 0.385 0.385 0.693 which includes phlogopite (sample MJE02-3-6). (b) Vesuvianite Fe2þ 0.000 0.541 0.000 with phlogopite and cymrite (sample MJE02-3-6). Mn 0.007 0.017 0.004 Zn 0.000 0.000 0.000 Mg 3.844 4.323 4.240 Allanite has high Ce2O3 and La2O3 (5.3–11 wt% La2O3, Ca 0.012 0.015 0.239 Ba 0.119 0.020 0.005 7.0–9.2 wt% Ce2O3, 13–20 wt% (Ce2O3 þ La2O3) and appears to vary between allanite-(La) and allanite-(Ce) Na 0.011 0.024 0.025 K 1.809 1.914 1.746 (Table 6). We report the analyses of Li (2003) with our Sum C 15.266 15.663 15.415 calculation of cations normalized to 6 Si atoms. There are OHa 444 inexplicable deficiencies in total M cations and, without a accounting for other REEs, deficiencies in A site cations, Note: H2O and OH calculated from mica stoichiometry assuming as well. Nevertheless, compositions resemble those of only OH in nominally monovalent anion site. allanite from Buca Della Vena mine, Apuan Alps (Orlandi & Pasero, 2006). found that the residual chromite core was directly sur- rounded by radial uvarovite aggregates, which were subse- 5.6. Garnets quently wrapped by radial kosmochlor aggregates and then by Cr-bearing jadeite aggregates (Fig. 8b). This succession Garnet group minerals identified from the Myanmar jadei- of uvarovite, kosmochlor, and Cr-bearing jadeite around tite sources are grossular and uvarovite. Grossular has been chromite adds an extra compositional complexity in com- identified in a jadeitized rodingite consisting primarily of parison with the kosmochlor coronas around chromite (Fig. jadeite, omphacite, and grossular in Myanmar (Wang 4c). The uvarovite varies greatly in composition, ranging et al., 2012), and in related rocks from other jadeitite from 61 to 85 mol% Uv although some analyses are not of localities (e.g., Kobayashi et al., 1987; Harlow, 1994; high quality (Qi et al., 1999); only a single analysis is shown Tsujimori et al., 2005). An example of the microtexture in Table 7. The texture and composition of uvarovite sug- (Fig. 8a) shows a late formational stage of jadeite and gest that Ca-rich metasomatism is more likely to have omphacite with grossular. Compositionally, grossular occurred before the growth of kosmochlor without the samples (Table 7) contain over 80 mol% Grs end-member, necessary presence of jadeite, at least for this sample. with less than 4.7 wt% Fe2O3 (corresponding to 11.1–13.6 mol% andradite), and a small amount of TiO2 (0.16–1.2 wt%), MnO (,0.4 wt%), and MgO (,0.1 wt%). 5.7. Feldspars Uvarovite is rare and has only been reported in one jadeitite sample from Myanmar (Qi et al., 1999). Using Minerals of the feldspar group identified in the Myanmar backscattered electron imaging on this sample (K068), we jadeitite include albite, celsian, hyalophane and banalsite. 358 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui

Table 6. Representative chemical compositions of allanites in rocks from the Jade Mine Tract, Myanmar.

22 Anal. No. aln14a aln15a aln2a

SiO2 38.70 38.85 35.62 TiO2 0.37 0.03 0.39 Al2O3 23.49 24.15 20.96 Ce2O3 6.98 8.18 9.16 La2O3 6.85 5.31 11.04 Cr2O3 0.00 0.00 0.00 FeOT 9.81 8.73 9.05 MnOT 0.00 0.18 0.08 NiO 0.00 0.38 0.00 MgO 0.15 0.00 0.15 CaO 11.31 11.70 10.40 Na2O 0.00 0.00 0.00 K2O 0.02 0.10 0.00 a H2O 1.93 1.94 1.78 Total 99.61 99.55 98.63 Mineral Aln Aln Aln Normalize to 6 Si Si 6 6 6 Ti 0.043 0.004 0.050 Al 4.292 4.397 4.161 Fe 1.272 1.127 1.275 Mn 0.000 0.024 0.011 Ni 0.000 0.048 0.000 Fig. 8. BSE images of (a) grossular including allanite in a jadeitized Mg 0.035 0.000 0.037 rodingite consisting of the major minerals grossular, omphacite and Sum M 5.642 5.599 5.534 jadeite in the Myanmar sample 22. (b) Uvarovite together with Ce 0.397 0.462 0.565 kosmochlor and chromian jadeite (Cr-Jd) forming a symplectite La 0.392 0.302 0.686 rim around a relict chromite core (sample K068). Ca 1.879 1.936 1.877 Na 0.000 0.000 0.000 K 0.004 0.020 0.000 (see details in Shi et al. 2010). In jadeitite, celsian crystals Sum A 2.671 2.721 3.128 (3–15 mm across) are surrounded by jadeite grains (Shi Sum All 14.313 14.320 14.662 et al., 2010); however, it is unclear whether the celsian is OHa 222in equilibrium with the jadeite. In late-stage assemblages a adjacent to jadeitite, celsian occurs in veins cutting banal- Note: H2O and OH calculated from allanite stoichiometry assuming only OH in nominally monovalent anion site. site (Fig. 9), indicating it formed after banalsite. Therefore, celsian may have formed both as a precursor and subse- quent phase relative to jadeite crystallization. All celsian Albite has been reported frequently from the Myanmar grains are compositionally homogeneous with 92–97 jadeitite area (Chhibber, 1934; Me´vel & Kie´nast, 1986; mol% Cls and less than 10 mol% of Ab þ Or þ An (Shi Harlow & Olds, 1987; Shi et al., 2003). Albite commonly et al., 2010). Late celsian in the multi-phase intergrowths occurs in albitite, a mono-mineralic rock comprised mainly adjacent to jadeitite contain 95 mol% Cls (Table 8). of albite that formed in late-stage veins cutting through Hyalophane was first reported in a Myanmar jadeitite by jadeitite, omphacitite, amphibole rock and/or kosmochlor Shi et al. (2010) as an interstitial phase within cracks or rock (Fig. 2f). In addition, albite also occurs as a cavity or along grain boundaries of jadeite or amphibole. Hyalophane intergranular filling phase within jadeitite and omphacitite. contains 10.7–16.7 wt% BaO and 9.5–12 wt% K2O, corre- Chemically the albite is very pure and homogeneous sponding to 21–33 mol% Cls and 62–77 mol% Or (Shi (Table 8). Similar to the jadeitite, albitite from Myanmar et al., 2010). This lies in the range between the Ba-rich can be classified into two types: undeformed albitite and (Cls56–59Or40–42Ab2An0–1) and Ba-poor deformed albitite, and some deformed albitite shows simi- (Cls7–15Or83–92Ab1–3An0–1) feldspars from a jadeitite from lar ‘‘icy and glassy’’ appearances as the jadeitite. Japan (Morishita, 2005) and is comparable to a hyalophane Celsian was first reported from the Jade Mine Tract by with 22 mol% Cls from Guatemala (Harlow, 1994). Shi et al. (2010) as being in jadeitite, chromian omphacitite Banalsite (Na2BaAl4Si4O16) was reported first in a and in late-stage veins adjacent to the jadeitite. In multi- jadeitite by Harlow & Olds (1987), and then Htein & phase pseudomorphs within chromian clinopyroxene rock, Naing (1994). It is also reported in Guatemala jadeitite celsian occurs with kaolinite, sometimes quartz, graphite, (Harlow, 1994; Harlow et al., 2011). In this study, banal- and diaspore, and is probably replacing cymrite by decom- site occurs as cavity- or vein-filling material in or adjacent position caused by decreasing pressure during exhumation to jadeite grains (Fig. 9). It is very pure, containing less Mineralogy of jadeitite and related rocks from Myanmar 359

Table 7. Representative chemical compositions of garnet minerals (Miyajima et al., 1999), Oeyama belt (Kobayashi et al., in rocks from the Jade Mine Tract, Myanmar. 1987), California – Clear Creek, New Idria, California (Coleman, 1961), Ketchpel, Polar Urals, Russia K068 22 Sample (Morkovkina, 1960), and Itmurundy, Kazakhstan Phase Uvr Grs (Dobretsov & Ponomareva, 1965). However, it has not been previously reported in the Myanmar jadeitite; it a a No. 2 3 G-54 G-56 38-9 38-12 occurs along jadeite grain boundaries or in veins cutting

SiO2 37.76 35.96 39.34 39.58 39.23 39.25 jadeitite (Fig. 10), obviously a late-stage phase. TiO2 0.62 0.29 0.12 0.16 0.22 0.34 Compositionally, it is mixed with other zeolites, so com- Al2O3 6.96 3.73 18.87 18.61 20.12 20.39 positions given in Table 9 are slightly non-stoichiometric. Cr2O3 18.95 24.03 1.19 1.3 0.67 0.92 Thomsonite-Ca has been reported in the Osayama jadei- Fe2O3 0.61 1.03 4.35 4.57 2.22 1.42 tite, SW Japan (Kobayashi et al., 1987) and has been FeO 1.37 0.00 0.50 0.29 0.80 2.16 MnO 0.27 0.23 0.42 0.39 0.41 0.42 confirmed by X-ray diffraction in late-stage veins cutting MgO 0.10 0.06 0.01 0.01 0.04 0.05 jadeitite in this study. In MJE02-3-9, a vein termination of CaO 31.72 34.08 36.02 36.41 35.58 34.43 a jadeitite body, we have found both thomsonite-Ca and SrO n.d. n.d. n.d. n.d. 0.00 0.01 thomsonite-Sr; the latter appears to be the second occur- Na2O 0.79 0.07 0.06 0.03 0.01 0.05 rence of this mineral. In Table 9 are presented representa- K2O 0.01 0.00 0.00 0.00 0.00 0.00 tive analyses of the two thomsonites, which show solid Total 99.16 99.48 100.88 101.36 99.3 99.46 solutions between the two types. Oxygens 24 24 24 24 24 24 Si 6.115 5.932 5.977 5.988 6.002 6.002 Ti 0.076 0.036 0.014 0.018 0.025 0.040 Al 1.328 0.726 3.378 3.318 3.628 3.675 5.9. Vesuvianite Cr 2.426 3.134 0.143 0.155 0.081 0.111 Fe3þ 0.075 0.128 0.497 0.521 0.256 0.163 Nyunt et al. (2009) describe an occurrence of vesuvianite Fe2þ 0.185 0.000 0.063 0.037 0.102 0.276 in a Myanmar jadeitite, the first report from HP/LT condi- Mn 0.037 0.032 0.054 0.050 0.053 0.055 tions. They report compositions with up to 1.5 wt% Na O Mg 0.024 0.015 0.002 0.002 0.009 0.012 2 Ca 5.504 6.024 5.863 5.902 5.832 5.640 and 3.2 wt% TiO2 and suggest that the formation of this Sr n.d. n.d. n.d. n.d. 0.000 0.001 vesuvianite is explained by an interaction with a hydrous Na 0.248 0.022 0.018 0.009 0.004 0.016 fluid phase with high chemical potentials of Ti and Ca. A K 0.002 0.000 0.000 0.000 0.000 0.001 comparable occurrence of vesuvianite with relatively high Total 16.020 16.049 16.009 16.001 15.992 15.991 Na and Ti has been recorded in a Guatemalan jadeitite

a (Harlow et al., 2011). In this study, vesuvianite has been Notes: From Wang et al. (2011). observed in a late-stage vein at the contact between jadei- tite and altered serpentinite (MJE02-3-6) and is intergrown with phlogopite and cymrite (Fig. 7b). The vesuvianite than 3 mol% Or þ An (Table 8), and a small amount of SrO contains less than 1 wt% Na2O and 0–3 wt% TiO2 (0.30–0.40 wt%). (Table 10). It may not have formed at comparable P-T conditions as those reported from other jadeitite occurrences. 5.8. Zeolites

Minerals of the zeolite group commonly occur in jadeitite 5.10. Other minerals and related rocks worldwide (e.g., Morkovkina, 1960; Coleman, 1961; Yudin, 1965; Kobayashi et al., 1987; Cymrite is the hydrous analog of celsian and was reported Harlow, 1994; Miyajima et al., 1999; Hughes et al., in Guatemala jadeitite (Harlow, 1994). As cymrite is the 2000; Morishita, 2005; Harlow et al., 2011). In this study, HP phase via the reaction BaAl2Si2O8 (Cls) þ H2O ¼ we report analcime, natrolite and thomsonite-Ca identified BaAl2Si2O8H2O (Cym) and defines a thermobarometer in Myanmar jadeitite and related rocks. All these minerals (Graham et al., 1992), it is petrogenetically as well as have been confirmed using powder X-ray diffraction. compositionally significant. It has been interpreted as the Analcime has been reported in Myanmar (Hughes et al., precursor phase for celsian in Myanmar (Shi et al., 2010). 2000), Guatemala and Japan jadeitite localities (Harlow, Cymrite has now been found along a jadeite grain bound- 1994; Morishita, 2005). In Myanmar jadeitite it occurs as a ary in a Myanmar jadeitite as euhedral hexagonal prisms late-stage phase with natrolite along jadeite grain boundary, and formed after jadeite as well as banalsite (Fig. 7a, b, 9 or as veins through jadeitite (Fig. 10). Compositionally, it and 10). Compositionally it is close to end-member Cym looks intermingled with other zeolites, so only rough com- (Table 9). positions of this phase are given in Table 9. Titanite has been reported from all jadeitite localities, Natrolite occurs in ultramafics of the Borus Ridge, West except perhaps those in the New Idria serpentinite body, Sayan (Yudin, 1965) and in jadeitite from the same locality Myanmar, California and the Yenisey River, Khakassia (Dobretsov, 1963), in addition to the Itoigawa area (see Harlow et al., 2007). In the present investigation it 360 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui

Table 8. Representative chemical compositions of feldspars from the Jade Mine Tract, Myanmar.

MJE02-3-6 MJE02-3-9 Ab-Jd01 WJ-01 Sample Phase Bnl Bnl Bnl Bnl Cls Cls Hyl Hyl Ab Ab Ab Ab No. 7-6 7-8 11-1 11-11 11-4 11-8 12-4 12-7 22 79 53 60 SiO2 37.17 36.49 35.69 35.63 32.96 34.31 55.21 56.93 68.67 68.95 68.86 68.57 TiO2 0.03 0.09 0.00 0.00 0.07 0.06 0.02 0.00 0.02 0.00 0.00 0.00 Al2O3 31.48 30.74 30.50 30.35 26.09 29.69 20.34 20.01 19.03 19.65 18.94 19.10 Cr2O3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.04 0.04 0.01 MgO 0.00 0.00 0.00 0.00 0.00 0.02 0.01 0.00 0.01 0.00 0.00 0.02 CaO 0.33 0.19 0.03 0.08 0.02 1.64 0.00 0.02 0.00 0.01 0.01 0.00 MnO 0.00 0.00 0.00 0.00 0.00 0.00 0.03 0.00 0.03 0.00 0.05 0.00 FeO 0.00 0.06 0.00 0.00 0.02 0.04 0.03 0.00 0.01 0.02 0.04 0.00 SrO 4.15 3.71 0.35 0.14 0.08 0.10 0.00 0.00 0.04 0.00 0.03 n.d. BaO 17.31 18.48 23.35 23.44 39.22 33.68 10.97 8.89 0.00 0.00 0.01 n.d. Na2O 9.56 9.80 9.29 9.25 0.11 0.74 0.07 0.10 11.96 12.03 11.94 11.94 K2O 0.00 0.00 0.00 0.01 0.75 0.65 12.38 13.19 0.01 0.01 0.02 0.03 Total 100.03 99.56 99.22 98.90 99.32 100.93 99.06 99.14 99.80 100.71 99.93 99.65 Oxygens 8 8888 8888 888 Si 1.998 1.991 1.987 1.990 2.057 1.998 2.783 2.824 3.007 2.992 3.011 3.005 Ti 0.001 0.004 0.000 0.000 0.004 0.003 0.001 0.000 0.001 0.000 0.000 0.000 Al 1.994 1.977 2.001 1.998 1.919 2.037 1.208 1.170 0.982 1.005 0.976 0.987 Cr 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.000 Mg 0.000 0.000 0.000 0.000 0.000 0.002 0.001 0.000 0.001 0.000 0.000 0.001 Ca 0.019 0.011 0.002 0.005 0.001 0.102 0.000 0.001 0.000 0.000 0.001 0.000 Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.001 0.000 0.002 0.000 Fe 0.000 0.003 0.000 0.000 0.001 0.002 0.001 0.000 0.000 0.001 0.001 0.000 Sr 0.129 0.117 0.011 0.005 0.003 0.003 0.000 0.000 0.001 0.000 0.001 0.000 Ba 0.365 0.395 0.509 0.513 0.959 0.768 0.217 0.173 0.000 0.000 0.000 0.000 Na 0.997 1.036 1.003 1.002 0.013 0.084 0.007 0.010 1.016 1.012 1.012 1.015 K 0.000 0.000 0.000 0.001 0.060 0.049 0.796 0.835 0.001 0.001 0.001 0.002 Total 5.502 5.535 5.514 5.512 5.017 5.048 5.014 5.013 5.009 5.012 5.007 5.010

has been found in an omphacite-bearing jadeitite and an rocks in the Dabieshan-Sulu UHP terrane, eastern China omphacitite from Myanmar along jadeite grain boundaries. (e.g., Ye et al., 2002). Some titanite grains contain ilmenite cores (Fig. 4b), show- Pectolite is a sodium calcium silicate mineral of the ing replacement of ilmenite by titanite. Compositionally, wollastonite group and is reported in jadeitite from Japan, Myanmar titanites have low Al (0.90–1.1 wt% Al2O3,XAl California, Guatemala (e.g., Coleman, 1961; Morishita, 3þ , 0.05 where XAl ¼ [Al /(Al þ Fe þ Ti)]; see Table 10), 2005; Tsujimori et al., 2005; Harlow et al., 2011) and even lower than those low-Al titanites (XAl ¼ 0.050 – also Myanmar (Nyunt et al., 2009). In this study it is 0.115; 1.3 – 3.0 wt% Al2O3) from carbonate-bearing found in late-stage veins in jadeitite (Fig. 7a, 10, Table 10).

Fig. 9. BSE image of celsian formed later than banalsite, and euhe- Fig. 10. BSE image showing that analcime and natrolite with pecto- dral cymrite occurring at the boundary between jadeite and banalsite lite occur as later vein surrounding earlier cymrite and banalsite; they (sample MJE02-3-9). all are adjacent to jadeitite (sample MJE02-3-9). Mineralogy of jadeitite and related rocks from Myanmar 361

Table 9. Representative chemical compositions of zeolite minerals in rocks from the Jade Mine Tract, Myanmar.

MJE02-3-6 MJE02-3-9 Sample No. M7-20 M7-17 M14-10 M14-17 M10-9 M10-11 M13-9 M13-1 Phase Ntr Ntr Ntr Ntr Anl Anl Thm-Ca Thm-Sr

SiO2 49.81 48.99 49.57 49.62 56.50 55.85 39.36 36.45 TiO2 0.02 0.03 0.00 0.01 0.00 0.00 0.00 0.00 Al2O3 26.92 26.10 27.74 26.83 22.85 23.20 30.15 27.63 Cr2O3 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.01 MgO 0.00 0.03 0.03 0.00 0.00 0.03 0.02 0.00 CaO 0.05 0.25 1.25 1.29 0.03 0.19 11.46 4.08 MnO 0.02 0.00 0.00 0.00 0.02 0.01 0.00 0.01 FeO 0.00 0.00 0.01 0.03 0.00 0.01 0.02 0.00 SrO 0.04 0.53 0.00 0.00 0.04 0.07 1.91 13.65 BaO 0.03 1.24 0.12 0.01 0.03 0.00 0.22 0.93 Na2O 14.43 14.45 13.23 13.71 13.04 14.42 4.04 3.43 K2O 0.01 0.01 0.02 0.01 0.04 0.05 0.00 0.02 a H2O 9.68 9.55 9.74 9.68 8.30 8.35 13.43 12.41 Total 101.04 101.19 101.72 101.19 100.85 102.18 100.60 98.62 Oxygens 10 10 10 10 96 96 20 20 Si 3.086 3.076 3.051 3.075 32.645 32.100 5.267 5.292 Ti 0.001 0.001 0.000 0.001 0.000 0.000 0.000 0.000 Al 1.966 1.931 2.012 1.959 15.562 15.714 4.756 4.727 Cr 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.001 Mg 0.000 0.003 0.003 0.000 0.000 0.026 0.004 0.001 Ca 0.003 0.017 0.083 0.086 0.020 0.115 1.642 0.634 Mn 0.001 0.000 0.000 0.000 0.011 0.004 0.000 0.001 Fe 0.000 0.000 0.001 0.001 0.000 0.004 0.002 0.000 Sr 0.002 0.019 0.000 0.000 0.013 0.024 0.148 1.149 Ba 0.001 0.031 0.003 0.000 0.006 0.000 0.011 0.053 Na 1.734 1.759 1.579 1.647 14.608 16.074 1.048 0.965 K 0.001 0.001 0.001 0.000 0.027 0.036 0.000 0.005 Sum 6.796 6.838 6.733 6.769 62.891 64.098 12.879 12.828 a H2O 2 2 2 2 16 16 6 6

a Note: H2O calculated from zeolite stoichiometry assuming full water occupancy of appropriate site.

Other rare minerals in the Myanmar jadeitite and related the origins of the fluids. The depleted Hf isotope feature in rocks include graphite, quartz, diaspore and kaolinite in the all zircons from the Myanmar jadeitite suggests their deri- multi-phase pseudomorphs surrounded by kosmochlor and vation from reworking of juvenile crust during the Cr-bearing jadeite aggregate (see details in Shi et al. 2010), Myanmar jadeitite crystallization from the Jd-saturated and the sulfide minerals pyrite and galena in jadeitite (Shi vein fluids (Qiu et al., 2009; Shi et al., 2009b). et al., 2008). Alternatively, such fluids could also have been produced by interaction between seawater, the subducted oceanic crust and its sedimentary cover (Sorensen et al., 2006; Simons et al., 2010) and possibly from rodingitization of 6. Discussion and conclusions oceanic mafic rock (Wang et al., 2012). Correlations between the jadeite-forming fluids and seawater or sea- 6.1. Origin of minerals in jadeitite and related rocks in floor sediments are revealed by the isotope features of fluid Myanmar inclusions in jadeitite, Ba-bearing minerals in jadeitites, and their bulk geochemical features (e.g., Me´vel & Growing numbers of observations support an origin of Kie´nast, 1986; Harlow, 1995; Johnson & Harlow, 1999; jadeite in pure jadeitite blocks by direct precipitation Morishita, 2005; Shi et al., 2005b, 2008, 2010; Sorensen from Na-Al-Si rich hydrous fluids. Trace-element compo- et al., 2006; Simons et al., 2010). Thus, the fluids are likely sitions of jadeitites (Sorensen et al., 2006; Morishita et al., derived from a subducted slab that has reacted with sea- 2007; Shi et al., 2008; Simons et al., 2010), together with water, possibly with minor addition from the dehydration oscillatory zoned jadeite, indicate the presence of a Jd- of serpentine minerals at greater depths (e.g., Hyndman & saturated vein fluid. Fluid inclusions and stable isotope Peacock, 2003). studies of the Guatemala and Myanmar jadeitite unam- The origin of omphacite in omphacitite is less well under- biguously indicate that jadeite grains formed from hydrous stood. Yi et al. (2006) have argued that it is a product of fluids (Johnson & Harlow, 1999; Shi et al., 2000, 2005b; reaction between jadeitic fluid and mantle pyroxenite at Simons et al., 2010). However, there are still debates about high P-T. Other possibilities include fluid interaction with 362 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui

Table 10. Representative chemical compositions of cymrite, vesuvianite, pectolite and titanite in rocks from the Jade Mine Tract, Myanmar.

MJE02-3-6 D2 YX-1 Sample Rma Phase Cym Cym Cym Ves Ves Ves Pct Pct Pct Pct Pct Ttn Ttn Ttn Ttn No. 8-4 8-11 8-16 9-4 9-6 9-8 8-19 7-3 73 74 75 26 30 31 32

SiO2 30.87 31.89 31.36 36.87 36.86 36.77 53.07 53.41 53.70 54.90 54.98 30.31 30.32 30.37 30.31 TiO2 0.11 0.06 0.03 1.90 2.73 2.29 0.00 0.03 0.00 0.00 0.02 39.37 39.05 39.02 39.88 Al2O3 25.75 25.78 25.79 18.53 21.77 17.88 0.23 0.12 0.04 0.15 0.39 1.03 1.06 1.15 1.21 Cr2O3 bdl bdl bdl 0.11 0.00 0.02 0.00 0.06 0.00 0.08 0.03 0.05 0.02 0.02 0.00 Fe2O3 nc nc nc 2.01 1.86 1.67 nc nc nc nc nc nc nc nc nc FeO 0.04 0.06 0.03 0.00 1.60 0.53 0.08 0.07 0.07 0.20 0.10 0.31 0.40 0.62 0.71 Mn2O3 nc nc nc 0.00 0.05 0.00 nc nc nc nc nc nc nc nc nc MnO bdl bdl bdl 0.03 0.00 0.01 0.03 0.33 0.18 0.16 0.16 0.02 0.00 0.02 0.04 MgO bdl bdl bdl 1.48 1.37 1.45 0.16 0.01 0.01 0.05 0.08 0.01 0.00 0.00 0.03 CaO 0.01 0.02 0.12 34.58 34.32 34.75 33.21 33.36 32.63 31.38 31.57 28.37 28.29 27.88 27.27 SrO bdl 0.03 0.02 bdl 0.05 bdl 0.02 0.07 n.d. n.d. n.d. n.d. n.d. 0.04 0.05 BaO 38.3 38.43 38.10 bdl bdl bdl 0.10 0.07 0.00 0.00 0.00 n.d. n.d. 0.00 0.00 Na2O 0.07 0.26 0.10 0.71 0.87 0.68 8.86 9.27 9.15 9.09 9.74 0.05 0.00 0.09 0.08 K2O 0.12 0.09 0.25 bdl bdl bdl 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.00 a H2O 4.60 4.68 4.64 3.07 2.98 2.69 2.67 2.69 2.67 2.70 2.72 – – – – Total 99.67 101.31 100.44 99.37 99.20 98.73 98.44 99.50 98.46 98.71 99.79 99.51 99.14 99.20 99.58 Normalization 8 O 8 O 8 O 18 Si 18 Si 18 Si 17 O 17 O 17 O 17 O 17 O 10 O 10 O 10 O 10 O Si 2.014 2.042 2.028 18.000 18.00 18.00 5.969 5.963 6.024 6.101 6.057 1.988 1.996 1.998 1.985 Ti 0.005 0.003 0.002 0.697 1.00 0.84 0.000 0.003 0.000 0.000 0.002 1.942 1.933 1.930 1.963 Al 1.980 1.946 1.965 10.662 10.447 10.316 0.030 0.015 0.005 0.020 0.051 0.080 0.082 0.089 0.094 Cr 0.000 0 0 0.044 0.026 0.006 0.000 0.005 0.000 0.007 0.003 0.003 0.001 0.001 0.000 Fe3þ nc nc nc 0.738 0.686 0.613 nc nc nc nc nc nc nc nc nc Mn3þ nc nc nc 0.000 0.019 0.000 nc nc nc nc nc nc nc nc nc Fe 0.002 0.003 0.002 0.013 0.000 0.003 0.007 0.007 0.007 0.019 0.009 0.017 0.022 0.034 0.039 Mn 0.000 0 0 0.031 0.000 0.218 0.003 0.031 0.017 0.015 0.015 0.001 0.000 0.001 0.002 Mg 0.000 0 0 1.076 0.996 1.057 0.026 0.002 0.002 0.008 0.013 0.001 0.000 0.000 0.003 Ca 0.001 0.001 0.008 18.088 17.994 18.227 4.002 3.991 3.922 3.736 3.726 1.994 1.995 1.966 1.913 Sr 0.000 0.001 0.001 0.000 0.012 0.000 0.005 0.001 0.000 0.000 0.000 – – 0.001 0.002 Ba 0.979 0.965 0.965 0.000 0.000 0.000 0.005 0.003 0.000 0.000 0.000 – – 0.000 0.000 Na 0.009 0.033 0.012 0.673 0.823 0.648 1.933 2.006 1.990 1.959 2.080 0.006 0.000 0.011 0.010 K 0.010 0.007 0.021 0.001 0.000 0.000 0.001 0.001 0.001 0.000 0.000 0.000 0.000 0.000 0.000 Total 5.000 5.002 5.004 50.024 50.007 49.933 11.983 12.028 11.969 11.865 11.955 6.032 6.029 6.032 6.010 OHa 10.000 9.742 10.000 2 2222 a H2O 11 1

a Note: H2O and OH determined by stoichiometry assuming ideal full occupancy of the appropriate site. channel metabasites or sediment. The precipitation of chromite. Subsequently, Na-dominant formation of kos- jadeite along cracks or cleavages in omphacite and the mochlor and Cr-bearing jadeite/omphacite took place formation of less pure jadeite reflect a replacement or infil- (Fig. 8). A tendency of Cr-decrease from chromite to tration of omphacite by jadeite. Since omphacite is inter- uvarovite, kosmochlor and to Cr-bearing jadeite (Fig. mediate between jadeite and diopside, the omphacite could 11b) is interpreted to be related to the progressive change be the result of a chemical admixture between diopside of the composition of the crystallizing fluid infiltrating the component from mantle pyroxenite and jadeite from jadei- replaced chromite. tization. The formation of fine jadeite veins crosscutting The six amphibole species from the amphibole rocks are both omphacite and replaced jadeite, and the absence of an the result of metamorphic and metasomatic reactions obvious compositional gap between omphacite and jadeite between jadeitites and peridotites at HP/LT conditions (Fig. 11a), as shown for another jadeitite-omphacitite (Me´vel & Kie´nast, 1986; Harlow & Olds, 1987; Shi et al., (AMNH 107991), supports a model of fine-scale dilution 2003). As the Myanmar jadeitite formed by direct precipita- of more diopsidic compositions by jadeite (or kosmochlor) tion from Na-Al-Si rich fluids, the amphibolite, being both component, probably as micro-scale intergrowths below the the spatial and chemical intermediate between jadeitite and spatial resolution of the microprobe, given the low tempera- serpentinite, is therefore considered to be the product of ture interpretation for these rocks (see below). water-rock interaction between the two (e.g., Shi et al., Before the formation of the jadeitite, Ca-rich metaso- 2003). The zoned amphibole porphyroblasts with magne- matism may have occurred. This is supported by the uvaro- siokatophorite in the cores and nybo¨ite and eckermannite in vite-bearing rock, which formed by replacement of the rims (Fig. 5) formed in the presence of jadeite, and the Mineralogy of jadeitite and related rocks from Myanmar 363

Fig. 11. Compositional plots for pyroxenes and amphiboles from rocks in the Jade Mine Tract (a) Pyroxenes, from Table 3 (not including K068-5, 6, 9, 10 due to high Cr contents), from Yi et al. (2006), and jadeitite-omphacitite AMNH 107991. (b) Pyroxenes (recalculated), from fig. 12 in Shi et al. (2005a); Ou Yang (1984); Me´vel & Kie´nast (1986) and Harlow & Olds (1987). (c) Amphiboles, from fig. 13c in Shi et al. (2003). Plot of BNa vs. Si. The closed symbols in these plots indicate amphibole compositions with tetrahedral Si of 7.5–8 apfu, open symbols amphiboles with Si , 7.5 apfu. The amphibole species associated with the symbols are open squares Mkt, open diamonds Nyb, closed diamonds Eck, upright closed triangles Gln, reversed closed triangles Wnc, closed squares Rct. The chemical analyses are all from tables 4–7 in Shi et al. (2003). metasomatic fluid infiltration led to the formation of diverse forming fluids or from later fluids after jadeite crystalliza- amphibole compositions spanning six species resulting from tion, is an important indication of Ba abundance and mobi- compositional changes during the infiltration event. lity in subduction zones at HP conditions. Such high Ba Because of extensive reactions, the variation of amphibole concentrations could result from deep-sea sediments where composition (Fig. 11c) at the jadeitite-serpentinite contact barite is deposited in regions of high biological productiv- obviously reflects non-equilibrium and transient states. ity (e.g., Schmitz, 1987; Dymond et al., 1992; Gingele & The presence of Ba- and (Ba, Sr)-bearing minerals and Dahmke, 1994; van Beek et al., 2003), as is obvious from their textures indicate that Ba and Sr enrichments are compilations of deep-sea sediment compositions (Plank & coupled with the development of jadeite-forming fluids. Langmuir, 1998) and hydrothermally infiltrated sediments, Crystallization of Ba and Sr silicates (celsian, cymrite, particularly near the source of hydrothermal fluids (e.g., hyalophane, thomsonite-Sr, barium mica–kinoshitalite Greinert et al., 2002; Plank, 2005). When these sediments (Harlow, 1995), banalsite, etc.), either from jadeite- were subducted with the down-going oceanic slab, they 364 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui became the source for barium released into jadeite-forming fluids (e.g., Shi et al., 2010) and subsequently crystallized in the barian minerals. This interpretation is supported by the common occurrence of Ba-bearing minerals in other well-documented jadeitite localities (e.g., Harlow, 1995; Morishita, 2005; Shi et al., 2010), and it is possibly the same source of the Sr-enrichments (Kobayashi et al., 1987; Harlow, 1994; Miyajima et al., 1999, 2001, 2002). The zeolites and other related hydrous minerals in the Myanmar jadeitite area occur spatially in close association with the jadeitite veins. All the zeolites are Na-rich. However, little attention has been paid to these minerals, and their parageneses are not well explained, although they may have significant implications for the fluid evolution (and jade quality). This is clearly a topic for future investigation.

6.2. Pressure and temperature of formation

Jadeitites are clearly the result of HP/LT conditions pro- duced only in subduction zone environments. However, the nearly monomineralic high variance assemblages do not provide ready P-T constraints, as has been pointed out previously (e.g., Sorensen et al., 2006; Harlow et al., 2007). Primary crystallization of jadeite from a fluid with- out quartz or albite only indicates pressure above the reac- tion Anl ¼ Jd þ H2O. Four estimates of P-T conditions are available (Fig. 12): Me´vel & Kie´nast (1986) give a rough Fig. 12. An approximate P-T path (broad dashed arrow) for jadeitite and related rocks in Myanmar based on available petrogenetic grids estimate based on the presence of jadeite and analogy with and phase equilibria (P-T condition diagram from Shi et al. (2010)). rocks from the western Alps – a broad band of 1 GPa , P , 1.5 GPa and 300 C , T ,500 C; Goffe´ et al. (2000) used textural constraints and a phase assemblage in a mineral diversity is considerable at all jadeitite localities if blueschist overprint in an eclogite recovered from allu- sampling is sufficient. Apart from the Myanmar jadeitite vium in the Jade Tract area (1.4 GPa , P , 1.6 GPa and occurrences, all the well-documented jadeitite localities 400 C , T , 450 C); Shi et al. (2003) included phase have a generally similar and diverse suite of minerals equilibria with amphiboles, and Oberha¨nsli et al. (2007) (Table 11). Minerals identified from all localities represent recalculated jadeite-omphacite-amphibole equilibria using more than 50 species. Even in recently reported localities, a pseudo-section approach. These broad PT estimates are such as Iran, Italy, Cuba, and the Dominican Republic shown in Fig. 12. Other jadeitite, notably that from Sierra (e.g., Oberha¨nsli et al., 2007; Compagnoni et al., 2007, del Convento in eastern Cuba (Garcia-Casco et al., 2009; 2012; Garcia-Casco et al., 2009; Schertl et al., 2012), Ca´rdenas-Pa´rraga et al., 2010), is interpreted to form at similar mineral associations among relatively rare rock- higher T, 550–560 C based on intimate Jd – Omp inter- forming phases have been reported, with some significant growths and their compositions. Whereas we cannot as yet variations with respect to the presence of thermobarometri- rule out such an interpretation, as with Harlow et al. (2011) cally important phases like lawsonite versus clinozoisite, the preponderance of nearly pure Jd with Ab and late particularly micas, and quartz. Similarities with respect to intergrown omphacite, in most cases, would suggest the enrichments in Ba or Sr phases have not been reported in the somewhat lower temperature maximum we present above. newer finds, but this may change with further sampling and Clearly from our discussion above, the applicability of research. Nevertheless, the commonalities lead to two these approaches assuming equilibria among the phases points. One is that the similar mineral suites in jadeitite and used have serious limitations. Subsequent formation of related rocks result from similar combinations of enrich- albite and analcime requires lower pressure which likely ments in several alkaline metals and alkaline earths, water, resulted from continued fluid infiltration during exhuma- and a broadly similar conditions and perhaps P-T-t evolu- tion. An estimate of P-T evolution is given in Fig. 12, tion. The other is that mineralogical distinctions, a function showing the requisite decrease of pressure with time. of bulk composition, conditions, and evolution, among the now 19 sources typically do exist among them – they are not 6.3. Final comments identical. This can be used for interpreting sources of the jadeite jade, particularly in archaeology. Although jadeitites can be cryptic rocks with few other Mineralogy of jadeitites worldwide, combined with stu- phases than jadeite, particularly in gem quality material, dies of tectonics, age dating and trace-element signatures Table 11. Phases present in jadeitites and their retrograde assemblages from most of the localities worldwide.

Jade N. of S. of New Osayama- Mine Motagua Motagua Idria Sierra del Itoigawa Wakasa- Nishisonogi Polar Borus Syros - Mineral Tract, Nansibon, Fault, Fault, Serp., Convento, Dominican area, Oya, Belt, Urals, Belt, Tinos, Italian group Species Myanmar Myanmar Guatemala Guatemala California Cuba Republic Japan Japan Japan Iran Russia Khakassia Kazakhstan Greece Alps

Pyroxene Jadeite PPPPPPPPPPPPPPPP Omphacite P P P, I P, I P P P P P P, I P S P P S P Augite U P? R Komoschlor P Diopside SS Chromian pyroxene P P P P PI P Feldspar Albite S S I, S S S S P S SS SSSS

K-feldspar SS U Myanmar from rocks related and jadeitite of Mineralogy Hyalophane I I I I Celsian ISSI I Banalsite I S U Stronalsite SS Amphibole Eckermannite P ? Nybo¨ite P ‘‘Hornblende’’ P Magnesio- katophorite P Katophorite Richterite P Glaucophane P P UPU Winchite P Taramite-ferrotaramite I, S Tremolite ? SS SS SS -actinolite Mica Phlogopite U I I? U USP P P Biotite SS P Paragonite P P P Muscovite-phengite PPP P Whitemica Preiswerkite S Talc S Chlorite SSS UU S Zeolite Analcime S S I,S S S SS SSSS Natrolite S US Thomsonite-Ca U US Thomsonite-Sr U U Pectolite U SU US Pumpellyite SP U Vesuvianite S SS S Garnet Grossular P I I,S UP Uvarovite P Almandine RR P? Titanite U P,I,S P,I,S UPUS PP Prehnite S

Zircon R, P P P P PP R, P R, P PP 365 366

Table 11. Continued

Jade N. of S. of New Osayama- Mine Motagua Motagua Idria Sierra del Itoigawa Wakasa- Nishisonogi Polar Borus Syros - Mineral Tract, Nansibon, Fault, Fault, Serp., Convento, Dominican area, Oya, Belt, Urals, Belt, Tinos, Italian Cui W. Cao, S. Wang, X. Ng, E. Wang, J. Wang, J. Harlow, G.E. Shi, G. group Species Myanmar Myanmar Guatemala Guatemala California Cuba Republic Japan Japan Japan Iran Russia Khakassia Kazakhstan Greece Alps

Epidote group Zoisite, clinozoisite SPI P P Epidote UP P S P, S Allanite U PP U R? or P PP Clinizoisite-(Sr) I Rutile R? R or P U P R? ? Ilmenite U U Lawsonite Lawsonite P, S U PU U Group Itoigawaite U Cymrite S I S U Nepheline S Phosphates Apatite PP P P? R? Monazite PP Spinel Group Chromite R R R R Magnetite Quartz S P, I, S PS P Sulfides Galena S S Pyrite U I Chalcopyrite I Calcite S SS P S Diaspore S Kaolinite S SS Perrierite group Rengeite S Matsubaraite S Native elements Graphite P I, S I R Iron R Copper U

Notes: Symbols refer to stage in assemblages: indicates distinct types with and without this phase, R, Relict (inherited); P, Primary; I, Intermediate; S, Secondary; U, unspecified;?, suspected but unconfirmed. Mineral occurrences are compiled according to all available related literatures of jadeitites, including Bauer (1895); Noetling (1893, 1896); Bleeck (1907, 1908); Chhibber (1934); Morkovkina (1960); Coleman (1961); Dobretsov (1963); Yudin (1965); Essene (1967); Chihara (1971); Bender (1983); Ou Yang (1984); Thin (1985); Me´vel & Kie´nast (1986); Harlow & Olds (1987); Kobayashi et al. (1987); Harlow (1994, 1995); Htein & Naing (1994); Miyajima et al. (1999, 2001, 2002); Qi et al. (1999); Hughes et al. (2000); Tsujimori (2002); Harlow et al. (2003, 2007, 2011); Harlow & Sorensen (2005); Shi et al. (2003, 2005a, 2010, 2011); Morishita (2005); Shigeno et al. (2005, 2012); Tsujimori et al. (2005); Tsujimori & Harlow (2012); Yi et al. (2006); Compagnoni et al. (2007, 2012); Oberha¨nsli et al. (2007); Garcia-Casco et al. (2009); Nyunt et al. (2009); Wang et al. (2012), Schertl et al. (2012); and data from this investigation. Mineralogy of jadeitite and related rocks from Myanmar 367 of depleted mantle from zircon, plus chemical and isotopic Compagnoni, R., Rolfo, F., Castelli, D. (2012): Jadeitite from the signatures (Morishita et al., 2007; Shi et al., 2008, 2009; Fu Monviso meta-ophiolite, western Alps: occurrence and genesis. et al., 2010; Simons et al., 2010; Yui et al., 2010, 2012) Eur. J. Mineral., 24, 333–343. suggest that jadeitites world-wide share similarities in ori- Couper, A.G., Hey, M.H., Hutchison, R. (1981): Cosmochlore: a gin, despite differences of formation ages, mineral assem- new examination. Mineral. Mag., 44, 37–44. blages and quality of the jadeite jade. 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