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Jade and associated rocks from jade mines area, northern Myanmar as record of a polyphased high-pressure metamorphism
... It approaches the Sagaing Fault near Mandalay, although it is not clear whether they actually join beneath the broad cover of alluvium. The only detailed surface mapping of the Panlaung Fault is from Garson et al. (1976) andthe United Nations (1978) who show the fault as long, straight, and sub-vertical, and forming the western boundary of a zone up to 3 km-wide of highly-deformed rocks that Garson et al. (1976) (Garson et al., 1976). The only formation found on both sides of the combined Panlaung Fault-Nwalabo Fault Complex is the largely brecciated Dahatpin Limestone, which lies with an angular unconformity over the Pan Laung Formation and other deformed Mesozoic units. ...
... It approaches the Sagaing Fault near Mandalay, although it is not clear whether they actually join beneath the broad cover of alluvium. The only detailed surface mapping of the Panlaung Fault is from Garson et al. (1976) andthe United Nations (1978) who show the fault as long, straight, and sub-vertical, and forming the western boundary of a zone up to 3 km-wide of highly-deformed rocks that Garson et al. (1976) (Garson et al., 1976). The only formation found on both sides of the combined Panlaung Fault-Nwalabo Fault Complex is the largely brecciated Dahatpin Limestone, which lies with an angular unconformity over the Pan Laung Formation and other deformed Mesozoic units. ...
... It approaches the Sagaing Fault near Mandalay, although it is not clear whether they actually join beneath the broad cover of alluvium. The only detailed surface mapping of the Panlaung Fault is from Garson et al. (1976) andthe United Nations (1978) who show the fault as long, straight, and sub-vertical, and forming the western boundary of a zone up to 3 km-wide of highly-deformed rocks that Garson et al. (1976) (Garson et al., 1976). The only formation found on both sides of the combined Panlaung Fault-Nwalabo Fault Complex is the largely brecciated Dahatpin Limestone, which lies with an angular unconformity over the Pan Laung Formation and other deformed Mesozoic units. ...
GEOLOGICAL REPORT COLLECTION MYANMAR -1
GEOLOGICAL REPORT COLLECTION MYANMAR -2
... It is composed of a dismembered, incompletely preserved ophiolitic sequence of serpentinite and peridotite (Htay et al., 2017). The Jade Mines Belt (JMB) includes jadeitite, eclogite, amphibolite, blueschist, chromitite, and serpentinized peridotite (Goffé et al., 2002) that reflect the effects of high-P/low-T metamorphism. The P-T conditions have been variously estimated at 10-15 kbar and 300-500°C (Mével and Kiénast, 1986), N14 kbar and 400-450°C (Goffé et al., 2002), N10 kbar and 250-370°C and 15 kbar and~380°C . ...
... The Jade Mines Belt (JMB) includes jadeitite, eclogite, amphibolite, blueschist, chromitite, and serpentinized peridotite (Goffé et al., 2002) that reflect the effects of high-P/low-T metamorphism. The P-T conditions have been variously estimated at 10-15 kbar and 300-500°C (Mével and Kiénast, 1986), N14 kbar and 400-450°C (Goffé et al., 2002), N10 kbar and 250-370°C and 15 kbar and~380°C . U-Pb Jurassic ages of zircon taken from jadeitite (163-160 Ma) have been interpreted as protolith ages for the ophiolite in the JMB (Shi et al., 2008;Yui et al., 2013). ...
... U-Pb Jurassic ages of zircon taken from jadeitite (163-160 Ma) have been interpreted as protolith ages for the ophiolite in the JMB (Shi et al., 2008;Yui et al., 2013). The timing of the HP metamorphic event is not well defined, with age estimates ranging from the Late Jurassic (U-Pb zircon age between 158 and 147 Ma, Shi et al., 2008;Qiu et al., 2009) to the Late Cretaceous (U-Pb zircon age of 77 ± 3 Ma, Yui et al., 2013 and an 40 Ar/ 39 Ar age of 80 Ma for phengite in eclogite, blueschist, jadeitite, and amphibolite, Goffé et al., 2002). Zhang et al. (2018b) recently reinterpreted all published zircon age data from the JMB and concluded that the main HP metamorphism and accretionary orogenesis in this segment of the COB was of Early to Middle Jurassic age. ...
Eclogite from two locations in a fossil accretionary complex now exposed in Nagaland, NE India, at the northern end of the Indo-Myanmar ranges, provides the oldest evidence for Neo-Tethyan subduction along the Yarlung-Tsangpo suture zone. Metamorphic texture, mineral composition, peak metamorphic P-T estimates, reconstructed metamorphic P-T paths, and U-Pb zircon ages from three eclogite samples collected near Mokie and Thewati villages collectively reveal snapshots of a c. 205-172 Ma subduction burial-exhumation cycle in the eastern Neo-Tethys. The Thewati eclogite records a clockwise metamorphic P-T path involving: (1) prograde metamorphism traversing the epidote blueschist facies and culminated in peak eclogite facies conditions at 25-28 kbar and ~650 o C; (2) an early retrograde stage involving decompression with cooling in the eclogite facies at ~18.3 kbar and 630 o C; followed by (3) cooling through the epidote blueschist, transitional lawsonite blueschist and greenschist facies to ~6 kbar and 300 o C. Circa 189-185 Ma peak metamorphism is inferred for the Mokie and Thewati eclogites, and was accompanied by an apparently low thermal gradient (~7-8 o C/km). Such conditions and the clockwise P-T path are associated with a tectonic scenario involving cold mature subduction within the Neo-Tethys in Nagaland. This is thus the first comprehensive dataset of an Early Jurassic subduction channel (with respect to present geographic coordinates) for the eastern margin of the Neo-Tethyan suture. The Nagaland samples offer a critical record of a pre-Cretaceous subduction system within the Neo-Tethys, which incorporated an Early-Middle Jurassic Andean-type convergent margin extending along the southern Eurasian margin from Pakistan to the Indo-Myanmar Ranges.
... The country rock of jadeitite is antigorite serpentinite or serpentinized peridotite (Shi et al., 2012). Rare eclogites and blueschists have been found in the Jade Mine Tract (Goffé et al., 2000;Nyunt, 2009). ...
... As experimental studies show, diffusion along a thermal or chemical potential gradient can be accompanied by significant isotopic fractionation Richter et al., 2003). Because of the lack of melt during the formation of jadeitites at low temperatures (<500°C; Goffé et al., 2000;Harlow et al., 2015;Shi et al., 2003Shi et al., , 2012, thermal diffusion is considered to be too sluggish to play an important role (Huang et al., 2009). Chemical diffusion by Mg-rich fluids can also induce significant Mg isotope fractionation (Pogge von Strandmann et al., 2011. ...
... carbonates can remain stable to very high pressures and temperatures in subduction zones, resulting in inefficient decarbonation in forearcs (Collins et al., 2015;Dasgupta & Hirschmann, 2010;Kerrick & Connolly, 2001;Molina & Poli, 2000;Poli et al., 2009;Thomsen & Schmidt, 2008). Furthermore, the formation temperatures of the Myanmar jadeitites (T < 500°C) are significantly lower than the decarbonation conditions (Goffé et al., 2000;Shi et al., 2003Shi et al., , 2012. This leaves carbonate dissolution as the best explanation for the incorporation of recycled carbonate into the jadeite-forming fluids. ...
Subduction zone fluids are critical for transporting materials from subducted slabs to the mantle wedge. Jadeitites from Myanmar record fluid compositions and reactions in the forearc subduction channel. Here, we present high-precision Mg isotope data of the Myanmar jadeitites and associated rocks to understand the Mg isotope composition of subduction zone fluids at forearc depths. Two types of jadeitites (white and green) exhibit distinct Mg isotope compositions. The white jadeitites precipitated from Na–Al–Si-rich fluids and have low δ26Mg values, varying from -1.55‰ to -0.92‰, whereas the green jadeitites have relatively higher δ26Mg values (-0.91‰ to -0.74‰) due to metasomatic reactions between fluids and Cr-spinel. The amphibole-rich blackwall in the contact boundaries between jadeitites and serpentinites also exhibits low δ26Mg values (-1.17‰ to -0.72‰). Therefore, the jadeite-forming fluids not only have high concentrations of Na–Al–Si but also low δ26Mg values. The low δ26Mg signature of the fluids is explained by the dissolution of Ca-rich carbonate in subducted sediments or altered oceanic crust, which is supported by the negative correlation of δ26Mg with CaO/TiO2, CaO/Al2O3, and Sr in the white jadeitites. Given the common occurrence of Ca-rich carbonates in the subduction channel, the Mg isotope composition of low-Mg aqueous fluids would be significantly modified by dissolved carbonates. Metasomatism by such fluids along conduits has the potential to generate centimeter-scale Mg isotope heterogeneity in the forearc mantle wedge. Therefore, Mg isotopes could be a powerful tracer for recycled carbonates not only in the deep mantle but also in the shallow regions of subduction zones.
... The majority of mined jade (Fig. 12.14) and analysed material comes from rounded boulders in young alluvial deposits, particularly along the Uru River. In addition to the abundant ultramafic clasts, Goffé et al. (2002) reported a variety of jade rock assemblages including pure jadeitite, nephrite-jadeite, omphacite-jadeite-zoisite-kyanite and kosmochlor (NaCrSi 2 O 6 ) with chromite, as well as less common eclogite, amphibolite and blueschist. The co-occurrence of (rare) jadeite and (more common) nephrite in the Jade Mines Belt suggests that any model of their origins will require an explanation of both mineral forms. ...
... Estimates of peak conditions fall within the broad range of 10-15 kbar and 300-500°C, as summarized by Shi et al. (2012). A more complex metamorphic history is implied by the suite of rocks studied by Goffé et al. (2002) where the sequence of overprinting assemblages seen in eclogite, jade veins, amphibolite and blueschist implies a four-stage evolution: (1) an eclogitic stage at P ≥ 14 kbar, 550-600°C; (2) overprinting by amphibole-epidote-albite during decompression to c. 8 kbar, 500-550°C; (3) blueschist-facies conditions at P ≥ 14 kbar, 400-450°C, with jadeitite vein formation at this stage; and (4) cooling and decompression represented by pumpellyite and albite-nepheline partial replacements. ...
... In contrast, a chemically distinct group of zircons showing a typical metasomatichydrothermal signature gave a U-Pb age of 77 ± 3 Ma, consistent with jadeitite formation during Late Cretaceous subduction. This Late Cretaceous age is supported by 39 Ar/ 40 Ar dating of phengites by Goffé et al. (2002) that gave a 'composite age' spread of 30-80 Ma. It is therefore possible that the protolith of these Hpakan jadeitites may have been older components of an ophiolitic suite, but that the high-pressure metamorphism was Late Cretaceous in age. ...
... The main source of jadeitite is in the Hpakant-Tawmaw area, Kachin State, northern Myanmar where it has been worked for more than 200 years. Jadeitite is also found in conglomerates and alluvial deposits derived from the original source (Chhibber 1934b;Bender 1983;Goffé et al. 2000;Hughes et al. 2000;Shi et al. 2001Shi et al. , 2005aNyan Thin 2002). At Nat-Maw (also Nammaw), c. 30 km north of Nansibon (about 20 km SE of Sinkaling/Hkamti, Sagaing division, Myanmar, on the Chindwin River, which is also about 50 km NW of Hpakant), a primary dyke (vein) of jadeitite and albitite in serpentinite has been reported but no further data are available (Avé Lallemant et al. 2000;Kane & Harlow 2006;Harlow et al. 2014 One of the sites where jade boulders and conglomerates are found is at Kyattakaung Hill where the stratigraphy is exposed (Nyan Thin 2002) ( Fig. 13.2a). ...
... These amphibolites are formed as a boundary zone or blackwall unit between serpentinized peridotite and the outermost albitite, inner albitejadeite rocks and innermost jadeitite units. Field relations and textural evidence suggest that the amphibolites are the result of metamorphic/metasomatic reactions between jadeitite and SiO 2 -depleted peridotites under HP-LT conditions (Shi et al. 2003), similar to those reported by Mével & Kiénast (1986), Harlow (1994), Goffé et al. (2000), and for similar jadeitite occurrences from all over the world. Shi et al. (2003) concluded that the amphibolite border zone between the jadeite veins and the peridotite body acts as a monitor of migrating fluids in a subduction zone. ...
... Monazite occurs exclusively in garnet-mica schists and 43 analyses of monazite by electron microprobe analyses yielded ages from 19 Ma (Miocene) to 74 Ma (Late Cretaceous); two grains gave 85 (Late Cretaceous) and 119 Ma (Early Cretaceous) (Thet Tin Nyunt 2009). Goffé et al. (2000) obtained 39 Ar-40 Ar ages of phengites in mica schists from the Jade Mines area of 80-50 Ma (Early Eocene). P-T conditions for the metamorphism of garnet-bearing mica schist, derived from thermodynamic calculations, are 1.6-1.9 ...
... The majority of mined jade (Fig. 12.14) and analysed material comes from rounded boulders in young alluvial deposits, particularly along the Uru River. In addition to the abundant ultramafic clasts, Goffé et al. (2002) reported a variety of jade rock assemblages including pure jadeitite, nephrite-jadeite, omphacite-jadeite-zoisite-kyanite and kosmochlor (NaCrSi 2 O 6 ) with chromite, as well as less common eclogite, amphibolite and blueschist. The co-occurrence of (rare) jadeite and (more common) nephrite in the Jade Mines Belt suggests that any model of their origins will require an explanation of both mineral forms. ...
... Estimates of peak conditions fall within the broad range of 10-15 kbar and 300-500°C, as summarized by Shi et al. (2012). A more complex metamorphic history is implied by the suite of rocks studied by Goffé et al. (2002) where the sequence of overprinting assemblages seen in eclogite, jade veins, amphibolite and blueschist implies a four-stage evolution: (1) an eclogitic stage at P ≥ 14 kbar, 550-600°C; (2) overprinting by amphibole-epidote-albite during decompression to c. 8 kbar, 500-550°C; (3) blueschist-facies conditions at P ≥ 14 kbar, 400-450°C, with jadeitite vein formation at this stage; and (4) cooling and decompression represented by pumpellyite and albite-nepheline partial replacements. ...
... In contrast, a chemically distinct group of zircons showing a typical metasomatichydrothermal signature gave a U-Pb age of 77 ± 3 Ma, consistent with jadeitite formation during Late Cretaceous subduction. This Late Cretaceous age is supported by 39 Ar/ 40 Ar dating of phengites by Goffé et al. (2002) that gave a 'composite age' spread of 30-80 Ma. It is therefore possible that the protolith of these Hpakan jadeitites may have been older components of an ophiolitic suite, but that the high-pressure metamorphism was Late Cretaceous in age. ...
The Mogok Metamorphic belt (MMB) in Myanmar (Burma) is thought to be a southward continuation of the Lhasa block of south Tibet around the East Himalayan syntaxis. South of Burma the MMB may extends into the tin granite province of the Mergui coast and south to Phuket. The MMB in Burma is a sequence of high-grade metamorphic rocks including phlogopite + diopside + spinel ± olivine ± ruby corundum marbles, scapolite + garnet + biotite calc-silicates, clinopyroxene-bearing quartzites and gneisses intruded by rare nepheline syenites (occasionally sapphire-bearing) and associated ultramafic rocks and a variety of granitic rocks. Pre-collisional hornblende and biotite bearing diorites and granodiorites are related to supra-subduction zone magmatism prior to Indian plate collision. Mogok gneisses show high-temperature paragenesis with sillimanite + muscovite replacing earlier andalusite (Kyaushe gneiss) in pelites and peak metamorphic anatexis resulting in tourmaline + garnet + muscovite leucogranites (Kyanikan). An earlier metamorphic event and fabric formation is preserved at Belin quarry where a post-kinematic biotite granite dyke has been dated at ~59 Ma. Evidence of older metamorphism along the Mogok belt has largely been overprinted by a Cenozoic high-temperature metamorphism constrained by U-Th-Pb ID-TIMS and in situ LA-ICPMS dating of metamorphic monazite and zircon. Growth of metamorphic monazite at sillimanite grade (680oC; 4.4 - 4.9 kbar) and growth of zircon rims occurred between 47-43 Ma. Syn-peak metamorphic tourmaline granites have ages ranging between 45.5 – 24.5 Ma. The tourmaline granites are in situ partial melts from a biotite + muscovite + K-feldspar augen gneiss protolith and their ages record Cenozoic periods of peak sillimanite grade metamorphism. Kyanite gneisses in the Katha Gangaw range record higher pressures. The MMB has little in common with the Western granite belt of peninsula Malaysia, dominated by Triassic tin-bearing biotite granites, which is regarded as a separate terrane.
... The COB Central Ophiolite Belt that passes through the Jade Mines Belt (JMB) is represented by a dismembered, incompletely preserved ophiolitic sequence of serpentinite and peridotite (Htay et al. 2017) and a package of HP/low-T (LT) metamorphic rocks from jadeitite, eclogite, amphibolite to blueschists, best recorded in the JMB (Goffé et al. 2002). While a Jurassic protolith age for the ophiolite in the JMB (c.163 -160 Ma) has been estimated from the jadeitites (Shi et al. 2008;Yui et al. 2013), the timing of the HP metamorphic event is controversial with age estimates ranging from an Early to Middle Jurassic (Zhang et al. 2018), Late Jurassic (c. ...
... 158 and147 Ma, Shi et al. 2008;Qiu et al. 2009) to Late Cretaceous (c. 77 -80 Ma, Goffé et al. 2002;Yui et al. 2013) have been suggested. ...
In this study, we make a review of the recent developments on the metamorphic and tectonic evolution of the Nagaland-Manipur Ophiolite Belt (NMOB) in the Indo-Myanmar Ranges. We collate key metamorphic findings and chronological constraints in the NMOB to demonstrate an exceptional record of the full life cycle of the thermal and dynamic history of the Early Mesozoic intra-oceanic subduction system within the eastern arm of the Neo-Tethys from its infancy to its cold-mature stage. The earliest stage of an Early Jurassic-aged oceanic subduction under warm thermal conditions (apparent peak thermal gradient of ~ 20 °C/km), and within the first 1–2 Myrs since subduction initiation is recorded in the newly discovered high- and low-temperature metamorphic sole rocks of the Tusom CV area in the Manipur segment of the ophiolite belt. The metamorphic sole sequence, comprising a package of ultra-high temperature mafic granulites → high-temperature mafic granulite → garnet + clinopyroxene-bearing amphibolite → garnetiferous amphibolite → non-garnetiferous amphibolite → epidote amphibolite and low greenschist facies metasediments, and structurally downward, constitutes an inverted metamorphic sequence. Tectonic slices of hornblende eclogite facies metasediments and metabasites from diffrrent locations in the Nagaland segment of the Ophiolite Belt, on the other hand, reveal an apparent peak thermal gradient of ~ 12–15 ℃/km, indicating an intermediate subduction cooling stage. The structurally upward metamorphic sequence of greenschist facies → pumpellyite-diopside facies → lawsonite blueschist facies and epidote eclogite facies, the latter locally reaching ultra-high pressure metamorphic conditions in metabasalts of the structurally lowermost unit of the Nagaland ophiolite mélange together record a cooler apparent peak thermal gradient of ~ 7–8 ℃/km. We relate this metamorphism with the end stage of the Early Jurassic-aged intra-oceanic subduction, when the Neo-Tethys evolved into a cold-mature stage of subduction.
... One of the world's largest jadeitite-bearing suture zones is exposed in the Kashin state of Myanmar in the famous Jade Mines Belt (e.g., Shi et al., 2012;Nyunt et al., 2017), where loose jadeitite fragments are found in conglomerates, river beds or exceptionally embedded within strongly-weathered antigorite schists (e.g., Harlow et al., 2015 and references therein;Ridd et al., 2019). The original jadeitite-bearing structures (likely ancient felsic dykes; e.g., Bleek, 1908) were formed within a serpentinized mantle wedge from a subduction zone of debated Late Jurassic to Late Cretaceous age (Goffé et al., 2002;Shi et al., 2009aShi et al., , 2012Yui et al., 2013;Harlow et al., 2016). These metasomatized dykes were extensively affected by exhumation and subsequent strike-slip deformation related to the Sagaing transform fault system Searle et al., 2007;Ridd et al., 2019). ...
... Na-amphibole-rich bands (mostly eckermannite and glaucophane; see Oberti et al., 2015 for further details on mineralogy) are also found either embedded within the jadeitite "dyke" or lining the contact with the ultramafic host (Bleek, 1908;Nyunt, 2009). Most pressure-temperature estimates for jadeitite formation in the Jade Mine Belt region span a wide range from 1.0-1.5 GPa and 300-500 • C (Mével and Kienast, 1986;Goffé et al., 2002;Shi et al., 2003). The herein studied samples, provided by a local miner, were found as boulders in a conglomerate near the Lonkin township (near Hpakan). ...
An increasing number of seismological studies report transient seismicity clusters in the mantle wedge several kilometers above the subduction interface. Their physical significance with respect to subduction zone seismo-tectonics remains poorly understood. Jadeitites are known to form and/or be associated with mantle wedge serpentinites in the c. 30–70 km depth range, and thus may yield information on deformation mechanisms in this region of deep subduction environments. We herein document and compare brittle-viscous features recorded in jadeitites from Polar Urals (Russia), Kashin state (Myanmar) and Motagua fault region (Guatemala) – some of the most important jadeitite occurrences worldwide. In the Polar Urals we identified ultramafic-hosted pristine jadeitite-bearing veins c. 1 km above a Devonian paleo-subduction interface, interpreted as metasomatized former felsic dyke networks crosscutting the mantle wedge peridotites. Here, both jadeitites and associated amphibole-rich dark granofels display widespread brittle-ductile deformation fabrics such as shear bands, foliated cataclasites and breccias, cemented through dissolution-precipitation processes by omphacite and sodic amphiboles, a mineral assemblage typical of high-pressure–low-temperature subduction zone conditions. Electron probe and laser ablation ICP-MS mapping indicate that these brittle-viscous networks display a substantial metasomatic imprint highlighted in the dark granofels by variations in major and trace elements. Switches between viscous and brittle deformation patterns are attested by crystallographic-preferred orientations of jadeite in some of the shear zones that crosscut the host jadeitites. Strikingly similar mineral assemblages and deformation patterns were observed in the Kashin and Motagua samples. Observed deformation features in these localities can be classified into three categories (tectonic breccias, foliated cataclasites and hydraulic breccias), which may occasionally form in sequence and exhibit mutually overprinting textures. Some of the foliated cataclasites contain fine-grained and foliated “shard-like” features forming a radial omphacite-jadeite spherulitic texture, interpreted as former pseudotachylyte that evokes a paleo-seismic origin. We interpret these healed fault networks as recording external fluid influx within fracture zones that repeatedly ruptured along former “dyke” networks. These high permeability drains likely (i) contribute to the transfer of highly pressurized plate-interface metamorphic fluids into the mantle wedge; and (ii) trigger seismic instabilities recorded in the basal part of active mantle wedge sections. These findings provide new insights into the current understanding of the rheology (e.g., serpentinization ratio) and stress state in the mantle wedge, with implications for subduction interface seismogenesis.
... However, Yui et al. (2013) suggested that the R-type jadeitite, with a protolith age of 160 ± 1 Ma, formed at around 77 ± 3 Ma. The P-T conditions recorded by the Myanmar jadeitites are 1-1.5 GPa and 300-450 °C (Goffé et al. 2000;Oberhänsli et al. 2007;Shi et al. 2005Shi et al. , 2012. ...
... The δ 30 Si of quartz is about 0.55 ± 0.10‰ higher than the fluids at 250 °C, suggesting that 1000lnα 30 Si quartz-fluid = (0.15 ± 0.0 3) × 10 6 /T 2 (T is temperature in kelvin). As a result, with the jadeitite-forming temperatures of 300-450 °C (Goffé et al. 2000;Oberhänsli et al. 2007;Shi et al. 2005Shi et al. , 2012, Δ 30 Si quartz-fluid = 0.3‰ to 0.5‰. ...
Silicon is one of the major elements in the solute of subduction zone fluids. The source information of Si in the fluids is useful for constraining the material exchange between the oceanic crust and mantle. Myanmar jadeitites result from crystallization of subduction zone fluids at high pressures, which can be used as a proxy for the chemical composition of the fluids. This paper reports high-precision Si isotope data of jadeitites, and associated amphibole-rich blackwall, serpentinites, and mica quartz schists to constrain the Si isotope composition of subduction zone fluids. The white jadeitites have higher δ³⁰Si (− 0.04‰ to 0.23‰) than any igneous rocks reported in literature. The δ³⁰Si of green jadeitites (− 0.35‰ to 0.03‰) and amphibole-rich blackwall (− 0.33‰ to 0.05‰) are generally lower than the values of white jadeitites. These data indicate that the jadeitite-forming fluids in the source subduction zone have heavy Si isotope compositions relative to the bulk silicate Earth. Based on the Si isotope fractionations among quartz, white jadeite, and the fluid, it is inferred that the subduction zone fluids have high δ³⁰Si of about 0.7‰ to 1.2‰. The δ³⁰Si of jadeitites and amphibole-rich blackwall show a positive correlation with SiO2 content with a slope of 0.0639, larger than that of the igneous rock array (0.0056). Such a correlation cannot be produced by magmatic differentiation or mineral fractional crystallization from fluids. Instead, it is more likely explained by a binary mixing model between fluids and mafic–ultramafic rocks. The model shows that about 0 to 25% of Si in green jadeitites and amphibole-rich blackwall is from the subduction zone fluids. In light of the relatively low δ³⁰Si of abyssal clay sediment, altered oceanic crust, and mantle serpentinite, it is proposed that the deep-sea siliceous rocks with high δ³⁰Si are likely the main source of Si in subduction zone fluids. In summary, this study shows that Si isotopes have useful application in tracing the source of solute in fluid-mediated processes.
... The possible origin of Myanmar's jade-bearing jadeitite has been discussed recently by Searle et al. (2017), Thet Tin Nyunt et al. (2017), and Mitchell (2018. They based their work on detailed analyses by Goffé et al. (2000), Shi et al. (2008Shi et al. ( , 2009Shi et al. ( , 2014, Qiu et al. (2009) and others. Recent papers by Harlow et al. (2014Harlow et al. ( , 2015 examine the isotopic dates and other findings of those authors, and integrate them into a valuable global study of jadeitite. ...
... In the Hpakant serpentinite mélange (Fig. 7) Goffé et al. (2000) found blueschist and eclogite, from which, by analogy with Alpine settings, they estimated a range of P-T conditions from 450 to 500 C at 1.0-1.5 gigapascals (GPa) as bracketing the jadeitite formation. Shi et al. (2003) studied a Myanmar jadeitite sample and estimated somewhat lower figures: T = 250 C to 370 C at P = 1 to $1.2 GPa. ...
The Hukawng Basin is bounded on its east by splays of the still-active Sagaing Fault. Palinspastically restoring Myanmar's blocks to their positions before the widely-accepted c.400 km dextral strike-slip fault displacement, places the Hukawng Block alongside the Tengchong Block, suggesting they were formerly connected. Additionally the Cretaceous–Paleogene Medial-Myanmar Shear Zone then aligns with the NW-SE Jade Mines Belt. Jadeitite formed there under HP/LT conditions in a Mesozoic subduction zone. It was exhumed at the intersection of the dextral Medial-Myanmar Shear Zone with the subduction-zone at the continental margin of Sundaland. The later Sagaing Fault played no part in that exhumation.
... The pressures (P) and temperatures (T ) for the formation of jadeitites in the Jade Mines Belt have been the subject of investigations by many research groups over the past three decades. Methods include the determination of the conditions for the crystallization of jadeite (Mével & Kiénast 1986;Goffé et al. 2000), those indicated by fluid inclusions in jadeite crystals (Shi et al. 2003(Shi et al. , 2005Oberhänsli et al. 2007;Fu et al. 2010;Harlow et al. 2014), and the determination of the pressure and temperature for the crystallization of mineral assemblages in associated rock types using thermodynamic reasoning (Thet Tin Nyunt 2009;Thet Tin Nyunt et al. 2017). All these methods have yielded similar results, with P of the order of 1-1.5 GPa (10-20 kbar) at comparatively moderate T of 300-400°C. ...
... They interpret this age as indicating the time of the subduction of the ocean crust; ages of c. 45 Ma (Eocene) are interpreted as the time of uplift of the complex along the Sagaing Fault, but there is no independent evidence that the fault was active this early. Ar/Ar ages on phengites from eclogite, blueschist, jadeitite and amphibolites gave 80 Ma (Late Cretaceous) for eclogites and 30 Ma (Oligocene) for blueschists (Goffé et al. 2000). U-Pb in monazite from garnet-mica schist yielded results between 120 Ma (Early Cretaceous) and <15 Ma (Middle Miocene) (Thet Tin Nyunt 2009). ...
... However, given the size of the jade boulders and classic serpentinite weathering pattern of ultramafic rocks it is suggested that some of the "boulders" are actually remnant serpentinite weathering of large in situ ophiolitic peridotite sheets, and are not alluvial. In addition to the abundant ultramafic clasts, Goffé et al. (2002) reported a variety of jade rock assemblages, including pure jadeitite, amphibole-jadeite, omphacite-jadeite-zoisitekyanite, and kosmochlor with chromite, as well as less common eclogite, amphibolite, and blueschist. ...
... There is consensus that the jade rocks formed at high pressure and low temperature, although P-T conditions are not precisely constrained, owing to the predominance of high-variance mineral assemblages, with estimates of peak conditions falling in the broad range of 10 to 15 kbars, 300° to 500°C (Shi et al., 2012). A more complex metamorphic history is implied by the suite of rocks studied by Goffé et al. (2002), where the sequence of overprinting assemblages seen in eclogite, jade veins, amphibolite, and blueschist implies a four-stage evolution from (1) an eclogitic stage at P ≥14 kbars, 550° to 600°C; (2) overprinting by amphibole-epidote-albite during decompression to ~8 kbars, 500° to 550°C; (3) blueschistfacies conditions at P ≥14 kbars, 400° to 450°C, with jadeitite vein formation at this stage; and (4) cooling and decompression represented by pumpellyite and albite-nepheline partial replacements. ...
The genesis of mineral deposits has been widely linked to speci c tectonic settings, but has less frequently been linked to tectonic processes. Understanding processes of oceanic and continental collision tectonics is crucial to understanding key factors leading to the genesis of magmatic-, metamorphic-, hydrothermal-, and sedimentary-related mineral deposits. Geologic studies of most ore deposits typically focus on the nal stages of concentration and emplacement. The ultimate source (mantle, lower crust, upper crust) of mineral deposits in many cases remains more cryptic. Uniquely, along the Tethyan collision zones of Asia, every stage of the conver- gence process can be studied from the initial oceanic settings where ophiolite complexes were formed, through subduction zone and island-arc settings with ultrahigh- to high-pressure metamorphism, to the continental col- lision settings of the Himalaya, and advanced, long-lived collisional settings such as Afghanistan, the Karakoram Ranges, and the Tibetan plateau. The India-Asia collision closed the intervening Neotethys ocean at ~50 Ma and resulted in the formation of the Himalayan mountain ranges, and increased crustal thickening, metamor- phism, deformation, and uplift of the Karakoram-Hindu Kush ranges, Tibetan plateau, and older collision zones across central Asia. Metallogenesis in oceanic crust (hydrothermal Cu-Au; Fe, Mn nodules) and mantle (Cr, Ni, Pt) can be deduced from ophiolite complexes preserved around the Arabia/India-Asia collision (Oman, Ladakh, South Tibet, Myanmar, Andaman Islands). Tectonic-metallogenic processes in island arcs and ancient subduc- tion complexes (VMS Cu-Zn-Pb) can be deduced from studies in the Dras-Kohistan arc (Pakistan) and the various arc complexes along the Myanmar-Andaman segment of the collision zone. Metallogenesis of Andean- type margins (Cu-Au-Mo porphyry; epithermal Au-Ag) can be seen along the Jurassic-Eocene Transhimalayan ranges of Pakistan, Ladakh, South Tibet, and Myanmar. Large porphyry Cu deposits in Tibet are related to both precollisional calc-alkaline granites and postcollisional alkaline adakite-like intrusions. Metallogenesis of continent-continent collision zones is prominent along the Myanmar-Thailand-Malaysia Sn-W granite belts, but less common along the Himalaya. The Mogok metamorphic belt of Myanmar is known for its gemstones associated with regional high-temperature metamorphism (ruby, spinel, sapphire, etc). In Myanmar it is likely that extensive alkaline magmatism has contributed extra heat during the formation of high-temperature meta- morphism. This paper attempts to link metallogeny of the Himalaya-Karakoram-Tibet and Myanmar collision zone to tectonic processes derived from multidisciplinary geologic studies.
... The Jade Mines Belt (JMB, Fig. 3), another metamorphic belt, lies along the northern segments of the Sagaing Fault. The Jade Belt is a high-P subduction-related assemblage (Goffe et al., 2002). Although dominated by outcrops of peridotite and serpentinite, it remains poorly exposed and little studied. ...
... The majority of mined jade is sourced from bounders in young alluvial deposits along the Uru River (e.g., Hughes et al., 2000). A variety of jade rock assemblages have been reported: pure jadeitite, amphibole jadeite, omphacite-jadeite-zoisite-kyanite and kosmochlor (Franz et al., 2014;Goffe et al., 2002). The Hpakant region is globally unique in the extensive occurrence of pure jade, jadeite (Hughes et al., 2000). ...
Myanmar is perhaps one of the world's most prospective but least explored minerals jurisdictions, containing important known deposits of tin, tungsten, copper, gold, zinc, lead, nickel, silver, jade and gemstones. A scarcity of recent geological mapping available in published form, coupled with an unfavourable political climate, has resulted in the fact that, although characterized by several world-class deposits, the nation's mineral resource sector is underdeveloped. As well as representing a potential new search space for a range of commodities, many of Myanmar's known existing mineral deposits remain highly prospective. Myanmar lies at a crucial geologic juncture, immediately south of the Eastern Himalayan Syntaxis, however it remains geologically enigmatic. Its Mesozoic-Recent geological history is dominated by several orogenic events representing the closing of the Tethys Ocean. We present new zircon U-Pb age data related to several styles of mineralization within Myanmar. We outline a tectonic model for Myanmar from the Late Cretaceous onwards, and document nine major mineralization styles representing a range of commodities found within the country. We propose a metallogenetic model that places the genesis of many of these metallotects within the framework of the subduction and suturing of Neo-Tethys and the subsequent Himalayan Orogeny. Temporal overlap of favourable conditions for the formation of particular deposit types during orogenic progression permits the genesis of differing metallotects during the same orogenic event. We suggest the evolution of these favourable conditions and resulting genesis of much of Myanmar's mineral deposits, represents a single, evolving, mineral system: the subduction and suturing of Neo-Tethys.
... Serpentinized peridotites occur as boulders in alluvial deposits together with pure jadeite, amphibole jade and kyanite-bearing omphacite jade. Goffé et al. [2002] determined eclogite facies P-T conditions P > 14 kbar and T $ 550-600°C overprinted by $8 kbar and 500 -550°C amphibolite facies conditions. Jadeite + quartz and omphacite + zoisite + kyanite blueschists record similar high pressures but lower temperatures around 400-450°C [Goffé et al., 2002]. ...
... Goffé et al. [2002] determined eclogite facies P-T conditions P > 14 kbar and T $ 550-600°C overprinted by $8 kbar and 500 -550°C amphibolite facies conditions. Jadeite + quartz and omphacite + zoisite + kyanite blueschists record similar high pressures but lower temperatures around 400-450°C [Goffé et al., 2002]. We speculate that late Mesozoic ophiolitic rocks obducted onto the Burma microplate were later metamorphosed during east dipping subduction, and then exhumed to the surface prior to dextral shearing along the Sagaing fault. ...
... Serpentinized peridotites occur as boulders in alluvial deposits together with pure jadeite, amphibole jade and kyanite-bearing omphacite jade. Goffé et al. [2002] determined eclogite facies P-T conditions P > 14 kbar and T $ 550-600°C overprinted by $8 kbar and 500 -550°C amphibolite facies conditions. Jadeite + quartz and omphacite + zoisite + kyanite blueschists record similar high pressures but lower temperatures around 400-450°C [Goffé et al., 2002]. ...
... Goffé et al. [2002] determined eclogite facies P-T conditions P > 14 kbar and T $ 550-600°C overprinted by $8 kbar and 500 -550°C amphibolite facies conditions. Jadeite + quartz and omphacite + zoisite + kyanite blueschists record similar high pressures but lower temperatures around 400-450°C [Goffé et al., 2002]. We speculate that late Mesozoic ophiolitic rocks obducted onto the Burma microplate were later metamorphosed during east dipping subduction, and then exhumed to the surface prior to dextral shearing along the Sagaing fault. ...
... The boundary with serpentinite is marked by a soft, green border zone that consists of a mixture of the adjacent vein minerals and chlorite, with or without calcite, actinolite, talc, and cherty masses Soe Win, 1968), i.e., a blackwall assemblage. Serpentinite conglomerate units in fault contact with the serpentinite mélanges contain jadeitite boulders, cobbles and pebbles that are also mined around Hpakan and about 60 km west of Hpakan at Nansibon (Avé Lallemant et al., 2000;Goffé et al., 2000;Hughes et al., 2000;. Jadeitite-bearing conglomerates also extend from Monhyn to Indaw-Tigyaing (United Nations, 1979), $100-230 km south of Hpakan, along the Sagaing fault. ...
... 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 without quartz or albite only indicates pressure above the reaction Anl ¼ Jd þ H 2 O. Four estimates of P-T conditions are available (Fig. 12): give a rough estimate based on the presence of jadeite and analogy with rocks from the western Alps -a broad band of 1 GPa , P , 1.5 GPa and 300 C , T ,500 C; Goffé et al. (2000) used textural constraints and a phase assemblage in a blueschist overprint in an eclogite recovered from alluvium in the Jade Tract area (1.4 GPa , P , 1.6 GPa and 400 C , T , 450 C); Shi et al. (2003) included phase equilibria with amphiboles, and Oberhänsli et al. (2007) recalculated jadeite-omphacite-amphibole equilibria using a pseudo-section approach. These broad PT estimates are shown in Fig. 12. ...
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, nyböite, eckermannite,
magnesiokatophorite, glaucophane, richterite, winchite, analcime, natrolite, thomsonite-Ca, pectolite, vesuvianite, titanite, grossular, uvarovite, allanite, phlogopite, cymrite, zircon, graphite, quartz, diaspore, kaolinite, pyrite, galena, chromite, and ilmenite have been documented from
these jadeitites and related rocks, which we review and update. Phlogopite, natrolite, thomsonite-Sr, titanite and ilmenite are newly reported here. Amphiboles, kosmochlor and omphacite formed closely related to the paragenetic sequence in the presence of jadeite; however, uvarovite is formed
by replacement of chromite and does not require the presence of jadeite. At least two stages of jadeitization have been identified for Myanmar jadeitite. Late-stage zeolites, pectolite and hyalophane, banalsite, titanite and some celsian formed at lower P and T. The spectrum
of minerals in Myanmar jadeitite indicates that the jadeite-forming fluids were rich in Na, Al, Ba, Sr, and Ca. Moreover, the variety of replacement textures suggests that most rocks in the serpentinite mélanges were subject to infiltration and potential replacement by jadeitite or
reaction with jadeitite. Serpentinite was replaced by sodic to sodic-calcic amphibole, chromite in ultramafic rock by kosmochlor and Cr-bearing jadeite, and the clinopyroxene in mafic rock by omphacite. Relict ilmenite replaced by titanite in omphacitite is evidence for metasomatism of mafic
rock. Sodium-rich fluids were likely dominant throughout jadeitite crystallization and metasomatic reactions. A general mineralogical comparison of jadeitites world-wide indicates both similarities and distinctions; these could be used for interpreting sources of the jadeite jade, particularly
in archaeology.
... The Asian plate east of the Sagaing fault includes the Palaeozoic Mogok Metamorphic belt (MMB), the Jurassic-Miocene granitoids that are intrusive into the MMB (Fig. 1b) and the Late Carboniferous-Lower Permian Mergui Group sedimentary rocks (Mitchell, 1992;Barley et al., 2003;Searle et al., 2007;Mitchell et al., 2012). The Jade Mines (JM) belt, an association of jadeitites, eclogite, amphibolite, BS, chromitite and serpentinized peridotite (Shi et al., 2001;Goff e et al., 2002), records characteristic high-P metamorphism, the P-T conditions of which have been variously estimated at 10-15 kbar, 300-500°C (M evel & Ki enast, 1986), >14 kbar, 400-450°C (Goff e et al., 2002), >10 kbar, 250-370°C (Shi et al., 2003) and~15 kbar,~380°C (Oberh€ ansli et al., 2007). Available U-Pb zircon ages in jadeitite from the JM belt indicate a Jurassic age (between 163 and 160 Ma) for the formation of the ophiolitic protolith (Shi et al., 2008;Yui et al., 2013). ...
... The Asian plate east of the Sagaing fault includes the Palaeozoic Mogok Metamorphic belt (MMB), the Jurassic-Miocene granitoids that are intrusive into the MMB (Fig. 1b) and the Late Carboniferous-Lower Permian Mergui Group sedimentary rocks (Mitchell, 1992;Barley et al., 2003;Searle et al., 2007;Mitchell et al., 2012). The Jade Mines (JM) belt, an association of jadeitites, eclogite, amphibolite, BS, chromitite and serpentinized peridotite (Shi et al., 2001;Goff e et al., 2002), records characteristic high-P metamorphism, the P-T conditions of which have been variously estimated at 10-15 kbar, 300-500°C (M evel & Ki enast, 1986), >14 kbar, 400-450°C (Goff e et al., 2002), >10 kbar, 250-370°C (Shi et al., 2003) and~15 kbar,~380°C (Oberh€ ansli et al., 2007). Available U-Pb zircon ages in jadeitite from the JM belt indicate a Jurassic age (between 163 and 160 Ma) for the formation of the ophiolitic protolith (Shi et al., 2008;Yui et al., 2013). ...
In this study, we have deduced the thermal history of the subducting Neotethys from its eastern margin, using a suite of partially hydrated metabasalts from a segment of the Nagaland Ophiolite Complex (NOC), India. Located along the eastern extension of the Indus-Tsangpo suture zone (ITSZ), the N-S trending NOC lies between the Indian and Burmese plates. The metabasalts, encased within a serpentinitic mélange, preserve a tectonically disturbed metamorphic sequence, which from west to east is greenschist, pumpellyite-diopside and blueschist facies. Metabasalts in all the three metamorphic facies record prograde metamorphic overprints directly on primary igneous textures and igneous augite. In the blueschist facies unit, the metabasalts interbedded with marble show centimetre to metre scale interlayering of lawsonite blueschist and epidote blueschist. Prograde HP/LT metamorphism stabilized lawsonite + omphacite (XJd = 0.50-0.56 to 0.26-0.37) + jadeite (XJd = 0.67 to 0.79) + augite + ferroglaucophane + high-Si phengite (Si =3.6-3.65 atoms per formula unit, a.p.f.u.) + chlorite + titanite + quartz in lawsonite blueschist and lawsonite + glaucophane/ferroglaucophane ± epidote ± omphacite (XJd = 0.34) + chlorite + phengite (Si = 3.5 a.p.f.u.) + titanite + quartz in epidote blueschist at the metamorphic peak. Retrograde alteration, which was pervasive in the epidote blueschist, produced a sequence of mineral assemblages from omphacite and lawsonite-absent, epidote + glaucophane/ferroglaucophane + chlorite + phengite + titanite + quartz through albite + chlorite + glaucophane to lawsonite + albite + high-Si phengite (Si = 3.6-3.7 a.p.f.u.) + glaucophane + epidote + quartz. In the pumpellyite-diopside facies metabasalts, the peak mineral assemblage, pumpellyite + chlorite + titanite + phengitic white mica (Si = 3.4-3.5 a.p.f.u.) + diopside appeared in the basaltic groundmass from reacting titaniferous augite and low-Si phengite, with prehnite additionally producing pumpellyite in early vein domains. In the greenschist facies metabasalts, incomplete hydration of augite produced albite + epidote + actinolite + chlorite + titanite + phengite + augite mineral assemblage. Based on calculated T-M(H2O), T-M(O2) (where M represents oxide mole %) and P-T pseudosections, peak P-T conditions of lawsonite blueschist are estimated at ~ 11.5 kbar and ~340 °C, epidote blueschist at ~10 kbar, 325 °C and pumpellyite-diopside facies at ~6 kbar, 335 °C. Reconstructed metamorphic reaction pathways integrated with the results of P-T pseudosection modeling define a near-complete, hairpin, clockwise P-T loop for the blueschists and a prograde P-T path with a steep dP/dT for the pumpellyite-diopside facies rocks. Apparent low thermal gradient of 8 °C km−1 corresponding to a maximum burial depth of 40 km and the hairpin P-T trajectory together suggest a cold and mature stage of an intra-oceanic subduction zone setting for the Nagaland blueschists. The metamorphic constraints established above when combined with petrological findings from the ophiolitic massifs along the whole ITSZ suggest that intra-oceanic subduction systems within the Neotethys between India and the Lhasa terrane / the Karakoram microcontinent were also active towards east between Indian and Burmese plates.This article is protected by copyright. All rights reserved.
... However, the published age data are very limited and somehow contradictory. Goffé et al. (2000) Shi et al., 2008;ca. 158 Ma by Qiu et al., 2009;Qi et al., 2013;Yui et al., 2013). ...
... They are interpreted as a recrystallization event, which is coeval with the onset of the Sagaing fault. Cenozoic ages have been reported in some previous studies and interpreted by Goffé et al. (2000) to represent the time of high-pressure metamorphic events. However, these authors did not present mineral compositions and textures of the analyzed phengite. ...
The Myanmar jadeite uplift forms an important link between the Indo-Burma Range and the Tagaung-Myitkyina Belt Two contrasting ages of Jurassic (152.4 +/- 1.5 Ma of glaucophane from blueschist) and Eocene (44.8 +/- 1.1 and 45.0 +/- 1.3 Ma of phengitic muscovites from quartz schists in the uplift) were yielded using Ar-40/Ar-39 dating. The Jurassic age of the glaucophane, even older than the forming age of the jadeitite from recent relevant literatures, and for the reason of possible excess argon involved, is interpreted as the lower limit of the subduction age. Previous studies correlated this subduction with the Woyla intra-oceanic arc, or the Incertus Arc to the west The Eocene ages of phengitic muscovites are interpreted as the time of an intra-continental shearing deformation event, against the timing of HP/LT metamorphism as previously suggested. Combined with other studies, it is suggested that the Tagaung-Myitkyina Belt and the Indo-Burma Range belonged to a single belt which has been separated by the Sagaing Fault, leaving the jadeite uplift straddling along the fault between the Belt and the Range. We propose a rapid exhumation model for the Myanmar jadeitite at similar to 45 Ma, coeval with onset of the Sagaing Fault.
... Serpentinized peridotites occur as boulders in alluvial deposits together with pure jadeite, amphibole jade and kyanite-bearing omphacite jade. Goffé et al. [2002] determined eclogite facies P-T conditions P > 14 kbar and T $ 550-600°C overprinted by $8 kbar and 500 -550°C amphibolite facies conditions. Jadeite + quartz and omphacite + zoisite + kyanite blueschists record similar high pressures but lower temperatures around 400-450°C [Goffé et al., 2002]. ...
... Goffé et al. [2002] determined eclogite facies P-T conditions P > 14 kbar and T $ 550-600°C overprinted by $8 kbar and 500 -550°C amphibolite facies conditions. Jadeite + quartz and omphacite + zoisite + kyanite blueschists record similar high pressures but lower temperatures around 400-450°C [Goffé et al., 2002]. We speculate that late Mesozoic ophiolitic rocks obducted onto the Burma microplate were later metamorphosed during east dipping subduction, and then exhumed to the surface prior to dextral shearing along the Sagaing fault. ...
The Mogok metamorphic belt (MMB) extends for over 1500 km along the
western margin of the Shan-Thai block, from the Andaman Sea north to the
eastern Himalayan syntaxis. Previous geochronology has suggested that a
long-lasting Jurassic-early Cretaceous subduction-related event resulted
in emplacement of granodiorites and orthogneisses (171-120 Ma) and a
poorly constrained Tertiary metamorphic event. On the basis of new U-Pb
isotope dilution thermal ionization mass spectrometry and U-Th-Pb laser
ablation-multicollector-inductively coupled plasma mass spectrometer
geochronology presented here, we propose two Tertiary metamorphic events
affected the MMB in Burma. The first was a Paleocene event that ended
with intrusion of crosscutting postkinematic biotite granite dikes at
˜59 Ma. A second metamorphic event spanned late Eocene to
Oligocene (at least from 37, possibly 47, to 29 Ma). This resulted in
the growth of metamorphic monazite at sillimanite grade, growth of
zircon rims at 47-43 Ma, sillimanite + muscovite replacing older
andalusite, and synmetamorphic melting producing garnet and tourmaline
bearing leucogranites at 45.5 ± 0.6 Ma and 24.5 ± 0.7 Ma.
These data imply high-temperature sillimanite + muscovite metamorphism
peaking at 680°C and 4.9 kbar between 45 and 33 Ma, to around
606-656°C and 4.4-4.8 kbar at 29.3 ± 0.5 Ma. The later
metamorphic event is older than 24.5 ± 0.3 Ma, the age of
leucogranites that crosscut all earlier fabrics. Our structural and
geochronological data suggest that the MMB links north to the unexposed
middle or lower crust rocks of the Lhasa terrane, south Tibet, and east
to high-grade metamorphic core complexes in northwest Thailand.
... 380 T. Tsujimori, G.E. Harlow However, the presence of relict igneous zircon would also indicate replacement features. The jadeitite-bearing serpentinite mélange also contains tectonic blocks of blueschist, eclogite, amphibolite and marble (Shi et al., 2001;Goffé et al., 2002). In the Jade Mines area, eclogites record both epidote-amphibolite facies and lawsonite-blueschist facies overprinting; phengite 40 Ar/ 39 Ar geochronology suggests about 80 Ma for eclogite-facies metamorphism and about 30 Ma for blueschist-facies overprinting (Goffé et al., 2002). ...
... The jadeitite-bearing serpentinite mélange also contains tectonic blocks of blueschist, eclogite, amphibolite and marble (Shi et al., 2001;Goffé et al., 2002). In the Jade Mines area, eclogites record both epidote-amphibolite facies and lawsonite-blueschist facies overprinting; phengite 40 Ar/ 39 Ar geochronology suggests about 80 Ma for eclogite-facies metamorphism and about 30 Ma for blueschist-facies overprinting (Goffé et al., 2002). Although neither a locality nor an occurrence of eclogites has so far been documented in the literature, Enami et al. (2011) recently described an eclogite boulder from the Kumon range, about 80 km to the east of the Jade Mines area. ...
Jadeitite-bearing serpentinite-matrix mélange is distributed in the Caribbean (Guatemala, Cuba, and Dominican Republic), circum-Pacific (Japan, Western USA, and Papua New Guinea), Alpine-Himalayan (Italy, Iran, Greece, and Myanmar), and Caledonian (Russia and Kazakhstan) orogenic belts, and always contains high-pressure, low-temperature (HP-LT) metamorphic rocks. There are also jadeitite xenoliths in kimberlitic pipes in the Colorado Plateau (USA). The oldest occurrences of jadeitite are Early Paleozoic in Japan, Russia, and Kazakhstan, suggesting subduction-zone thermal structures evolved the necessary high pressure/temperature conditions for jadeitite formation since Early Paleozoic; the youngest occurrence is a xenolith from the Colorado Plateau. Major occurrences consist principally of fluid precipitates (P-type) that infiltrated the mantle wedge; fewer occurrences document metasomatic replacement (R-type) of plagiogranite, metagabbro and eclogite, and both types may be possible in the same occurrence or system. The P-T conditions for jadeitite formation can be extended beyond the previously argued limits of blueschist-facies conditions. Some jadeitite formed at epidote amphibolite and others at eclogite facies conditions. Available geochronological data of both jadeitite and associated HP-LT rock show temporal discrepancies between jadeitite formation and HP-LT metamorphism at some localities. The close association between older jadeitite and younger HP-LT rock in a single mélange complex implies different histories for the subduction channel and jadeitite-bearing mélange. Jadeitite-bearing serpentinite mélange can stay at the mantle wedge for a considerable time and, as a result, experience multiple fluid-infiltration events. The subduction channel can occasionally incorporate overlying serpentinized mantle wedge material due to tectonic erosion. With time, the disrupted mantle wedge containing jadeitite veins is mixed with younger blueschists, exhumed eclogites and various fragments of suprasubduction-zone lithologies. Consequently, recrystallization and re-precipitation of jadeitite are reactivated along a slab–mantle wedge interface. All these possible scenarios and their combinations yield a complicated petrological record in jadeitite. With further investigation, the rock association of jadeitite–HP-LT metamorphic rocks–serpentinite has the potential to yield a greater understanding of subduction channels and overlying mantle wedge.
... Jadeitite is much rarer than nephrite: only ~12 occurrences have been described worldwide (Table 1; Fig. 10). The largest and most important deposit is the Hpakan-Tawmaw tract, Kachin State, northern Myanmar (Burma), and in conglomerates and alluvial deposits derived from that source (Chhibber, 1934;Bender, 1983;Goffe et al. 2000;Hughes et al., 2000). Related sedimentary rock units that contain jadeitite detritus are also mined at Nansibon, Chin State (about 60 km west of Hpakan; Hughes et al., 2000;Avé Lallemant et al., 2000) and conglomeratic units from the Monhyn (Thin, 1985) to the Indaw-Tigyaing areas (United Nations, 1979), ~100 to 230 km south of Hpakan, along the Sagaing fault. ...
... As noted above, many in situ jadeitite bodies are hosted by serpentinite that consists of antigorite (± brucite) adjacent to the jadeitite. The metamorphic rocks associated with jadeitite, either adjacent to the host serpentinite body or as mélange blocks within it, include blueschist-facies metabasites (Myanmar-Chhibber, 1934;Goffe et al., 2000;Guatemala-Harlow, 1994;Harlow et al., 2004, Japan-Shidô, 1958Chihara, 1971;Komatsu, 1987). Rutile mantled by titanite is characteristic of jadeitites and is also ubiquitous in accompanying metabasites, suggesting blueschistfacies retrogression of higher-T assemblages. ...
The lapidary term "jade" refers to two very tough, virtually monomineralic rocks used for ornamental carvings or gems. Both have metasomatic origins that are intimately connected with their host serpentinite bodies and convergent-margin petrotectonics. Amphibole jade is nephrite, a trem-olite-actinolite rock with a felted, microcrystalline habit; pyroxene jade is jadeite rock (jadeitite), which varies from micro-to macrocrystalline textures. Most nephrite occurs along fault contacts between serpentinite and mafic to felsic igneous rocks or metagraywacke in obduction settings. It forms by Ca-and Si-rich, aqueous fluid–mediated metasomatic replacement of serpentinite, typi-cally antigorite, at greenschist-facies or lower P-T conditions. Other nephrite bodies reflect contact metasomatic replacement of dolomite by Si-rich aqueous fluids during felsic pluton emplacement. Like most nephrite, jadeitite is hosted by antigorite-dominated serpentinite bodies. However, these serpentinites are associated with HP/LT metamorphic terranes, in which jadeitite occurs as isolated tabular bodies or tectonized blocks. Based on textural evidence, particularly clear from cathodoluminescence studies, nearly all jadeitite bodies appear to have formed originally as vein crystallization of an aqueous fluid, most readily interpreted as Na-Al-Si–rich fluid at HP/LT condi-tions in subduction/collisional settings. The host serpentinite influences jadeitite compositions by lowering fluid a SiO2 during serpentinization, and contributing Ca + Mg ± Cr to late-stage jadeitite-forming fluids. Thus, although both types of jade form in convergent-margin tectonic settings, jade has two distinct primary modes of origin: (1) by siliceous replacement of already serpentinized ultramafic rock at low-P, low-to moderate-T conditions following obduction (nephrite); or (2) by the interaction of serpentinizing peridotite and Na-Al-Si fluids at HP/LT conditions during active subduction/collision (jadeitite).
... Signatures of HP/LT metamorphism, producing jadeitite, eclogite, amphibolite, and blueschists are recorded in the Jade Mines Belt (Goffé, Rangin, & Maluski, 2002). A large range of P-T conditions of metamorphism from 10-15 kbar, 300-500 C (Mével & Kiénast, 1986), >14 kbar, 400-450 C , >10 kbar and 250-370 C (Shi et al., 2003), and~15 kbar and~380 C (Oberhänsli, Bousquet, Moinzadeh, Moazzen, & Arvin, 2007) have been recorded in the terrane. ...
In this study, we made a review of the published metamorphic and geochronological data of an array of high-pressure metamorphic rocks from the Nagaland Ophiolite Complex, North-east India, and present them in the tectonic framework of two temporally separate subduction systems within the eastern arm of the Neo-Tethys. The
metamorphic rocks are studied in terms of three structural units. The structurally lowermost Mokie–Satuza–Thewati (MST) unit shows a metamorphic zonation from greenschist through pumpellyite–diopside (TMax ~ 335 oC at ~6 kbar) to lawsonite blueschist (TMax ~ 340 oC at ~11.5 kbar) to epidote eclogite (TMax ~ 550–660 oC at
~24 kbar in Mokie to TMax ~ 630 oC at ~26–28 kbar in Thewati localities) facies structurally upward. Both the blueschists and eclogites record a clockwise (CW) P–T path of evolution. We relate the low apparent thermal gradient at the metamorphic peak (7–9 oC/km), the steep dP/dT slope of the metamorphic field gradient, the general CW metamorphic P–T paths, and the published U–Pb zircon dates in the eclogites (between ca. 205 and ca. 172 Ma) and radiolarian biostratigraphy data in the MST metamorphic sequence with the development of a Late Triassic to Middle Jurassic aged cold mature stage of an intra-oceanic subduction system within the NeoTethys. This is considered to be one of the oldest in the Yarlung–Tsangpo Suture Zone. The metamorphosed uppermost part of the structurally intermediate unit, named the Moya–Salumi (MS) sequence, consists of a structurally upper hornblende eclogite (Hbl-EC) to epidote amphibolite facies subunit and a lower epidote
blueschist (EBS) facies subunit. The eclogite subunit is polyphase metamorphosed (Hbl-EC facies M1 with TMax ~ 625 oC at ~13.8 kbar and garnetiferous EBS facies M2 with TMax ~ 540 oC at ~14.4 kbar) with both the events recording counterclockwise P–T paths. The monocyclic EBS facies subunit, on the other hand, has a memory of
the M2 cycle of metamorphism only. We relate this combined M1–M2 cycles of metamorphism in the MS sequence to a second oceanic subduction beneath the continental Naga Metamorphics, the latter constituting the structurally uppermost unit. The metamorphic pulses together reflect progressive cooling of the second subduction
channel from an initially warm stage during subduction infancy to a later cold mature stage of subduction. The different metamorphic rocks in the MST and MS units reveal architectures of two temporally separate accretionary complexes. Their present occurrence as a tectonic collage is likely to be the product of the Eocene collision of the Indian and the Myanmar plates.
... The location of the Jade Belt is too far east to be comfortably linked with the Indo-Burma Range history, and so arises the question, could the Jade Belt rocks actually represent the suture between West Burma and Sibumasu instead (also see Ridd et al., 2019)? While the jadeite appears to have formed much earlier than the Palaeogene West Burma-Sibumasu collision required by palaeomagnetic data, Goffe et al. (2000) reported Ar 39 /Ar 40 dates from phengites that yielded a composite age of 80-30 Ma related to eclogitic and blueschists conditions respectively. Hence, an origin for part of the Jade Belt rocks in an accretionary prism between West Burma and Sibumasu remains a possibility, that needs to be addressed in future studies. ...
Recent, high quality palaeomagnetic data from the West Burma Terrane (WBT) indicates rapid northwards translation (>2000 km) of the terrane, at about the velocity of the Indian Plate, from a near equatorial position in the Late Eocene until the present. This interpretation has important implications for: 1) the controversy over the configuration of Greater India prior to collision with Eurasia, 2) Cretaceous-Cenozoic plate restorations for the eastern Tethys and India Ocean, 3) when the terrane was rift from northern Gondwana, 4) the configuration of SE Asia at the end of the Indosinian orogeny, 5) understanding the general tectonic development and processes of oblique collision zones on the margins of unequal-size colliding continents. The palaeomagnetic data suggest coupling of the WBT with NE India and subsequent encounter of the WBT with SE Asia along a transform margin during the latest Eocene or Oligocene. Due to the significant implications of the palaeomagnetic model, it is important to test the implied development of the WBT against what is known of the regional geology. This study reviews the possible tectonic reconstructions for the Andaman Sea and proposes a configuration that minimises the problems with the testable geological observations. However, it remains difficult to justify the reconstruction with respect to the following aspects: 1) transform fault zone location in the Andaman Sea, 2) Andaman-Sumatra subduction zone evolution, 3) location of the Cretaceous-Eocene eastern boundary of the WBT, and 4) weak evidence for the loss of oceanic crust between the Burma Terrane and Sibumasu during Palaeocene-Eocene convergence. Consequently, there are considerable incompatibilities between geological data and the palaeomagnetic model. Substantial work is required to determine whether these incompatibilities reflect unidentified issues with the palaeomagnetic data, or deficiencies in our geological understanding.
... Serpentinized peridotites, some with pure jadeite and others with amphibole jade or kyanite-bearing omphacite jade, record pressures .14 kbar and temperatures c. 550-600 8C (Goffé et al. 2000). Searle et al. (2007) proposed that Mesozoic ophiolites obducted onto the Burma Plate were later metamorphosed during east-dipping subduction and then exhumed to the surface prior to right-lateral shearing along the Sagaing Fault. ...
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... In addition, the P-T conditions deduced from the Sorkhan jadeitite fit well with the values deduced for the adjacent lawsonite blueschists (Agard et al. 2006). We thus are quite confident about the significance of our P-T grid, although pressures and temperatures deduced for the Sorkhan area differ significantly from published values for similar metasomatic rocks with blue jadeitite, e.g.: Itoigawa-Ohmi in Japan (Morishita 2005), Guatemala (Harlow 1994) or Myanmar (Goffé et al. 2000, Shi et al. 2003. We showed that observations similar to the ones recently published for lawsonite eclogites from Olmec, Guatemala (Tsujimori et al. 2005) can be reproduced accurately, and therefore used the new thermodynamic calculations to re-estimate P-T conditions of the other occurrences of blue jadeitite based on their mineralogy (Fig. 4d). ...
... Serpentinized peridotites, some with pure jadeite and others with amphibole jade or kyanite-bearing omphacite jade, record pressures .14 kbar and temperatures c. 550-600 8C (Goffé et al. 2000). Searle et al. (2007) proposed that Mesozoic ophiolites obducted onto the Burma Plate were later metamorphosed during east-dipping subduction and then exhumed to the surface prior to right-lateral shearing along the Sagaing Fault. ...
... Recognition of mantle Lu-Hf isotopic signatures of Middle Jurassic-Early Cretaceous aged zircon in jadeitite from the Jade Mines belt (Shi et al., 2009) and syn-orogenic, Late Cretaceous, I-type arc magmatism (Wuntho-Popa-Mokpalin arc of Mitchell et al., 2012) at the western margin of the Burmese plate led several workers to suggest the existence of an intra-oceanic subduction setting between the Indian and Burmese plates (schematic plate tectonic framework in Fig. 1a), in the eastern extension of the ITSZ during Middle Jurassic-Early Cretaceous time (Shi et al., 2009(Shi et al., , 2014. As in the NAC, the Jade Mines Belt has also recorded HP/LT metamorphism in the eclogite and blueschist facies (Shi et al., 2001;Goff e et al., 2002;Oberh€ ansli et al., 2007), the timing of which is constrained either at Mid-Jurassic (Shi et al., 2009(Shi et al., , 2014 or alternatively at Late Cretaceous (Yui et al., 2013). Recent suggestions that the ophiolite belts of the Jade Mines Belt and Nagaland are segments of once continuous Neo-Tethyan oceanic crust of the ITSZ (Shi et al., 2014) raise an interesting possibility that the history of the Neo-Tethyan evolution from its formation in a Jurassic event to its destruction at an intra-basinal subduction zone, and resulting in the formation of a younger SSZ ophiolites in the upper plate, as deconvolved from the central part of ITSZ, is also valid from its easternmost margin. ...
High-pressure metamorphic rocks that are formed at the onset of oceanic subduction usually record a single cycle of subduction and exhumation along counterclockwise P-T paths. Conceptual and thermo-mechanical models, however, predict multiple burial-exhumation cycles, but direct observations of these from natural rocks are rare. In this study, we provide new insight into this complexity of subduction channel dynamics from a fragment of Middle-Late Jurassic Neo-Tethys in the Nagaland Ophiolite Complex, northeastern India. Based on integrated textural, mineral compositional, metamorphic reaction history and geothermobarometric studies of a medium-grade amphibolite tectonic unit within a serpentinite mélange, we establish two overprinting metamorphic cycles (M1–M2). These cycles with counterclockwise P-T trajectories are part of a single tectonothermal event. We relate the M1 metamorphic sequence to prograde burial and heating through greenschist and epidote blueschist facies to peak metamorphism, transitional between amphibolite and hornblende-eclogite facies at 13.8 ± 2.6 kbar, 625 ± 45 °C (error two sigma values) and subsequent cooling and partial exhumation to greenschist facies. The M2 metamorphic cycle reflects epidote blueschist facies prograde re-burial of the partially exhumed M1 cycle rocks to peak metamorphism at 14.4 ± 2 kbar, 540 ± 35 °C and their final exhumation to greenschist facies along a relatively cooler exhumation path. We interpret the M1 metamorphism as the first evidence for initiation of subduction of the Neo-Tethys from the eastern segment of the Indus-Tsangpo suture zone. Reburial and final exhumation during M2 are explained in terms of material transport in a large-scale convective circulation system in the subduction channel as the latter evolves from a warm nascent to a cold and more mature stage of subduction. This Neo-Tethys example suggests that multiple burial and exhumation cycles involving the first subducted oceanic crust may be more common than presently known.This article is protected by copyright. All rights reserved.
... As pointed out by Tsujimori and Harlow (2012), zircons from Japanese Paleozoic jadeitites (Omi and Osayama) are more than 200−180 Ma older than the associated Late Paleozoic HP-LT schists (Table 3; Kunugiza and Goto, 2010;Tsujimori et al., 2005), although there may be some question about the dates from the schists being an appropriate age bracket. The same relationship has been described at the Jade mine tract (Myanmar), where the 163−146 Ma jadeitite formation age indicated by the U-Pb zircon data (Table 3; Qiu et al., 2009;Shi et al., 2008) is much older than the composite phengite Ar-Ar age of 80−30 Ma (Goffé et al., 2002); however, the earlier formation Zrn age here is disputed as being inherited from protoliths (Yui et al., 2013). ...
The Guatemala Suture Zone (GSZ) is located along the left-lateral strike slip boundary between the North American and Caribbean plates in central Guatemala. This highly tectonized geotectonic unit contains a variety of metamorphic complexes thrusted north and south of the plate boundary. The northern section of the GSZ consists of (a) a serpentinite-matrix mélange that contains high-pressure–low-temperature (HP–LT) rocks, (b) a continental high-grade felsic belt that includes relics of eclogite facies, (c) a low-grade disrupted volcano-sedimentary sequence, and (d) large ultramafic bodies associated with fragments of Cretaceous island arc sequences. Currently, this section of the GSZ is interpreted as the result of subduction-exhumation-collision and obduction in a back-arc basin.
However, our new petrochronological study challenges this simple interpretation because multiple metamorphic ages (Sm–Nd, U–Pb and Ar–Ar) and different PT paths are recorded in the HP–LT rocks. Eclogites within the mélange display a polymetamorphic history consisting of a metamorphic peak at 130–125 Ma and ~60 km depth, an early exhumation to the middle section of a subduction channel (~35 km) at 117–116 Ma, a subsequent metamorphic event at amphibolite facies and a final exhumation at ~85 Ma. In contrast, continental eclogites show a younger metamorphic peak of 77–75 Ma at ~80 km depth, and exhumation ages of ~76–66 Ma. Synchronous jadeitite and mica rocks within the mélange yielded crystallization and exhumation ages of ~ 95 Ma and ~77–53 Ma, respectively.
These PTt paths reveal a complex history that can be linked to multiple tectonic events during subduction. Ages and PT conditions of eclogites within the mélange suggest an early coupling and storage of eclogitic slices in the subduction channel. Their subsequent record at lower P and higher T may indicate the initiation of continental crust subduction which will have increased the subduction thermal gradient. Continuous subduction and fluid infiltration into the mantle wedge is indicated by the occurrence of jadeitites and mica rocks within the serpentinite mélange. Finally, the metamorphic peak of continental eclogites may mark the end of subduction and beginning of exhumation of the subduction channel and the subducted continental crust during a major collisional event.
... Serpentinized peridotites, some with pure jadeite and others with amphibole jade or kyanite-bearing omphacite jade, record pressures .14 kbar and temperatures c. 550-600 8C (Goffé et al. 2000). Searle et al. (2007) proposed that Mesozoic ophiolites obducted onto the Burma Plate were later metamorphosed during east-dipping subduction and then exhumed to the surface prior to right-lateral shearing along the Sagaing Fault. ...
... In addition, the P-T conditions deduced from the Sorkhan jadeitite fit well with the values deduced for the adjacent lawsonite blueschists (Agard et al. 2006). We thus are quite confident about the significance of our P-T grid, although pressures and temperatures deduced for the Sorkhan area differ significantly from published values for similar metasomatic rocks with blue jadeitite, e.g.: Itoigawa-Ohmi in Japan (Morishita 2005), Guatemala (Harlow 1994) or Myanmar (Goffé et al. 2000, Shi et al. 2003. We showed that observations similar to the ones recently published for lawsonite eclogites from Olmec, Guatemala (Tsujimori et al. 2005) can be reproduced accurately, and therefore used the new thermodynamic calculations to re-estimate P-T conditions of the other occurrences of blue jadeitite based on their mineralogy (Fig. 4d). ...
A new occurrence of “blue jade” is described. The jadeitite occurs as metasomatic veins in magnesite bodies within metaultramafic
rocks in the Sorkhan area of southeastern Iran. The veins are composed of almost pure jadeite, 90 to 99.5 mol.% Jd, contain
minor amounts of Ba-bearing K-feldspar, lawsonite and katophoritic amphibole, but unlike other occurrences of “blue” or “lavender
jade”, do not contain high amounts of Ti. The jadeitite veins formed at low-temperature – high-pressure conditions, around
1.6 GPa and 420°C. Such P–T conditions are characteristic of zones of cold subduction in which lawsonite blueschists to lawsonite
eclogites typically form. Thermodynamic studies show that the mineral assemblage within the blue jade is strongly pressure-
and temperature-dependent. Jadeitites containing two clinopyroxenes (jadeite and omphacite) are stable at high pressure (≥0.8
GPa) and low temperature (≤430°C) conditions, whereas blue jade with only one clinopyroxene (jadeite) forms at higher temperature
or lower pressure. On the basis of these new calculations, P–T conditions of formation are re-examined for all occurrences
of blue jade.
... Previous genetic models for the origin of pure jadeitite include metasomatism and metamorphism (Coleman 1961(Coleman , 1980Mével & Kiénast 1986;Goffé et al. 2000;Harlow & Sorensen 2005), pressure solution and redeposition in fractures (Harlow 1994), and crystallization from a fluid phase (Shi et al. 2000). The systematic absence of quartz coexisting with jadeite precludes formation of jadeitite by reaction in a closed system from preexisting albite. ...
Combined geochemistry and geochronology of the Myanmar jadeitite were determined. Bulk-rock trace element compositions display U-shaped REE patterns with pronounced positive Eu anomalies. The total REE abundances are very low, less than half chondritic, and the high field strength elements and some large ion lithophile elements are moderately enriched. These features indicate a metasomatic origin. There are three groups of zircons with different interior characteristics, cathodoluminescence, mineral inclusions, chemical compositions and sensitive high-resolution ion microprobe U-Pb ages. Group-I zircons, with a mean age of 163.2 +/- 3.3 Ma, mostly have distinct oscillatory zoning, highest U and Th contents, and Na-free, Mg-rich mineral inclusions, and thus indicate an igneous (formation of oceanic crust) or hydrothermal (serpentinization and/or rodingitization) event in the Middle Jurassic. Group-II zircons, with a mean age of 146.5 +/- 3.4 Ma, have bright luminescence without oscillatory zoning and include jadeite and jadeitic pyroxene inclusions, suggesting that formation of the Myanmar jadeitites, as well as subduction of the eastern Indian oceanic plate, occurred in the Late Jurassic. Group-III zircons have an age of 122.2 +/- 4.8 Ma, which represents a later unknown thermal event. Discovery of the Middle Jurassic zircons provides geochronological constraint on the tectonic evolution of the eastern Indo-Burman Range.
... The fields in the diagram illustrate the P-T conditions of jadeite formation. The lightly-shaded field (area 1) is from Shi et al. (2003), darkly-shaded (area 2) from Goffé et al. (2000), the mediumshaded (area 3) from Mével & Kiénast (1986), The dark solid triangle indicates a new estimate of the Myanmar jadeitite by Oberhänsli et al. (2007). Mineral abbreviations are from Kretz (1983). ...
Barium (Ba) minerals identified in clinopyroxene rocks from the Myanmar jadeitite area include celsian, hyalophane, and hydrated barium aluminum silicate (an inferred barian zeolite). The hyalophane and hydrated barium aluminum silicate occur as interstitial phases and sometimes crosscut jadeite crystals, indicating they were formed at a later stage than jadeitite. The celsian has two modes of occurrence: (i) in association with jadeite in jadeitite; (ii) as a single-phase mineral forming part of multi-phase pseudomorphs in chromian omphacite rock (omphacitite). The latter rock type was formed predominantly during the same episode as the jadeitite under almost the same P-T conditions. Multi-phase pseudomorphs, mostly showing hexagonal form, contain celsian and kaolinite, with or without quartz, graphite and diaspore. The P-T condition constraints on celsian suggest that a precursor phase, probably cymrite, once existed under high-pressure conditions, and that celsian was formed by decomposition of the phase under decreasing pressure during uplift of the jadeitite. The frequent occurrence of Ba silicates in jadeitites worldwide reflects a Ba-enriched environment for the formation of jadeitite, which is inferred to be related to subducted barite-bearing slab sediments. Therefore, the jadeitite records metasomatism and metamorphism, as well as fluid interactions and phase changes in the BaO-Al2O3-SiO 2-H2O system. In this way, jadeitite provides information on Ba phase transformations and Ba recycling within the subduction zone. Taken together with previous results, this study further suggests that jadeite-forming fluids are derived from the dehydration of the altered oceanic slab containing deep-sea sediments Myanmar, cymrite.
... As pointed out by Tsujimori and Harlow (2012), zircons from Japanese Paleozoic jadeitites (Omi and Osayama) are more than 200−180 Ma older than the associated Late Paleozoic HP-LT schists (Table 3; Kunugiza and Goto, 2010;Tsujimori et al., 2005), although there may be some question about the dates from the schists being an appropriate age bracket. The same relationship has been described at the Jade mine tract (Myanmar), where the 163−146 Ma jadeitite formation age indicated by the U-Pb zircon data (Table 3; Qiu et al., 2009;Shi et al., 2008) is much older than the composite phengite Ar-Ar age of 80−30 Ma (Goffé et al., 2002); however, the earlier formation Zrn age here is disputed as being inherited from protoliths (Yui et al., 2013). ...
... In the south, the fault connects to the Andaman back-arc spreading centre, and in the north it splays into three prominent metamorphic belts. The central belt (Katha-Gangaw) may be the equivalent of the ophiolite of the Indo-Burman Ranges (Mitchell, 1993), whereas the western belt (Jade Mines) contains eclogite facies rocks metamorphosed at >1.4 GPa and 550-600°C (Goffe´et al., 2002). An alternative hypothesis for the emplacement of the Naga Hills-Manipur ophiolite based on the gravity data of Nandy (1986) proposes that the ophiolite of north-central Myanmar were emplaced during the closure of small ocean basins between several microcontinental blocks and the Sino-Burma block, and were transported westward through nappes during a terminal collision in the Oligocene (Sengupta et al., 1990;Acharyya, 2007). ...
A variety of low- to high-pressure metamorphic assemblages occur in the metabasic rocks and metachert in the Upper Cretaceous–Eocene ophiolite belt of the central part of the Naga Hills, an area in the northern sector of the Indo–Myanmar Ranges in the Indo–Eurasian collision zone. The ophiolite suite includes peridotite tectonite containing garnet lherzolite xenoliths, layered ultramafic–mafic cumulates, metabasic rocks, basaltic lava, volcaniclastics, plagiogranite, and pelagic sediments emplaced as dismembered and imbricated bodies at thrust contacts between moderately metamorphosed accretionary rocks/basement (Nimi Formation/Naga Metamorphics) and marine sediments (Disang Flysch). It is overlain by coarse clastic Paleogene sediments of ophiolite-derived rocks (Jopi/Phokphur Formation). The metabasic rocks, including high-grade barroisite/glaucophane-bearing epidote eclogite and glaucophane schist, and low-grade greenschist and prehnite–clinochlore schist, are associated with lava flows and ultramafic cumulates at the western thrust contact. Chemically, the metabasites show a low-K tholeiitic affinity that favors derivation from a depleted mantle source as in the case of mid-ocean ridge basalt. Thermobarometry indicates peak P–T conditions of about 20 kb and 525°C. Retrogression related to uplift is marked by replacement of barroisite and omphacite by glaucophane followed by secondary actinolite, albite, and chlorite formation. A metabasic lens with an eclogite core surrounded by successive layers of glaucophane schist and greenschist provides field evidence of retrogression and uplift. Presence of S-C mylonite in garnet lherzolite and ‘mica fish’ in glaucophane schist indicates ductile deformation in the shear zone along which the ophiolite was emplaced.
... In the south, the fault connects to the Andaman back-arc spreading centre, and in the north it splays into three prominent metamorphic belts. The central belt (Katha-Gangaw) may be the equivalent of the ophiolite of the Indo-Burman Ranges (Mitchell, 1993), whereas the western belt (Jade Mines) contains eclogite facies rocks metamorphosed at >1.4 GPa and 550-600°C (Goffe´et al., 2002). An alternative hypothesis for the emplacement of the Naga Hills-Manipur ophiolite based on the gravity data of Nandy (1986) proposes that the ophiolite of north-central Myanmar were emplaced during the closure of small ocean basins between several microcontinental blocks and the Sino-Burma block, and were transported westward through nappes during a terminal collision in the Oligocene (Sengupta et al., 1990;Acharyya, 2007). ...
Tectonic slices and lenses of eclogite within mafic and ultramafic rocks of the Early Cretaceous–Eocene Naga Hills ophiolite were studied to constrain the physical conditions of eastward subduction of the Indian plate under the Burma microplate and convergence rate prior to the India–Eurasia collision. Some of the lenses are composed of eclogite, garnet-blueschist, glaucophanite and greenschist from core to margin, representing a retrograde hydrothermal alteration sequence. Barroisite, garnet, omphacite and epidote with minor chlorite, phengite, rutile and quartz constitute the peak metamorphic assemblage. In eclogite and garnet-blueschist, garnet shows an increase in Mg and Fe and decrease in Mn from core to rim. In chlorite in eclogite, Mg increases from core to rim. Inclusions of epidote, glaucophane, omphacite and quartz in garnet represent the pre-peak assemblage. Glaucophane also occurs profusely at the rims of barroisite. The matrix glaucophane and epidote represent the post-peak assemblage. The Fe3+ content of garnet-hosted omphacite is higher than that of matrix omphacite, and Fe3+ increases from core to rim in matrix glaucophane. Albite occurs in late stage veins. P–T pseudosection analysis indicates that the Naga Hills eclogites followed a clockwise P–T path with prograde metamorphism beginning at ∼1.3 GPa/525 °C and peaking at 1.7–2.0 GPa/580–610 °C, and subsequent retrogression to ∼1.1 GPa/540 °C. A comparison of these P–T conditions with numerical thermal models of plate subduction indicates that the Naga Hills eclogites probably formed near the top of the subducting crust with convergence rates of ∼ 55–100 km Myr−1, consistent with high pre-collision convergence rates between India and Eurasia.
UPDATE MYANMAR GEOLOGY REPORT COLLECTION 16 JUNE 2022 ONE TO FOUR FILES
Carrying out jadeitite diagenesis in its basic state as well as in combination with the multiple fluid activities of water, we focused on jadeite grains in production areas such as Myanmar, Guatemala and Russia to determinethe essence of nominal anhydrous jadeite grains and the distribution of structural hydroxyl in individual jadeite grains via infrared microscope. This is a scientific problem that urgently needs to be solved. The results show that a microscale of structural water in the form of structural hydroxyl is widely found in the jadeite grains of primary jadeitite in Myanmar, Guatemala and Russia. There are certain differences in the three groups of characteristic infrared absorption bands generated by the stretching vibration of the structural hydroxyl in jadeite from these different producing areas. The structural hydroxyl content of the individual jadeite grain shows obvious differences according to the producing areas, and the structural hydroxyl content in jadeite grains in Myanmar is up to 2522.11 × 10 ⁻⁶ . By contrast, jadeite grains in Guatemala and Russia yield lower results. In addition, the structural hydroxyl content in individual jadeite grains in the three producing areas are inhomogeneous, showing an increasing trend from interior to exterior. However, dynamic metamorphism of different intensities and multi-period fluid participation lead to differences in the increase, whereby an increase in structural hydroxyl content in jadeite grains from Guatemala and Russia is slower. The study of the distribution of structural hydroxyl in jadeite grain from different producing areas is helpful for exploring the interaction trajectory of fluids involved in jadeitite and the diagenesis mechanism of jadeitite, a fact that is of great scientific significance for revealing the formation process and conditions of jadeitite.
The Payangazu complex in the central Myanmar is composed mainly of quartz diorite, granodiorite, and some synplutonic mafic dikes. The quartz diorite and granodiorite have zircon U-Pb ages of 130.5±4.0 (MSWD=3.5) and 118.4±2.5 Ma (MSWD=2.4), respectively. Rock samples of the quartz diorite and granodiorite are metaluminous, enriched in large-ion lithophile elements like LREE, Rb, Th, and U, and depleted in high field-strength elements such as HREE, Nb, Ta, P, and Ti, indicative of arc-type magmatic affinities. Whole rock samples of the quartz diorite have εHf(t) value of +0.6, initial ⁸⁷Sr/⁸⁶Sr ratios of 0.708 6 to 0.710 0, and εNd(t) values of -4.8 to -4.9; whereas rocks of the granodiorite are relatively isotopically enriched, with εHf(t) values of -5.1 to -7.2, initial ⁸⁷Sr/⁸⁶Sr ratios of 0.711 7 to 0.711 8, and εNd(t) values of -8.7 to -8.8. The isotopic data together with the high Mg# (both the quartz diorite and granodiorite have Mg# values of >40) suggest a strong involvement of mantle materials in the genesis of the parent magmas. The possible petrogenetic process may be that the ascending of melts from partial melting of metasomatized mantle wedge triggered by dehydration of subducted slab resulted in partial melting of the lower crust and mixed with the latter. These Early Cretaceous intrusions from the complex are older than those found in the eastern Wuntho-Popa arc in western Myanmar, eastern Himalaya, and western Yunnan which are interpreted to be related to the Neo-Tethyan subduction, and have εNd(t), εHf(t) values lower than the latter. On the contrary, the ages and geochemical characteristics of the Payangazu complex are consistent with some of the intrusions in the northern magmatic belt in Tibet, eastern Himalaya, and western Yunnan which are believed to be associated with the subduction of the Bangong-Nujiang Ocean crust. Thus, we propose that the Early Cretaceous intrusions in the central Myanmar are most likely related to the southward subduction of an ocean slab that was possibly an extension of the Bangong-Nujiang Ocean.
The Mogok metamorphic belt in central Myanmar is composed mainly of high-temperature paragneisses, marbles, calc-silicate rocks, and granitoids. The garnet-biotite-plagioclase-sillimanite-quartz and garnet-cordierite- sillimanite-biotite-quartz assemblages and their partial systems suggest pressure-temperature (P-T) conditions of 0.60-0.79 GPa/800-860 °C and 0.65 GPa/820 °C, respectively, for the peak metamorphic stage, and 0.40 GPa/620 °C for the exhumation stage. Ti-in-biotite and Zr-in-rutile geothermometers also indicate metamorphic equilibrium under upper amphibolite- and granulite facies conditions. Comparison of these estimates with previously described P-T conditions suggests that (1) the metamorphic conditions of the Mogok metamorphic belt vary from the lower amphibolite- to granulite facies, (2) metamorphic grade seems to increase from east to west perpendicular to the north-trending extensional direction of the Mogok belt, (3) granulite facies rocks are widespread in the middle segment of the Mogok belt, and (4) the granulite facies rocks were locally re-equilibrated at lower amphibolite facies conditions during the exhumation.
A wide range of tectonic models exist for the Cretaceous–Cenozoic development of the Sumatra–Andaman–Myanmar region, reflecting outstanding regional issues including: (1) suture zone correlation between Tibet and Myanmar; (2) understanding ophiolitic fragment emplacement; (3) timing of ophiolite emplacement; (4) tectonic setting of ophiolite formation; (5) post-emplacement ophiolite history; (6) number, distribution and accretion timing of different tectonic continental blocks in western SE Asia; (7) how the Andaman–Sumatra subduction zone developed during the Cenozoic, and location and timing of inactive, v. obliquely subducting segments; and (8) considerable variations in regional plate tectonic reconstructions (e.g. latitude of Lhasa Block at the time of collision, amount and direction of block rotation within SE Asia). Following reviews of these issues we propose a relatively simple model whose characteristics are continuity of a single continental mass between Myanmar and Sumatra during the Cenozoic, early Cenozoic ophiolite emplacement as imbricate slices within an accretionary complex and no emplacement of a major overthrusting oceanic slab. Subsequent collisional deformation further dismembered the ophiolites. Approximately 30° clockwise rotation of SE Asia occurred following Asia–India collision, accompanied by transition from a paired Andean-type magmatic belt to regional oblique-slip and strike-slip tectonics. During the Neogene the Andaman sea region became dominantly transtensional, while Myanmar in the Late Neogene became transpressional.
The Jadeite rocks, which usually produced by the interaction between subduction-related fluids and ultramafic rocks (peridotite), are generally occurs in serpentinized ultramafic rocks in oceanic subduction zones. The Myanmar jadeitite is the largest and most important jadeitite deposits in the world, which occurs in a distinctive tectonic unit of the Tethys subduction zone. This paper presents a combined study of zircon geochronology, microstructure and trace elements in one Myanmar purple jadeitite. Most of the studied zircon grains occur as irregular crystals and experienced various degrees of recrystallization. Zircon U-Pb ages are positively correlated with Ti content indicating that the zircon with low Ti content are experienced higher degree of recrystallization. Unrecrystallized zircons are identified according CL images, they are characterized by relatively high Th/U ratios (0. 11 ∼ 0. 29), relatively high REE concentrations (∑REE = 607 × 10-6 ∼ 2494 × 10-6) and Ti contents between 1. 58 × 10-6 ∼ 8.0 × 10-6. Crystallization temperature estimated by Ti-in-zircon geothermometer are 598 ∼ 732°C. The 206Pb/238U weighted mean age is 158 ± 4Ma (MSWD = 3. 5, N =6), which should represents the protolith age. Recrystallization zircons, which show discrepant patches zoning, can be divided into recrystallized zircon and incomplete recrystallized zircon according to their Th/U ratio and REE contents. Recrystallized zircons have relatively low Th/U ratios (0. 11 ∼ 0. 17), relatively low REE concentrations (∑REE = 143 ∼ 362 × 10-6), and very low contents of Ti. Ti-in-zircon geothermometer gives the crystallization temperature of 473 ∼ 543°C, which is consistent with the jadeite formation temperature. The 206Pb/238 U weighted mean age is 79 ± 2Ma (MSWD = 0. 88, N = 5), which represents the formation age of the studied jadeitite. Incompletely recrystallized zircons give Th/U ratios of 0. 14 ∼ 0. 43, Ce/Ce* ratios of 2. 83 ∼ 44. 8 and Ti contents between 0. 25 ∼ 7. 17. The U-Pb ages range between 91 ∼ 142Ma and we believed such ages has no clear geological implications. The results, together with previous studies, suggest that multi stages of metasoamtism during the Neo-Tethys subduction and formed different generation of jadeitite between 147 ∼ 79Ma.
A new rock type in the Hpakant jadeitite area, Myanmar is identified as jadeitized rodingite. The rock consists of omphacite, garnet and jadeite, with minor allanite-(La), phlogopite, zeolite, chlorite, and a barian mineral. The garnet contains more than 80 mol% of the grossular end-member.
Omphacite has variable composition and is Mg-rich (XMg-aver = 90), while jadeite contains 82–92 mol% of jadeite end-member. Petrography shows that the garnet formed before omphacite, and many omphacite grains have jadeite rims or occur as island surrounded by replacement jadeite,
indicating that a jadeitization event occurred subsequent to grossular and omphacite formation. Considering the geochemical interpretation that the protolith of rodingite (gabbro, plagiogranite or pyroxenite) has considerable Na2O (mostly >2.0 wt% bulk), whereas rodingite has
low Na2O (mostly
The jadeitite that occurs in Myanmar is one of the largest and most
important jadeite deposits in the world. However, the formation age of
the Myanmar jadeitite remains poorly constrained. Here, we conduct an
integrated study using petrology and 40Ar/39Ar
geochronology to analyze the Myanmar jadeitite. Petrological
observations show that the studied jadeitite consists mainly of jadeite
minor sodic-calcic amphibole and analcime and that the jadeitite
was cut by late amphibole rock consisting of sodic amphibole and minor
chlorite. 40Ar/39Ar laser stepwise heating dating
of jadeite from the jadeitite yielded a plateau age of 123.9 ±
3.4 Ma, the sodic-calcic amphibole associated with jadeite yielded
a plateau age of 134.8 ± 1.4 Ma, and the sodic amphibole of late
amphibole rock yielded a plateau age of 92.7 ± 1.2 Ma. These
results indicate that the studied jadeitite was formed during the early
Cretaceous from (135 Ma) high-pressure (HP) metasomatism and then
experienced a late Cretaceous (93 Ma) HP metasomatism. Combining our
results with previous studies using petrography and geochronology, we
suggest that the formation process of Myanmar jadeitite involved
multistages of metasomatism.
Zircons from two Myanmar jadeitite samples were separated for texture,
mineral inclusion, U-Pb dating and trace element composition
analyses. Three types of zircons, with respect to U-Pb isotope
system, were recognized. Type I zircons are inherited ones, yielding an
igneous protolith age of 160 ± 1 Ma; Type II zircons are
metasomatic/hydrothermal ones, giving a (minimum) jadeitite formation
age of 77 ± 3 Ma; and Type III zircons are incompletely
recrystallized ones, with non-coherent and geologically meaningless ages
from 153 to 105 Ma. These Myanmar jadeitites would therefore have formed
through whole-sale metasomatic replacement processes.
Four distinct textures and related compositions of kosmochlor (Ko) and chromian jadeite in rocks from the Myanmar jadeitite area are described: (1) spheroidal or ellipsoidal aggregates with a corona texture surrounding relict chromite; (2) spheroidal or ellipsoidal aggregates with a core of jadeite; (3) granoblastic textures in undeformed coarse-grained clinopyroxene rocks; and (4) recrystallized fine-grained aggregates in deforme in jadeitite. Nearly pure kosmochlor (97 mol.% NaCrSi2O6) Was found in type 2 textures, closest to the end-member reported so far from a terrestrial rock. Sharp compositional boundaries between kosmochlor and chromian jadeite of variable composition are interpreted to be related to progressive crystallization or replacement at differing conditions. The compositions analysed plot along the kosmochlor-jadeite join. In contrast to conclusions of previous studies on the Myanmar clinopyroxenes there is no unequivocal evidence for miscibility gaps. The preservation of relict chromite in the centre of coronitic spheroidal or ellipsoidal aggregates of kosmochlor and jadeite indicates a metasomatic origin from a peridotite protolith at an inferred minimum pressure of 1.0 GPa and temperatures of 250-370°C. Recrystallization during later ductile deformation of the clinopyroxene rocks in the dislocation creep regime leads to fine-grained aggregates of chromian jadeite, which are of particular gemmological interest.
In the Myanmar jadeitite area of Pharkan, amphibole felses occur between jadeitites and serpentinized dunites. These so-called amphibole fels boundary zones were studied optically and by electron microprobe, and found to include the six amphibole species magnesiokatophorite (Mg-kat), nybite (Nyb), eckermannite (Eck), glaucophane (Gln), richterite (Rich) and winchite (Win). In most samples, the two main amphibole species Mg-kat and Eck coexist with amphiboles containing variable amounts of components of the remaining four species, as well as with the clinopyroxenes jadeite (Jd), omphacite (Omp) and kosmochlor (Ko). However, Mg-kat, Nyb and Eck are also present as separate phases as well as in zoned porphyroblasts with Mg-kat in the core, Nyb in the inner rims, and Eck in the outer rims. The analytical data on such zoned amphiboles reveal that the chemistry changes from core to inner rim by virtue of the substitution NaAlCa -1Mg -1 (glaucophane vector), and from the inner to the outer rim along MgSiAl -1Al -1 (tschermak vector). The overall substitution from core to outer rim is, therefore, along NaSiCa -1Al -1 (plagioclase vector). Based on the Si content, three groups can be distinguished within Eck: Eck coexisting with Nyb has low Si contents of 1.0GPa) and rather low temperatures of about 250–370C. Based on compositional trends within the amphiboles as well as phase-equilibrium constraints between amphibole and coexisting pyroxene solid solutions, the chemical composition of zoned amphibole porphyroblasts indicates two growth episodes—increasing pressures from stage1 to stage2 lead to the formation of Nyb from Mg-kat, and subsequently decreasing pressures lead to the formation of stage3 Eck from Rich.
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