Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?

Shi, Gongle; Zhu, Xiangkun; Deng, Jun; Mao, Qian; Liu, Ying-Xin; Li, Guo-Wu

doi:10.1016/j.gca.2011.01.005

Cited by 18 publications

(9 citation statements)

References 70 publications

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“…However, this principle lacks any proven evidence through scienti c studies on spherules, as per our knowledge. Also, the discovery of cosmic spherules from Myanmar jadeitite, a rock type from subduction zone forming at high pressure (> 1 GPa) and relatively low temperatures of about ~ 250-370°C, indicates that the cosmic spherules can withstand such alteration conditions 7 . Though the spherules from Myanmar jadeitite consist of higher Mn (up to 2 wt.%) in the cortex, they also consist of Ni and pure iron cores 7 .…”

Section: Genetic Constraints On the Origin Of Spherules: Mn Hypothesismentioning

confidence: 99%

“…Among these, Fe-rich spherules of extraterrestrial origin are widely investigated to establish the ux of extraterrestrial dust to Earth (Prasad et al 8 and references therein). Earlier studies on cosmic spherules have suggested three types: the chondritic stony spherules (type-S), the glass spherules with dendritic magnetite (type-G), and the nonchondritic iron spherules (type-I) 7,11 . Several criteria have been proposed for the identi cation of the type-I cosmic spherules: (1) morphological features like spherical shape, dendritic phases, and void spaces; (2) chemical signatures like Ni-bearing wustite/magnetite, FeNi metal, and particles of MET, OXMET, and OX type 3 .…”

Section: Introductionmentioning

confidence: 99%

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Recovery of Hydrothermal Wustite-Magnetite Spherules from the Central Indian Ridge, Indian Ocean.

Agarwal

Palayil

2021

Preprint

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Not many studies have reported the hydrothermal-related origin of the magnetite-bearing spherules, and hardly any literature discusses the hydrothermal-related origin of wustite-magnetite-bearing spherules. A sediment sample with high abundance (19 spherules in ~85 g) of spherules is recovered from Central Indian Ridge (CIR) segment S2 (70°54′E, 25°14′S to 70°50′E, 24°41′S), ~85 km north of Rodrigues triple junction (RTJ). On the external surface of the spherules, magnetite appears as crystals, whereas wustite mostly appears as a homogenous glass phase. These spherules are composed of wustite and magnetite hosting Mn, unlike micrometeorites which essentially hosts Ni. Mn is more heterogeneously distributed with a relatively higher concentration in the wustite phase than the magnetite, suggesting hydrothermal origin. Furthermore, the presence of sulfide nano-particles in the wustite phase and a minor quantity of Pb and S in the ferrihydrite matrix points to the fact that CIR spherules are of hydrothermal origin. We propose that the CIR spherules originated by the interaction of the reduced hydrothermal fluids with the ultramafic/basaltic rocks or silica-undersaturated magmatic melts. The finding of Mn hosting wustite-magnetite assemblage suggests an active hydrothermal system in the near vicinity and can be considered as an additional proxy for locating hydrothermal vents.

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Section: Genetic Constraints On the Origin Of Spherules: Mn Hypothesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Recovery of Hydrothermal Wustite-Magnetite Spherules from the Central Indian Ridge, Indian Ocean.

Agarwal

Palayil

2021

Preprint

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“…The highly depleted mantle Hf isotope signatures of zircons in jadeitites suggest that the fluids were derived from the dehydration of altered oceanic mafic crust (Qiu et al, ; Shi et al, ). However, the presence of Ba‐rich minerals, deep‐sea spherules, and CH 4 ‐rich fluid inclusions in the Myanmar jadeitites suggests that subducted sediments were also incorporated into the jadeite‐forming fluids (Shi et al, , , ). In addition, Mg‐Cr‐rich jadeite rims in jadeitites reflect a minor addition of serpentinite‐derived fluid into the jadeite‐forming fluids (Sorensen et al, ).…”

Section: Geological Setting and Samplesmentioning

confidence: 99%

“…The jadeites in the white jadeitites commonly exhibit rhythmic zoning in Ca and Mg (Figure 3b), suggesting that they were most likely precipitated from Na-Al-Si-rich fluids (Figure 7; Shi et al, 2003Shi et al, , 2012Sorensen et al, 2006). Such fluids were mainly derived from subducted AOC and sediments (e.g., Harlow et al, 2015;Qiu et al, 2009;Shi et al, 2010Shi et al, , 2011. Minor locally serpentinite-derived fluids might also contribute to the jadeitite-forming fluids (Sorensen et al, 2006); however, no direct mineral evidence for serpentinite dehydration was observed.…”

Section: Fluid Sources Along the Subduction Interfacementioning

confidence: 99%

“…However, Mg values of white jadeitites. Data sources: Seawater (Ling et al, 2011); oceanic island basalt (OIB), and midocean ridge basalt (MORB; Bourdon et al, 2010;Teng et al, 2010); altered MORB (Huang, 2013;Teng et al, 2016); marine sediments (Hu et al, 2017;Teng et al, 2016); abyssal peridotite (Liu et al, 2017); talc and antigorite (Beinlich et al, 2014); chlorite (Pogge von Strandmann et al, 2015); olivine (Handler et al, 2009;Yang et al, 2009;Young et al, 2009;Huang et al, 2011;Liu et al, 2011;Pogge von Strandmann et al, 2011;Xiao et al, 2013); carbonates (Brenot et al, 2008;Fantle & Higgins, 2014;Geske et al, 2014;Higgins & Schrag, 2010;Hippler et al, 2009;Huang & Xiao, 2016;Jacobson et al, 2010;Kasemann et al, 2014;Tipper et al, 2006;Wombacher et al, 2011).…”

Section: Low δ 26 Mg Fluids: the Role Of Carbonate Dissolutionmentioning

confidence: 99%

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Magnesium Isotope Composition of Subduction Zone Fluids as Constrained by Jadeitites From Myanmar

et al. 2018

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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 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 have not only 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.

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Locality determination of inky black omphacite jades from Myanmar and Guatemala by nondestructive analysis

Xing

Shi

Long³

et al. 2022

J Raman Spectroscopy

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Locality identification of high‐quality inky black omphacite jades (inky jades) from Myanmar and Guatemala is becoming increasingly urgent. In this study, Raman, Fourier transform infrared (FTIR), and energy‐dispersive X‐ray fluorescence spectroscopy (EDXRF) were performed to distinguish samples of inky jade from the two localities. The Raman spectra revealed the presence of several types of minor minerals in Guatemalan samples, including titanite, albite, orthoclase, taramite, celsian, and cymrite, whereas the Myanmar samples consisted almost entirely of omphacite. Taramite and lath‐like celsian occurred only in Guatemalan samples and had significance in locality tracing. The Raman and FTIR reflectance spectra of omphacite shifted to low wavenumbers in proportional to isomorphic substitution Na+Al3+ → Ca2+(Mg2+, Fe2+). Semiquantitative calculations based on the Raman (~680 cm−1) and IR modes (~658, ~576, and ~424 cm−1) showed consistent jadeite end‐member components (~43% to ~64%) in the Myanmar samples, whereas those (~23% to ~87.5%) of the Guatemalan samples were wider and generally lower. In addition, the full width at half maximum values (FWHMs) of Raman shifts near 680 cm−1 in the Myanmar samples (avg. 15.03 cm−1) were less than those (avg. 16.81 cm−1) of the Guatemalan specimens. Linear discriminant analysis (LDA) based on Raman spectroscopy identified most samples with accuracy of 85.5%. Combined with results by EDXRF, these analyses revealed the characteristics of a relatively narrow range of Na+Al3+ → Ca2+Mg2+ isomorphism for the Myanmar jades and a more developed Na+Al3+ → Ca2+(Mg2+, Fe2+) isomorphism for the Guatemalan jades. This study might have implications for commercial applications, archeological research, and judicial expertise.

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Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?

Cited by 18 publications

References 70 publications

Recovery of Hydrothermal Wustite-Magnetite Spherules from the Central Indian Ridge, Indian Ocean.

Recovery of Hydrothermal Wustite-Magnetite Spherules from the Central Indian Ridge, Indian Ocean.

Magnesium Isotope Composition of Subduction Zone Fluids as Constrained by Jadeitites From Myanmar

Locality determination of inky black omphacite jades from Myanmar and Guatemala by nondestructive analysis

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