Volatile (Li, B, F and Cl) mobility during amphibole breakdown in subduction zones

Debret, Baptiste; Koga, Kenneth T.; Cattani, F.; Nicollet, Christian; Bleeken, Greg Van den; Schwartz, Stéphane

doi:10.1016/j.lithos.2015.12.004

Cited by 33 publications

(40 citation statements)

References 85 publications

(140 reference statements)

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“…Measured F contents in phengite in our samples are similar, but those in Na-amphibole and lawsonite are higher than those in blueschist facies metagabbros reported by Debret et al (2016). Furthermore, their estimated bulk F contents based on concentrations in these minerals and their modal abundances are much lower than our measured values.…”

Section: Halogens In Apatitecontrasting

confidence: 49%

Halogen (F, Cl, Br, I) behaviour in subducting slabs: A study of lawsonite blueschists in western Turkey

Pagé

Hattori

Hoog

et al. 2016

Earth and Planetary Science Letters

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We examined the F, Cl, Br and I abundance of minimally retrogressed lawsonite blueschists from the Tavsanli Zone in northwest Turkey to evaluate the behaviour of halogens in subduction zones, and to determine the role coexisting high pressure minerals may play in transporting the halogens to the Earth's mantle. The blueschists contain sodic amphibole and lawsonite, with variable amounts of phengite and chlorite, and minor apatite. A positive correlation between Cl, Br and I contents in bulk rocks suggests their overall coherent behaviour in subduction zones, although high ratios of I/Cl and Br/Cl compared to altered oceanic crust indicate that Cl is preferentially lost relative to Br and I before or during blueschist metamorphism. Iodine and F are enriched relative to altered oceanic crust, suggesting incorporation from marine sediments. In situ analyses of minerals in thin sections reveal F preferentially concentrates in apatite (avg. 3.13 wt%), over phengite (482 ppm), lawsonite (avg. 413 ppm) and Na-amphibole (257 ppm). Chlorine also preferentially resides in apatite (138 ppm), followed by equal partitioning between phengite (59 ppm) and Na-amphibole (56 ppm), and lower concentrations in lawsonite (27 ppm). Upon apatite decomposition at a depth of ~200 km, F may redistribute into lawsonite and phengite in slabs, whilst Cl is likely expelled to the overlying mantle wedge. Given the stability of lawsonite and phengite to a depth of 280-300 km in cold subduction zones, they may transport F beyond subarc depths, contributing to the high F in magmas derived from the deep mantle.

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Section: Halogens In Apatitecontrasting

confidence: 49%

Halogen (F, Cl, Br, I) behaviour in subducting slabs: A study of lawsonite blueschists in western Turkey

Pagé

Hattori

Hoog

et al. 2016

Earth and Planetary Science Letters

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“…This is supported by much higher concentrations of Cl, Br and I in seafloor and obducted abyssal lizardite serpentinites than subducted abyssal antigorite serpentinites [41,48,53,55]. This is also in agreement with lower Cl contents in other subducted lithologies (i.e., metasediments and metabasites) compared to their pre-subduction equivalents [60,[66][67][68]. The transition is temperature-dependent.…”

Section: Lizardite-antigorite Transitionsupporting

confidence: 64%

Abyssal Serpentinites: Transporting Halogens from Earth’s Surface to the Deep Mantle

Pagé

Hattori

2019

Minerals

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Serpentinized oceanic mantle lithosphere is considered an important carrier of water and fluid-mobile elements, including halogens, into subduction zones. Seafloor serpentinite compositions indicate Cl, Br and I are sourced from seawater and sedimentary pore fluids, while F may be derived from hydrothermal fluids. Overall, the heavy halogens are expelled from serpentinites during the lizardite–antigorite transition. Fluorine, on the other hand, appears to be retained or may be introduced from dehydrating sediments and/or igneous rocks during early subduction. Mass balance calculations indicate nearly all subducted F is kept in the subducting slab to ultrahigh-pressure conditions. Despite a loss of Cl, Br and I from serpentinites (and other lithologies) during early subduction, up to 15% of these elements are also retained in the deep slab. Based on a conservative estimate for serpentinite thickness of the metamorphosed slab (500 m), antigorite serpentinites comprise 37% of this residual Cl, 56% of Br and 50% of I, therefore making an important contribution to the transport of these elements to the deep mantle.

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“…Although traditional view associates trace element and metal mobility in subduction zones with water-silicate fluids [12], recent experimental data [13] and direct measurements of chlorine in basaltic glasses from Lau [14] and Manus [15] back-arc basins suggest that halogens play an important role in mantle wedge metasomatism and formation of island-arc magmas and associated ore deposits. Inclusions of potassic chloride in metamorphic olivine and pargasite in association with sulfides in the ILC rocks suggest involvement of saline metasomatic fluids derived from a downgoing slab during subduction-related amphibolite metamorphism (~ 140 Ma).…”

Section: Slab-derived Geochemical Signature: Halogen-rich Aqueous Fluidsmentioning

confidence: 99%

Gold, platinum and palladium enrichments in arcs: role of mantle wedge, arc crust and halogen-rich slab fluids

Kepezhinskas¹,

Kepezhinskas

Бердников

2019

E3S Web Conf.

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Arc-related magmas are frequently enriched in Au, Pt and Pd in respect to MORB and OIB igneous suites. Magmatic arcs commonly host large-scale hydrothermal Au and Au-Cu and PGE mineralization related to young volcanic systems and zoned ultramafic complexes respectively. Island-arc mantle xenoliths show Au, Pt, Pd enrichments related to mantle wedge metasomatism by slab-derived fluids. Long-lived plumbing systems in arc crust (arc magma chambers) show further enhancement of Au, Pt and Pd enrichments through subduction-related metamorphic and metasomatic processes in the presence of halogen-rich, aqueous fluids. We propose that Au-Pt-Pd enrichments in arcs are caused by mantle wedge-slab interactions followed by differentiation and metamorphism of magmatic conduits in arc crust.

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Volatile (Li, B, F and Cl) mobility during amphibole breakdown in subduction zones

Cited by 33 publications

References 85 publications

Halogen (F, Cl, Br, I) behaviour in subducting slabs: A study of lawsonite blueschists in western Turkey

Halogen (F, Cl, Br, I) behaviour in subducting slabs: A study of lawsonite blueschists in western Turkey

Abyssal Serpentinites: Transporting Halogens from Earth’s Surface to the Deep Mantle

Gold, platinum and palladium enrichments in arcs: role of mantle wedge, arc crust and halogen-rich slab fluids

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