Copper enrichment in arc magmas controlled by overriding plate thickness

Chiaradia, Massimo

doi:10.1038/ngeo2028

Cited by 295 publications

(150 citation statements)

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“…Thus, the thickened modern south Tibetan crust is not a robust indicator of the partial melting of metabasalt in the lower crust during the Miocene. In fact, the crustal thickness in the Andes reaches 68 km (Chiaradia, 2014), however, adakites associated with porphyry Cu deposits are all slab melts (Sun et al, 2010), which are closely related to the subduction of oceanic ridges (Cooke et al, 2005;Sun et al, 2010).…”

Section: Formation Of Gangdese Adakitesmentioning

confidence: 99%

The formation of Qulong adakites and their relationship with porphyry copper deposit: Geochemical constraints

Liu

Ling

et al. 2015

Lithos

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Section: Formation Of Gangdese Adakitesmentioning

confidence: 99%

The formation of Qulong adakites and their relationship with porphyry copper deposit: Geochemical constraints

Liu

Ling

et al. 2015

Lithos

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“…While sulfide saturation in the lower crust inevitably drives the amount of Cu down during magmatic evolution of calc-alkaline magmatic suites (Chiaradia 2014), the oxidation state of sulfur can dramatically change upon magma ascent and decompression (Matjuschkin et al 2016). Indeed, for a magma having ƒO 2 buffered around NNO + 1 to NNO + 2 such as the ore-forming porphyries at Coroccohuayco, magmatic sulfur is dominantly a reduced species at lower crustal pressures (Matjuschkin et al 2016), but is dominantly in the form of more oxidized sulfates at upper crustal pressures.…”

Section: Resultsmentioning

confidence: 99%

“…11), respectively. Initial melt Cu concentrations were assumed to be 20-50 ppm as commonly advocated for such intermediate arc magmas (Cline and Bodnar 1991;Steinberger et al 2013;Chiaradia 2014). Fluid/melt partition coefficients for S were computed from the calibration of Masotta et al (2016) using the whole-rock composition of the porphyries and ranged from 2 to 15.…”

Section: Melt Fractionmentioning

confidence: 99%

Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

Chelle-Michou

Chiaradia

2017

Contrib Mineral Petrol

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Chlorine and sulfur are of paramount importance for supporting the transport and deposition of ore metals at magmatichydrothermal systems such as the Coroccohuayco Fe-Cu-Au porphyry-skarn deposit, Peru. Here, we used recent partitioning models to determine the Cl and S concentration of the melts from the Coroccohuayco magmatic suite using apatite and amphibole chemical analyses. The pre-mineralization gabbrodiorite complex hosts S-poor apatite, while the syn-and post-ore dacitic porphyries host S-rich apatite. Our apatite data on the Coroccohuayco magmatic suite are consistent with an increasing oxygen fugacity (from the gabbrodiorite complex to the porphyries) causing the dominant sulfur species to shift from S 2− to S 6+ at upper crustal pressure where the magmas were emplaced. We suggest that this change in sulfur speciation could have favored S degassing, rather than its sequestration in magmatic sulfides. Using available partitioning models for apatite from the porphyries, pre-degassing S melt concentration was 20-200 ppm. Estimates of absolute magmatic Cl concentrations using amphibole and apatite gave highly contrasting results. Cl melt concentrations obtained from apatite (0.60 wt% for the gabbrodiorite complex; 0.2-0.3 wt% for the porphyries) seems much more reasonable than those obtained from amphibole which are very low (0.37 wt% for the gabbrodiorite complex; 0.10 wt% for the porphyries). In turn, relative variations of the Cl melt concentrations obtained from amphibole during magma cooling are compatible with previous petrological constraints on the Coroccohuayco magmatic suite. This confirms that the gabbrodioritic magma was initially fluid undersaturated upon emplacement, and that magmatic fluid exsolution of the gabbrodiorite and the pluton rooting the porphyry stocks and dikes were emplaced and degassed at 100-200 MPa. Finally, mass balance constraints on S, Cu and Cl were used to estimate the minimum volume of magma required to form the Coroccohuayco deposit. These three estimates are remarkably consistent among each other (ca. 100 km 3 ) and suggest that the Cl melt concentration is at least as critical as that of Cu and S to form an economic mineralization.

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“…Ruscitto et al 2012), the best evidence for slab devolatilization beneath volcanic arcs is based on a combination of experimental studies, high-pressure phase equilibria considerations and mass-balance calculations (e.g. Kerrick & Connolly 1998, 2001aAlt et al 2013;Jego & Dasgupta 2013, 2014. Evidence from these studies converge on the notion that much of the subducted sulphur and carbon is returned to the deeper mantle rather than recycled, thus suggesting only moderate devolatilization at the P-T conditions relevant to subduction environments (e.g.…”

Section: Devolatilization Of the Subducting Slabmentioning

confidence: 95%

“…1). Through a global review of copper porphyries, it has been shown that copper sulphide accumulations are most significant in arcs with thick overriding plates and with magmas exhibiting strong calc-alkaline (iron depletion) trends; this suggests that plate thickness exerts a first-order control on magma differentiation and metal segregation (Chiaradia 2014). At Merapi volcano, Indonesia, metals and sulphur outgas in the same proportions as found in sulphide minerals contained in minerals as inclusions, suggesting that entrainment of sulphide and its subsequent dissolution is the source for outgassing metals (Nadeau et al 2010).…”

Section: The Role Of Volatiles In Subvolcanic Processes and Eruptionmentioning

confidence: 99%

Volatiles in subduction zone magmatism

Zellmer

Edmonds

Straub

2014

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Abstract:The volatile cycle at subduction zones is key to the petrogenesis, transport, storage and eruption of arc magmas. Volatiles control the flux of slab components into the mantle wedge, are responsible for melt generation through lowering the solidi of mantle materials, and influence the crystallizing phase assemblages in the overriding crust. Globally, magma ponding depths may be partially controlled by melt volatile contents. Volatiles also affect the rate and extent of degassing during magma storage and decompression, influence magma rheology and therefore control eruption style. The style of eruptions in turn determines the injection height of environmentally sensitive gases into the atmosphere and the impact of explosive arc volcanism. In this overview we summarize recent advances regarding the role of volatiles during slab dehydration, melt generation in the mantle wedge, magmatic evolution in the overriding crust, eruption triggering, and the release of some magmatic volatiles from volcanic edifices into the Earth's atmosphere.In contrast to mid-ocean ridge magmatism, where upwelling and adiabatic decompression of the mantle is the primary cause of melt generation, subduction zone magmatism is triggered by the depression of the mantle solidus due to influx of volatiles (dominantly There is ongoing debate about the processes that form extractable melts of the hydrated mantle wedge. One model suggests that efficient melt extraction requires a degree of melting of the wedge so large that melts are generally extracted at or above the 1300 8C isotherm, that is, close to the anhydrous solidus (Kushiro 1987;Schmidt & Poli 1998). The advective flux of heat carried by this melt then perturbs the location of the anhydrous solidus upwards (England & Katz 2010b), and melts eventually penetrate the lithosphere and enter the crust by hydrofracture and dyking. Alternatively, melting is dominated by decompression in slab and mantle diapirs that may rise upwards through the wedge (Behn et al. 2011).Here, we address volatile cycling from the dehydration of the subducting slab to arc volcanic degassing into the atmosphere (Fig. 1). A product of subduction is the output of volatiles as volcanic gases; another is the sinking of the slab containing 'residual' volatiles into the deep mantle. Volcanic gases in arcs are rich in H 2 O, chlorine, bromine and iodine compared to gases at rift and ocean island settings, which directly reflects the influence of slab-derived fluids on primary melt compositions by guest on May 10, 2018 http://sp.lyellcollection.org/ Downloaded from (Pyle & Mather 2009;Kutterolf et al. 2013; Kendrick et al. 2014a, b). Arc magmas are in general far richer in sulphur than their oceanic counterparts, reflecting the higher oxygen fugacity characteristic of arc melts and their enhanced capacity to carry dissolved sulphate (Wallace & Edmonds 2011). There is little direct evidence that primary arc melts are inherently richer in CO 2 than ocean island basalts, although it has been suggested that deep and pe...

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Copper enrichment in arc magmas controlled by overriding plate thickness

Cited by 295 publications

References 25 publications

The formation of Qulong adakites and their relationship with porphyry copper deposit: Geochemical constraints

The formation of Qulong adakites and their relationship with porphyry copper deposit: Geochemical constraints

Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

Volatiles in subduction zone magmatism

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