Coupling of Redox Conditions of Mantle Melting and Copper and Sulfur Contents in Primary Magmas of the Tolbachinsky Dol (Kamchatka) and Juan de Fuca Ridge (Pacific Ocean).

Mironov, N. L. and Portnyagin, Maxim V. (2018) Coupling of Redox Conditions of Mantle Melting and Copper and Sulfur Contents in Primary Magmas of the Tolbachinsky Dol (Kamchatka) and Juan de Fuca Ridge (Pacific Ocean). Petrology, 26 (2). pp. 145-166. DOI 10.1134/S0869591118020030.

[thumbnail of Mironov.pdf] Text
Mironov.pdf - Published Version
Restricted to Registered users only

Download (1MB) | Contact

Supplementary data:

Abstract

The compositions of parental melts of Tolbachinsky Dol (Kamchatka) basalts were estimated from the compositions of olivine-hosted (Fo90.5-83.1) primitive melt inclusions in the rocks of the Northern breakthrough of the Great Tolbachik Fissure Eruption (1975 A.C.) and of the late-Holocene cone “1004”. The parental melts contain 100–150 ppm Cu and 0.16–0.30 wt % S. These concentrations are much higher than those determined for the initial magmas of mid-ocean ridge basalts (MORB), for example of the Juan de Fuca ridge (Cu = 55–105 ppm, S=0.09–0.12 wt %). Modeling of mantle melting under variable redox conditions demonstrated that the high Cu and S contents in the Tolbachinsky Dol melts can be obtained by 6–12% melting of DMM-like source under oxidized conditions (ΔQFM = +1.2 ± 0.1) and do not require a significant (>30–35% for S) subduction-related influx of these elements to the mantle source. The high contents of Cu and S in the Tolbachinsky Dol melts are largely explained by the increase of sulfide solubility in a silicate melt under oxidized conditions. In contrast, relatively reduced (ΔQFM ∼ 0) conditions of MORB generation result in low contents of Cu and S in their initial magmas. The estimated ΔQFM values agree well with the data obtained using the Cr-spinel–olivine oxybarometer. The high oxygen potential of Tolbachinsky Dol primary magmas is inherited by more evolved magmas, thus favouring Cu enrichment up to 270 ppm during magma fractionation, approaching maximum copper contents in the global systematics of island-arc rocks.

Document Type: Article
Additional Information: Original Russian Text © N.L. Mironov, M.V. Portnyagin, 2018, published in Petrologiya, 2018, Vol. 26, No. 2, pp. 140–162
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
Publisher: Pleiades Publishing
Date Deposited: 13 Apr 2018 07:32
Last Modified: 08 Feb 2021 07:40
URI: https://oceanrep.geomar.de/id/eprint/42261

Actions (login required)

View Item View Item