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A Calcium-in-Olivine Geohygrometer and its Application to Subduction Zone Magmatism

Gavrilenko M., Herzberg C., Vidito C., Carr M., Tenner T., Ozerov A. (2016) A Calcium-in-Olivine Geohygrometer and its Application to Subduction Zone Magmatism // Journal of Petrology. Vol. 57, No. 9. pp. 1811-1832. doi: 10.1093/petrology/egw062.

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Official URL: http://doi.org/10.1093/petrology/egw062

Abstract

High-precision electron microprobe analyses were obtained on olivine grains from Klyuchevskoy, Shiveluch and Gorely volcanoes in the Kamchatka Arc; Irazu, Platanar and Barva volcanoes of the Central American Arc; and mid-ocean ridge basalt (MORB) from the Siqueiros Transform. Calcium contents of these subduction zone olivines are lower than those for olivines from modern MORB, Archean komatiite and Hawaii. A role for magmatic H2O is likely for subduction zone olivines, and we have explored the suggestion of earlier workers that it has affected the partitioning of CaO between olivine and silicate melt. We provide a provisional calibration of DCaO Ol/L as a function of magmatic MgO and H2O, based on nominally anhydrous experiments and minimally degassed H2O contents of olivine-hosted melt inclusions. Application of our geohygrometer typically yields 3–4 wt % magmatic H2O at the Kamchatka and Central American arcs for olivines having 1000 ppm Ca, which agrees with H2O maxima from melt inclusion studies; Cerro Negro and Shiveluch volcanoes are exceptions, with about 6% H2O. High-precision electron microprobe analyses with 10–20 lm spatial resolution on some olivine grains from Klyuchevskoy and Shiveluch show a decrease in Ca content from the core centers to the rim contacts, and a sharp increase in Ca in olivine rims. We suggest that the zoning of Ca in olivine from subduction zone lavas may provide the first petrological record of temporal changes that occur during hydration of the mantle wedge and dehydration during ascent, and we predict olivine H2O contents that can be tested by secondary ionization mass spectrometry analysis.
Item Type: Article
Title: A Calcium-in-Olivine Geohygrometer and its Application to Subduction Zone Magmatism
Language: English
Journal or Publication Title: Journal of Petrology
ISSN Print: 0022-3530
Subjects: State scientific and technical information rubricator (ГРНТИ) > 38 ГЕОЛОГИЯ > 38.33 Геохимия > 38.33.15 Геохимия отдельных элементов
State scientific and technical information rubricator (ГРНТИ) > 38 ГЕОЛОГИЯ > 38.37 Петрография > 38.37.25 Вулканология
Volcanoes > 1 Volcanoes of the Kurile-Kamchatka Region > 1.1 Kamchatka > Gorely
Volcanoes > 1 Volcanoes of the Kurile-Kamchatka Region > 1.1 Kamchatka > Sheveluch
Volcanoes > 1 Volcanoes of the Kurile-Kamchatka Region > 1.1 Kamchatka > Sheveluch
Volcanoes > 1 Volcanoes of the Kurile-Kamchatka Region > 1.1 Kamchatka > Sheveluch

Volcanoes > 1 Volcanoes of the Kurile-Kamchatka Region > 1.1 Kamchatka > Klyuchevskoy
Depositing User: А.Ю. Озеров
Date Deposited: 11 Mar 2019 04:45
Last Modified: 11 Mar 2019 04:45
URI: http://repo.kscnet.ru/id/eprint/3543

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