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The effect of small amounts of H2O on crystallisation of mid-ocean ridge and backarc basin magmas


Danyushevsky, LV, The effect of small amounts of H2O on crystallisation of mid-ocean ridge and backarc basin magmas, Journal of Volcanology and Geothermal Research, 110, (3-4) pp. 265-280. ISSN 0377-0273 (2001) [Refereed Article]

DOI: doi:10.1016/S0377-0273(01)00213-X


The main effects of H2O on crystallisation of basaltic liquids are to decrease melt liquidus temperature and to suppress plagioclase crystallisation relative to olivine and clinopyroxene. Although MORB magmas contain small amounts of H2O, for petrological purposes these magmas have been considered to be anhydrous. In this paper, the effect of small amounts of H2O on fractionation paths of MORB and BABB magmas is investigated by comparing the compositions of MORB and BABB glasses with the results of anhydrous experiments on MORB-like compositions. This effect is shown to be large enough that it should be considered when using glass compositions for the purposes of understanding MORB petrogenesis. The effect of H2O is strongly non-linear. The decrease of melt liquidus temperature can be obtained from the effect of H2O on the olivine crystallisation: Olivine Liquidus Depression (°C) = 74.403 × (H2O wt%)0.352. The suppression of plagioclase crystallisation relative to olivine is: Plagioclase Liquidus Depression Relative to Olivine (°C) = 47.346 × (H2O wt%)0.685. The presence of H2O produces the most pronounced effect on concentrations of A12O3, FeO* and TiO2 in cogenetic suites of MORB and BABB. It also results in a smaller degree of fractionation for a given cooling interval. The computer program PETROLOG that performs modelling of magma fractionation at variable H2O contents is available from the author. © 2001 Elsevier Science B.V. All rights reserved.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and metamorphic petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Danyushevsky, LV (Professor Leonid Danyushevsky)
ID Code:23232
Year Published:2001
Web of Science® Times Cited:259
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2001-08-01
Last Modified:2011-11-18

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