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Hydrous partial melting within the lower oceanic crust
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We studied more than 60 oceanic gabbros from the recent oceanic crust and from ophiolites (East Pacific Rise, Mid-Atlantic Ridge, Southwest Indian Ridge, Oman ophiolite) by scanning electron microscopy and found in nearly all samples microstructures suggesting that hydrous partial melting reactions proceeded. The characteristic paragenesis consists of orthopyroxene and pargasite rimming olivine and clinopyroxene primocrysts in intimate contact with neoblastic plagioclase strongly enriched in anorthite. This is in agreement with recent water-saturated melting experiments on a variety of natural gabbros between 900 and 1000 C. The observed microtextures in the natural gabbros imply the propagation of water-rich fluids on grain boundaries in a ductile regime causing hydrous partial melting. Thus, this type of hydrothermal activity proceeds within the deep oceanic crust at very high temperatures (900–1000 C) without a crack system, a prerequisite in current models for enabling hydrothermal circulation.
|Keywords:||gabbro; oceanic crust; ODP; partial melting; plagioclase|
|Journal or Publication Title:||Terra Nova|
|Page Range:||pp. 286-291|
|Identification Number - DOI:||10.1111/j.1365-3121.2005.00613.x|
The original publication is available at
|Date Deposited:||02 Jun 2009 04:25|
|Last Modified:||18 Nov 2014 04:00|
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