Talk:Boninite
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[edit] Comments
I'm not sure about the Sanukitoid link; sanukitoids are not a common term used in Australian literature, and it seems like they are basically high-Mg diorites at best, but, that aside, boninites are extrusive, not intrusive, and are actually fairly enriched at times in alkalis.
Boninites are associated exclusively with back arcs, and are typically envisaged as beng brewed-up from deleted peridotite mantle via the action of the volatile plme behind the subduction zone. They are a phenomenon of slab-drag initiated convection behind the subduction zone (or vice-versa, who cares, really about semantics), and attain high MgO contents due to the previous depletion in Fe, Ti, etc, and the addition of volatiles. Boninites from the Marrianas Back Arc Basin are typically quite hydrous.
Boninites are also, in the Gympie Terrane, associated with M-type granitoids which inherit their Ti-Zr ratios and are examples of slab roll-back causing a change from melting of fertile mantle to re-melting it and producing higher-MgO Ti-depleted rocks.
Um...and thats all I can remember this side of pawing through my notes!
Rolinator 11:06, 28 October 2006 (UTC)
