Melt stagnation in peridotites from the Godzilla Megamullion Oceanic Core Complex, Parece Vela Basin, Philippine Sea

Loocke, Matthew ORCID: https://orcid.org/0000-0001-7660-2516, Snow, Jonathan e. and Ohara, Yasuhiko 2013. Melt stagnation in peridotites from the Godzilla Megamullion Oceanic Core Complex, Parece Vela Basin, Philippine Sea. Lithos 182-18 , pp. 1-10. 10.1016/j.lithos.2013.09.005

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Abstract

The Godzilla Megamullion, located in the Parece Vela Backarc Basin of the Izu–Bonin–Mariana (IBM) system, is the largest known example of an Oceanic Core Complex (OCC). Peridotites recovered from the megamullion are divided petrographically into fertile (e.g. lherzolites), depleted (e.g. harzburgites), and plagioclase-bearing groups (Ohara et al., 2003a). A total of 151 thin sections were studied from the Kairei KR03-01, Hakuho Maru KH07-02, and Yokosuka YK09-05 cruises. Melt stagnation is studied via the incidence of plagioclase-bearing peridotites and the major element chemistry of Cr-spinels in the plag-bearing samples. A distinct trend in melt stagnation is evident along the length of the megamullion representing a secular evolution in the entrapment of melts rising through the lithosphere. The distal (furthest from the termination of spreading), depleted portion of the mullion represents a robust mantle section that was still producing abundant melt and can be compared to typical oceanic spreading with its relatively “normal” percentage of plagioclase peridotites and average spinel Cr# of 0.35. The medial, fertile portion of the mullion represents a steep falloff in melt productivity represented by fertile spinel compositions (i.e. Cr# < 0.25) and the presence of plagioclase-free lherzolites. The proximal (closest to termination of spreading), heavily plagioclase impregnated portion (with spinel Cr#s covering nearly the entire range of abyssal peridotite spinel compositions) of the mullion then represents a period of increasing stagnation of melt into a lithosphere that was undergoing progressive thickening. We infer that the processes of mantle evolution through melt stagnation and impregnation, as evidenced by the systematic variations in plag–peridotites along Godzilla Megamullion, represent a possibly common way in which the mantle reacts to OCC formation. In this case, Godzilla Megamullion may represent an extreme endmember in OCC formation.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	G Geography. Anthropology. Recreation > GC Oceanography
Uncontrolled Keywords:	Spinel; Plagioclase peridotite; Oceanic Core Complex; Backarc basin; Philippine Sea; Melt–rock reaction
Publisher:	Elsevier
ISSN:	0024-4937
Date of Acceptance:	18 September 2013
Last Modified:	27 Oct 2022 09:17
URI:	https://orca.cardiff.ac.uk/id/eprint/65124

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