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Article: Melt - Peridotite interactions in shallow mantle at the East Pacific Rise: Evidence from ODP Site 895 (Hess Deep)

TitleMelt - Peridotite interactions in shallow mantle at the East Pacific Rise: Evidence from ODP Site 895 (Hess Deep)
Authors
KeywordsEast Pacific Rise
Harzburgite
Hess Deep
Mantle Refertilization
Melt-Peridotite Interaction
Mid-Ocean Ridge Basalt
Odp Leg 147
Issue Date1996
Citation
Mineralogical Magazine, 1996, v. 60 n. 1, p. 191-206 How to Cite?
AbstractOcean Drilling Program (ODP) Leg 147 recently drilled at Site 895 in Hess Deep (eastern Equatorial Pacific), where a structurally dissected section of the East Pacific Rise (EPR) is preserved, and intersected the mantle-crust transition zone of a fast-spreading centre for the first time. The core from Hole 895D (latitude 2°16.635′N, longitude 101°26.777′W) revealed that harzburgite is predominant over dunite in the top section of the Hole, but the reverse relationship is found lower in the section where dunite is closely associated with gabbroic rocks (gabbro and troctolite). Texture, mineralogy and mineral chemistry suggest a two-stage evolution for harzburgite preserved at the transition zone. Harzburgite with a porphyroclastic texture was produced by partial melting of peridotite to, or beyond the clinopyroxene-out phase boundary before or during asthenospheric (>1000°C) flow, which suggests a higher degree of mantle melting than normally expected below mid-ocean ridges. Subsequently, basaltic melt(s) interacted with this refractory harzburgite (olivine + orthopyroxene + spinel), which resulted in dissolution of orthopyroxene, re-equilibration and formation of olivine and spinel, and formation of clinopyroxene ± plagioclase, this is manifested as a progressive conversion of harzburgite to gabbroic rock through an intermediate dunite. At low melt/peridotite ratios, harzburgite was refertilised as the plagioclase component of the melt completely reacted with the peridotite matrix to produce clinopyroxene-spinel intergrowths and Al enrichment in ferromagnesian minerals. At high ratios, orthopyroxene completely dissolved incongruently, plagioclase appeared, and spinel was partially to completely resorbed; this produced olivine-bearing and olivine-free gabbroic rocks. Residual minerals in peridotites adjacent to gabbroic zones were enriched in Fe and Ti and depleted in Al.
Persistent Identifierhttp://hdl.handle.net/10722/178206
ISSN
2015 Impact Factor: 2.212
2015 SCImago Journal Rankings: 0.592
References

 

DC FieldValueLanguage
dc.contributor.authorEdwards, SJen_US
dc.contributor.authorMalpas, Jen_US
dc.date.accessioned2012-12-19T09:43:24Z-
dc.date.available2012-12-19T09:43:24Z-
dc.date.issued1996en_US
dc.identifier.citationMineralogical Magazine, 1996, v. 60 n. 1, p. 191-206en_US
dc.identifier.issn0026-461Xen_US
dc.identifier.urihttp://hdl.handle.net/10722/178206-
dc.description.abstractOcean Drilling Program (ODP) Leg 147 recently drilled at Site 895 in Hess Deep (eastern Equatorial Pacific), where a structurally dissected section of the East Pacific Rise (EPR) is preserved, and intersected the mantle-crust transition zone of a fast-spreading centre for the first time. The core from Hole 895D (latitude 2°16.635′N, longitude 101°26.777′W) revealed that harzburgite is predominant over dunite in the top section of the Hole, but the reverse relationship is found lower in the section where dunite is closely associated with gabbroic rocks (gabbro and troctolite). Texture, mineralogy and mineral chemistry suggest a two-stage evolution for harzburgite preserved at the transition zone. Harzburgite with a porphyroclastic texture was produced by partial melting of peridotite to, or beyond the clinopyroxene-out phase boundary before or during asthenospheric (>1000°C) flow, which suggests a higher degree of mantle melting than normally expected below mid-ocean ridges. Subsequently, basaltic melt(s) interacted with this refractory harzburgite (olivine + orthopyroxene + spinel), which resulted in dissolution of orthopyroxene, re-equilibration and formation of olivine and spinel, and formation of clinopyroxene ± plagioclase, this is manifested as a progressive conversion of harzburgite to gabbroic rock through an intermediate dunite. At low melt/peridotite ratios, harzburgite was refertilised as the plagioclase component of the melt completely reacted with the peridotite matrix to produce clinopyroxene-spinel intergrowths and Al enrichment in ferromagnesian minerals. At high ratios, orthopyroxene completely dissolved incongruently, plagioclase appeared, and spinel was partially to completely resorbed; this produced olivine-bearing and olivine-free gabbroic rocks. Residual minerals in peridotites adjacent to gabbroic zones were enriched in Fe and Ti and depleted in Al.en_US
dc.languageengen_US
dc.relation.ispartofMineralogical Magazineen_US
dc.subjectEast Pacific Riseen_US
dc.subjectHarzburgiteen_US
dc.subjectHess Deepen_US
dc.subjectMantle Refertilizationen_US
dc.subjectMelt-Peridotite Interactionen_US
dc.subjectMid-Ocean Ridge Basalten_US
dc.subjectOdp Leg 147en_US
dc.titleMelt - Peridotite interactions in shallow mantle at the East Pacific Rise: Evidence from ODP Site 895 (Hess Deep)en_US
dc.typeArticleen_US
dc.identifier.emailMalpas, J: jgmalpas@hku.hken_US
dc.identifier.authorityMalpas, J=rp00059en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-0029773241en_US
dc.identifier.hkuros13196-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0029773241&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume60en_US
dc.identifier.issue1en_US
dc.identifier.spage191en_US
dc.identifier.epage206en_US
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridEdwards, SJ=7401520329en_US
dc.identifier.scopusauthoridMalpas, J=7006136845en_US

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