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dc.description.abstractThe Doldrums Megatransform System (~7–8°N, Mid-Atlantic Ridge) shows a complex architecture including four intra-transform ridge segments bounded by five active transform faults. Lower crustal rocks are exposed along the Doldrums and Vernadsky transform walls that bound the northernmost intra-transform ridge segment. The recovered gabbros are characterized by variably evolved chemical compositions, ranging from olivine gabbros to gabbronorites and oxide gabbros, and lack the most primitive gabbroic endmembers (troctolites, dunites). Notably, the numerous recovered gabbronorites show up to 20 vol. % of coarse-grained orthopyroxene. Although covariations in mineral and bulk-rock chemical compositions of the olivine and oxide gabbros define trends of crystallization from a common parental melt, the gabbronorites show elevated light over heavy rare earth elements (LREE/HREE) ratios in both bulk-rock and mineral compositions. These features are not consistent with a petrological evolution driven solely by fractional crystallization, which cannot produce the preferential enrichments in highly incompatible elements documented in the orthopyroxene-bearing lithologies. We suggest that gabbronorites crystallized from evolved melts percolating and partly assimilating a pre-existing olivine gabbro matrix. Saturation in orthopyroxene and selective enrichments in LREE relative to M-HREE are both triggered by an increase in assimilated crystal mass, which ranges from negligible in the oxide-gabbros to abundant in the gabbronorites. This melt–rock reaction process has been related to lateral melt migration beneath ridge-transform intersections, where variably evolved melts injected from the peripheral parts of the melting region towards the transform zone may interact with a gabbroic crystal mush to form abundant oxide-bearing gabbronoritic associations.en_US
dc.publisher.nameOxford University Pressen_US
dc.relation.ispartofJournal of petrologyen_US
dc.relation.ispartofseries9/63 (2022)en_US
dc.titleGenesis of Oceanic Oxide Gabbros and Gabbronorites During Reactive Melt Migration at Transform Walls (Doldrums Megatransform System; 7–8°N Mid-Atlantic Ridge)en_US
dc.description.obiettivoSpecifico3A. Geofisica marina e osservazioni multiparametriche a fondo mareen_US
dc.description.journalTypeJCR Journalen_US
dc.contributor.authorBasch, Valentin-
dc.contributor.authorSanfilippo, Alessio-
dc.contributor.authorSkolotnev, Sergey G-
dc.contributor.authorFerrando, Carlotta-
dc.contributor.authorMuccini, Filippo-
dc.contributor.authorPalmiotto, Camilla-
dc.contributor.authorPeyve, Alexander A-
dc.contributor.authorErmolaev, B V-
dc.contributor.authorOkina, O I-
dc.contributor.authorLigi, Marco-
dc.contributor.departmentIstituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione Roma2, Roma, Italiaen_US
item.fulltextWith Fulltext-
item.openairetypearticle- Nazionale di Geofisica e Vulcanologia (INGV), Sezione Roma2, Roma, Italia- Nazionale di Geofisica e Vulcanologia-
crisitem.department.parentorgIstituto Nazionale di Geofisica e Vulcanologia-
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