scholarly journals Oxidized Mantle Sources of HIMU and EM-type Ocean Island Basalts

2021 ◽  
Author(s):  
Robert Nicklas ◽  
Rachel Hahn ◽  
Lori Willhite ◽  
Matthew Jackson ◽  
Vittorio Zanon ◽  
...  
Keyword(s):  
Trace Element ◽  
Parental Magma ◽  
Igneous Petrology ◽  
Isotopic Signatures ◽  
Ocean Island ◽  
Radiogenic Isotope ◽  
Ocean Island Basalts ◽  
Enriched Mantle ◽  
Mantle Component ◽  
Ocean Ridge

Oxygen fugacity (fO2) is a fundamental variable in igneous petrology with utility as a potential tracer of recycled surficial materials in the sources of mantle-derived lavas. It has been postulated that ocean island basalts (OIB) have elevated fO2 relative to mid-ocean ridge basalts (MORB) owing to more oxidized source regions. To clarify this issue, trace-element systematics of olivine grains are reported from OIB lavas with HIMU (high-; Mangaia, Canary Islands), enriched mantle (EM; Samoa; São Miguel, Azores Islands) and depleted MORB mantle (DMM; Pico, Azores) Sr-Nd-Pb-Os isotopic signatures, to constrain the fO2 of each magmatic system. Despite sampling distinct mantle reservoirs based on radiogenic isotope systematics, these OIB suites show similar fO2, ranging from +1.5 to +2.9 FMQ, with an average of 2.0 ± 0.7 FMQ, significantly higher than MORB at +0.6 ± 0.2 FMQ using the same oxybarometer. OIBs show no correlation between fO2 and bulk rock isotopic ratios or parental magma compositions. The lack of correlations with isotopic signatures likely results from radiogenic isotope signatures being hosted in volumetrically minor trace element enriched mantle lithologies, while fO2 reflects the volumetrically dominant mantle component. Higher fO2 in OIB relative to MORB implies a uniformly oxidizing plume source mantle that may be the result of either a common oxidized oceanic crust-rich reservoir parental to all modern plume lavas, or preservation of un-degassed and oxidized mantle domains formed early in Earth history.

scholarly journals The stable strontium isotopic composition of ocean island basalts, mid-ocean ridge basalts, and komatiites

2018 ◽  
Vol 483 ◽  
pp. 595-602 ◽  
Author(s):  
Elsa Amsellem ◽  
Frédéric Moynier ◽  
James M.D. Day ◽  
Manuel Moreira ◽  
Igor S. Puchtel ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Ocean Island ◽  
Ocean Island Basalts ◽  
Mid Ocean Ridge ◽  
Stable Strontium ◽  
Ocean Ridge

Trace Element and Isotopic Evidence for Recycled Lithosphere from Basalts from 48 to 53°E, Southwest Indian Ridge

2020 ◽  
Author(s):  
Jixin Wang ◽  
Huaiyang Zhou ◽  
Vincent J M Salters ◽  
Henry J B Dick ◽  
Jared J Standish ◽  
...  
Keyword(s):  
Trace Element ◽  
Southwest Indian Ridge ◽  
Isotopic Compositions ◽  
Depleted Mantle ◽  
Bone Segment ◽  
Mid Ocean Ridge ◽  
Mantle Component ◽  
Indian Ridge ◽  
Basalt Glasses ◽  
Ocean Ridge

Abstract Mantle source heterogeneity and magmatic processes have been widely studied beneath most parts of the Southwest Indian Ridge (SWIR). But less is known from the newly recovered mid-ocean ridge basalts from the Dragon Bone Amagmatic Segment (53°E, SWIR) and the adjacent magmatically robust Dragon Flag Segment. Fresh basalt glasses from the Dragon Bone Segment are clearly more enriched in isotopic composition than the adjacent Dragon Flag basalts, but the trace element ratios of the Dragon Flag basalts are more extreme compared with average mid-ocean ridge basalts (MORB) than the Dragon Bone basalts. Their geochemical differences can be explained only by source differences rather than by variations in degree of melting of a roughly similar source. The Dragon Flag basalts are influenced by an arc-like mantle component as evidenced by enrichment in fluid-mobile over fluid-immobile elements. However, the sub-ridge mantle at the Dragon Flag Segment is depleted in melt component compared with a normal MORB source owing to previous melting in the subarc. This fluid-metasomatized, subarc depleted mantle is entrained beneath the Dragon Flag Segment. In comparison, for the Dragon Bone axial basalts, their Pb isotopic compositions and their slight enrichment in Ba, Nb, Ta, K, La, Sr and Zr and depletion in Pb and Ti concentrations show resemblance to the Ejeda–Bekily dikes of Madagascar. Also, Dragon Bone Sr and Nd isotopic compositions together with the Ce/Pb, La/Nb and La/Th ratios can be modeled by mixing the most isotopically depleted Dragon Flag basalts with a composition within the range of the Ejeda–Bekily dikes. It is therefore proposed that the Dragon Bone axial basalts, similar to the Ejeda–Bekily dikes, are sourced from subcontinental lithospheric Archean mantle beneath Gondwana, pulled from beneath the Madagascar Plateau. The recycling of the residual subarc mantle and the subcontinental lithospheric mantle could be related to either the breakup of Gondwana or the formation and accretion of Neoproterozoic island arc terranes during the collapse of the Mozambique Ocean, and is now present beneath the ridge.

scholarly journals The alkaline intraplate volcanism of the Antalya nappes (Turkey): a Late Triassic remnant of the Neotethys

2008 ◽  
Vol 179 (4) ◽  
pp. 397-410 ◽  
Author(s):  
René C. Maury ◽  
Henriette Lapierre ◽  
Delphine Bosch ◽  
Jean Marcoux ◽  
Leopold Krystyn ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Late Triassic ◽  
Primitive Mantle ◽  
Heavy Rare Earth Element ◽  
Alkali Basalts ◽  
Crustal Component ◽  
Ocean Island ◽  
Ocean Island Basalts ◽  
Enriched Mantle

AbstractLate Triassic submarine alkali basalts and hawaiites were collected from two superimposed tectonic slices belonging to the Kara Dere – Sayrun unit of the Middle Antalya nappes, southwestern Turkey. New determinations on conodont faunas allow to date this sequence to the Lower Carnian (Julian). The volcanic rocks show rather homogeneous compositions, with high TiO2 and relatively low MgO and Ni contents which suggest olivine fractionation. Their primitive mantle-normalised multi-elements plots show Nb and Ta enrichments relative to La, Pb negative anomalies and heavy rare earth element and Y depletions typical of intraplate ocean island basalts. These characteristics are consistent with the major and trace element compositions of their primary clinopyroxene phenocrysts, which do not show any feature ascribable to crustal contamination. The studied lavas display a restricted range of εNd (+4.6 to +5.2) which falls within the range of ocean island basalts. Their initial (143Nd/144Nd)i ratios are too low to be explained by a simple mixing line between depleted MORB mantle (DMM) and HIMU components. Their Pb and Nd isotopic compositions plot along a mixing line between HIMU component and an enriched mantle, the composition of which could be the result of the addition of about 5 to 8% of an EM2 component (recycled marine sediments) to DMM. The lack of evidence for any continental crustal component in their genesis could be consistent with their emplacement in an intra-oceanic setting.

scholarly journals Melt Inclusions in Plagioclase Macrocrysts at Mount Jourdanne, Southwest Indian Ridge (~64° E): Implications for an Enriched Mantle Source and Shallow Magmatic Processes

Minerals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 493 ◽  
Author(s):  
Wei Li ◽  
Chunhui Tao ◽  
Wen Zhang ◽  
Jia Liu ◽  
Jin Liang ◽  
...  
Keyword(s):  
Mantle Source ◽  
Melt Inclusions ◽  
Parental Magma ◽  
Southwest Indian Ridge ◽  
Host Magma ◽  
Enriched Mantle ◽  
Magma Supply ◽  
General Chemical ◽  
Indian Ridge ◽  
Ocean Ridge

Plagioclase ultraphyric basalts (PUBs) with up to 40% millimeter-sized plagioclase crystals, were sampled from the Mount Jourdanne volcanic massif (~64° E) in the Southwest Indian Ridge. The geochemistry of the host glass, the glassy melt inclusions and their host plagioclase macrocrysts (An60-69) are used to reveal the mantle heterogeneity and to discuss the origin of Mount Jourdanne PUBs. The melt inclusions trapped in plagioclase display low MgO and high SiO2 contents and show rare earth element (REE) patterns resembling enriched mid-ocean ridge basalts (E-MORB). Together with their positive Sr and Eu anomalies, these features indicate that they were derived from an enriched mantle source, likely a refertilized peridotite or a pyroxenite. In contrast to some 61–67° E basalts, there is a lack of negative Eu anomalies in the PUB host glasses, precluding large amounts of plagioclase crystallization from their parental magma. Petrographic observations and the general chemical similarity between melt inclusions and melts equilibrated with the clinopyroxene cores in regional gabbros and/or troctolites suggest that these plagioclase macrocrysts originate from gabbroic mush within the lower crust. The density contrasts allow the effective segregation of plagioclase prior to their incorporation into the host magma. We propose that these plagioclase macrocrysts were entrained when a new batch of magma passed through the crustal mush zone, and resulted in the formation of the PUB. Eruption of Mount Jourdanne PUBs requires a minimum ascending velocity of 5 m d−1 for the host magma, which is not as high as the eruption rate for typical MORB samples. It is likely that the PUB host magma erupts during a period with reduced magma supply, whereas eruption of aphyric lavas correspond to the fast volcanic formation of the Mount Jourdanne massif.

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