Geochemistry of deep Manihiki Plateau crust: Implications for compositional diversity of large igneous provinces in the Western Pacific and their genetic link.

Golowin, Roman, Portnyagin, Maxim , Hoernle, Kaj , Hauff, Folkmar , Werner, Reinhard and Garbe-Schönberg, Dieter (2018) Geochemistry of deep Manihiki Plateau crust: Implications for compositional diversity of large igneous provinces in the Western Pacific and their genetic link. Open Access Chemical Geology, 493 . pp. 533-566. DOI 10.1016/j.chemgeo.2018.07.016.

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Supplementary data:

Abstract

Highlights

• First data on the composition of deep crust and primitive rocks of high-Ti magmatic series of Manihiki Plateau
• High potential mantle temperature for Manihiki sources (>1460oC) suggests a lower mantle plume origin
• EM1 signature in high-Ti Manihiki basalts could originate from recycled lower continental crust or re-fertilized SCLM
• The presence of refractory mantle in the Manihiki plume explains 30% lower crustal thickness compared to OJP
• Manihiki and OJP could have been formed from a geochemically zoned plume or from two spatially separated mantle plumes

Abstract

Geochemical studies revealed two major (high- and low-Ti) magmatic series composing the Manihiki Plateau in the Western Pacific. Here we report new geochemical data (major and trace element and Sr-Nd-Pb isotope compositions) of the Manihiki rocks. The rocks belong to the previously rarely sampled high-Ti Manihiki series and represent a section of deep crust of the plateau. The rocks were collected by remotely operated vehicle ROV Kiel 6000 during R/V SONNE SO225 expedition from a tectonic block at a stretched and faulted boundary between the Northern and Western Manihiki sub-plateaus. Additional data is presented on samples obtained by dredging during the same cruise. Judging from the age of stratigraphically higher lavas, most samples must be ≥125 Ma old. They comprise fully crystalline microdolerites, aphyric and Ol-Px-Pl-phyric basalts and breccias metamorphosed under greenschist to amphibolite facies with peak metamorphic temperatures of 636–677 °C and pressures of 2.0–2.7 kbar. A single sample of hornblende gabbro was also recovered and likely represents a late stage intrusion. Despite strong metamorphism, the samples from the ROV profile reveal only minor to moderate chemical alteration and their initial compositions are well preserved. The rocks are relatively primitive with MgO up to 13 wt%, range from enriched to depleted in LREE (LaN/SmN = 0.7–1.1), exhibit variable but mostly depleted Nb contents (Nb/Nb* = 0.8–1.3) and display only a narrow range in isotope compositions with strong EM1 characteristics (εNd (t) = 1.8–3.6, 206Pb/204Pb (t) = 17.9–18.1, 207Pb/204Pb (t) = 15.49–15.53, 208Pb/204Pb (t) = 38.08–38.42). The parental magmas are interpreted to originate from a thermochemical plume with a potential mantle temperature >1460 °C. The trace element and isotope EM1 signature of the high-Ti rocks reflects the presence of recycled lower continental crust material or re-fertilized subcontinental lithospheric mantle in the plume source. A highly refractory mantle was the primary source of the low-Ti basalts and could also contribute to the origin of high-Ti basalts. On average a more depleted mantle source for the Manihiki rocks can explain ~30% lower crustal thickness of this plateau compared to Ontong Java Plateau, which was mainly formed by melting of similarly hot but more fertile mantle. The presently available data suggest that the sources of Ontong Java and Manihiki Plateaus were compositionally different and could represent two large domains of a single plume or two contemporaneous but separate plumes.

Document Type: Article
Keywords: LIP, Manihiki Plateau, Ontong Java Plateau, Sr-Nd-Pb isotopes, Trace elements, Mantle components, Depleted mantle, Enriched mantle one, EM1, Mantle recycling, Subcontinental lithospheric mantle, SCLM
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Kiel University
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Projects: MANIHIKI II
Expeditions/Models/Experiments:
Date Deposited: 23 Jul 2018 12:02
Last Modified: 08 Feb 2021 07:33
URI: https://oceanrep.geomar.de/id/eprint/43795

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