A trace element perspective on the source of ocean island basalts (OIB) and fate of subducted ocean crust (SOC) and mantle lithosphere (SML)

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.

Download Full-text

Modeling of Olivine and Clinopyroxene Fractionation in Intracontinental Alkaline Basalts: A Case Study from the Carpathian-Pannonian Region

10.5772/intechopen.94808 ◽

2021 ◽

Author(s):

Tamás Sági ◽

Szabolcs Harangi ◽

Theodoros Ntaflos

Keyword(s):

Trace Element ◽

Fractionation Process ◽

Ocean Island ◽

Ocean Island Basalts ◽

Mantle Peridotites ◽

Petrology And Geochemistry ◽

Mantle Petrology ◽

Basaltic Melts ◽

Primary Melt

Besides mantle peridotites primary basaltic melts are the best tool to investigate upper mantle petrology and geochemistry. However, de facto primitive melts are hard to found, as basaltic melts usually go through a fractionation process during their ascent towards the surface. Most primary melt calculators are based on the major or trace element compositions of olivine-phyric ocean island basalts and peridotites and are less accurate if clinopyroxene fractionation occurred. In this chapter a new fractionation modeling method of alkaline basalts will be introduced, which has been published earlier only in Hungarian. Olivine ± clinopyroxene fractionation of four basaltic volcanoes have been modeled from different Miocene-Quaternary volcanic fields from the Carpathian-Pannonian Region (Stiavnica (Selmec) VF, Novohrad-Gemer (Nógrád-Gömör) VF, Perşani Mts. (Persányi Mts.) VF and from the Lucaret-Sanoviţa (Lukácskő-Sziklás) volcano.

Download Full-text

186Os–187Os systematics of Hawaiian picrites revisited: New insights into Os isotopic variations in ocean island basalts

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2011.05.015 ◽

2011 ◽

Vol 75 (16) ◽

pp. 4456-4475 ◽

Cited By ~ 27

Author(s):

T.J. Ireland ◽

R.J. Walker ◽

A.D. Brandon

Keyword(s):

Ocean Island ◽

Ocean Island Basalts ◽

Isotopic Variations

Download Full-text

Lithospheric roots beneath western Laurentia: the geochemical signal in mantle garnets

Canadian Journal of Earth Sciences ◽

10.1139/e03-003 ◽

2003 ◽

Vol 40 (8) ◽

pp. 1027-1051 ◽

Cited By ~ 28

Author(s):

D Canil ◽

D J Schulze ◽

D Hall ◽

B C Hearn Jr. ◽

S M Milliken

Keyword(s):

Rare Earth ◽

North America ◽

Trace Element ◽

Earth Element ◽

Geochemical Data ◽

Trace Element Data ◽

Mantle Lithosphere ◽

Western North America ◽

Wyoming Province ◽

Thick Mantle

This study presents major and trace element data for 243 mantle garnet xenocrysts from six kimberlites in parts of western North America. The geochemical data for the garnet xenocrysts are used to infer the composition, thickness, and tectonothermal affinity of the mantle lithosphere beneath western Laurentia at the time of kimberlite eruption. The garnets record temperatures between 800 and 1450°C using Ni-in-garnet thermometry and represent mainly lherzolitic mantle lithosphere sampled over an interval from about 110260 km depth. Garnets with sinuous rare-earth element patterns, high Sr, and high Sc/V occur mainly at shallow depths and occur almost exclusively in kimberlites interpreted to have sampled Archean mantle lithosphere beneath the Wyoming Province in Laurentia, and are notably absent in garnets from kimberlites erupting through the Proterozoic Yavapai Mazatzal and Trans-Hudson provinces. The similarities in depths of equilibration, but differing geochemical patterns in garnets from the Cross kimberlite (southeastern British Columbia) compared to kimberlites in the Wyoming Province argue for post-Archean replacement and (or) modification of mantle beneath the Archean Hearne Province. Convective removal of mantle lithosphere beneath the Archean Hearne Province in a "tectonic vise" during the Proterozoic terminal collisions that formed Laurentia either did not occur, or was followed by replacement of thick mantle lithosphere that was sampled by kimberlite in the Triassic, and is still observed there seismically today.

Download Full-text