The geophysical signature of a continental intraplate volcanic system: From surface to mantle source

AbstractMagma plumbing systems underlying subduction zone volcanoes extend from the mantle through the overlying crust and facilitate protracted fractional crystallisation, assimilation, and mixing, which frequently obscures a clear view of mantle source compositions. In order to see through this crustal noise, we present intracrystal Secondary Ion Mass Spectrometry (SIMS) δ18O values in clinopyroxene from Merapi, Kelut, Batur, and Agung volcanoes in the Sunda arc, Indonesia, under which the thickness of the crust decreases from ca. 30 km at Merapi to ≤20 km at Agung. Here we show that mean clinopyroxene δ18O values decrease concomitantly with crustal thickness and that lavas from Agung possess mantle-like He-Sr-Nd-Pb isotope ratios and clinopyroxene mean equilibrium melt δ18O values of 5.7 ‰ (±0.2 1 SD) indistinguishable from the δ18O range for Mid Ocean Ridge Basalt (MORB). The oxygen isotope composition of the mantle underlying the East Sunda Arc is therefore largely unaffected by subduction-driven metasomatism and may thus represent a sediment-poor arc end-member.

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Extreme isotopic heterogeneity in Samoan clinopyroxenes constrains sediment recycling

Nature Communications ◽

10.1038/s41467-021-21416-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jenna V. Adams ◽

Matthew G. Jackson ◽

Frank J. Spera ◽

Allison A. Price ◽

Benjamin L. Byerly ◽

...

Keyword(s):

Mantle Source ◽

Magma Mixing ◽

Major And Trace Elements ◽

Mantle Heterogeneity ◽

Isotopic Data ◽

Nd Isotopes ◽

Isotopic Heterogeneity ◽

Total Variability ◽

High Silica ◽

Insight Into

AbstractLavas erupted at hotspot volcanoes provide evidence of mantle heterogeneity. Samoan Island lavas with high 87Sr/86Sr (>0.706) typify a mantle source incorporating ancient subducted sediments. To further characterize this source, we target a single high 87Sr/86Sr lava from Savai’i Island, Samoa for detailed analyses of 87Sr/86Sr and 143Nd/144Nd isotopes and major and trace elements on individual magmatic clinopyroxenes. We show the clinopyroxenes exhibit a remarkable range of 87Sr/86Sr—including the highest observed in an oceanic hotspot lava—encompassing ~30% of the oceanic mantle’s total variability. These new isotopic data, data from other Samoan lavas, and magma mixing calculations are consistent with clinopyroxene 87Sr/86Sr variability resulting from magma mixing between a high silica, high 87Sr/86Sr (up to 0.7316) magma, and a low silica, low 87Sr/86Sr magma. Results provide insight into the composition of magmas derived from a sediment-infiltrated mantle source and document the fate of sediment recycled into Earth’s mantle.

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Geochemistry of Ferrar Dolerite sills and dykes at Terra Cotta Mountain, south Victoria Land, Antarctica

Antarctic Science ◽

10.1017/s0954102095000113 ◽

1995 ◽

Vol 7 (1) ◽

pp. 73-85 ◽

Cited By ~ 11

Author(s):

A.D. Morrison ◽

A. Reay

Keyword(s):

Trace Element ◽

Mantle Source ◽

Source Region ◽

Crustal Component ◽

Enriched Mantle ◽

Victoria Land ◽

Trace Element Signature ◽

Geochemical Variation ◽

Element Enrichment ◽

Taylor Glacier

At Terra Cotta Mountain, in the Taylor Glacier region of south Victoria Land, a 237 m thick Ferrar Dolerite sill is intruded along the unconformity between basement granitoids and overlying Beacon Supergroup sedimentary rocks. Numerous Ferrar Dolerite dykes intrude the Beacon Supergroup and represent later phases of intrusion. Major and trace element data indicate variation both within and between the separate intrusions. Crystal fractionation accounts for much of the geochemical variation between the intrusive events. However, poor correlations between many trace elements require the additional involvement of open system processes. Chromium is decoupled from highly incompatible elements consistent with behaviour predicted for a periodically replenished, tapped and fractionating magma chamber. Large ion lithophile element-enrichment and depletion in Nb, Sr, P and Ti suggests the addition of a crustal component or an enriched mantle source. The trace element characteristics of the Dolerites from Terra Cotta Mountain are similar to those of other Ferrar Group rocks from the central Transantarctic Mountains and north Victoria Land, as well as with the Tasmanian Dolerites. This supports current ideas that the trace element signature of the Ferrar Group is inherited from a uniformly enriched mantle source region.

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Central European Cenozoic plume volcanism with OIB characteristics and indications of a lower mantle source

Contributions to Mineralogy and Petrology ◽

10.1007/s004100050534 ◽

1999 ◽

Vol 136 (3) ◽

pp. 225-239 ◽

Cited By ~ 61

Author(s):

K. Hans Wedepohl ◽

Albrecht Baumann

Keyword(s):

Mantle Source ◽

Lower Mantle ◽

Central European

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Provenance of basaltic tephra from Vatnajökull subglacial volcanoes, Iceland, as determined by major- and trace-element analyses

The Holocene ◽

10.1177/0959683611400456 ◽

2011 ◽

Vol 21 (7) ◽

pp. 1037-1048 ◽

Cited By ~ 62

Author(s):

Bergrún Arna Óladóttir ◽

Olgeir Sigmarsson ◽

Gudrún Larsen ◽

Jean-Luc Devidal

Keyword(s):

Trace Element ◽

Inductively Coupled Plasma ◽

Major Element ◽

Element Composition ◽

Major Element Composition ◽

Volcanic System ◽

The Holocene ◽

Inductively Coupled ◽

Ice Cap ◽

The North

The Holocene eruption history of subglacial volcanoes in Iceland is largely recorded by their tephra deposits. The numerous basaltic tephra offer the possibility to make the tephrochronology in the North Atlantic area more detailed and, therefore, more useful as a tool not only in volcanology but also in environmental and archaeological studies. The source of a tephra is established by mapping its distribution or inferred via compositional fingerprinting, mainly based on major-element analyses. In order to improve the provenance determinations for basaltic tephra produced at Grímsvötn, Bárdarbunga and Kverkfjöll volcanic systems in Iceland, 921 samples from soil profiles around the Vatnajökull ice-cap were analysed for major-element concentrations by electron probe microanalysis. These samples are shown to represent 747 primary tephra units. The tephra erupted within each of these volcanic system has similar chemical characteristics. The major-element results fall into three distinctive compositional groups, all of which show regular decrease of MgO with increasing K2O concentrations. The new analyses presented here considerably improve the compositional distinction between products of the three volcanic systems. Nevertheless, slight overlap of the compositional groups for each system still remains. In situ trace-element analyses by laser-ablation-inductively-coupled-plasma-mass-spectrometry were applied for better provenance identification for those tephra having similar major-element composition. Three trace-element ratios, Rb/Y, La/Yb and Sr/Th, proved particularly useful. Significantly higher La/Yb distinguishes the Grímsvötn basalts from those of Bárdarbunga and Rb/Y values differentiate the basalts of Grímsvötn and Kverkfjöll. Additionally, the products of Bárdarbunga, Grímsvötn and Kverkfjöll form distinct compositional fields on a Sr/Th versus Th plot. Taken together, the combined use of major- and trace-element analyses in delineating the provenance of basaltic tephra having similar major-element composition significantly improves the Holocene tephra record as well as the potential for correlations with tephra from outside Iceland.

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