Solidus Curves, Mantle Plumes, and Magma Generation Beneath Hawaii

Wyllie, Peter J.

doi:10.1002/9781118782064.ch5

Cited by 5 publications

(5 citation statements)

References 47 publications

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“…In spite of that, garnet and/or its breakdown products seem to melt selectively and • The lack of pervasive chemical and textural re-equilibration of the rock with symplectites documents the existence of metastable domain in the uppermost, probably lithospheric, mantle beneath the Zinst locality in the Tertiary. As indicated by geothermometry, the P-T conditions in the upper mantle prior to the volcanic event were well above the solidus of H+C+O fluid-bearing, fertile lherzolite and close to the solidus of water-free, carbonated lherzolite (Wyllie, 1988;Falloon & Green 1990). Under these conditions garnet peridotite domains could have been easily destabilised by local advective heating and addition of fluids.…”

Section: Model Of Garnet Breakdown On a P-t Pathmentioning

confidence: 88%

Garnet Breakdown, Symplectite Formation and Melting in Basanite-hosted Peridotite Xenoliths from Zinst (Bavaria, Bohemian Massif)

Špaček

Ackerman

Habler

et al. 2013

Journal of Petrology

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Complex, symplectite-bearing pseudomorphs after garnet recently found in unique basanite-hosted peridotite xenoliths from Zinst, Bavaria, allow the study of the interaction between garnet peridotite and melts/fluids both prior to entrainment of the xenoliths and during their ascent. Based on microstructures and crystallographic fabric, major and trace element mineral chemistry, four distinct concentric zones were defined in various types of pseudomorphs: I) coarse grained (≤ 1 mm) aggregate of orthopyroxene+clinopyroxene+spinel with a granular structure, II) fine-to medium grained (order of 10-100 µm) orthopyroxene+spinel symplectite, III) fine grained (5-300 µm), radially fibrous orthopyroxene+spinel symplectite with interstitial anorthite, and, IV) ultrafine grained (≤ 1 µm) orthopyroxene+spinel+anorthite symplectite with an internal domain sub-structure. Zones III and IV have bulk compositions of pyrope rich garnet. All zones exhibit perfect inter-sample correlation and document the discontinuous evolution of peridotite under changing conditions with successively increasing rates of garnet breakdown. Based on thermometry and microstructural relations, a sequence of three pre-and syn-volcanic events is discerned: The first traceable event corresponds to regional heating in the uppermost mantle probably related to the early stages of Tertiary rifting, which triggered the reaction between garnet and olivine (Zone I) leading to a partial re-equilibration of the rock at 1040-1080°C within the spinel peridotite stability field. Subsequently a short period of heating by ~100-250°C lead to largely isochemical, fluidmediated in situ melting of garnet and to the formation of kelyphite by crystallization from the melt (Zone III). The subsequent metasomatic alteration by external, Na-rich, K-poor, carbonate-bearing melts/fluids suggests that this phase of garnet breakdown occured largely prior to formation of the xenolith, preceding the emplacement of the basanite magma. Finally, after xenolith formation, and associated with the rapid, isochemical, decompression during ascent, the garnet relics were transformed into microsymplectite (Zone IV). The positive volume change associated with this reaction caused fracturing, producing radial cracks that emanate from Zone IV and extend into the adjacent peridotite allowing infiltration of basanite-derived melt components. The well developed and clearly separated symplectite zones indicating the isochemical breakdown of garnet are uncommon to garnet peridotites worldwide. Their existence at Zinst is explained by an extremely short time span between the formation of the kelyphite, Na-carbonate metasomatism and the final garnet breakdown on the basanite eruption, allowing for rapid quenching of the multiple advancing reaction fronts.

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Section: Model Of Garnet Breakdown On a P-t Pathmentioning

confidence: 88%

Garnet Breakdown, Symplectite Formation and Melting in Basanite-hosted Peridotite Xenoliths from Zinst (Bavaria, Bohemian Massif)

Špaček

Ackerman

Habler

et al. 2013

Journal of Petrology

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“…An interesting question that follows is: Was this depleted subcontinental lithospheric mantle a preexisting feature of the Laurentian lithosphere, or is it a consequence of the mantle plume suggested for the Franklin large igneous province? The thermochemical plume model (Campbell, 2007;Campbell and Griffiths, 1990;Griffiths and Campbell, 1990;Watson and McKenzie, 1991;Wyllie, 1988) suggests that hot, adiabatically decompressing mantle (plume head) impinges on and flattens at the base of the lithosphere, and so most melting should occur in the plume head, resulting in flood basalt vol canism. Such extensive melting associated with this flood magmatism would consequently leave a meltdepleted (and lowerdensity) mantle that may flow laterally away from the plume center.…”

Section: Low-ti Province Of the Franklin Large Igneous Province?mentioning

confidence: 99%

Kikiktat volcanics of Arctic Alaska—Melting of harzburgitic mantle associated with the Franklin large igneous province

et al. 2015

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The Kikiktat volcanics (new name) of the northeastern Brooks Range of Arctic Alaska are exceptionally well-preserved Neoproterozoic continental tholeiites. This volcanic suite includes high-temperature picritic compositions, making them an excellent probe of mantle composition and temperature underlying the northern margin of Laurentia during the breakup of Rodinia. Detrital zircons from a volcaniclastic sample directly overlying basaltic flows of the Kikiktat volcanics were dated at 719.47 ± 0.29 Ma by U-Pb chemical abrasion-thermal ionization mass spectrometry. This age suggests that the Kikiktat volcanics are an extension of the Franklin large igneous province. Petrogenetic modeling indicates a simple crystallization sequence of olivine → plagioclase → clinopyroxene, recording anhydrous low-pressure fractionation of a picritic parental melt. The composition of this parental liquid requires melting of harzburgite in the spinel stability field, while temperature estimates of the primary melt indicate elevated mantle potential temperatures. In contrast to the ca. 720 Ma Natkusiak basalts of Victoria Island, the Kikiktat volcanics have very low Ti concentrations, consistent with melting of harzburgitic mantle possibly by thermal conduction of an underlying plume. These data are consistent with Neoproterozoic to early Paleozoic tectonic reconstructions that restore the North Slope of Arctic Alaska to the northeastern margin of Laurentia and not directly adjacent to Victoria Island.

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“…This simple analysis makes an important general point: At this particular "cusp", the system partially crystallizes via the reaction coesite ϩ melt ϭ quartz; that is, the widely held notion (Presnall and others, 1979;Natland and Melson, 1980;Presnall, 1980;Flower, 1981;Presnall and Hoover, 1987;Wyllie, 1988;Salters and Hart, 1989) that cusps lead to enhanced melting is not likely to be universally valid. The reason for this is easy to understand using figure 22A.…”

Section: The Case Of a Solid-solid Transition With A Positive Dt/dpmentioning

confidence: 99%

Insights Into Mantle Melting From Graphical Analysis of Two-Component Systems

Asimow¹,

Stolper²,

Antoshechkina³

2017

Geological Society of America Abstracts With Programs

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Solidus Curves, Mantle Plumes, and Magma Generation Beneath Hawaii

Abstract: Abstract.The eruption of nepheline-normative material, or (4) local decrease of pressure (for lavas in the early and late stages of formation a source already near its solidus temperature

Cited by 5 publications

References 47 publications

Garnet Breakdown, Symplectite Formation and Melting in Basanite-hosted Peridotite Xenoliths from Zinst (Bavaria, Bohemian Massif)

Garnet Breakdown, Symplectite Formation and Melting in Basanite-hosted Peridotite Xenoliths from Zinst (Bavaria, Bohemian Massif)

Kikiktat volcanics of Arctic Alaska—Melting of harzburgitic mantle associated with the Franklin large igneous province

Insights Into Mantle Melting From Graphical Analysis of Two-Component Systems

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