Melt inclusions in high-An plagioclase from the Gorda Ridge: an example of the local diversity of MORB parent magmas

Nielsen, Roger L.; Crum, Jennifer; Bourgeois, Rene; Hascall, Kaylea; Forsythe, L.; Fisk, Martin; Christie, David M.

doi:10.1007/s004100050111

Cited by 116 publications

(122 citation statements)

References 31 publications

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“…Most lacked shrinkage bubbles; those that did have them were noted. Melt inclusions were not rehomogenised prior to analysis for several reasons: heating experiments can affect the oxidation state of the inclusion, promoting diffusion of H, for example (Rowe et al 2007); it is easy to over-or under-heat melt inclusions (Nielsen 2011); and heating may cause physical changes such as cracks (Nielsen et al 1995). The potential role of natural post-entrapment processes is discussed in "Melt inclusion compositions".…”

Section: Methodsmentioning

confidence: 99%

“…Melt inclusion data for silicic lavas from Dabbahu volcano indicated a shallow magma reservoir, with crystallisation driven by cooling rather than decompression (Field et al 2012b). More broadly, basaltic melt inclusion studies of intraplate and riftrelated volcanic systems have focussed primarily on Hawaii [e.g., (Edmonds et al 2013;Norman et al 2002;Sides et al 2014)], Iceland (Maclennan 2008;Neave et al 2014;Winpenny and Maclennan 2011) and Piton de la Fournaise (Bureau et al 1998) in addition to studies of Mid-Ocean Ridge Basalts [MORB; e.g., (Font et al 2007;Nielsen et al 1995)]. These studies reveal that there is considerable variation in mantle volatile content and provide evidence that mantle plumes may be enriched in volatiles compared to MORB (Dixon and Clague 2001;Dixon et al 2002;Wallace 1998).…”

Section: Regional Backgroundmentioning

confidence: 99%

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The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Donovan

Blundy

Oppenheimer

et al. 2017

Contrib Mineral Petrol

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The 2011 eruption of Nabro volcano, Eritrea, produced one of the largest volcanic sulphur inputs to the atmosphere since the 1991 eruption of Mt. Pinatubo, yet has received comparatively little scientific attention. Nabro forms part of an off-axis alignment, broadly perpendicular to the Afar Rift, and has a history of large-magnitude explosive silicic eruptions, as well as smaller more mafic ones. Here, we present and analyse extensive petrological data obtained from samples of trachybasaltic tephra erupted during the 2011 eruption to assess the pre-eruptive magma storage system and explain the large sulphur emission. We show that the eruption involved two texturally distinct batches of magma, one of which was more primitive and richer in sulphur than the other, which was higher in water (up to 2.5 wt%). Modelling of the degassing and crystallisation histories demonstrates that the more primitive magma rose rapidly from depth and experienced degassing crystallisation, while the other experienced isobaric cooling in the crust at around 5 km depth. Interaction between the two batches occurred shortly before the eruption. The eruption itself was likely triggered by recharge-induced destabilisation of vertically extensive mush zone under the volcano. This could potentially account for the large volume of sulphur released. Some of the melt inclusions are volatile undersaturated, and suggest that the original water content of the magma was around 1.3 wt%, which is relatively high for an intraplate setting, but consistent with seismic studies of the Afar plume. This eruption was smaller than some geological eruptions at Nabro, but provides important insights into the plumbing systems and dynamics of off-axis volcanoes in Afar.

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Section: Methodsmentioning

confidence: 99%

Section: Regional Backgroundmentioning

confidence: 99%

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Donovan

Blundy

Oppenheimer

et al. 2017

Contrib Mineral Petrol

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“…1 continued Contrib Mineral Petrol (2013) 165:305-326 307 Lowenstern 1995Lowenstern , 2003Frezzotti 2001;Danyushevsky et al 2002;Schiano 2003;Ren et al 2005;Kamenetsky 2006;Kent 2008;Métrich and Wallace 2008;Moore 2008;Blundy and Cashman 2008; and references in these papers). Comparing with whole rocks, melt inclusions have advantages as below (Kent 2008): (1) Because of being trapped in different minerals growing at various stages of magma evolution, melt inclusions often bear wider compositions than bulk rocks (e.g., Sobolev and Shimizu 1993;Nielsen et al 1995;Gurenko and Chaussidon 1995;Saal et al 1998Saal et al , 2005Kent et al 1999Kent et al , 2002Norman et al 2002;Sours-Page et al 2002;Ren et al 2004Ren et al , 2005Jackson and Hart 2006;Kamenetsky and Gurenko 2007). More importantly, compositions of melt inclusions within the earliest mineral phenocrysts, for example, olivines with the highest Fo, are comparable to those of the primitive magmas (e.g., Sobolev and Shimizu 1993;Sobolev 1996).…”

Section: Introductionmentioning

confidence: 99%

Constraints from melt inclusions and their host olivines on the petrogenesis of Oligocene-Early Miocene Xindian basalts, Chifeng area, North China Craton

Zhang

Qian

et al. 2012

Contrib Mineral Petrol

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The geochemical characteristics of melt inclusions and their host olivines provide important information on the processes that create magmas and the nature of their mantle and crustal source regions. We report chemical compositions of melt inclusions, their host olivines and bulk rocks of Xindian basalts in Chifeng area, North China Craton. Compositions of both bulk rocks and melt inclusions are tholeiitic. Based on petrographic observations and compositional variation of melt inclusions, the crystallizing sequence of Xindian basalts is as follows: olivine (at MgO [ *5.5 wt%), plagioclase (beginning at MgO = *5.5 wt%), clinopyroxene and ilmenite (at MgO \ 5.0 wt%). High Ni contents and Fe/Mn ratios, and low Ca and Mn contents in olivine phenocrysts, combining with low CaO contents of relatively high MgO melt inclusions (MgO [ 6 wt%), indicate that Xindian basalts are possibly derived from a pyroxenite source rather than a peridotite source. In the CS-MS-A diagram, all the high MgO melt inclusions (MgO [ 6.0 wt%) project in the field between garnet ? clinopyroxene ? liquid and garnet ? clinopyroxene ? orthopyroxene ? liquid near 3.0 GPa, further suggesting that residual minerals are mainly garnet and clinopyroxene, with possible presence of orthopyroxene, but without olivine. Modeling calculations using MELTS show that the water content of Xindian basalts is 0.3-0.7 wt% at MgO = 8.13 wt%. Using 20-25 % of partial melting estimated by moderately incompatible element ratios, the water content in the source of Xindian basalts is inferred to be C450 ppm, much higher than 6-85 ppm in dry lithospheric mantle. The melting depth is inferred to be *3.0 GPa, much deeper than that of tholeiitic lavas (\2.0 GPa), assuming a peridotite source with a normal mantle potential temperature. Such melting depth is virtually equal to the thickness of lithosphere beneath Chifeng area (*100 km), suggesting that Xindian basalts are derived from the asthenospheric mantle, if the lithospheric lid effect model is assumed.

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“…Thus, to the extent that the phenocrysts crystallized from a less evolved or less well-mixed melt, the melt inclusions record the nature of more primitive melt compositions. Studies of melt inclusions have revealed that, although they are broadly similar in major element composition to their host lavas, they tend to extend to more primitive (higher MgO) compositions, suggesting that they indeed record an earlier point in the evolutionary history of the magma (e.g., Nielsen et al, 1995;Shimizu, 1998;Sinton et al, 1993;Sobolev and Shimizu, 1993;Sours-Page et al, 1999Zhang et al, 2010). Maclennan (2008) found that melt inclusions in Icelandic lavas were more heterogeneous than whole-rock samples of the same flow.…”

mentioning

confidence: 99%

Composition of the Oceanic Crust

White

Klein²

2014

Treatise on Geochemistry

195

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Melt inclusions in high-An plagioclase from the Gorda Ridge: an example of the local diversity of MORB parent magmas

Cited by 116 publications

References 31 publications

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Constraints from melt inclusions and their host olivines on the petrogenesis of Oligocene-Early Miocene Xindian basalts, Chifeng area, North China Craton

Composition of the Oceanic Crust

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