Melt segregation and the architecture of magmatic reservoirs: insights from the Muroto sill (Japan)

Floess, David; Caricchi, Luca; Simpson, Guy; Wallis, Simon

doi:10.1007/s00410-019-1563-9

Cited by 15 publications

(9 citation statements)

References 43 publications

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“…Considering that magmas typically reach the rigid percolation threshold at about 50 vol% crystallinity 18,[40][41][42] , we consider all magma below this threshold to be potentially extractable. Furthermore, we assume that interstitial liquids of magmas with more than 50 vol% crystals are potentially extractable by melt segregation or by mixing/mingling processes during disruption of highly crystallized crystal mushed associated with recharge [40][41][42][43][44][45][46][47] . Probabilities of melt extraction may significantly decrease in magma bodies with > 75% crystal content 41 .…”

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confidence: 99%

Magma diversity reflects recharge regime and thermal structure of the crust

Weber

Simpson

Caricchi

2020

Sci Rep

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The chemistry of magmas erupted by volcanoes is a message from deep within the Earth's crust, which if decrypted, can provide essential information on magmatic processes occurring at inaccessible depths. While some volcanoes are prone to erupt magmas of a wide compositional variety, others sample rather monotonous chemistries through time. Whether such differences are a consequence of physical filtering or reflect intrinsic properties of different magmatic systems remains unclear. Here we show, using thermal and petrological modelling, that magma flux and the thermal structure of the crust modulate diversity and temporal evolution of magma chemistry in mid to deep crustal reservoirs. Our analysis shows that constant rates of magma input leads to extractable magma compositions that tend to evolve from felsic to more mafic in time. Low magma injection rates into hot or deep crust produces less chemical variability of extractable magma compared to the injection of large batches in colder or shallower crust. Our calculations predict a correlation between magma fluxes and compositional diversity that resembles trends observed in volcanic deposits. Our approach allows retrieval of quantitative information about magma input and the thermal architecture of magmatic systems from the chemical diversity and temporal evolution of volcanic products.

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confidence: 99%

Magma diversity reflects recharge regime and thermal structure of the crust

Weber

Simpson

Caricchi

2020

Sci Rep

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“…Recent hypotheses for the emplacement of magmas in small volume sub-volcanic environments have proposed that large continuously fractionating magma chambers do not exist (Emeleus & Troll, 2014;Floess et al 2019;Hepworth et al 2020;Savard & Mitchell, 2021). Following these concepts, the mineralogical variations of the Type 1-3 lavas can be explained by fractional crystallization of many individual batches of magmas derived from a common source coupled with magma mixing as a result of intrusion of magma into crystal-melt mushes and/or entrainment of crystals derived from disaggregation of pre-existing fully crystallized melts; i.e.…”

Section: Discussionmentioning

confidence: 99%

Petrology and Sr–Nd isotope geochemistry of Mosonik: a polygenetic phonolitic nephelinite–phonolite volcano located in the North Tanzanian Divergence of the East African Rift

Mitchell

Dawson

2022

Geol. Mag.

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Mosonik, a 3.25 Ma extensively dissected stratovolcano located in the North Tanzanian Divergence of the East African Rift, consists predominantly of phonolite and three types of phonolitic nephelinite distinguished by the presence or absence of amphibole or garnet antecrysts and differing populations of complexly zoned antecrystal and phenocrystal pyroxenes. The antecryst–phenocryst assemblage is typical of hybrid lavas derived by magma mixing. Compositional data are given for all major minerals. Owing to the high modal proportions (30–60 vol. %) of antecrysts and phenocrysts of pyroxene and nepheline plus the hybrid character of the lavas, bulk-rock compositions do not represent those of the parental liquids. Thus, assimilation–fractional crystallization modelling of the bulk-rock major- and trace-element abundances is inappropriate and an unevolved parental magma cannot as yet be defined. Sr–Nd isotopic data for Mosonik and other Older Extrusive Series rocks suggest derivation by partial melting of ancient metasomatized lithospheric mantle with mixing of Sr and Nd from two sources coupled with minor lower crustal contamination, melting being induced by the plume currently impinging on the Tanzanian craton, and representing the initial interaction of the plume with the cratonic lithosphere. In contrast, the Younger Extrusives, as exemplified by Oldoinyo Lengai nephelinite–carbonatite volcanism, could be derived from this ancient metasomatized lithospheric mantle plus a recent plume-derived asthenospheric component and no contamination by crustal material. The isotopically and genetically distinct Natron–Engaruka melilitites are considered to represent direct adiabatic melting of the Tanzanian plume without lithospheric contributions. Carbonatites and melilite-bearing nephelinites also occur at Mosonik but are not considered in this study as they are only a very minor volumetric component of the volcano.

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“…Segregations of FeS were sucked from the sample into polycrystalline alumina pistons to form alignments of connected melt pockets driven by reductions in pore fluid pressure associated with dilatancy (see Petford et al 2007;Fonseca et al 2013, and supplementary materials Figs. 7-9) Bachmann and Huber 2018;Floess et al 2019). Attempts to explain crystal mush reactivation in silicic systems via an interplay of melting and gas addition (Huber et al 2011), strike us as unnecessarily complex.…”

Section: Dilatancy In Crustal Melt Columns: Turbo-charging the Segregmentioning

confidence: 99%

Igneous differentiation by deformation

Petford

Koenders

Clemens

2020

Contrib Mineral Petrol

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In a paper published in 1920, Bowen conceived of a situation where forces acting on a crystalline mesh could extract the liquid phase from the solid, and in doing so cause variations in chemistry distinct from the purely gravitational effects of fractional crystallisation. His paper was a call-to-arms to explore the role of deformation as a cause of variation in igneous rocks, but was never followed-up in a rigorous way. Inspired by this, we have developed a quantitative model showing how shear deformation of a crystallised dense magma (ϕ > 70%) with poro-elastic properties is analogous to a granular material. The critical link between the mechanics and associated compositional changes of the melt is the degree to which the crystallising magma undergoes dilation (volume increase) during shear. It is important to note that the effect can only take place after the initial loose solid material has undergone mechanical compaction such that the grains comprising the rigid skeleton are in permanent contact. Under these conditions, the key material parameters governing the dilatancy effect are the physical permeability, mush strength, the shear modulus and the contact mechanics and geometry of the granular assemblage. Calculations show that dilation reduces the interstitial fluid (melt) pressure causing, in Bowen's words, "the separation of crystals and mother liquor" via a suction effect. At shear strain rates in excess of the tectonic background, deformation-induced melt flow can redistribute chemical components and heat between regions of crystallising magma with contrasting rheological properties, at velocities far in excess of diffusion or buoyancy forces, the latter of course the driving force behind fractional crystallisation and viscous compaction. Influx of hotter, less evolved melt drawn internally from the same magma body into regions where crystallisation is more advanced (auto-intrusion), may result in reverse zoning and/or resorption of crystals. Because dilatancy is primarily a mechanical effect independent of melt composition, evolved, chemically distinct melt fractions removed at this late stage may explain miarolitic alkaline rocks, intrusive granophyres in basaltic systems and late stage aplites and pegmatites in granites (discontinuous variations), as proposed by Bowen. Post-failure instabilities include hydraulic rupture of the mush along shear zones governed by the angles of dilation and internal friction. On the macro-scale, a combination of dilatancy and fracturing may provide a means to extract large volumes of chemically evolved melt from mush columns on short (< 1000 year) geological timescales.

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Melt segregation and the architecture of magmatic reservoirs: insights from the Muroto sill (Japan)

Cited by 15 publications

References 43 publications

Magma diversity reflects recharge regime and thermal structure of the crust

Magma diversity reflects recharge regime and thermal structure of the crust

Petrology and Sr–Nd isotope geochemistry of Mosonik: a polygenetic phonolitic nephelinite–phonolite volcano located in the North Tanzanian Divergence of the East African Rift

Igneous differentiation by deformation

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