A review of mesoscopic magmatic structures and their potential for evaluating the hypersolidus evolution of intrusive complexes

Paterson, Scott R.; Ardill, Katie E.; Vernon, R. H.; Žák, Jiří

doi:10.1016/j.jsg.2018.04.022

Cited by 52 publications

(32 citation statements)

References 126 publications

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“…These microphenocrysts (now embedded within the matrix) were able to rotate within the interstitial space between larger plagioclase phenocrysts and align in response to magma flow (e.g., Benn, 1994;Paterson et al, 2019). The magnetic fabrics thus represent proxies for magmatic strain during late-stage flow and emplacement that were likely captured instantaneously along inward propagating crystallization fronts (e.g., Gutiérrez et al, 2013;Marsh, 1996;Paterson et al, 1998Paterson et al, , 2019. In addition, we infer a simple AMS-to-strain relation in which the principal AMS axes (k 1 , k 2 , and k 3 ) correspond to the X i , Y i , and Z i axes of the instantaneous strain ellipsoid (e.g., Borradaile, 1991;Borradaile & Henry, 1997;Cogné & Perroud, 1988;Hrouda, 1993;Ježek & Hrouda, 2002).…”

Section: Geochemistry Geophysics Geosystemsmentioning

confidence: 99%

Protracted Multipulse Emplacement of a Postresurgent Pluton: The Case of Platoro Caldera Complex (Southern Rocky Mountain Volcanic Field, Colorado)

Tomek

Gilmer

Petronis

et al. 2019

Geochem Geophys Geosyst

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Many eroded calderas expose associated postcollapse plutons, but detailed fieldwork‐supported studies have rarely focused on the internal structure that can contribute to understanding of emplacement dynamics. The Alamosa River monzonite pluton is a postcollapse intrusion at the Platoro caldera complex that erupted six large ignimbrites between 30.2 and 28.8 Ma in the Southern Rocky Mountains volcanic field. Magnetic fabrics in this intrusion indicate the pulsed emplacement of a vertically extensive pluton. The magmatic pulses are documented by three concentric domains of magnetic foliations elongated in ~NE‐SW direction, corresponding to structural trends at the Platoro caldera complex and preexisting regional structures. As no evidence for deformation of wall rocks and the adjacent resurgent block has been identified, we interpret the Alamosa River pluton as a postresurgent intrusion. The space‐opening process involved magmatic stoping and small‐scale magma wedging. New SHRIMP‐RG U/Pb zircon dates (28.98 ± 0.18, 27.42 ± 0.35, and 27.32 ± 0.38 Ma) suggest a magmatic lifespan of ~1.7 My for the Alamosa River pluton. Our results indicate that postcaldera magmatism includes pulsed and protracted activity from large intracaldera resurgent plutons to smaller postresurgent stocks and sheeted complexes. As demonstrated by the Alamosa River pluton, some intrusions are emplaced shortly after collapse and resurgence, but postcaldera volcano‐plutonic systems may remain active for several million years or more. We also suggest that subvolcanic magma bodies may be assembled incrementally and that the record of early composite magma lenses preserved as magma wedges are later obliterated by convective flowage and crystallization.

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Section: Geochemistry Geophysics Geosystemsmentioning

confidence: 99%

Protracted Multipulse Emplacement of a Postresurgent Pluton: The Case of Platoro Caldera Complex (Southern Rocky Mountain Volcanic Field, Colorado)

Tomek

Gilmer

Petronis

et al. 2019

Geochem Geophys Geosyst

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“…Structures formed in this way, along with the rotation and preferred alignment of larger suspended crystals frozen in during cooling, could account for some 'sedimentary-type' features preserved in plutonic rocks (e.g. Barriere 1981;Paterson et al 2019). The mechanical consequence of permeability (physical and geometric) fluctuations more generally, linked to fluid flow in solidification fronts, is discussed later.…”

Section: Potential Structures and Textures Resulting From Dilatancymentioning

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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“…120°C below the wet granite solidus at 1 kbar (Johannes 1984;Smith and Parsons 1974). Granoblastic recrystallization of feldspar could have also begun already at the magmatic stage in the presence of a minor melt phase (Paterson et al 2018;Vernon 2000). However, Suomenniemi granites Fig.…”

Section: Episyenites or Syenitesthe Role Of Magmatic Processesmentioning

confidence: 99%

Clinopyroxene episyenites in a Proterozoic rapakivi granite, SE Finland — recrystallization textures, mass transfer and implications for the petrology of A-type granite complexes

et al. 2019

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Na-metasomatic augite and aegirine-augite episyenites are hosted by subalkaline amphibole granites in the 1.644 Ga Suomenniemi rapakivi granite complex, southeastern Finland. In an examined drill core, episyenites are bordered by up to 50cm-wide zones of Na-enriched augite-bearing granite in which alkali feldspar forms rims on plagioclase, and aggregates of augite and magnetite have formed by fluid-induced dehydration of hastingsite and biotite. In the episyenites, quartz has been partially removed, alkali feldspar (An <1 Ab 50 Or 50 ) and plagioclase have been partially recrystallized to granoblastic polygonal aggregates, and clinopyroxene (augite or aegirine-augite) has coarsened and been enriched in the aegirine component. Mass balance modeling implies addition of mainly Na, depletion of Si, F, Rb, Ba, Sr and 10-20% volume loss (by quartz dissolution) in the episyenitized zones in the drill core. Quartz-depletion and recrystallization may have been caused by several superimposed stages of alteration, probably related to voluminous dike-and A-type granite magmatism in the Suomenniemi area 10-15 m.y. after the emplacement of the Suomenniemi complex. Because of the coarse recrystallization textures and near-solidus recrystallization temperatures, distinguishing these fenite-like metasomatic rocks from igneous syenites is not trivial. In epizonal A-type granite complexes, high-temperature episyenites may be more common than currently thought.

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A review of mesoscopic magmatic structures and their potential for evaluating the hypersolidus evolution of intrusive complexes

Cited by 52 publications

References 126 publications

Protracted Multipulse Emplacement of a Postresurgent Pluton: The Case of Platoro Caldera Complex (Southern Rocky Mountain Volcanic Field, Colorado)

Protracted Multipulse Emplacement of a Postresurgent Pluton: The Case of Platoro Caldera Complex (Southern Rocky Mountain Volcanic Field, Colorado)

Igneous differentiation by deformation

Clinopyroxene episyenites in a Proterozoic rapakivi granite, SE Finland — recrystallization textures, mass transfer and implications for the petrology of A-type granite complexes

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