Growth of plutons by incremental emplacement of sheets in crystal-rich host: Evidence from Miocene intrusions of the Colorado River region, Nevada, USA

Miller, Calvin F.; Furbish, David Jon; Walker, B. A.; Claiborne, Lily L.; Koteas, G. Christopher; Bleick, Heather A.; Miller, Jonathan S.

doi:10.1016/j.tecto.2009.07.011

Cited by 188 publications

(118 citation statements)

References 69 publications

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“…This is in agreement with models that suggest that a magma chamber can be regarded as a patchwork of melt-rich and melt-poor zones caused by remobilization of the crystal mush, triggered by magma replenishment throughout its lifetime (e.g. Miller et al 2009). This would explain the different crystal contents (cf.…”

Section: Characteristics Of Alkali-feldspar and Plagioclasesupporting

confidence: 91%

“…The initial emplacement of a subhorizontal dike acted as a trap for the upward-propagating silicic magma (e.g. Kavanagh et al 2006;Menand 2008;Miller et al 2009). The laccolithic complex was progressively built by stacking and upward inflation of sills (e.g.…”

Section: Characteristics Of Alkali-feldspar and Plagioclasementioning

confidence: 99%

“…A growing number of recent studies indicate that the majority of ''inflated'' plutons are not actually balloon-shaped, but are instead rather tabular, and resemble laccoliths, in that they grow by amalgamation of individual magma pulses (e.g. Saint Blanquant et al 2001;Glazner et al 2004;Coleman et al 2004;Matzel et al 2006;Cruden 2008;Morgan et al 2008;Horsman et al 2009;Miller et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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Multi-stage emplacement of the Götemar Pluton, SE Sweden: new evidence inferred from field observations and microfabric analysis, including cathodoluminescence microscopy

Friese

Vollbrecht

Tanner

et al. 2011

Int J Earth Sci (Geol Rundsch)

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The emplacement of the Mesoproterozoic Götemar Pluton into Paleoproterozoic granitoid host rocks of the Transscandinavian Igneous Belt is re-examined by microfabric analysis, including cathodoluminescence microscopy. Field data on the pluton-host rock system are used to strengthen the model. The Götemar Pluton, situated on the Baltic Shield of SE Sweden, is a horizontally zoned tabular structure that was constructed by the intrusion of successive pulses of magma with different crystal/melt ratios, at an estimated crustal depth of 4-8 km. Initial pluton formation involved magma ascent along a vertical dike, which was arrested at a mechanical discontinuity within the granitoid host rocks; this led to the formation of an initial sill. Subsequent sill stacking and their constant inflation resulted in deformation and reheating of existing magma bodies, which also raised the pluton roof. This multi-stage emplacement scenario is indicated by complex dike relationships and the occurrence of several generations of quartz (Si-metasomatism). The sills were charged by different domains of a heterogeneous magma chamber with varying crystal/melt ratios. Ascent or emplacement of magma with a high crystal/melt ratio is indicated by syn-magmatic deformation of phenocrysts. Complex crystallization fabrics (e.g. oscillatory growth zoning caused by high crystal defect density, overgrowth and replacement features, resorbed and corroded crystal cores, rapakivi structure) are mostly related to processes within the main chamber, that is repeated magma mixing or water influx.

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Section: Characteristics Of Alkali-feldspar and Plagioclasesupporting

confidence: 91%

Section: Characteristics Of Alkali-feldspar and Plagioclasementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multi-stage emplacement of the Götemar Pluton, SE Sweden: new evidence inferred from field observations and microfabric analysis, including cathodoluminescence microscopy

Friese

Vollbrecht

Tanner

et al. 2011

Int J Earth Sci (Geol Rundsch)

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“…There is general agreement that magmatic systems in all tectonic settings are open to input of heat and mass, and are incrementally assembled 4 . This is manifested in complex crystal zoning patterns, age diagnostics, and volatile degassing budgets [2][3][6][7] , which are all evidence that the magmatic systems experienced periods of rejuvenation by chemical and thermal fluctuations.…”

mentioning

confidence: 99%

A rapid mechanism to remobilize and homogenize highly crystalline magma bodies

Burgisser

Bergantz

2011

Nature

214

145

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International audienceThe largest products of magmatic activity on Earth, the great bodies of granite and their corresponding large eruptions, have a dual nature: homogeneity at the large scale and spatial and temporal heterogeneity at the small scale1-4. This duality calls for amechanism that selectively removes the large-scale heterogeneities associated with the incremental assembly4 of these magmatic systems and yet occurs rapidly despite crystal-rich, viscous conditions seemingly resistant to mixing2,5. Here we show that a simple dynamic template can unify a wide range of apparently contradictory observations from both large plutonic bodies and volcanic systems by a mechanism of rapid remobilization (unzipping) of highly viscous crystalrich mushes. We demonstrate that this remobilization can lead to rapid overturn and produce the observed juxtaposition ofmagmatic materials with very disparate ages and complex chemical zoning. What distinguishes our model is the recognition that the process has two stages. Initially, a stiff mushy magma is reheated from below, producing a reduction in crystallinity that leads to the growth of a subjacent buoyant mobile layer. When the thickening mobile layer becomes sufficiently buoyant, it penetrates the overlying viscous mushy magma. This second stage rapidly exports homogenized material from the lower mobile layer to the top of the system, and leads to partial overturn within the viscous mush itself as an additional mechanism of mixing. Model outputs illustrate that unzipping can rapidly produce large amounts of mobile magma available for eruption. The agreement between calculated and observed unzipping rates for historical eruptions at Pinatubo and at Montserrat demonstrates the general applicability of the model. This mechanism furthers our understanding of both the formation of periodically homogenized plutons (crust building) and of ignimbrites by large eruptions

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“…There has been much debate regarding magma emplacement in the crust; in addition to the theory of large molten bodies ascending diapirically in single events (Pitcher, 1993;Miller and Paterson, 1999), there is a contrasting view of magma emplacement as more protracted and pulsed, occurring through a series of dikes and sills (Petford et al, 2000;Coleman et al, 2004;Glazner et al, 2004;Farina et al, 2010;Miller et al, 2011). It is important to assess how magma pulses within the BLS accumulated in the crust to understand how HPE-enrichments might have arisen (and therefore vary) during emplacement.…”

Section: Relationship Between Heat-producing Element Enrichment and Dmentioning

confidence: 99%

Petrological, geochemical and geochronological characterisation of heat-producing granites

Marshall¹

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Granitic magma generation has the ability to strongly differentiate the continental crust and concentrate elements such as the heat-producing elements (HPE) uranium (U), thorium (Th) and potassium (K). These elements can be enriched above average upper continental crustal values, and these granites are referred to as moderately (4-8 µW/m 3 ) or high (>8 µW/m 3 ) heat-producing granites (HHPGs); when overlain by insulating sedimentary cover these may be considered a target for enhanced geothermal systems (EGS).The composition of the source, and differentiation during magma ascent and emplacement, can influence the magmatic elemental budget, as can the accessory mineral assemblage, tectonic setting and history of regional magmatism. It is of importance to investigate whether there is a combination of these factors that promotes HPE enrichment and, if so, can these factors be used to provide a criteria for HHPGs prospective for future EGS development?To address the relative influence of factors on the ability to affect elemental enrichments three HHPG examples with an established history in EGS development studies were selected: the Big Lake Suite (BLS), South Australia; Cornwall, UK; and Soultz-sous-Forêts (Soultz), France. These sites represent the three most common granite types: A-, S-and I-type, respectively. Comparing their mineralogy, major and trace element abundances, and zircon geochemistry and associated U/Pb ages will inform the timing and controls on enrichment at each location. iii an enriched source. The emplacement ages for BLS samples range from 325 ± 2 Ma to 312 ± 2 Ma; this spread in ages implies continual granite emplacement over ~13 Myr. Some zircons dating to the time of emplacement record extreme U (>5000 ppm) and Th (4000 ppm) enrichments.Inherited zircon populations were also dated in European analogues: 363 ± 9 Ma, 408 ± 9 Ma and 420 ± 6 Ma (Cornwall) and 426 ± 14 Ma ages (Soultz) are associated with granite emplacement in a syn-collisional environment during closure of the Rheic Ocean. Although some inherited grains inCornwall record high Th contents (~800 ppm), extreme enrichments (>6000 ppm U) are analysed in some emplacement-aged grains. Th enrichment (~1600 ppm) is observed in emplacement-aged zircons in Soultz.Zircon locations in thin section were studied to address where these extreme enrichments could have developed. Zircons bordering mineral boundaries or adjacent to phenocrysts likely crystallised in differentiated chemical boundary layers, and elemental abundances in these regions would have been different to those of the pluton as a whole. Localised enrichment could explain the extreme enrichments present in some emplacement-aged zircons; the extreme levels of differentiation required to attain these enrichments -up to 99% -are not plausible on a pluton scale. Zircons armoured within earlier crystallising mafic silicates (e.g., biotite) would not have been exposed to these extreme enrichments, and this could account for the range of elemental abundances recorded in empl...

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Growth of plutons by incremental emplacement of sheets in crystal-rich host: Evidence from Miocene intrusions of the Colorado River region, Nevada, USA

Cited by 188 publications

References 69 publications

Multi-stage emplacement of the Götemar Pluton, SE Sweden: new evidence inferred from field observations and microfabric analysis, including cathodoluminescence microscopy

Multi-stage emplacement of the Götemar Pluton, SE Sweden: new evidence inferred from field observations and microfabric analysis, including cathodoluminescence microscopy

A rapid mechanism to remobilize and homogenize highly crystalline magma bodies

Petrological, geochemical and geochronological characterisation of heat-producing granites

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