Emplacement and assembly of shallow intrusions from multiple magma pulses, Henry Mountains, Utah

Horsman, Eric; Morgan, Sven; Blanquat, Michel de Saint; Habert, Guillaume; Nugent, Andrew; Hunter, Robert J.; Tikoff, Basil

doi:10.1130/2010.2472(08)

Cited by 24 publications

(40 citation statements)

References 53 publications

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“…Incremental accumulation and pulsed growth of magma bodies occurs over multiple timescales (e.g. Glazner, 2005;Menand, 2008;Horsman et al, 2010;Annen, 2011;Zieg and Marsh, 2012). These experiments show that even a single emplacement pulse of magma is not a simple process.…”

Section: Discussionmentioning

confidence: 98%

“…(e.g. Ferré et al, 2002;Morgan et al, 2008;Horsman et al, 2010). Crystal Size Distributions (CSDs) have been used extensively to analyze cooling and emplacement history in many magmatic bodies including the Sudbury impact sheet (Zieg and Marsh, 2002;2005) and much smaller sills and dikes (Marsh, 2007;Zieg and Marsh, 2012;Marsh, 2013).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Trachyte Mesa), are, as mentioned above, most certainly the result of multiple, discrete pulses of magma, stacked atop one another (e.g. Menand, 2006;Morgan et al, 2008;Horsman et al, 2010). These have been interpreted as multiple, small intrusions occurring over a range of time, such that each pulse is distinctly separate from the others.…”

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confidence: 96%

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Mapping real time growth of experimental laccoliths: The effect of solidification on the mechanics of magmatic intrusion

Currier

Marsh

2015

Journal of Volcanology and Geothermal Research

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The dynamics of solidification front growth along the margins of magmas have been widely found to be fundamental in controlling magma transport and emplacement. In this vein, the role of solidification fronts in determining the basic growth mechanics of laccoliths are investigated here in a series of scaled experiments using two contrasting magma analogs, water and molten wax that are injected into a visco-elastic gelatin based crustal analog. In non-solidifying, waterstyle experiments, intrusion is a relatively simple process. In contrast, wax magma emplacement displays a vast palette of compelling behaviors: propagation can slow, stop, and reactivate, and the directionality of lateral growth becomes much more variable. Small flow deviations in water-based intrusions are likely the product of flow instabilities, the result of injecting a viscous fluid along an interface (similar toHele-Shaw cell experiments). However, the much more complex emplacement style of the wax experiments is attributed to solidification at the leading edge of the crack.The overall effects of solidification during emplacement can be described by a nondimensional parameter measuring the relative competition between the rates of crack propagation and solidification at the crack leading edge. In this context, laccolith growth mechanics can be separated into three distinctive characteristic stages. Namely, I: A thin pancake style sill initially emanating radially from a central feeder zone, II: As solidification stalls magma propagation at the leading edges, enhanced thickening begins, forming a true, low aspect ratio laccolith, and III: As stresses accumulate, tears and disruptions readily occur in the solidified margin causing fresh breakouts, thus reactivating lateral growth into new lobes. The competitive combination of these latter stages often leads to a characteristic pulsatile growth. The unexpected richness of these results promises to add fundamentally to the basic understanding of laccolith growth mechanisms, and alsoadds key observations to growth processes to be sought in field studies that have been hitherto suspected but rarely observed. Despite seemingly simple shapes, the growth history of laccolithic intrusions is likely quite complex.

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Section: Discussionmentioning

confidence: 98%

Section: Accepted Manuscriptmentioning

confidence: 99%

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Mapping real time growth of experimental laccoliths: The effect of solidification on the mechanics of magmatic intrusion

Currier

Marsh

2015

Journal of Volcanology and Geothermal Research

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“…Processes of incremental pluton assembly, by recurrent addition of subhorizontal magma lenses, are well documented for some laccoliths and isolated plutons of modest size that are exposed at optimum crustal levels (Wiebe et al, 2002;Miller and Miller, 2002;Michel et al, 2008;Horsman et al, 2009;Rocchi et al, 2010;Miller et al, 2011). Such structural and compositional evidence of incremental assembly is unlikely to survive, however, in longer-lived and larger intrusive systems constructed by recurrent open-system recharge at high magma-supply rates, such as inferred for the San Juan batholith.…”

Section: Assembly Of Cordilleran Plutonsmentioning

confidence: 99%

Ignimbrites to batholiths: Integrating perspectives from geological, geophysical, and geochronological data

2015

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Multistage histories of incremental accumulation, fractionation, and solidification during construction of large subvolcanic magma bodies that remained sufficiently liquid to erupt are recorded by Tertiary ignimbrites, source calderas, and granitoid intrusions associated with large gravity lows at the Southern Rocky Mountain volcanic field (SRMVF). Geophysical data combined with geological constraints and comparisons with tilted plutons and magmatic-arc sections elsewhere are consistent with the presence of vertically extensive (>20 km) intermediate to silicic batholiths (with intrusive:extrusive ratios of 10:1 or greater) beneath the major SRMVF volcanic loci (Sawatch, San Juan, Questa-Latir). Isotopic data require involvement of voluminous mantle-derived mafic magmas on a scale equal to or greater than that of the intermediate to silicic volcanic and plutonic rocks. Early waxing-stage intrusions (35-30 Ma) that fed intermediate-composition central volcanoes of the San Juan locus are more widespread than the geophysically defined batholith; these likely heated and processed the crust, preparatory for ignimbrite volcanism (32-27 Ma) and largescale upper-crustal batholith growth. Age and compositional similarities indicate that SRMVF ignimbrites and granitic intrusions are closely related, but the extent to which the plutons record remnants of former magma reservoirs that lost melt to volcanic eruptions has been controversial. Published Ar/Arfeldspar and U-Pb-zircon ages for plutons spatially associated with ignimbrite calderas document final crystallization of granitoid intrusions at times indistinguishable from the tuff to ages several million years younger. These ages also show that SRMVF caldera-related intrusions cooled and solidified soon after zircon crystallization, as magma supply waned. Some researchers interpret these results as recording pluton assembly in small increments that crystallized rapidly, leading to temporal disconnects between ignimbrite eruption and intrusion growth. Alternatively, crystallization ages of the granitic rocks are here inferred to record late solidification, after protracted open-system evolution involving voluminous mantle input, lengthy residence (10 5 -10 6 yr) as near-solidus crystal mush, and intermittent separation of liquid to supply volcanic eruptions. The compositions of the least-evolved ignimbrite magmas tend to merge with those of caldera-related plutons, suggesting that the plutons record nonerupted parts of long-lived cogenetic magmatic systems, variably modified prior to final solidification. Precambrian-source zircons are scarce in caldera plutons, in contrast to their abundance in some peripheral waning-stage intrusions of the SRMVF, implying dissolution of inherited crustal zircon during lengthy magma assembly for the ignimbrite eruptions and construction of a subvolcanic batholith. Broad age spans of zircons (to several million years) from individual samples of some ignimbrites and intrusions, commonly averaged and interpreted as "intrusion-emplacement age,...

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“…These processes resulted in the development of a cylindrical laccolith that is morphologically similar to a bysmalith with gently outward dipping external contacts (Habert & De Saint-Blanquat 2004;Horsman et al 2010). However, as it has an up-faulted roof, this intrusion is best described as a punched laccolith (Corry 1988).…”

Section: Mechanism Of Emplacementmentioning

confidence: 95%

Distinguishing diapirs from inflated plutons: an integrated rock magnetic fabric and structural study on the Roundstone Pluton, western Ireland

McCarthy

Petronis

Reavy

et al. 2015

JGS

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Granitoid plutons account for much of the continental crust and are critical in the generation of several economic resources. Despite over a century of research, the fundamental process by which large felsic bodies intrude remains controversial. Two contrasting models persist: (1) mass ascent and subsequent cooling of magma (diapirism); (2) sheet ascent and subsequent emplacement (laccoliths). The latter hypothesis is different from the former as distinct ascent and emplacement processes must occur and be identifiable; traditional field methods rarely allow this important distinction to be made. We present field, petrographic and anisotropy of magnetic susceptibility data from the Roundstone Pluton, Connemara, western Ireland, which was previously considered a diapiric intrusion. The new data reveal anomalous subvertical magmatic lineations in the core of this circular intrusion as well as a suite of magmatic and submagmatic fabrics that parallel NNW-SSE country rock faults and coeval G2 sheets within the pluton. We deduce that these structures reflect a distinct centralized ascent process along a NNW-SSE conduit. Lateral emplacement and pluton inflation followed, ultimately forming a punched laccolith. We conclude that the combined application of the above techniques provides a unique insight into pluton architecture that removes ambiguity between contrasting diapiric and inflated pluton models.Supplementary material: Complete rock magnetic data tables and sample site coordinates (Irish Grid) are available at

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Emplacement and assembly of shallow intrusions from multiple magma pulses, Henry Mountains, Utah

Cited by 24 publications

References 53 publications

Mapping real time growth of experimental laccoliths: The effect of solidification on the mechanics of magmatic intrusion

Mapping real time growth of experimental laccoliths: The effect of solidification on the mechanics of magmatic intrusion

Ignimbrites to batholiths: Integrating perspectives from geological, geophysical, and geochronological data

Distinguishing diapirs from inflated plutons: an integrated rock magnetic fabric and structural study on the Roundstone Pluton, western Ireland

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