The role of magma chamber-fault interaction in caldera forming eruptions

Simakin, A. G.; Ghassemi, Ahmad

doi:10.1007/s00445-009-0306-6

Cited by 27 publications

(30 citation statements)

References 39 publications

(57 reference statements)

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“…Subsequent analysis of the interaction between magma batches and a rising dike often employs consideration of the principle stress (σ 1 ) directions around a magma reservoir, defi ning approximate trajectories for diking via hydraulic fracturing of rocks (Jellinek and DePaolo, 2003;Simakin and Ghassemi, 2010;Karlstrom et al, 2012). This analysis leads to the observation that for the overpressurized deep spherical magma reservoir (equally inelas-tic, viscoelastic, or viscous media), σ 1 directions are such that the greatest compressive stress is radial to the magma body and σ 3 is tangential (Fig.…”

Section: Formation Of Magma Sills and Batchesmentioning

confidence: 99%

“…Pressure lower than lithostatic may develop in a magma body with a low supply fl ux during the solidifi cation of magma due to the volume effect of crystallization and escape of exsolved fl uid phases, and due to extensional tectonics. Numerical simulations of viscoelastic elliptic chambers (see Simakin and Ghassemi, 2010) demonstrated that at magma pressures lower than lithostatic pressures, expressed through the bottom-parallel σ 1 stress directions, the rock envelope presses into the chamber and undergoes radial extension. These arguments support accumulation of newly arriving batches of magma into a single growing magma body in sites of active magma generation and high intrusion rate.…”

Section: Formation Of Magma Sills and Batchesmentioning

confidence: 99%

“…An additional factor promoting separate magma batch formation may be preexisting oblique faults that serve as structural traps for rising magmas and relieve stress from overpressured magma bodies ( Fig. 9B; Simakin and Ghassemi, 2010). This is particularly relevant for Basin and Range faults and extension along the SRP (Fig.…”

Section: Formation Of Magma Sills and Batchesmentioning

confidence: 99%

“…Overpressure defi nes the amplitude of the induced stress, and for the expanded two-dimensional (2-D) circular shell around a magma body it was shown to be (e.g., Jellinek and DePaolo, 2003;Simakin and Ghassemi, 2010):…”

Section: Effects Of Overpressurementioning

confidence: 99%

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Rhyolites—Hard to produce, but easy to recycle and sequester: Integrating microgeochemical observations and numerical models

Bindeman

Simakin

2014

Geosphere

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Recent discoveries of isotopically diverse minerals, i.e., zircons, quartz, and feldspars, in large-volume ignimbrites and smaller lavas from the Snake River Plain (SRP; Idaho, USA), Iceland, Kamchatka Peninsula, and other environments suggest that this phenomenon characterizes many silicic units studied by in situ methods. This observation leads to the need for new models of silicic magma petrogenesis that involve double or triple recycling of zircon-saturated rocks. Initial partial melts are produced in small quantities in which zircons and other minerals undergo solution reprecipitation and inherit isotopic signatures of the immediate environment of the host magma batch. Next, isotopically diverse polythermal magma batches with inherited crystals merge together into larger volume magma bodies, where they mix and then erupt. Concave-up and polymodal crystal size distributions of zircons and quartz observed in large-volume ignimbrites may be explained by two or three episodes of solution and reprecipitation. Hafnium isotope diversity in zircons demonstrates variable mixing of crustal melts and mantle-derived silicic differentiates. The low δ 18 O values of magmas with δ 18 O-diverse zircons indicate that magma generation happens by remelting of variably hydrothermally altered, and thus diverse in δ 18 O, protoliths from which the host magma batch, minute or voluminous, inherited low-δ 18 O values. This also indicates that the processes that generate zircon diversity happen at shallow depths of a few kilometers, where meteoric water can circulate at large water/rock ratios to imprint low δ 18 O values on the protolith. We further review newly emerging isotopic evidence of diverse zircons and their appearance at the end of the magmatic evolution of many longlived large-volume silicic centers in the SRP and elsewhere, evidence indicating that the genesis of rhyolites by recycling their sometimes hydrothermally altered subsolidus predecessors may be a common evolutionary trend for many rhyolites worldwide, especially in hotspot and rift environments with high magma and heat fl uxes. Next, we use thermomechanical fi nite element modeling of rhyolite genesis and to explain (1) the formation of magma batches in stress fi elds by dike capture or defl ection as a function of underpressurization and overpressurization, respectively; (2) the merging of neighboring magma batches together via four related mechanisms: melting through the screen rock and melt zone expansion, brittle failure of a separating screen of rocks, buoyant merging of magmas, and explosive merging by an overpressurized interstitial fl uid phase (heated meteoric water); and (3) mixing time scales and their effi cacies on extended horizontal scales, as expressed by marker method particle tracking. The en visioned advective thermomechanical mechanisms of magma segregation in the upper crust may characterize periods of increased basaltic output from the mantle, leading to increased silicic melt production, but may also serve as analogues for magma chambers ...

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Section: Formation Of Magma Sills and Batchesmentioning

confidence: 99%

Section: Formation Of Magma Sills and Batchesmentioning

confidence: 99%

Section: Formation Of Magma Sills and Batchesmentioning

confidence: 99%

Section: Effects Of Overpressurementioning

confidence: 99%

See 2 more Smart Citations

Rhyolites—Hard to produce, but easy to recycle and sequester: Integrating microgeochemical observations and numerical models

Bindeman

Simakin

2014

Geosphere

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“…Grouping of dikes in certain directions is less dependent on the magma chamber overpressure and is controlled by regional tectonic stresses (Nakamura, 1977;Acocella and Neri, 2009). The size and configuration of volcanic edifice and magma reservoir, and the edifice load also may have effect on the direction of the dike emplacement (e.g., Pinel and Jaupart, 2003;Simakin and Chassemi, 2009). Fig.…”

Section: The Position Of Dikes In the Old Shiveluch Edifice And Prerementioning

confidence: 99%

Volcanic structure and composition of Old Shiveluch volcano, Kamchatka

Gorbach

Portnyagin

Тембрел

2013

Journal of Volcanology and Geothermal Research

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. The pronounced change in the Shiveluch magma compositions could have been related to adjustments of the magma plumbing system beneath Old Shiveluch following the large scale sector collapse in the Late Pleistocene that enabled a common mixing of evolved and primitive magmas on the later, Holocene stage of the volcano evolution.

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The Role of Pore Fluid Pressure on the Failure of Magma Reservoirs: Insights From Indonesian and Aleutian Arc Volcanoes

2018

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We use numerical models to study the mechanical stability of magma reservoirs embedded in elastic host rock. We quantify the overpressure required to open tensile fractures (the failure overpressure), as a function of the depth and the size of the reservoir, the loading by the volcanic edifice, and the pore fluid pressure in the crust. We show that the pore fluid pressure is the most important parameter controlling the magnitude of the failure overpressure rather than the reservoir depth and the edifice load. Under lithostatic pore fluid pressure conditions, the failure overpressure is on the order of the rock tensile strength (a few tens of megapascals). Under zero pore fluid pressure conditions, the failure overpressure increases linearly with depth (a few hundreds of megapascals at 5 km depth). We use our models to forecast the failure displacement (the cumulative surface displacement just before an eruption) on volcanoes showing unrest: Sinabung and Agung (Indonesia) and Okmok and Westdahl (Aleutian). By comparison between our forecast and the observation, we provide valuable constraint on the pore fluid pressure conditions on the volcanic system. At Okmok, the occurrence of the 2008 eruption can be explained with a 1,000 m reservoir embedded in high pore fluid pressure, whereas the absence of eruption at Westdahl better suggests that the pore fluid pressure is much lower than lithostatic. Our finding suggests that the pore fluid pressure conditions around the reservoir may play an important role in the triggering of an eruption by encouraging or discouraging the failure of the reservoir.

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The role of magma chamber-fault interaction in caldera forming eruptions

Cited by 27 publications

References 39 publications

Rhyolites—Hard to produce, but easy to recycle and sequester: Integrating microgeochemical observations and numerical models

Rhyolites—Hard to produce, but easy to recycle and sequester: Integrating microgeochemical observations and numerical models

Volcanic structure and composition of Old Shiveluch volcano, Kamchatka

The Role of Pore Fluid Pressure on the Failure of Magma Reservoirs: Insights From Indonesian and Aleutian Arc Volcanoes

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