Chapter 6. The Fracture Mechanisms of Magma Transport From The Mantle to The Surface

Shaw, Herbert R.

doi:10.1515/9781400854493.201

Cited by 245 publications

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“…states of stress, c.) mechanical properties of the lithosphere, and d.) density contrast between magma and country rock, where lower density lithologies act as barriers for denser magma (cf. Shaw 1980;Stolper and Walker 1980;Gudmundsson 1986;Kuntz 1992;Yang et al 1999;. Below Anak Krakatau, the crust can be broadly divided into three main lithological packages (Fig.…”

Section: Discussionmentioning

confidence: 99%

Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions

Dahrén

Troll

Andersson

et al. 2011

Contrib Mineral Petrol

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Understanding magma plumbing is essential for predicting the behaviour of explosive volcanoes. We investigate magma plumbing at the highly active Anak Krakatau volcano (Indonesia), situated on the rim of the 1883 Krakatau caldera by employing a suite of thermobarometric models. These include, clinopyroxene-melt thermobarometry, plagioclasemelt thermobarometry, clinopyroxene composition barometry and olivine-melt thermometry. Petrological studies have previously identified shallow magma storage in the region of 2-8 km beneath Krakatau, while existing seismic evidence points towards midto deep-crustal storage zone(s), at 9 and 22 km respectively. Our results show that clinopyroxene in Anak Krakatau lavas crystallized at a depth of 7-12 km, while plagioclase record both shallow crustal (3-7 km) and sub-Moho (23-28 km) levels of crystallisation. These magma storage regions coincide with well constrained major lithological boundaries in the crust, implying that magma ascent and storage at Anak Krakatau is strongly controlled by crustal properties. A tandem seismic tomography survey independently identified a separate upper crustal (< 7 km) and a lower to mid-crustal magma storage region (> 7 km). Both petrological and seismic methods are sensitive in detecting magma bodies in the crust, but suffer from various limitations. Combined geophysical and petrological surveys, in turn, offer increased potential for a comprehensive characterization of magma plumbing at active volcanic complexes.

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Section: Discussionmentioning

confidence: 99%

Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions

Dahrén

Troll

Andersson

et al. 2011

Contrib Mineral Petrol

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“…For tensile cracks to form by hydraulic fracturing, the pore fluid pressure must exceed the magnitude of the least principal stress by the tensile strength of the rock (e.g. Secor, 1965;Shaw, 1980). The condition for hydraulic fracturing is commonly written as P fluid Rs 3 CT, with T denoting tensile strength, s 3 the least principal stress and P fluid the pore fluid pressure.…”

Section: Microcrack Density As a Function Of Distance From The Centramentioning

confidence: 99%

“…Furthermore, for purely tensile failure to occur, the differential stress s 1 Ks 3 is restricted to less than about 4T, based on the form of the Griffith failure envelope (e.g. Shaw, 1980;Suppe, 1985). This strength criterion holds until failure is initiated.…”

Section: Microcrack Density As a Function Of Distance From The Centramentioning

confidence: 99%

“…For tensile cracks to form by hydraulic fracturing, the fluid pressure must exceed the magnitude of the least principal stress by the tensile strength of the rock (e.g. Secor, 1965;Shaw, 1980) or, in fracture mechanics terminology, exceed the fracture toughness of the rock. Upon cooling and crystallisation, the portion of volatiles in the pegmatitic melt that is not incorporated into minerals is liberated as a fluid phase (Burnham, 1979).…”

Section: Introductionmentioning

confidence: 99%

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Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Engvik

Bertram

Kalthoff

et al. 2005

Journal of Structural Geology

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Excellent outcrops in Dronning Maud Land, Antarctica, provide unique insight into the mode and extent of fluid infiltration into metamorphic and plutonic rocks in the middle crust. The fluids are liberated from pegmatitic veins and give rise to alteration halos. In the alteration halos, the conspicuous change in colour is correlated with (1) hydration mineral reactions, and (2) high density of microcracks in quartz and feldspar exceeding that observed in the unaltered host rock by an order of magnitude. The field relations indicate that the veins originated as melt-driven hydraulic fractures, sealed by pegmatite and aplite crystallising from volatile-rich melts, with the alteration halo being the wake of the process zone formed at the tip of the propagating fractures. It is proposed that (1) the size of the alteration zone and the width of the vein are correlated, resulting in higher values of both these quantities for cracks propagating at higher velocities and consequently higher crack propagation toughnesses; (2) the damage zone is characterised by a transient state of high permeability which was short-lived due to rapid healing and sealing of microcracks; (3) the infiltration and retrogression of the high-grade rocks can be considered as a quasi-instantaneous process on geologic time scales with a duration of hours to weeks. q

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“…The mechanical properties of crystal-glass silicates of volcanic origin under high temperature and low-pressure conditions have not been sufficiently investigated (Ryan & Sammis, 1981) for modelling of volcanological processes. The need for such data remains and is becoming essential as the importance of brittle failure of volcanic rocks at high temperatures both at surface levels (fracturing of lava flows) and at magmatic levels (fracturing of the country rock surrounding the magma chamber) becomes widely recognised (Blake and Bruno, 2000;Kilburn, 1993;1996, Shaw, 1980.…”

Section: ) Introductionmentioning

confidence: 99%

Fracture toughness measurements on igneous rocks using a high-pressure, high-temperature rock fracture mechanics cell

Balme

Rocchi

Jones

et al. 2004

Journal of Volcanology and Geothermal Research

165

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How to cite:Balme, M.R.; Rocchi, V.; Jones, C.; Sammonds, P.R.; Meredith, P.G. and Boon, S. (2004). Fracture toughness measurements on igneous rocks using a high-pressure, high-temperature rock fracture mechanics cell. Journal of Volcanology and Geothermal Research, ABSTRACTA sound knowledge of mechanical properties of rocks at high temperatures and pressures is essential for modelling volcanological problems such as fracture of lava flows and dike emplacement. In particular, fracture toughness is a scale invariant material property of a rock that describes its resistance to tensile failure. A new fracture mechanics apparatus has been constructed enabling fracture toughness measurements on large (60mm diameter) rock core samples at temperatures up to 750°C and pressures up to 50 MPa. We present a full description of this apparatus and, by plotting fracture resistance as a function of crack length, show that the size of the samples is sufficient for reliable fracture toughness measurements. A series of tests on Icelandic, Vesuvian and Etnean basalts at temperatures from 30-600 o C and confining pressures up to 30 MPa gave fracture toughness values between 1.4 and 3.8 MPam 1/2 . The Icelandic basalt is the strongest material and the Etnean material sampled from the surface crust of a lava flow the weakest. Increasing temperature does not greatly affect the fracture toughness of the Etnean or Vesuvian material but the Icelandic samples showed a marked increase in toughness at around 150 o C, followed by a return to ambient toughness levels. This material also became tougher under moderate confining pressure but the other two materials showed little change in toughness. We describe in terms of fracture mechanics probable causes for the changes in fracture toughness and compare our experimental results with values obtained from dike propagation modelling found in the literature.

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Chapter 6. The Fracture Mechanisms of Magma Transport From The Mantle to The Surface

Cited by 245 publications

References 0 publications

Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions

Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions

Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Fracture toughness measurements on igneous rocks using a high-pressure, high-temperature rock fracture mechanics cell

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