Deformation of host rocks and flow of magma during growth of minette dikes and breccia-bearing intrusions near Ship Rock, New Mexico

Delaney, Paul T.; Pollard, David D.

doi:10.3133/pp1202

Cited by 279 publications

(366 citation statements)

References 58 publications

Supporting

Mentioning

350

Contrasting

Unclassified

Order By: Relevance

“…[20] The estimated stress intensity factors (38 to 117 MPa m 1/2 ; average, 69 MPa m 1/2 ) fall within the range of previous field or in situ values (30 to 150 MPa m 1/2 ), as obtained in many studies [e.g., Delaney and Pollard, 1981;Rubin and Pollard, 1987;Parfitt, 1991;Rivalta and Dahm, 2006;Gudmundsson, 2009]. Thus, the estimated stress intensity factor may be regarded as reliable and appropriate for the fracture toughness of the uppermost layers of Miyake-jima because dikes are arrested.…”

Section: Discussionmentioning

confidence: 84%

“…Here overpressure is defined as the total magmatic pressure in the dike minus the minimum principal compressive (maximum tensile) stress s 3 acting on the dike walls. Many have estimated the magma overpressure based on dike thickness (or aperture for a magma-filled dike fracture) and the assumption that the host rock behaves as elastic [e.g., Delaney and Pollard, 1981;Pollard et al, 1983;Pollard and Segall, 1987]. In such studies, the following fundamental equation [e.g., Sneddon and Lowengrub, 1969] is used:…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Aspect ratios and magma overpressures of non‐feeder dikes observed in the Miyake‐jima volcano (Japan), and fracture toughness of its upper part

Kusumoto

Geshi

Guðmundsson

2013

Geophysical Research Letters

View full text Add to dashboard Cite

[1] We present a new method for estimating the length and maximum thickness (aperture) of a dike from the observed opening at one dike tip. We apply the method to 15 arrested non-feeder dikes (where the upper tip is known, the lower tip unknown) in the caldera walls of Miyake-jima, Japan, to estimate the length-thickness ratio, as well as the magma overpressure and fracture toughness. The calculated length-thickness ratio ranges from 61 to 246, with an average of 136. The ratios are low because the dikes are emplaced close to the surface in comparatively compliant (soft) rocks. Using these ratios and the appropriate elastic constants, the calculated magmatic overpressures of the dikes are between 2.3 and 8.9 MPa, and the stress intensity factors between 38 and 117 MPa m 1/2 . All these values are within the range of typical in situ estimates, supporting the validity of this new method. Citation: Kusumoto S., N.Geshi, and A. Gudmundsson (2013), Aspect ratios and magma overpressures of non-feeder dikes observed in the Miyake-jima volcano (Japan), and fracture toughness of its upper part,

show abstract

Section: Discussionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Aspect ratios and magma overpressures of non‐feeder dikes observed in the Miyake‐jima volcano (Japan), and fracture toughness of its upper part

Kusumoto

Geshi

Guðmundsson

2013

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…One should note that this estimate is weakly sensitive to the various inputs because of the small power law dependence involved and does not depend on magma buoyancy at all (see equation (A5)). Values of the fracture toughness have been measured on rock samples in the laboratory [Atkinson and Meredith, 1987] and deduced from the dimensions of dikes (breadth and thickness) in the field [Delaney and Pollard, 1981]. The two methods indicate values of about 1 and 100 MPa m 1/2 , respectively.…”

Section: Discussionmentioning

confidence: 99%

Dike propagation through layered rocks

Taisne

Jaupart

2009

J. Geophys. Res.

View full text Add to dashboard Cite

[1] Dike penetration through a succession of upper crustal layers with different densities is studied with a new numerical code. For an individual layer to significantly affect dike ascent, its thickness must be of order 1 when scaled to the characteristic length-scale for the inflated nose region that develops below the dike tip. This characteristic length is L* / (mQ) 1/6 (G/(1 À n)) 1/2 (Drg) À2/3 , where m and Dr are the viscosity and buoyancy of magma, G and n are elastic moduli for the encasing rocks, Q is the magma flow rate and g gravity. For basaltic dikes, L* is %1 km, which is of the same order of magnitude as the typical thickness of sedimentary strata and volcanic deposits. In such conditions, dike ascent proceeds irregularly, with large changes of velocity and width at an interface. Scaling laws for the ascent rate and dike width are derived. Penetration through low-density layers is determined by a local buoyancy balance in the inflated nose region of the dike, independently of the total buoyancy of the magma column between source and tip. In such conditions, a dike develops an internal overpressure that may be large enough to generate a horizontally propagating sill. For this to occur, the thickness of the low-density layers must exceed a threshold value, which depends only on the rock strength and on the average negative buoyancy of magma. For basaltic melt, we estimate that this threshold thickness cannot be less than about 700 m and is 2 km on average.

show abstract

“…However, the two dikes are only separated by about 2 km vertically, so the presence of a magma conduit between them is highly likely. The connection between both dikes is probably via another dike, as this is the most efficient means of transporting magma through the lithosphere [Rubin, 1995;Delaney and Pollard, 1981]. This dike might be too narrow to cause detectable InSAR displacements.…”

Section: Magma Originmentioning

confidence: 99%

Magma sources involved in the 2002 Nyiragongo eruption, as inferred from an InSAR analysis

Wauthier¹,

Cayol²,

Kervyn³

et al. 2012

J. Geophys. Res.

View full text Add to dashboard Cite

along a 20 km-long fracture network extending from the volcano to the city of Goma. The event was captured by InSAR data from the ERS-2 and RADARSAT-1 satellites. A combination of 3D numerical modeling and inversions is used to analyze these displacements. Using Akaike Information Criteria, we determine that a model with two subvertical dikes is the most likely explanation for the 2002 InSAR deformation signal. A first, shallow dike, 2 km high, is associated with the eruptive fissure, and a second, deeper dike, 6 km high and 40 km long, lies about 3 km below the city of Goma. As the deep dike extends laterally for 20 km beneath the gas-rich Lake Kivu, the interaction of magma and dissolved gas should be considered as a significant hazard for future eruptions. A likely scenario for the eruption is that the magma supply to a deep reservoir started ten months before the eruption, as indicated by LP events and tremor. Stress analysis indicates that the deep dike could have triggered the injection of magma from the lake and shallow reservoir into the eruptive dike. The deep dike induced the opening of the southern part of this shallow dike, to which it transmitted magma though a narrow dike. This model is consistent with the geochemical analysis, the lava rheology and the pre-and post-eruptive seismicity. We infer low overpressures (1-10 MPa) for the dikes. These values are consistent with lithostatic crustal stresses close to the dikes and low magma pressure. As a consequence, the dike direction is probably not controlled by stresses but rather by a reduced tensile strength, inherited from previous rift intrusions. The lithostatic stresses indicate that magmatic activity is intense enough to relax tensional stresses associated with the rift extension.

show abstract

Deformation of host rocks and flow of magma during growth of minette dikes and breccia-bearing intrusions near Ship Rock, New Mexico

Abstract: Page 36 38 38 41 42 45 46 48 52 magma flow in the northweastern dike may have been about 25 Pa/m (0.25 bars/km), or 0.1 percent of the weight per unit volume of magma, and that less than 1 percent of the heat convected upward from the source region was lost to wallrocks.

Cited by 279 publications

References 58 publications

Aspect ratios and magma overpressures of non‐feeder dikes observed in the Miyake‐jima volcano (Japan), and fracture toughness of its upper part

Aspect ratios and magma overpressures of non‐feeder dikes observed in the Miyake‐jima volcano (Japan), and fracture toughness of its upper part

Dike propagation through layered rocks

Magma sources involved in the 2002 Nyiragongo eruption, as inferred from an InSAR analysis

Contact Info

Product

Resources

About