Geometric Scaling of Tabular Igneous Intrusions: Implications for Emplacement and Growth

Cruden, A. R.; McCaffrey, Kenneth J. W.; Bunger, Andrew P.

doi:10.1007/11157_2017_1000

Cited by 33 publications

(35 citation statements)

References 94 publications

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“…The geometrical aspect ratios Π 4 = T/L for laccoliths in our experiments concur with values from field observations and seismic interpretation, i.e., 0.02-1 for laccoliths and thick sills ( Figure 4) (Bunger & Cruden, 2011;Cruden et al, 2017;de Saint-Blanquat et al, 2006;Delpino et al, 2014;Magee et al, 2017, and references therein;McCaffrey & Petford, 1997;Schmiedel et al, 2015). Thus, we conclude that our models are able to simulate the diversity of observed intrusion geometries in nature.…”

Section: Discussionsupporting

confidence: 88%

“…Thus, we conclude that our models are able to simulate the diversity of observed intrusion geometries in nature. The values of Π 4 for our model sills (0.014 to 0.02) are in the range, close to the upper bound, of those for sills in nature (0.0001 to 0.05) (Bunger & Cruden, 2011;Cruden et al, 2017;Hansen & Cartwright, 2006;Schmiedel et al, 2017). This suggests that our models simulate the emplacement of magmas that are more viscous than mafic magmas, e.g., andesite to rhyolite sills (Breitkreuz et al, 2017, and references therein).…”

Section: Discussionsupporting

confidence: 78%

“…The main difference between our models and the established elastic models of sills and laccoliths is the ability of the overburden to fail along shear fractures (Kavanagh et al, 2006;Pollard & Johnson, 1973). Several studies discuss that overburden failure is likely of primary importance for understanding magma emplacement mechanisms (e.g., Abdelmalak et al, 2012;Cruden et al, 2017;Guldstrand et al, 2017;Haug et al, 2017), and our models confirm that the elasto-plastic deformation modes of the overburden play an important role on magma emplacement. Similar to our results, the numerical models of Bunger and Cruden (2011) also reproduced the natural range of laccoliths aspect T/L ratios, up to 0.6 (Figures 1 and 4).…”

Section: Discussionmentioning

confidence: 54%

See 2 more Smart Citations

Dynamics of Sill and Laccolith Emplacement in the Brittle Crust: Role of Host Rock Strength and Deformation Mode

2017

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Igneous intrusions in sedimentary basins exhibit a great diversity of shapes from thin sheets (e.g., dikes, sills and cone sheets) to massive intrusions (e.g., laccoliths and plugs). Presently, none of the established models of magma emplacement have the capability to simulate this diversity because they account for either purely elastic or purely plastic or purely viscous host rocks, whereas natural rocks are complex visco‐elasto‐plastic materials. In this study, we investigate the effects of elasto‐plastic properties of host rock on magma emplacement using laboratory experiments made of dry granular materials of variable cohesion. Our results show how the deformation mechanism of the host rock controls the emplacement of magma: thin sheet sills form in high‐cohesion materials, which dominantly deform by elastic bending, whereas massive intrusions such as punched laccoliths form in low‐cohesion materials, which dominantly deform by shear failure. Our models also suggest that combined elastic/shear failure deformation modes likely control the emplacement of cone sheets. Our experiments are the first to spontaneously produce diverse, geologically relevant intrusion shapes. Our models show that accounting for the elasto‐plastic behavior of the host rock is essential to filling the gap between the established elastic and plastic models of magma emplacement, and so to reveal the dynamics of magma emplacement in the Earth's brittle crust.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 54%

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Dynamics of Sill and Laccolith Emplacement in the Brittle Crust: Role of Host Rock Strength and Deformation Mode

2017

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“…The geometry and volume of these intrusions are in agreement with previous work on the Questa batholith and detailed studies of laccoliths in other settings. The aspect ratios of these projected intrusions are in agreement with exposed laccoliths elsewhere (L/T = 3.3-16.7), where the thickness of the intrusive sheet is positively correlated with its length (Corry, 1988;Cruden et al, 2017). Assuming that these intrusions have geometries of ellipsoidal discs, we estimate the total volume of intrusive rock in the Questa batholith to be approximately 820 km 3 (Table 1).…”

Section: Correlating Plutonic Rocks and Bouguer Anomalysupporting

confidence: 70%

Geochronology of a Bouguer Gravity Low

et al. 2019

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Dense drill core and subsurface mapping at the Questa molybdenum mine, combined with regional structural tilt, permit detailed 3‐D documentation of plutonic rocks in the Latir magmatic center, New Mexico. Integration of mapping with new and existing U‐Pb zircon geochronology (a total of 136 analyses from 15 intrusions) allows for examination of the space‐time evolution of the Bouguer gravity low associated with the magmatic center. The Questa batholith at Latir was assembled by discrete pulses of magma over a 5.5‐Ma interval (approximately 25.3–19.8 Ma) of generally downward stacking intrusions following the volcanic peak at 25.52 Ma. This contradicts interpretations that the Bouguer gravity lows here and elsewhere are the plutonic crystal cumulate residues left after extraction of large‐volume silicic magmas. Estimates of magma flux based on the volume of plutonic rocks inferred from gravity data combined with the extrapolation of geochronology of exposed surface rocks are questionable because the assumption that unexposed plutonic rocks are the same age as dated surface rocks directly above them likely underestimates the true range of ages.

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“…Because the shape of a forced fold is typically controlled by that of the underlying forcing member (Stearns, 1978), the topographic expression of Alu may suggest that it formed above a laccolith because (1) the morphology of Alu is reminiscent of flat-topped laccoliths with steep sides (e.g., Fig. 2B) (Cruden et al, 2017); and (2) the aspect ratio of Alu (L/A = 10.1) equals the mean aspect ratio of laccoliths (L/T = 10) (Corry, 1988;McCaffrey and Petford, 1997;Bunger and Cruden, 2011). However, where underlying intrusions can be assessed, e.g., in seismic reflection data (e.g., Jackson et al, 2013), forced folds that developed above laccoliths and sills can have similar geometries (Fig.…”

Section: Origin and Growth Of The Alu Dome And Surrounding Lava Fieldmentioning

confidence: 99%

Structure and dynamics of surface uplift induced by incremental sill emplacement

Magee

Bastow

Vries

et al. 2017

Geology

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Shallow-level sill emplacement can uplift Earth's surface via forced folding, providing insight into the location and size of potential volcanic eruptions. Linking the structure and dynamics of ground deformation to sill intrusion is thus critical in volcanic hazard assessment. This is challenging, however, because (1) active intrusions cannot be directly observed, meaning that we rely on transient host-rock deformation patterns to model their structure; and (2) where ancient sill-fold structure can be observed, magmatism and deformation has long since ceased. To address this problem, we combine structural and dynamic analyses of the Alu dome, Ethiopia, a 3.5-km-long, 346-m-high, elliptical dome of outward-dipping, tilted lava flows cross-cut by a series of normal faults. Vents distributed around Alu feed lava flows of different ages that radiate out from or deflect around its periphery. These observations, coupled with the absence of bounding faults or a central vent, imply that Alu is not a horst or a volcano, as previously thought, but is instead a forced fold. Interferometric synthetic aperture radar data captured a dynamic growth phase of Alu during a nearby eruption in A.D. 2008, with periods of uplift and subsidence previously attributed to intrusion of a tabular sill at 1 km depth. To localize volcanism beyond its periphery, we contend that Alu is the first forced fold to be recognized to be developing above an incrementally emplaced saucershaped sill, as opposed to a tabular sill or laccolith.

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Geometric Scaling of Tabular Igneous Intrusions: Implications for Emplacement and Growth

Cited by 33 publications

References 94 publications

Dynamics of Sill and Laccolith Emplacement in the Brittle Crust: Role of Host Rock Strength and Deformation Mode

Dynamics of Sill and Laccolith Emplacement in the Brittle Crust: Role of Host Rock Strength and Deformation Mode

Geochronology of a Bouguer Gravity Low

Structure and dynamics of surface uplift induced by incremental sill emplacement

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