Pascal’s Principle, a Simple Model to Explain the Emplacement of Laccoliths and Some Mid-crustal Plutons

Morgan, Sven

doi:10.1016/b978-0-12-809749-6.00006-6

Cited by 11 publications

(14 citation statements)

References 58 publications

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“…The internal structure of Cerro Bayo resembles that of both continuously inflating laccoliths and lava domes. Stages I and II of the emplacement of Cerro Bayo are in agreement with sill inflation, dome‐shaped laccolith growth, and host rock “punching” (i.e., faulting) reported for other laccoliths (Morgan, ) and the endogenous growth of lava domes. Stage III, however, has not been described for laccoliths, which continue to grow as “bysmaliths” by vertically lifting their overburden on the faults surrounding the intrusion (Morgan, ).…”

Section: Discussionsupporting

confidence: 84%

“…The steeply dipping, concentric shear zones in the margin of the cryptodome (Figure b) and faults in the host rock near the intrusion (Figures a and b) enabled vertical growth, giving the intrusion the shape of a punched laccolith or bysmalith (cf. Morgan, , and references therein).…”

Section: Discussionmentioning

confidence: 99%

“…Journal of Geophysical Research: Solid Earth 2018) and the endogenous growth of lava domes. Stage III, however, has not been described for laccoliths, which continue to grow as "bysmaliths" by vertically lifting their overburden on the faults surrounding the intrusion (Morgan, 2018). In contrast, Stage III of the growth of Cerro Bayo resembled the exogenous growth of lava domes through the emplacement of spines that pierce through the previously extruded magma.…”

Section: 1029/2019jb017543mentioning

confidence: 99%

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Progressive Growth of the Cerro Bayo Cryptodome, Chachahuén Volcano, Argentina—Implications for Viscous Magma Emplacement

et al. 2019

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Cryptodome and dome collapse is associated with volcanic hazards, such as explosive eruptions, pyroclastic density currents, and volcanic edifice collapse. The study of the growth and evolution of volcanic domes provides vital information on the link between dome growth and the development of weakness zones that may cause collapse. The Cerro Bayo cryptodome is superbly exposed in the eroded Miocene Chachahuén volcano in the Neuquén basin, Argentina. Cerro Bayo is a >0.3‐km3 trachyandesitic cryptodome that intruded within the uppermost kilometer of the Chachahuén volcano. Here we investigate the emplacement of the Cerro Bayo cryptodome using structural mapping, photogrammetry and measurement of magma flow indicators, brittle deformation features, and magnetic fabrics with anisotropy of magnetic susceptibility. Magma flow fabrics near the margin are concentric and indicate contact‐parallel flow and internal inflation of the body. Magmatic and magnetic fabrics and fracture patterns in the interior of the cryptodome are more complex and outline several structural domains. These domains are separated by magmatic shear zones that accommodated intrusion growth. The shear zones locally overprint the earlier formed concentric fabric. The nature of the structural domains shows that the emplacement of Cerro Bayo occurred in three stages that resemble the endogenous to exogenous growth of volcanic domes. The formation of magmatic shear zones during cryptodome formation may have a profound effect on cryptodome stability by creating weakness zones that increase the risk of collapse.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: 1029/2019jb017543mentioning

confidence: 99%

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Progressive Growth of the Cerro Bayo Cryptodome, Chachahuén Volcano, Argentina—Implications for Viscous Magma Emplacement

et al. 2019

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“…The aureole to the Eastern Mourne pluton therefore records different stages of emplacement of the granite. A pattern of initial alteration followed by deformation has also been documented in aureoles to other plutons (see Morgan et al, 1998;Morgan, 2018). The deformed contact-metamorphic segregations in the host rock could reflect different laccolith growth stages, where the initial sill emplacement is accommodated by elastic deformation of the host rock (e.g., Pollard and Johnson, 1973;Jackson and Pollard, 1990;Bunger and Cruden, 2011;Michaut, 2011).…”

Section: Deformation In the Contact-metamorphic Aureolementioning

confidence: 73%

Host-rock deformation during the emplacement of the Mourne Mountains granite pluton: Insights from the regional fracture pattern

et al. 2019

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The Mourne Mountains magmatic center in Northern Ireland consists of five successively intruded granites emplaced in the upper crust. The Mourne granite pluton has classically been viewed as a type locality of a magma body emplaced by cauldron subsidence. Cauldron subsidence makes space for magma through the emplacement of ring dikes and floor subsidence. However, the Mourne granites were more recently re-interpreted as laccoliths and bysmaliths. Laccolith intrusions form by inflation and dome their host rock. Here we perform a detailed study of the deformation in the host rock to the Mourne granite pluton in order to test its emplacement mechanism. We use the host-rock fracture pattern as a passive marker and microstructures in the contact-metamorphic aureole to constrain large-scale magma emplacement-related deformation. The dip and azimuth of the fractures are very consistent on the roof of the intrusion and can be separated into four steeply inclined sets dominantly striking SE, S, NE, and E, which rules out pluton-wide doming. In contrast, fracture orientations in the northeastern wall to the granites suggest shear parallel to the contact. Additionally, contact-metamorphic segregations along the northeastern contact are brecciated. Based on the host-rock fracture pattern, the contact aureole deformation, and the north-eastward–inclined granite-granite contacts, we propose that mechanisms involving either asymmetric “trap-door” floor subsidence or laccolith and bysmalith intrusion along an inclined or curved floor accommodated the emplacement of the granites and led to deflection of the northeastern wall of the intrusion.

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“…There is little geophysical evidence for large melt-dominated magma chambers in active volcanic areas, however, causing researchers to propose that large magma bodies are transient and that magmatic systems are instead dominated by partially crystalline "magma mush" with small melt fractions (Glazner et al, 2004;Annen et al, 2015;Sparks et al, 2019). An emerging view is that magma chambers are emplaced incrementally via amalgamation of numerous smaller intrusions into a single body, so that at any one time, only a small fraction of the chamber is molten (Glazner et al, 2004;Menand, 2011;Michaut and Jaupart, 2011;Annen et al, 2015;Morgan, 2018).…”

Section: Introductionmentioning

confidence: 99%

A Baltic heritage in Scotland: Basement terrane transfer during the Grenvillian orogeny

Strachan

Johnson

Kirkland

et al. 2020

Geology

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Archean basement inliers within the Northern Highland terrane (NHT), Scottish Caledonides, have been correlated with the Lewisian Gneiss Complex of the Laurentian foreland. New zircon U-Pb ages indicate that the NHT basement contains evidence for magmatism at 2823–2687 Ma and 1772–1655 Ma. The first group compares with crystallization ages of the foreland Archean gneisses. However, the second group, and a supracrustal unit, formed ~100–250 m.y. after the youngest major phase of juvenile magmatism and sedimentation in the foreland. Also, there is no indication within the NHT basement of the Paleoproterozoic mafic and felsic intrusions common within the foreland, leading us to conclude that there is no firm basis for correlation of the two crustal blocks. The Caledonian Moine thrust, which separates the foreland and the NHT basement, is thought to have reworked a Grenvillian suture indicated by the presence of the ca. 1100–1000 Ma Eastern Glenelg eclogites. On the basis of the new isotopic data, we propose that the NHT basement was a fragment of Baltica that was emplaced onto Laurentia during the Grenvillian orogeny, representing a further example of basement terrane transfer in the circum–North Atlantic orogens.

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Pascal’s Principle, a Simple Model to Explain the Emplacement of Laccoliths and Some Mid-crustal Plutons

Cited by 11 publications

References 58 publications

Progressive Growth of the Cerro Bayo Cryptodome, Chachahuén Volcano, Argentina—Implications for Viscous Magma Emplacement

Progressive Growth of the Cerro Bayo Cryptodome, Chachahuén Volcano, Argentina—Implications for Viscous Magma Emplacement

Host-rock deformation during the emplacement of the Mourne Mountains granite pluton: Insights from the regional fracture pattern

A Baltic heritage in Scotland: Basement terrane transfer during the Grenvillian orogeny

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