Ranking welding intensity in pyroclastic deposits

Quane, Steven L.; Russell, James K.

doi:10.1007/s00445-004-0367-5

Cited by 120 publications

(75 citation statements)

References 32 publications

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“…One post-caldera unit that we sampled in the caldera floor (sc09, Cerro Evermann Fm), which was mapped as a rhyolitic flow, is the one unit that we are confident is highly welded and ignimbritic in nature (Quane and Russell, 2005). The thin section in Fig.…”

Section: Ignimbrites?mentioning

confidence: 91%

Paleomagnetic behavior of volcanic rocks from Isla Socorro, Mexico

et al. 2009

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The direction and magnitude of the geomagnetic field vary both spatially and temporally and undergo significant departures from that of a geocentric axial dipole. In order to properly characterize persistent behaviors, time-averaged field models must be based on the highest quality data. Here we present full-vector paleomagnetic data for volcanic units exposed in the southeast quadrant of the island of Socorro, Mexico. We carried out a joint expedition between the Scripps Institution of Oceanography and the Universidad Nacional Autónoma México to Isla Socorro in January of 2005 during which we collected oriented paleomagnetic samples from 21 sites, representing as many as 10 different volcanic units (the oldest of which is ∼540 ka). We subjected over 100 specimens to the most up-to-date paleointensity methods, and included the standard reliability checks. In an earlier study, Bohrson et al. (1996) proposed a series of widespread eruptive events, based on similarities of argon/argon dates. Paleointensity from specimens that conform to the strictest acceptance criteria are available from both the (unoriented) original sample collection and our fully oriented (but as yet undated) new collection. Correlation between the two collections is however problematic. The time-averaged direction from Socorro is consistent with that expected from a geocentric axial dipole, and the time-averaged intensity is 30.0±7.1 μT, equivalent to a virtual axial dipole moment (VADM) of 67.6±16.0 ZAm 2 .

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Section: Ignimbrites?mentioning

confidence: 91%

Paleomagnetic behavior of volcanic rocks from Isla Socorro, Mexico

et al. 2009

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“…Smith 1960;Quane and Russell 2005). This study demonstrates that fragmentation and deformation of crystals in pumice (and bulk ignimbrite) provide useful additional parameters for quantifying compaction and welding.…”

Section: Discussionmentioning

confidence: 80%

“…These processes are controlled by the residence time of the pyroclastic material above the glass transition temperature, the deposit thickness, the compactional load (Smith 1960;Riehle et al 1995;Quane and Russell 2005;Wright and Cashman 2014) and rates of volatile absorption by glass components (Sparks et al 1999). The degree of welding can be quantified by measuring the density and porosity of the matrix, the aspect ratios of pumice clasts (fiamme), and the deformation of glass shards (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…The degree of welding can be quantified by measuring the density and porosity of the matrix, the aspect ratios of pumice clasts (fiamme), and the deformation of glass shards (e.g. Peterson 1979;Quane and Russell 2005;Wright and Cashman 2014). Despite the large literature on welding and compaction of ignimbrites, however, there are no studies of crystal deformation during compaction.…”

Section: Introductionmentioning

confidence: 99%

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Causes of fragmented crystals in ignimbrites: a case study of the Cardones ignimbrite, Northern Chile

2018

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Broken crystals have been documented in many large-volume caldera-forming ignimbrites and can help to understand the role of crystal fragmentation in both eruption and compaction processes, the latter generally overlooked in the literature. This study investigates the origin of fragmented crystals in the > 1260 km 3 , crystal-rich Cardones ignimbrites located in the Central Andes. Observations of fragmented crystals in non-welded pumice clasts indicate that primary fragmentation includes extensive crystal breakage and an associated ca. 5 vol% expansion of individual crystals while preserving their original shapes. These observations are consistent with the hypothesis that crystals fragment in a brittle response to rapid decompression associated with the eruption. Additionally, we observe that the extent of crystal fragmentation increases with increasing stratigraphic depth in the ignimbrite, recording secondary crystal fragmentation during welding and compaction. Secondary crystal fragmentation aids welding and compaction in two ways. First, enhanced crystal fragmentation at crystal-crystal contacts accommodates compaction along the principal axis of stress. Second, rotation and displacement of individual crystal fragments enhances lateral flow in the direction(s) of least principal stress. This process increases crystal aspect ratios and forms textures that resemble mantled porphyroclasts in shear zones, indicating lateral flow adds to processes of compaction and welding alongside bubble collapse. In the Cardones ignimbrite, secondary fragmentation commences at depths of 175-250 m (lithostatic pressures 4-6 MPa), and is modulated by both the overlying crystal load and the time spent above the glass transition temperature. Under these conditions, the existence of force-chains can produce stresses at crystal-crystal contacts of a few times the lithostatic pressure. We suggest that documenting crystal textures, in addition to conventional welding parameters, can provide useful information about welding processes in thick crystal-rich ignimbrites.

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“…무등산응회암 내 용결구조는 일부 하부지역에서 잘 발견되는데 (Ahn et. al., 2014), 이러한 용결구조가 국지적으로 나타나는 이유 는 용결응회암이 형성 시에 용결구조의 발달정도가 심도에 따라 차이가 날 수 있기 때문으로 보인다 (Quane and Russell, 2005). 또한 용결구조는 화산쇄 설물이 쌓이고 탈유리화가 진행되는 과정 속에서 대 부분이 사라질 수 있다.…”

Section: 무등산응회암의 암석기재 형성 시기가 다른 천왕봉과 안양산 무등산응회암은 오랜 시간 삭박되고 암상이 유사하여unclassified

A Petrological Study of the Mudeungsan Tuff Focused on Cheonwangbong and Anyangsan

Jung¹,

Kil

Huh³

2014

The Journal of the Petrological Society of Korea

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Even though Mesozoic Mudeungsan tuff, located within Neungju Basin, has been named several rock names, it should be named as Mudeungsan tuff due to several evidences, such as fiamme, welded texture and rock fragments in the Mudeungsan tuff. Volcanic eruption boundary between the Cheonwangbong and Anyangsan areas is not clear, but petrochemical and mineral chemical evidences with different ages indicate clear petrological boundary between Cheonwangbong and Anyangsan. The Mudeungsan tuffs from Cheonwangbong and Anyangsan is welded crystal tuff with dacitic composition and were generated from cogenetic calc-alkaline magma in the volcanic arc environment. Geochemical events indicate that magma beneath Cheonwangbong was seems to have been evolved from the magma beneath Anyangsan due to fractional crystallization dominated by plagioclase.

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Ranking welding intensity in pyroclastic deposits

Cited by 120 publications

References 32 publications

Paleomagnetic behavior of volcanic rocks from Isla Socorro, Mexico

Paleomagnetic behavior of volcanic rocks from Isla Socorro, Mexico

Causes of fragmented crystals in ignimbrites: a case study of the Cardones ignimbrite, Northern Chile

A Petrological Study of the Mudeungsan Tuff Focused on Cheonwangbong and Anyangsan

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