Experimental evidence for fluidization processes in breccia pipe formation

McCallum, M. E.

doi:10.2113/gsecongeo.80.6.1523

Cited by 74 publications

(40 citation statements)

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“…This assertion was clearly validated by the field evidences (for active and fossil phreatomagmatic manifestations) as well as by experiments (McCallum, 1985).…”

Section: Matrixsupporting

confidence: 60%

“…The clasts from this zone are more rounded, but their size has considerably diminished. The rock fragments prove a longer term processing within the pipe because they were brought about into the fluidization cell (McCallum, 1985). The fluidization channel is usually located on the axial part of the pipe, but there are also field evidences that suggest that it could be also eccentrically situated (Ro¿ia Montan¾ , Romania, T¾ ma¿, 2002).…”

Section: Facies Changesmentioning

confidence: 99%

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Hydrovolcanic Breccia Pipe Structures-General Features and Genetic Criteria. I. Phreatomagmatic Breccias

Tămaş¹,

Milési²

2002

Studia UBB Geologia

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ABSTRACT. Two types of hydrovolcanic breccias are generally accepted: phreatomagmatic and phreatic. Due to their specific characteristics generated during the brecciation, characteristics that control the ore deposition, these breccias represent favourable hosts for mineralization. The depth of formation, the general form and dimensions, the breccia -host rock contact, as well as fragments, matrix, and open spaces altogether control the position and the size of the breccia hosted ore bodies and contribute in different degrees to the rise of the ore grades in phreatomagmatic and phreatic structures. Consequently, the recognition of the genetic type of breccia allows an appropriate strategy in mineral exploration.Describing a breccia necessarily implies a check of its general features, such as environment/depth of formation, general form/geometry, dimensions, brecciahost rock contact, fragments, matrix, alteration, mineralization, surface connection, as well as of its additional features, namely fluidization and facies changes (see Table 2). There are several characteristics with high genetic significance among the abundant descriptive features regarding breccia structures. To point out such evidences means to find out the keys for the genetic intrepretation. A complete list of genetic criteria is proposed for phreatomagmatic breccias (see Table 3).

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“…This assertion was clearly validated by the field evidences (for active and fossil phreatomagmatic manifestations) as well as by experiments (McCallum, 1985).…”

Section: Matrixsupporting

confidence: 60%

Section: Facies Changesmentioning

confidence: 99%

Hydrovolcanic Breccia Pipe Structures-General Features and Genetic Criteria. I. Phreatomagmatic Breccias

Tămaş¹,

Milési²

2002

Studia UBB Geologia

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“…Evidence for volatile-induced fluidization of the blocks Fluidization has commonly been invoked as an emplacement mechanism for kimberlite diatremes (e.g., Lorenz 1975;McCallum 1985), and in this paper we support the suggestion of Ferguson and McCarthy (1970) that the Bushveld breccia pipe may have been similarly emplaced. Fluidization can simply be viewed as an equilibrium state wherein the buoyant weight of a bed of particles is balanced by the upward drag force on the particles created by an upwardly moving fluid (Wilson 1984;Davidson et al 1985).…”

Section: Discussionsupporting

confidence: 85%

“…The acceleration due to gravity (g) is 9.81 m/s 2 , and the viscosity of the liquid is taken to be that of water, 0.01 Pas. Although these equations were derived for small (micron scale) particles, the values obtained have generally been deemed acceptable for much larger geologic materials (e.g., Wilson 1984;McCallum 1985).…”

mentioning

confidence: 99%

Fluid overpressure in layered intrusions: formation of a breccia pipe in the Eastern Bushveld Complex, Republic of South Africa

et al. 2003

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Fluids and volatile fluid overpressures in layered intrusions are becoming recognized as having important functions in magma chamber processes for the formation of magmatic structures and for the movement and concentration of economically important ore elements. We re-examine a breccia pipe in the Bushveld Complex to investigate the role of volatile fluid overpressure in its emplacement. This 10-m-diameter breccia pipe was emplaced vertically in the anorthosite of the Upper Critical Zone of the Bushveld Complex and contains blocks of Bushveld anorthosite, norite, and pyroxenite, apparently derived from lower in the stratigraphy. The blocks are commonly elongate, and are tightly packed within an ultramafic pegmatite groundmass. Ultramafic pegmatitic dikes radiate bilaterally from the pipe. Microprobe analyses of plagioclase in the breccia pipe blocks reveal that these grains are unzoned and have higher anorthosite content ($An 85 ) than host rock plagioclase ($An 75 ), indicating that the breccia pipe blocks were transported considerable vertical distances. Whole-rock major-and trace-element data show enrichment in fluid-soluble incompatible elements, supporting the role of volatile fluids in the formation of the pipe. A model is examined in which the segregation of a fluid phase from interstitial liquids in the cumulate section below the breccia pipe leads to the development of sufficient overpressure for its explosive emplacement. Fluid overpressure can develop by compaction and during crystallization of plagioclase-saturated silicate liquids as fluids exsolve from the solidifying interstitial liquid. If fluids separate faster than they can escape from the crystal pile, significant overpressures can develop. The minimum fluidization velocity which would be required to emplace blocks of the size and density found within the breccia pipe is found to be 10-110 m/s. The crystallization model predicts the development of about 400 bar of overpressure, an amount calculated to be sufficient for pipe emplacement.

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“…These pioneering experiments did not address fluidisation processes, however, which geological observations suggest is prominent during diatreme and breccia pipe formation. In contrast, the later experiments of Woolsey et al (1975) and McCallum (1985) did so. These authors used granular materials of various grain sizes (clay to gravels) and cohesions to simulate the behaviour (Galland et al, 2006) ( Román-Berdiel et al, 1997) (Montanari et al, 2010a) (Galland et al, 2007a) (a)…”

Section: Explosive Volcanic Ventsmentioning

confidence: 60%

Laboratory Modelling of Volcano Plumbing Systems: A Review

Galland

Holohan

Vries

et al. 2015

Advances in Volcanology

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We review the numerous experimental studies dedicated to unravelling the physics and dynamics of various parts of a volcanic plumbing system. Section 1 lists the model materials commonly used for model magmas or model rocks. We describe these materials' mechanical properties and discuss their suitability for modelling sub-volcanic processes. Section 2 examines the fundamental concepts of dimensional analysis and similarity in laboratory modelling. We provide a step-by-step explanation of how to apply dimensional analysis to laboratory models in order to identify fundamental physical laws that govern the modelled processes in dimensionless (i.e. scale independent) form. Section 3 summarises and discusses the past applications of laboratory models to understand numerous features of volcanic plumbing systems. These include: dykes, cone sheets, sills, laccoliths, caldera-related structures, ground deformation, magma/fault interactions, and explosive vents. We outline how laboratory models have yielded insights into the main geometric and mechanical controls on the development of each part of the volcanic

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Experimental evidence for fluidization processes in breccia pipe formation

Cited by 74 publications

References 0 publications

Hydrovolcanic Breccia Pipe Structures-General Features and Genetic Criteria. I. Phreatomagmatic Breccias

Hydrovolcanic Breccia Pipe Structures-General Features and Genetic Criteria. I. Phreatomagmatic Breccias

Fluid overpressure in layered intrusions: formation of a breccia pipe in the Eastern Bushveld Complex, Republic of South Africa

Laboratory Modelling of Volcano Plumbing Systems: A Review

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