Diatremes with Kimberlitic Affinities in North-Central Montana

Hearn, B.C.

doi:10.1126/science.159.3815.622

Cited by 105 publications

(43 citation statements)

References 9 publications

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“…At the current levels of exposure, the Paleogene Missouri River Breaks diatremes (Montana) are filled mostly by deeply subsided tuff and lapilli tuff beds (Hearn, 1968; author's observations). Each bed was originally deposited on the syn-eruptive crater floor, yet the bedded sequence in these diatremes extends to more than one kilometer below the pre-eruptive ground surface.…”

Section: Upper Diatremementioning

confidence: 95%

“…Among three highly influential summary diatreme descriptions published in the 20 th century (Hearn, 1968;Lorenz, 1973;Hawthorne, 1975), a key difference is the presence or absence of bedded volcaniclastic deposits of inferred primary origin within the upper diatreme. Some diatremes preserve only unbedded pyroclastic deposits overlain by sediments deposited in the post-eruptive maar crater, whereas others contain great thicknesses of bedded pyroclastic deposits in their upper part.…”

Section: Upper Diatremementioning

confidence: 99%

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Maar-diatreme volcanoes: A review

White

Ross

2011

Journal of Volcanology and Geothermal Research

342

251

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Maar-diatreme volcanoes are produced by explosive eruptions that cut deeply into the country rock. A maar is the crater cut into the ground and surrounded by an ejecta ring, while the diatreme structure continues downward and encloses diatreme and root zone deposits. Here we attempt an evenhanded review of maardiatreme volcanology that extends from mafic to kimberlitic varieties, and from historical maar eruptions to deeply eroded or mined diatreme structures. We conclude that maar-diatreme eruptions are episodic. Ejecta rings provide invaluable insight into eruption processes and sequence, but are incomplete records of diatreme formation. Deposits within the diatreme structure include, in varying proportions, lower unbedded deposits sometimes typified by subvertical contacts among domains of debris emplaced sequentially, and upper bedded deposits formed by sedimentation on surfaces open to the atmosphere. A basal root zone comprises the transition from coherent magmatic feeder dike to clastic deposits formed by fragmentation of magma and enclosing country rock; root zones are irregular in form, and the clastic deposits are typically intruded by contorted dikes. Irregular root zone-like chaotic breccias cut by contorted dikes are also present within diatreme deposits, where they represent intra-diatreme fragmentation zones and record changes in the location of the explosion locus during eruption.

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Section: Upper Diatremementioning

confidence: 95%

Section: Upper Diatremementioning

confidence: 99%

Maar-diatreme volcanoes: A review

White

Ross

2011

Journal of Volcanology and Geothermal Research

342

251

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“…1a, 1c). If repeated several times such injections -whether erupting or wholly subterranean -, accompanied by collapsecapture of a central zone of initially upward-driven material, provide a compelling explanation for the origin and characteristics of multiple cross-cutting bodies that have been documented for diatreme deposits (e.g., Hearn 1968;White, 1991;Naidoo et al, 2004;Nowicki et al, 2004;Stiefenhofer and Farrow, 2004;Webb et al, 2004;McClintock and White, 2006;Ross and White, 2006). A key conclusion from our experiments is that the geometry of cross-cutting granular deposits is not directly informative of the geometry of the "intrusions" that formed them.…”

Section: Applicability To Diatremesmentioning

confidence: 99%

Multiphase flow above explosion sites in debris-filled volcanic vents: Insights from analogue experiments

Ross

White

Zimanowski

et al. 2008

Journal of Volcanology and Geothermal Research

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Discrete explosive bursts are known from many volcanic eruptions. In maar-diatreme eruptions, they have occurred in debris-filled volcanic vents when magma interacted with groundwater, implying that material mobilized by such explosions passed through the overlying and enclosing debris to reach the surface. Although other studies have addressed the form and characteristics of craters formed by discrete explosions in unconsolidated material, no details are available regarding the structure of the disturbed debris between the explosion site and the surface. Field studies of diatreme deposits reveal cross-cutting, steep-sided zones of non-bedded volcaniclastic material that have been inferred to result from sedimentation of material transported by "debris jets" driven by explosions. In order to determine the general processes and deposit geometry resulting from discrete, explosive injections of entrained particles through a particulate host, we ran a series of analogue experiments. Specific volumes of compressed (0.5-2.5 MPa) air were released in bursts that drove gas-particle dispersions through a granular host. The air expanded into and entrained coloured particles in a small crucible before moving upward into the host (white particles). Each burst drove into the host an expanding cavity containing air and coloured particles. Total duration of each run, recorded with high-speed video, was approximately 0.5-1 second. The coloured beads sedimented into the transient cavity. This same behaviour was observed even in runs where there was no breaching of the surface, and no coloured beads ejected. A steep-sided body of coloured beads was left that is similar to the cross-cutting pipes observed in deposits filling real volcanic vents, in which cavity collapse can result not only from gas escape through a granular host as in the experiments, but also through condensation of water vapour. A key conclusion from these experiments is that the geometry of cross-cutting volcaniclastic deposits in volcanic vents is not directly informative of the geometry of the "intrusions" that formed them. An additional conclusion is that complex structures can form quickly from discrete events.

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“…A diatreme is the subsurface part of a maar volcano [47,170]. To express the close relationship between maar and diatreme, they are commonly referred to as maardiatreme volcanoes [171].…”

Section: Intrusive Forms Related To Na-alkalic and Ultrapotassic Rocksmentioning

confidence: 99%

Neogene-Quaternary Volcanic forms in the Carpathian-Pannonian Region: a review

et al. 2010

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Neogene to Quaternary volcanic/magmatic activity in the Carpathian-Pannonian Region (CPR) occurred between 21 and 0.1 Ma with a distinct migration in time from west to east. It shows a diverse compositional variation in response to a complex interplay of subduction with roll-back, back-arc extension, collision, slab break-off, delamination, strike-slip tectonics and microplate rotations, as well as in response to further evolution of magmas in the crustal environment by processes of differentiation, crustal contamination, anatexis and magma mixing. Since most of the primary volcanic forms have been affected by erosion, especially in areas of post-volcanic uplift, based on the level of erosion we distinguish: (1) areas eroded to the basement level, where paleovolcanic reconstruction is not possible; (2) deeply eroded volcanic forms with secondary morphology and possible paleovolcanic reconstruction; (3) eroded volcanic forms with remnants of original morphology preserved; and (4) the least eroded volcanic forms with original morphology quite well preserved. The large variety of volcanic forms present in the area can be grouped in a) monogenetic volcanoes and b) polygenetic volcanoes and their subsurface/intrusive counterparts that belong to various rock series found in the CPR such as calc-alkaline magmatic rock-types (felsic, intermediate and mafic varieties) and alkalic types including K-alkalic, shoshonitic, ultrapotassic and Na-alkalic. The following volcanic/subvolcanic forms have been identified: (i) domes, shield volcanoes, effusive cones, pyroclastic cones, stratovolcanoes and calderas with associated intrusive bodies for intermediate and basic calc-alkaline volcanism; (ii) domes, calderas and ignimbrite/ash-flow fields for felsic calc-alkaline volcanism and (iii) dome flows, shield volcanoes, maars, tuffcone/tuff-rings, scoria-cones with or without related lava flow/field and their erosional or subsurface forms (necks/ plugs, dykes, shallow intrusions, diatreme, lava lake) for various types of K-and Na-alkalic and ultrapotassic magmatism. Finally, we provide a summary of the eruptive history and distribution of volcanic forms in the CPR using several sub-region schemes.

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Diatremes with Kimberlitic Affinities in North-Central Montana

Cited by 105 publications

References 9 publications

Maar-diatreme volcanoes: A review

Maar-diatreme volcanoes: A review

Multiphase flow above explosion sites in debris-filled volcanic vents: Insights from analogue experiments

Neogene-Quaternary Volcanic forms in the Carpathian-Pannonian Region: a review

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