Petrologic variations in quaternary volcanic rocks, British Columbia, and the nature of the underlying upper mantle

Nicholls, J.; Stout, Mavis Z.; Fiesinger, D. W.

doi:10.1007/bf01132888

Cited by 33 publications

(11 citation statements)

References 48 publications

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“…1). These are generally considered to be related to local zones of transtension that developed along dextral transform faults between the North American and Paciµc plates (Feisinger and Nicholls, 1977;Souther, 1977;Nicholls et al, 1982;Bevier, 1983;Souther et al, 1984;Eiché et al, 1987;Francis and Ludden, 1990;Carignan et al, 1994). Typically, these volcanic centers consist of hypersthene-normative basalt to nephelinite; intermediate and felsic rocks are rarely present.…”

Section: Cretaceous To Holocene Extension In the Bering Shelf Regionmentioning

confidence: 96%

Evolution of crust and mantle beneath the Bering Sea region: Evidence from xenoliths and late Cenozoic basalts

Wirth¹,

Grandy²,

Kelley³

et al. 2002

Tectonic Evolution of the Bering Shelf-Chukchi Sea-Artic Margin and Adjacent Landmasses

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Late Cenozoic volcanic centers throughout the Bering Sea region of Alaska consist of small-volume eruptions of ×ows and cones of tholeiitic to alkaline basalt. Peridotite (spinel lherzolite, websterite, wehrlite, and pyroxenite) and gabbro xenoliths are abundant in some of the most alkaline ×ows and cones. Spinel lherzolite xenoliths are characterized by granuloblastic-equant and coarse-equant textures typical of mantle peridotites and yield equilibration temperatures of 1000-1200 °C (1.5 GPa). Relative to other spinel lherzolites worldwide, these xenoliths have low MgO and high Fe 2 O 3 T and are similar to some modeled compositions for fertile mantle. However, these xenoliths are relatively enriched in the light rare earth elements (REE), Th, U, K, Nb, and Ta. Rare amphibole peridotite xenoliths have textures and compositions that are consistent with an origin as pyroxenite veins in the mantle that were variably deformed and metasomatized with potassium-rich ×uids. These xenoliths have concave-up light REE patterns similar to those of the host basalts, suggesting that the alkaline melts may have been produced by melting of amphibole-bearing mantle peridotites. Gabbroic xenoliths are variably deformed and recrystallized at relatively high pressure (0.4-0.6 GPa). Trace element ratios (e.g., Ba/Nb, La/Nb) indicate that these xenoliths crystallized from melts that were produced in a suprasubduction-zone setting and suggest that they represent cumulates that formed in the lower crust during Late Cretaceous subduction. We suggest that these cumulates are the source of the strong re×ec-tions that are observed in seismic re×ection proµle images of the Bering Sea region.Volcanic ×ows consist of tholeiite, olivine tholeiite, alkali-olivine basalt, and basanite, whereas cones consist mostly of alkali-olivine basalt and basanite. Geochemical variations within each volcanic µeld largely re×ect the effects of fractionation and melting (depth and fraction of melting), whereas between-µeld geochemical differences are largely due to source composition differences. The enriched incompatible trace element compositions (light REE, Ba, Th, Nb, Ta) and ratios (Th/Ta, Rb/Zr, Nb/La, La/Yb) are similar to intraplate basalts from ocean island and continental extensional settings. In particular, the compositions of Bering Sea basalts are similar to those of the diffuse volcanic province of Southeast Asia, a region where late Cenozoic volcanism has been related to tectonic extrusion along reactivated strike-slip faults.

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Section: Cretaceous To Holocene Extension In the Bering Shelf Regionmentioning

confidence: 96%

Evolution of crust and mantle beneath the Bering Sea region: Evidence from xenoliths and late Cenozoic basalts

Wirth¹,

Grandy²,

Kelley³

et al. 2002

Tectonic Evolution of the Bering Shelf-Chukchi Sea-Artic Margin and Adjacent Landmasses

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“…Further details concerning the nature and distribution of the deposits derived from the 2360 BP eruption are described in detail by Stasiuk and Russell (1990). Background information on the Cheakamus basalt lava flow can be found in Green et al (1988) and Nicholls et al (1982).…”

Section: Field Surveysmentioning

confidence: 99%

“…1; Table 1). The basalt is holocrystalline and lithologically homogeneous (Nicholls et al 1982;Green et al 1988). The lava flow is 3-6 m thick, poorly vesicular and has both regular vertical columnar joints (0.7 m spacing) and irregular subhorizontal joints (Fig.…”

Section: Cheakamus Valley Basalt Lava (Site 1)mentioning

confidence: 99%

Characterization of volcanic deposits with ground-penetrating radar

Russell

Stasiuk

1997

Bulletin of Volcanology

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Field-based studies of surficial volcanic deposits are commonly complicated by a combination of poor exposure and rapid lateral variations controlled by unknown paleotopography. The potential of ground-penetrating radar (GPR) as an aid to volcanological studies is shown using data collected from traverses over four well-exposed, Recent volcanic deposits in western Canada. The deposits comprise a pumice airfall deposit (3-4 m thick), a basalt lava flow (3-6 m thick), a pyroclastic flow deposit (15 m thick), and an internally stratified pumice talus deposit (60 m thick). Results show that GPR is effective in delineating major stratigraphic contacts and hence can be used to map unexposed deposits. Different volcanic deposits also exhibit different radar stratigraphic character, suggesting that deposit type may be determined from radar images. In addition, large blocks within the pyroclastic deposits are detected as distinctive point diffractor patterns in the profiles, showing that the technique has potential for providing important grain-size information in coarse poorly sorted deposits. Laboratory measurements of dielectric constant (K') are reported for samples of the main rock types and are compared with values of K' for the bulk deposit as inferred from the field data. The laboratory values differ significantly from the "field" values of K'; these results suggest that the effectiveness of GPR at any site can be substantially improved by initial calibration of well-exposed locations.

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“…Firstly, it is unlikely that the mantle xenoliths were incorporated into the base of the flow during surface transport because, other Bas Basanite, Ne nephelinite, AOB alkali olivine basalt, mx mantle, cx crustal xenoliths c 1 Aitken (1959); 2 Nicholls et al (1982); 3 Higgins and Allen (1985); 4 Carignan et al (1994); 5 Francis and Ludden (1995); 6 Harder et al (2003); 7 Edwards et al (2003) than the volcanic edifice itself, there is no immediate source of peridotite and they are much more abundant than the crustal xenoliths. Stokes settling velocity calculations (based on a purely Newtonian fluid) suggest that even smaller (5 cm diameter) mantle xenoliths will have settling velocities of~0.01-0.1 m/s (cf.…”

Section: Llangorse Mountain Basanitementioning

confidence: 99%

“…1). This volcanic field largely overlies Jurassic granodiorite of the Llangorse Mountain Batholith and Cache Creek Group cherts (Aitken 1959) and many of the volcanic occurrences have been described previously (e.g., Nicholls et al 1982;Higgins and Allen 1985;Carignan et al 1994;Francis and Ludden 1995). Lavas in the LVF include alkali olivine basalts, basanites, and olivine nephelinites ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Basanite glaciovolcanism at Llangorse mountain, northern British Columbia, Canada

Harder

Russell

2006

Bull Volcanol

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The Llangorse volcanic field is located in northwest British Columbia, Canada, and comprises erosional remnants of Miocene to Holocene volcanic edifices, lava flows or dykes. The focus of this study is a single overthickened, 100-m-thick-valley-filling lava flow that is Middle-Pleistocene in age and located immediately south of Llangorse Mountain. The lava flow is basanitic in composition and contains mantle-derived peridotite xenoliths. The lava directly overlies a sequence of poorly sorted, crudely bedded volcaniclastic debris-flow sediments. The debris flow deposits contain a diverse suite of clast types, including angular clasts of basanite lava, blocks of peridotite coated by basanite, and rounded boulders of granodiorite. Many of the basanite clasts have been palagonitized. The presence and abundance of clasts of vesicular to scoriaceous, palagonitized basanite and peridotite suggest that the debris flows are syngenetic to the overlying lava flow and sampled the same volcanic vent during the early stages of eruption. They may represent lahars or outburst floods related to melting of a snow pack or ice cap during the eruption. The debris flows were water-saturated when deposited. The rapid subsequent emplacement of a thick basanite flow over the sediments heated pore fluids to at least 80-100°C causing in-situ palagonitization of glassy basanite clasts within the sediments. The over-thickened nature of the Llangorse Mountain lavas suggests ponding of the lava against a down-stream barrier. The distribution of similar-aged glaciovolcanic features in the cordillera suggests the possibility that the barrier was a lower-elevation, valleywide ice-sheet.

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Petrologic variations in quaternary volcanic rocks, British Columbia, and the nature of the underlying upper mantle

Cited by 33 publications

References 48 publications

Evolution of crust and mantle beneath the Bering Sea region: Evidence from xenoliths and late Cenozoic basalts

Evolution of crust and mantle beneath the Bering Sea region: Evidence from xenoliths and late Cenozoic basalts

Characterization of volcanic deposits with ground-penetrating radar

Basanite glaciovolcanism at Llangorse mountain, northern British Columbia, Canada

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