scholarly journals Mantle xenoliths and xenocrysts from the Cross kimberlite, British Columbia, Canada: implications for upper mantle evolution beneath western Canada

2019 ◽  
Keyword(s):  
British Columbia ◽  
Upper Mantle ◽  
Mantle Xenoliths ◽  
Western Canada ◽  
Mantle Evolution ◽  
The Cross

Petrology of ultramafic xenoliths from Rayfield River, south-central British Columbia

1987 ◽  
Vol 24 (8) ◽  
pp. 1679-1687 ◽  
Author(s):  
Dante Canil ◽  
Mark Brearley ◽  
Christopher M. Scarfe
Keyword(s):  
British Columbia ◽  
Phase Equilibrium ◽  
Partial Melting ◽  
Upper Mantle ◽  
Mantle Xenoliths ◽  
Spinel Lherzolite ◽  
Equilibrium Constraints ◽  
Host Magma ◽  
South Central ◽  
Ultramafic Xenoliths

One hundred mantle xenoliths were collected from a hawaiite flow of Miocene–Pliocene age near Rayfield River, south-central British Columbia. The massive host hawaiite contains subrounded xenoliths that range in size from 1 to 10 cm and show protogranular textures. Both Cr-diopside-bearing and Al-augite-bearing xenoliths are represented. The Cr-diopside-bearing xenolith suite consists of spinel lherzolite (64%), dunite (12%), websterite (12%), harzburgite (9%), and olivine websterite (3%). Banding and veining on a centimetre scale are present in four xenoliths. Partial melting at the grain boundaries of clinopyroxene is common and may be due to natural partial melting in the upper mantle, heating by the host magma during transport, or decompression during ascent.Microprobe analyses of the constituent minerals show that most of the xenoliths are well equilibrated. Olivine is Fo89 to Fo92, orthopyroxene is En90, and Cr diopside is Wo47En48Fs5. More Fe-rich pyroxene compositions are present in some of the websterite xenoliths. The Mg/(Mg + Fe2+) and Cr/(Cr + Al + Fe3+) ratios in spinel are uniform in individual xenoliths, but they vary from xenolith to xenolith. Equilibration temperatures for the xenoliths are 860–980 °C using the Wells geothermometer. The depth of equilibration estimated for the xenoliths using geophysical and phase equilibrium constraints is 30–40 km.

A large-scale magnetotelluric survey in Western Canada

1969 ◽  
Vol 6 (5) ◽  
pp. 1245-1261 ◽  
Author(s):  
B. Caner ◽  
P. A. Camfield ◽  
F. Andersen ◽  
E. R. Niblett
Keyword(s):  
British Columbia ◽  
Upper Mantle ◽  
Large Scale ◽  
Conducting Layer ◽  
Western Canada ◽  
Period Range ◽  
A Value ◽  
Depth Sounding ◽  
Lower Crustal ◽  
Conducting Zone

Five magnetotelluric stations were operated in two clusters in southern British Columbia and Alberta, in order to determine the conductivity structures in each of the two main regions delineated by geomagnetic depth-sounding. A wide period range was covered (20 to 7500 seconds), to permit resolution of structure at lower crustal and upper mantle depths.At the eastern cluster (Pincher, Fernie), a moderately conducting zone (30–50 ohm-meters) is defined starting at depth 30–35 km and extending to a depth of at least 100 km. At the western cluster (Penticton, Osoyoos, Grand Forks) a conducting layer (10 ± 5 ohm-meters) starts at depth 15 ± 5 km; below this layer (of thickness 20–40 km) the resistivity increases to a value of the same order (30–50 ohm-meters) as at the eastern cluster.

scholarly journals Phlogopite-pargasite coexistence in an oxygen reduced spinel-peridotite ambient

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Costanza Bonadiman ◽  
Valentina Brombin ◽  
Giovanni B. Andreozzi ◽  
Piera Benna ◽  
Massimo Coltorti ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Upper Mantle ◽  
Mantle Xenoliths ◽  
Spinel Peridotite ◽  
Simultaneous Formation ◽  
Empirical Potentials ◽  
Elastic Data ◽  
Mineralogical Study ◽  
Semi Empirical ◽  
T Locus

AbstractThe occurrence of phlogopite and amphibole in mantle ultramafic rocks is widely accepted as the modal effect of metasomatism in the upper mantle. However, their simultaneous formation during metasomatic events and the related sub-solidus equilibrium with the peridotite has not been extensively studied. In this work, we discuss the geochemical conditions at which the pargasite-phlogopite assemblage becomes stable, through the investigation of two mantle xenoliths from Mount Leura (Victoria State, Australia) that bear phlogopite and the phlogopite + amphibole (pargasite) pair disseminated in a harzburgite matrix. Combining a mineralogical study and thermodynamic modelling, we predict that the P–T locus of the equilibrium reaction pargasite + forsterite = Na-phlogopite + 2 diopside + spinel, over the range 1.3–3.0 GPa/540–1500 K, yields a negative Clapeyron slope of -0.003 GPa K–1 (on average). The intersection of the P–T locus of supposed equilibrium with the new mantle geotherm calculated in this work allowed us to state that the Mount Leura xenoliths achieved equilibrium at 2.3 GPa /1190 K, that represents a plausible depth of ~ 70 km. Metasomatic K-Na-OH rich fluids stabilize hydrous phases. This has been modelled by the following equilibrium equation: 2 (K,Na)-phlogopite + forsterite = 7/2 enstatite + spinel + fluid (components: Na2O,K2O,H2O). Using quantum-mechanics, semi-empirical potentials, lattice dynamics and observed thermo-elastic data, we concluded that K-Na-OH rich fluids are not effective metasomatic agents to convey alkali species across the upper mantle, as the fluids are highly reactive with the ultramafic system and favour the rapid formation of phlogopite and amphibole. In addition, oxygen fugacity estimates of the Mount Leura mantle xenoliths [Δ(FMQ) = –1.97 ± 0.35; –1.83 ± 0.36] indicate a more reducing mantle environment than what is expected from the occurrence of phlogopite and amphibole in spinel-bearing peridotites. This is accounted for by our model of full molecular dissociation of the fluid and incorporation of the O-H-K-Na species into (OH)-K-Na-bearing mineral phases (phlogopite and amphibole), that leads to a peridotite metasomatized ambient characterized by reduced oxygen fugacity.

Fluid inclusions in upper mantle xenoliths from Northern Patagonia, Argentina: Evidence for an upper mantle diapir

1997 ◽  
Vol 60 (3-4) ◽  
pp. 145-164 ◽  
Author(s):  
M. E. Varela ◽  
E. A. Bjerg ◽  
R. Clocchiatti ◽  
C. H. Labudia ◽  
G. Kurat
Keyword(s):  
Fluid Inclusions ◽  
Upper Mantle ◽  
Mantle Xenoliths ◽  
Northern Patagonia ◽  
Mantle Diapir

scholarly journals Challenging the Stereotypes: Unexpected Features of Sexual Exploitation among Homeless and Street-Involved Boys in Western Canada

2021 ◽  
Vol 18 (11) ◽  
pp. 5898
Author(s):  
Elizabeth M. Saewyc ◽  
Sneha Shankar ◽  
Lindsay A. Pearce ◽  
Annie Smith
Keyword(s):  
British Columbia ◽  
Sexual Exploitation ◽  
Western Canada ◽  
Youth Health

Research about the sexual exploitation of homeless and street-involved boys is limited and often combined with that of girls. As aggregation can distort unique issues among genders which are exploited, this study provides information about the context of exploitation for homeless boys. Boys participated in the anonymous, multi-city British Columbia (BC), Canada Homeless and Street-Involved Youth Health paper surveys of 2006 and 2014. Measures included questions about trading sex for money, shelter, or other consideration; age first exploited; for whom; where they were living when first traded sex; gender of exploiters; and demographics. Analyses, separately for younger/older boys, explored the prevalence, timing of exploitation vs. homelessness, and ANOVAs to evaluate the patterns of the age of first exploitation by the genders of exploiters. Just over one in four boys reported exploitation (n = 132), with a median age of 14–15 in most groups. Most were runaway or homeless before their first exploitation, but 25.5% (2006) and 41% (2014) were living with family. Most boys were exploited by women (78%–85%), with 62%–65% were exclusively exploited by women.

Impact of cultivars and herbicides on weed management in alfalfa

2006 ◽  
Vol 86 (3) ◽  
pp. 875-885 ◽  
Author(s):  
J. R. Moyer ◽  
S. N. Acharya
Keyword(s):  
British Columbia ◽  
Weed Control ◽  
Weed Management ◽  
Forage Quality ◽  
Western Canada ◽  
Downy Brome ◽  
Weed Species ◽  
Standard Type ◽  
Southern Alberta ◽  
Medicago Sativa L

Weeds, especially dandelion (Taraxacum officinale Weber in F.H. Wigg.), tend to infest a forage alfalfa (Medicago sativa L.) stand 2 to 4 yr after establishment. To develop better weed management systems, experiments were conducted at Lethbridge, Alberta, from 1995 to 2002 and Creston, British Columbia, from 1998 to 2001, which included the alfalfa cultivars Beaver (standard type) and AC Blue J (Flemish type) and annual applications of metribuzin and hexazinone. These herbicides are registered for weed control in irrigated alfalfa in Alberta and alfalfa grown for seed. In addition, two sulfonylurea herbicides, metsulfuron and sulfosulfuron, and glyphosate were included. All of the herbicides except glyphosate controlled or suppressed dandelion and mustard family weeds. Metsulfuron at 5 g a.i. ha-1 almost completely controlled dandelion at both locations. However, after metsulfuron application at Lethbridge, dandelion was replaced with an infestation of downy brome, which is unpalatable for cattle. None of the herbicides increased total forage (alfalfa + weed) yield, and in some instances herbicides reduced forage quality by causing a shift from a palatable to an unpalatable weed species. However, it was observed that AC Blue J consistently yielded more than Beaver, and weed biomass was consistently less in the higher-yielding cultivar. AC Blue J was developed primarily for the irrigated area in southern Alberta and for southern British Columbia. Therefore, additional experiments should be conducted to determine which alfalfa cultivars have the greatest ability to compete with weeds in other regions of western Canada. Key words: Alfalfa yield, dandelion, forage quality, weed control

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