Nature and evolution of the Slave Province subcontinental lithospheric mantleThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.

2010 ◽  
Vol 47 (4) ◽  
pp. 369-388 ◽  
Author(s):  
Larry M. Heaman ◽  
D. Graham Pearson
Keyword(s):  
Great Depth ◽  
Peridotite Xenolith ◽  
Special Issue ◽  
Mantle Material ◽  
Slave Craton ◽  
Multiple Origins ◽  
Slave Province ◽  
Abundant Evidence ◽  
Subducted Oceanic Crust ◽  
Continental Lithospheric Mantle

A review of the ages determined for mantle material (xenoliths and xenocrysts entrained in kimberlite) derived from the Slave Province continental lithospheric mantle (CLM) indicates that a portion of the central Slave lithosphere may be ancient (3.5–3.3 Ga) harzburgite, but the majority of this lithosphere is much younger (2.9–2.0 Ga). Relying on the most robust chronometers, the majority of Slave lithosphere peridotite formed in the Neoarchean (peak at 2.75 Ga), whereas the majority of eclogite formed in the Paleoproterozoic (2.2–2.0 Ga). The northern Slave lithosphere contains evidence of peridotite xenolith ages that young with depth. The Paleoproterozoic eclogites may have multiple origins including remnants of subducted oceanic crust and mafic–ultramafic magmas that crystallized at great depth (100–200 km). Re–Os studies of sulfide inclusions in diamond indicate that some diamonds currently mined are ancient (∼3.5 Ga), but many Slave diamonds could be considerably younger. Most eclogitic diamonds recovered from the Slave craton are interpreted to be related to the formation of Paleoproterozoic eclogite. There is abundant evidence for Mesoproterozoic modification of the Slave lithosphere (e.g., heating by magma emplacement at great depth and metasomatism) and possible new addition to the lithosphere at that time. The Canadian Slave and African Kaapvaal lithospheres have similar peaks in cratonic peridotite formation ages at about 2.8 Ga, indicating that a large portion of the CLM in these two cratons formed and stabilized in the Neoarchean. One difference is that the Slave peridotites are much less enriched in SiO2, possibly reflecting the more metasomatized nature of the Kaapvaal CLM. The dominance of Paleoproterozoic formation ages for Slave mantle eclogites contrasts with the dominance of Neoarchean formation ages for Kaapvaal mantle eclogites.

scholarly journals Introduction to the Special Issue on Individual Differences in Multisensory Perception: an Overview

2017 ◽  
Vol 30 (6) ◽  
pp. 461-466 ◽  
Author(s):  
Clare Jonas ◽  
Mary Jane Spiller ◽  
Paul B. Hibbard ◽  
Michael Proulx
Keyword(s):  
Individual Differences ◽  
Great Depth ◽  
Developmental Changes ◽  
Psychological Characteristics ◽  
Sensory Loss ◽  
Multisensory Perception ◽  
Special Issue ◽  
British Psychological Society ◽  
The World ◽  
New Research

The world is full of objects that can be perceived through multiple different senses to create an integrated understanding of our environment. Since each of us has different biological and psychological characteristics, different people may perceive the world in quite different ways. However, the questions of how and why our multisensory perceptions differ have not been explored in any great depth. This special issue, arising from a series of British Psychological Society-funded seminars, presents new research and opinions on the impacts of a variety of individual differences on multisensory perception. We hope that readers will enjoy this collection of eight papers on individual differences in multisensory perception arising from developmental changes, autism, Down syndrome, migraine, sensory loss and substitution, and personality.

Petrology and textural classification of the Jericho kimberlite, northern Slave Province, Nunavut, Canada

2008 ◽  
Vol 45 (6) ◽  
pp. 701-723 ◽  
Author(s):  
Maya G. Kopylova ◽  
Patrick Hayman
Keyword(s):  
South African ◽  
Small Volume ◽  
Bulk Rock ◽  
Slave Craton ◽  
Slave Province ◽  
Core Logging ◽  
Kimberlite Magma ◽  
Mineral Compositions ◽  
Two Phases

The paper presents data on petrology, bulk rock and mineral compositions, and textural classification of the Middle Jurassic Jericho kimberlite (Slave craton, Canada). The kimberlite was emplaced as three steep-sided pipes in granite that was overlain by limestones and minor soft sediments. The pipes are infilled with hypabyssal and pyroclastic kimberlites and connected to a satellite pipe by a dyke. The Jericho kimberlite is classified as a Group Ia, lacking groundmass tetraferriphlogopite and containing monticellite pseudomorphs. The kimberlite formed during several consecutive emplacement events of compositionally different batches of kimberlite magma. Core-logging and thin-section observations identified at least two phases of hypabyssal kimberlites and three phases of pyroclastic kimberlites. Hypabyssal kimberlites intruded as a main dyke (HK1) and as late small-volume aphanitic and vesicular dykes. Massive pyroclastic kimberlite (MPK1) predominantly filled the northern and southern lobes of the pipe and formed from magma different from the HK1 magma. The MPK1 magma crystallized Ti-, Fe-, and Cr-rich phlogopite without rims of barian phlogopite, and clinopyroxene and spinel without atoll structures. MPK1 textures, superficially reminiscent of tuffisitic kimberlite, are caused by pervasive contamination by granite xenoliths. The next explosive events filled the central lobe with two varieties of pyroclastic kimberlite: (1) massive and (2) weakly bedded, normally graded pyroclastic kimberlite. The geology of the Jericho pipe differs from the geology of South African or the Prairie kimberlites, but may resemble Lac de Gras pipes, in which deeper erosion removed upper facies of resedimented kimberlites.

scholarly journals Light oxygen isotopes in mantle-derived magmas reflect assimilation of sub-continental lithospheric mantle material

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jing-Yao Xu ◽  
Andrea Giuliani ◽  
Qiu-Li Li ◽  
Kai Lu ◽  
Joan Carles Melgarejo ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Lithospheric Mantle ◽  
Secondary Ion Mass Spectrometry ◽  
Crustal Contamination ◽  
Alternative View ◽  
Crustal Material ◽  
Mantle Material ◽  
Oxygen Isotope Ratios ◽  
Continental Lithospheric Mantle ◽  
Lower Crustal

AbstractOxygen isotope ratios in mantle-derived magmas that differ from typical mantle values are generally attributed to crustal contamination, deeply subducted crustal material in the mantle source or primordial heterogeneities. Here we provide an alternative view for the origin of light oxygen-isotope signatures in mantle-derived magmas using kimberlites, carbonate-rich magmas that assimilate mantle debris during ascent. Olivine grains in kimberlites are commonly zoned between a mantle-derived core and a magmatic rim, thus constraining the compositions of both mantle wall-rocks and melt phase. Secondary ion mass spectrometry (SIMS) analyses of olivine in worldwide kimberlites show a remarkable correlation between mean oxygen-isotope compositions of cores and rims from mantle-like 18O/16O to lower ‘crustal’ values. This observation indicates that kimberlites entraining low-18O/16O olivine xenocrysts are modified by assimilation of low-18O/16O sub-continental lithospheric mantle material. Interaction with geochemically-enriched domains of the sub-continental lithospheric mantle can therefore be an important source of apparently ‘crustal’ signatures in mantle-derived magmas.

scholarly journals Timing and provenance of Paleoproterozoic supracrustal rocks in the central Thelon tectonic zone, Canada: implications for the tectonic evolution of western Laurentia from ca. 2.1 to 1.9 Ga

2021 ◽  
pp. 1-18
Author(s):  
W.J. Davis ◽  
M. Sanborn-Barrie ◽  
R.G. Berman ◽  
S. Pehrsson
Keyword(s):  
Detrital Zircon ◽  
Foreland Basin ◽  
Tectonic Zone ◽  
Zircon Age ◽  
Slave Craton ◽  
Magmatic Arc ◽  
Tectonic Model ◽  
Metasedimentary Rocks ◽  
Clastic Rocks ◽  
Slave Province

Depositional ages and provenance of metasedimentary rocks provide constraints on the architecture of the interface between the Slave and Rae cratons and processes related to the Thelon Orogen. Clastic rocks analysed from the central Thelon tectonic zone are Paleoproterozoic in age and not remnants of the Archean Yellowknife Supergroup (Slave Province), as originally considered. Two assemblages are recognized. An older clastic assemblage deposited after 2.09 Ga contains detrital zircon age modes of 2.3 and 2.17 Ga, with subordinate Neoarchean and Paleoarchean detritus. Its deposition is interpreted to predate Thelon magmatic activity given that (1) it lacks ca. 2.01–1.97 Ga detritus of Thelon magmatic origin, and (2) correlative clastic rocks occur as inclusions in Thelon plutons and contain ca. 2.0 Ga metamorphic monazite. This assemblage is correlative with both the Mary Frances and Rutledge River groups, establishing a >800 km long basin at ca. 2.1 Ga that received detritus from the western Rae and (or) Buffalo Head terrane(s). Separation from the Slave craton at this time is consistent with the absence of any Slave-affinity detritus. A younger assemblage deposited after 1.95 Ga and prior to 1.91 Ga contains mainly 2.02–1.95 Ga detrital zircon, age modes comparable with adjacent Thelon convergent-margin plutonic rocks. The younger assemblage records deposition of the uplifted and eroded Thelon magmatic arc in an intermontane or foreland basin setting during the later stages of post-collisional convergence. These U–Pb zircon data support a tectonic model for western Laurentia that reconciles differences between the Thelon and Taltson magmatic zones involving ca. 2.1 Ga rifting, ca. 2.01–1.97 Ga convergence, followed by <1.95 Ga thrust-driven exhumation.

Petrology and oxygen-isotope geochemistry of the Yamba Lake kimberlite rocks, N.W.T.

2000 ◽  
Vol 37 (7) ◽  
pp. 1053-1071 ◽  
Author(s):  
Pauline Orr ◽  
Robert W Luth
Keyword(s):  
Major Element ◽  
Isotope Geochemistry ◽  
Isotopic Fractionation ◽  
Kimberlite Pipe ◽  
Spinel Lherzolite ◽  
Garnet Lherzolite ◽  
Slave Province ◽  
Low Concentrations ◽  
Subducted Oceanic Crust ◽  
Indicator Minerals

The Torrie, Sputnik, and Eddie kimberlite rocks, located near Yamba Lake, central Slave province, N.W.T., are volcaniclastic, macrocrystic, heterolithic, olivine-rich tuff, and olivine-rich tuff breccia. Torrie and Sputnik kimberlite rocks contain pyroxene and garnet xenocrysts and megacrysts with major-element compositions consistent with derivation mostly from disaggregated garnet lherzolite, with subordinate contributions from eclogite, spinel lherzolite, garnet harzburgite, and websterite. The presence of primary groundmass phlogopite and compositionally evolved spinel, and the absence of mantle xenocrysts, xenoliths, and megacrystic ilmenite distinguish the Eddie kimberlite pipe from the other two kimberlite pipes. Large variations in δ18O of garnet and clinopyroxene in xenocrysts and xenoliths (+3.98 to +6.36‰), nonequilibrium intermineral isotopic fractionation, and major-element heterogeneity are interpreted as resulting from infiltration of fluids or melts produced by dehydration or melting of subducted oceanic crust into overlying peridotite. Although the timing is unconstrained for the xenocysts, the xenolith must have experienced this metasomatic interaction shortly before entrainment in the kimberlite. Variable δ18O values for magnesian ilmenite are also interpreted to result indirectly from such metasomatic activity in the mantle as well. The Torrie and Sputnik kimberlite rocks have low concentrations of diamond indicator minerals consistent with their low-diamond grades. These kimberlite rocks did not sample a significant amount of garnet harzburgite, the rock type commonly associated with high-diamond grades in other kimberlite rocks. Furthermore, metasomatism just prior to kimberlite eruption may have caused the resorption of any diamond present.

Teleseismic studies of the Canadian landmass: Lithoprobe and its legacyThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.ESS Contribution 20090305.

2010 ◽  
Vol 47 (4) ◽  
pp. 445-461 ◽  
Author(s):  
M.G. Bostock ◽  
D.W. Eaton ◽  
D.B. Snyder
Keyword(s):  
British Columbia ◽  
Subduction Zones ◽  
Canadian Shield ◽  
Plate Motion ◽  
Special Issue ◽  
The Past ◽  
Structure And Dynamics ◽  
Slave Province ◽  
Shallow Subduction

Although teleseismic research was only modestly represented within the Lithoprobe program, the analysis of deeper lithospheric structure beneath Canada using teleseismic methods has intensified in the past decade. This development is due in large part to a legacy of improved understanding of shallower lithospheric structures afforded by Lithoprobe. Most recent teleseismic experiments have been conducted in regions lying within Lithoprobe transects and coverage is particularly good in the Slave Province, southern and eastern Ontario, and southwestern British Columbia. A number of key results have arisen out of this collective body of work. Studies on the Slave Province and environs have placed strong constraints on the origin of the high-velocity continental root that underlies most of the Canadian Shield. Fine-scale, anisotropic stratigraphy in this region has been definitively tied to underplated lithosphere, indicating that shallow subduction has played a fundamental role in craton stabilization. Modification of continental lithosphere by the underlying convecting mantle has been extensively documented in the southeastern Canadian Shield and Slave Province, yielding insights into the forces driving plate motion and those that induce intraplate volcanism. Teleseismic investigations in British Columbia point to the importance of water in controlling the structure and dynamics of subduction zones, but have rekindled controversy concerning the location and characterization of the downgoing oceanic plate.

The Broad Applications of the Scanning Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 20-21
Author(s):  
C. T. Nightingale ◽  
S. E. Summers ◽  
T. P. Turnbull
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Light Microscopy ◽  
Surface Topography ◽  
Great Depth ◽  
Resolving Power ◽  
Depth Of Field ◽  
Pictorial Representations ◽  
Scanning Electron

The ease of operation of the scanning electron microscope has insured its wide application in medicine and industry. The micrographs are pictorial representations of surface topography obtained directly from the specimen. The need to replicate is eliminated. The great depth of field and the high resolving power provide far more information than light microscopy.

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