The east–northeast-striking Thelon and Judge Sissons faults of south-central Nunavut are well preserved and record long-lived dextral transcurrent movement with complex reactivation and fluid flow histories. The faults cut across Archean gneisses, Paleoproterozoic plutons, and a Mesoproterozoic sedimentary basin in the Rae domain of the western Churchill Province. They formed and were reactivated during multiple deformation events beginning with an initial faulting event at 1830–1760 Ma, followed by an epithermal faulting event at 1760–1750 Ma and late reactivation events at 1600–1300 Ma. The initial faulting event produced the core-damage zone architecture of the faults. Damage zones are characterized by multiple fracture sets, quartz veins and hydrothermal crackle breccias, surrounding core zones defined by multiple mosaic to chaotic breccias and cataclasites with dextral slip indicators. The epithermal faulting event is expressed by the presence of crosscutting comb, crustiform-cockade and lattice-bladed quartz ± hematite ± carbonate veins, and is likely associated with a magmatic event of similar age. The late reactivation events resulted in the formation of irregular, non-cohesive crackle to mosaic breccias and gouges, which became the primary pathways for uranium-bearing hydrothermal fluids and the formation of unconformity-type uranium deposits. The Thelon and Judge Sissons faults are similar to other major continental faults in the Rae domain (e.g., McDonald fault, Wager Bay shear zone), which formed during the Paleoproterozoic Taltson–Thelon and Trans-Hudson orogenies and to modern analogues, such as the Karakorum, Altyn Tagh, and Hunan–Jiangxi faults, which formed during the Himalayan–Tibetan orogeny and experienced prolonged hydrothermal and even hot spring activity.

The Aberdeen Lake supracrustal belt is one of several Neoarchean greenstone belts preserved within the Rae domain of the Western Churchill Province. We divide the belt into: (1) a Lower Sequence of ca. 2750 Ma komatiite, TTG (tonalite-trondhjemite-granodiorite) intrusions, and TTG-contaminated Fe-tholeiitic mafic gneiss; (2) a Middle Sequence of ca. < 2687 Ma psammopelite gneiss, iron formation and ca. 2680 Ma intermediate to felsic intrusive rock; and (3) a ca. < 2650 Ma Upper Sequence of pelite to psammopelite gneiss with minor iron formation and arkosic gneiss. The common association of komatiite with quartzite units and bimodal metavolcanic rocks, has previously been interpreted to indicate a continental rift setting for the formation of Neoarchean greenstone belts across the Rae domain. However, the lack of clastic metasedimentary rocks and felsic metavolcanic rocks in the Lower Sequence of the Aberdeen Lake supracrustal belt, the presence of uncontaminated komatiite, and the general absence of inherited zircons older than ca. 2750 Ma in the TTG and mafic gneiss units, suggest that the Lower Sequence formed as an oceanic plateau or oceanic crust between older, Paleoarchean to Mesoarchean, proto-Rae microcratons. Erosion of the cratons and the emergence of the oceanic plateaux due to their accretion/subcretion to these cratons shed ca. 2687-2870 Ma detritus that were deposited as the Middle Sequence into adjacent oceanic basins. Renewed uplift of the Lower and Middle sequences led to the emplacement of ca. 2680 Ma felsic intrusions, and the later deposition of the ca. < 2650 Ma Upper Sequence. The involvement of oceanic plateaux is a new tectonic interpretation for the formation of Neoarchean greenstone belts in the Rae domain.

The middle Paleoproterozoic Thluicho Lake Group comprises coarse-grained continental clastic rocks deposited in fault-controlled alluvial basin(s) in the southwestern Rae Province of the Canadian Shield. The group nonconformably overlies crystalline basement that records late-Taltson high-grade metamorphism, ca. 1.93 Ga, and is folded and metamorphosed to greenschist facies, providing an important window of insight into tectonic activity in this region. This paper reports ∼100 detrital zircon ages for two samples from the lower and upper parts of the Thuicho Lake Group. Four analyses of one of the youngest detrital zircons from the stratigraphically higher member define a weighted mean 207Pb/206Pb age of 1922 ± 6 Ma, establishing a maximum depositional age for the group. This result accords with regional geological relationships indicating that the group is intermediate in age between development of two major tectonic fronts; an older, ca. 1.93 Ga east-southeast-trending front that formed at the height of Thelon-Taltson orogeny, and a younger, ca. 1.91–1.90 Ga northeast-striking front expressed by the Black Bay Fault and related northeast-striking structures affiliated with the Snowbird tectonic zone. The younger age limit of the group may therefore be older (≥1.91–1.90 Ga) than the previously reported minimum age, constrained by cross-cutting dykes dated at ca. 1.82 Ga. In terms of isotopic provenance, the bulk of analyses of the combined dataset lie within two principal age-ranges: 2750–2500 Ma and 2475–2250 Ma. The older of these is dominated by ca. 2600 Ma zircons, whereas the younger contains two statistically distinct subgroups of 2410 and 2310 Ma. This signature is consistent with derivation almost exclusively from immediately surrounding basement rocks of the Nolan, Taltson, Zemlak, Ena and Beaverlodge domains. Abundant 2475–2250 Ma zircons provide indirect evidence for the 2.45–2.3 Ga Arrowsmith orogeny. Despite proximity to the Taltson magmatic zone, 1990–1960 Ma zircons are nearly completely absent, suggesting that Thluicho Lake basins formed in the hinterland of the orogen, possibly separated from the foreland (Taltson arc) by a continental divide. Alternatively, Taltson arc plutons may not have been unroofed at the time of deposition of Thluicho Lake strata. The data presented herein support the previously proposed broad correlation between the Thuicho Lake and Nonacho groups; however, there are apparent differences in detail between respective basin settings and controls, suggesting that this correlation requires further investigation.

The Thluicho Lake Group is a middle-Paleoproterozoic succession of greenschist-facies continental clastic rocks that was deposited on variably mylonitized crystalline basement rocks in the southwestern Rae Province of the Canadian Shield, near the end of 2.02-1.92-Ga Thelon-Taltson orogenesis. Two informal formations are proposed for this fining-upward succession. The Powder Lake formation comprises predominantly coarse-grained rocks including conglomerate (Gulo Lake member), pebbly sandstone (Camel Lake member), and sandstone (Wellington Lake member), whereas the overlying Camsell Portage formation consists of sandstone to siltstone (Falls member), rhythmic sandstone and argillite (Waterloo Lake member), and argillite (Slate Island member). The two informal formations represent two principal facies associations: a lower conglomerate-sandstone facies association representing an alluvial fan to distal braided plain that underwent episodic flash flooding events and an upper sandstone siltstone-mudstone facies association representing a lacustrine environment. The Thluicho Lake basins are interpreted to have been symmetrical and elongate, and are broadly parallel to older, west-to northwest-trending basement structures. Transverse alluvial fans and braided rivers and/or fan deltas developed on elevated basin margins and drained into a large perennial lake. Similarities in lithology, age, and provenance suggest that the Thluicho Lake Group may correlate with the more extensive Nonacho Group to the north. Both groups represent remnants of a strike-slip and intermontane basin system that formed in the hinterland of the Taltson orogen at ca. 1.92 Ga.

The southern Rae Province of the western Canadian Shield underwent extensive reworking during Paleoproterozoic time. Widespread granitic plutonism and poorly defined metamorphism resulting from the ca. 2.5 to 23 Ga Arrowsmith Orogen was followed by more intense thermotectonic overprints attributed to the 1.99-1.92 Ga Taltson Orogen in the west and ca. 1.91-1.90 Ga tectonic activity associated with the Snowbird Tectonic Zone in the east. The Thluicho Lake Group is a fining-upwards, conglomerate-arkose-argillite succession deposited in an intermontane setting towards the end of the Taltson Orogen. Following deposition, the Thluicho Lake Group underwent two phases of regional folding and greenschist-facies metamorphism marking the latest Taltson and Snowbird overprints, respectively, prior to the emplacement of extensive 1.82 Ga mafic dykes. These depositional constraints support correlation of the Thluicho Lake Group with the lithologically similar Nonacho Group in the Northwest Territories, whereas petrological similarities and coeval emplacement ages indicate that the mafic dykes represent a southeastward extension of the Sparrow dykes.Mafic volcanic rocks geochemically linked to the dykes are intercalated within the Martin Group, a continental redbed succession deposited in trans-tensional basin settings, indicating that deposition was ongoing at 1.82 Ga. Similarities in age, lithological association and depositional setting suggest that the Martin Group is broadly correlative with the Baker Lake Group of the lower Dubawnt Supergroup in Nunavut. Widespread lamprophyre dykes of the type that fed minette volcanic rocks of the Christopher Island Formation in the Baker Lake Group are also spatially associated with the Martin Group. The broadly coeval Hudson granites, which extend over much of the same ground as the lamprophyres in Nunavut, also appear to have analogs in the southern Rae Province.The formation of widespread trans-tensional basins, together with extensive dyke emplacement, implies a period of intense brittle to brittle-ductile deformation throughout the western Churchill Province at about 1.83-1.82 Ga. This deformation is attributed to a broadly east-west stress regime imposed by accretion of the Nahanni-Fort Simpson Terrane to the west, combined with terminal collision in the Trans-Hudson Orogen to the east. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

This article reviews educational initiatives of state and federal government that were designed to remedy the effects of racial segregation on Black public school students in the United States after the famous Brown v. Board of Education decisions. Several policy and legal initiatives are reviewed, including school desegregation, compensatory education, decentralization, school reform and restructuring, school finance litigation, state accountability models, school district takeovers, vouchers, charter schools, No Child Left Behind, and privatization.

Results of a U-Pb detrital zircon geochronological study of the middle Paleoproterozoic Thluicho Lake Group are reported. The Thluicho Lake Group is a succession of coarse clastic rocks that was deposited in continental alluvial basins in the central Zemlak domain of the southwest Rae Province. Over 100 analyses were performed on detrital zircons from two stratigraphically well controlled samples from the Waterloo-Wellington lakes area, 10 km west of Uranium City – the ‘Camel Lake Member’ pebbly arkose of the ‘Powder Lake Formation’ and the ‘Falls Member’ arkose-argillite of the ‘Camsell Portage Formation’. Four analyses of one of the youngest zircons recovered from the stratigraphically higher Falls Member yielded a weighted mean 207 Pb/ 206 Pb age of 1922 ±6 Ma, establishing a new maximum depositional age for the group. This result, together with regional geological relationships, suggests that the group is intermediate in age between development of two major tectonic fronts in this part of the Rae Province; an older, ca. 1.93 Ga east-southeast–trending front that formed at the tail end of Thelon-Taltson orogeny, and a younger, ca. 1.91 to 1.90 Ga northeast-striking front expressed by the Black Bay Fault and associated northeast-striking structures affiliated with the Snowbird Tectonic Zone. The younger age limit for the group may therefore be significantly older than the previously reported minimum age of ca. 1.82 Ga. The distribution of detrital zircon ages defined by the two samples is remarkably similar, with the majority falling within two age ranges: 2750 to 2500 Ma and 2450 to 2250 Ma. The older age range is dominated by ca. 2600 Ma zircons whereas the younger contains two distinct subgroups of ca. 2420 and ca. 2320 Ma. The principal sources of the Thluicho Lake Group were therefore local basement rocks of the Nolan, Taltson, Zemlak (Ena), Beaverlodge, and possibly Train Lake domains. Abundant 2450 to 2250 Ma zircons indicate that the ca. 2.4 to 2.3 Ga Arrowsmith Orogen of the western Rae Province was also a major source of detritus. A few older (>3100 Ma) and younger (<2250 to 1920 Ma) zircons were likely sourced, locally or regionally, within the Rae Province. All told, the bulk of the Thluicho Lake Group detritus came from rocks that can be inferred to have formed the exhumed hinterland of the Taltson mountain belt. A notable feature of the Thluicho Lake dataset is the near-complete absence of 1990 to 1960 Ma zircons, an age range typical of subduction-related plutons of the Taltson Magmatic Zone. The Taltson arc did not supply detritus to the Thluicho depositional basins, supporting the inference that such basins were located in the hinterland of the orogen, which was possibly separated from the foreland by a continental divide. The data reported herein support correlation of the Thluicho Lake and Nonacho groups.

The LeBlanc-Wellington lakes area of the eastern Zemlak Domain is dominated by upper amphibolite facies leucogranites, gneissic to migmatitic granitoids, and massive anatectic granites derived from these sources and from subordinate supracrustal rocks of the Murmac Bay Group. Coarse-grained granites of the ca. 2.3 Ga regional suite and pink leucogranite inferred elsewhere to have been emplaced at 1.9 Ga are both represented, and at least some of the remaining granitoid rocks are considered part of the ca. 3.0 Ga basement to the Murmac Bay Group. All of these rocks underwent three initial phases of deformation (D1 to D3), the last of which was responsible for the regional northeast-trending structural fabric that is thought to have formed during a ca. 1.9 Ga metamorphic event attributed to the Thelon-Taltson Orogeny. During the uplift following this thermotectonic culmination, widespread brittle-ductile mylonitization was particularly intense in the western map area. The post-1.9 Ga exhumation was followed by deposition of the siliciclastic Thluicho Lake Group which, together with the basement rocks, was subjected to two more phases of deformation (D4 and D5) under greenschist facies metamorphic conditions prior to ca. 1.82 Ga deposition and subsequent folding (D6) of the Martin Group. Cu-Pb-Ag vein mineralization occurs in late fracture zones best developed in mylonitic granitoids at or near the basal Thluicho Lake Group unconformity. East-trending ca. 1.82 Ga diabase dykes at several showings may have locally provided chemical traps for the mineralizing fluids, but are not considered the metal source.

In the past decade, systemic school reform has taken hold in America in the form of "school-based management" (SBM) or shared decision making as a mechanism for improving schooling. Despite the lack of positive findings from research on the ability of this innovation to improve schooling the reform innovation continues to grow. This article reviews the research on SBM for urban minority students and posits ways in which minority students may use SBM as a tool to improve education for their children and how their involvement may be enhanced with the assistance of properly prepared school principals. Given the ability of schools to sort students into social-economic classes, effective advocacy by parents of minority children at the school level may serve to counter the sorting function of schools based on one's race or ethnicity.