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Drawing from the Sheldon and Manktelow collections at SUNY Oswego's Penfield Library, along with sociological criteria for a profession – graduate-level training, autonomy, peer evaluation and responsibility to the public – this article reassesses Oswego State Normal School's impact on nineteenth-century teacher education. Descriptions of Oswego identify the school as an active site of object teaching and Pestalozzianism in the US. Yet, as this analysis reveals, Edward Austin Sheldon and Oswego's faculty oversaw the development of practices and innovations that were designed to enhance teacher autonomy and to involve teachers in their own learning and evaluation. With Oswego's reputation for innovation spreading, Sheldon took responsibility to describe and defend the teacher preparation work conducted at Oswego. This article argues that Oswego should be remembered not just for the promotion of object teaching and Pestalozzian principles, but also for its efforts to leverage such practices and principles to cultivate a stronger teaching profession. [ABSTRACT FROM AUTHOR]

Dr. Martha Jane Powell was a distinguished chytrid taxonomist and mentor who made significant contributions to the field of mycology. She began her career studying chytrid fungi and later focused on using zoospore ultrastructure to revise chytrid taxonomy. She also conducted research on host-parasite interactions and worked with various organisms including oomycetes and the clade that includes Rozella. Throughout her career, she mentored numerous students and authored over 160 papers and book chapters. Dr. Powell's impact on the field of mycology and her dedication to her students are remembered and celebrated. [Extracted from the article]

Lung cancer patients treated with targeted therapies frequently respond well but invariably relapse due to the development of drug resistance. Drug resistance is in part mediated by a subset of cancer cells termed "drug-tolerant persisters" (DTPs), which enter a dormant, slow-cycling state that enables them to survive drug exposure. DTPs also exhibit stem cell-like characteristics, broad epigenetic reprogramming, altered metabolism, and a mutagenic phenotype mediated by adaptive mutability. While several studies have characterised the transcriptional changes that lead to the altered phenotypes exhibited in DTPs, these studies have focused predominantly on protein coding changes. As long non-coding RNAs (lncRNAs) are also implicated in the phenotypes altered in DTPs, it is likely that they play a role in the biology of drug tolerance. In this review, we outline how lncRNAs may contribute to the key characteristics of DTPs, their potential roles in tolerance to targeted therapies, and the emergence of genetic resistance in lung adenocarcinoma. [ABSTRACT FROM AUTHOR]

The purpose of this case study was to examine Utah's Grades 1-6 social studies standards and the instructional resources provided by the state for Chinese Dual Language Immersion (DLI) teachers to investigate how social studies instruction supported cultural learning for DLI students. A collaborative, Didaktik analysis of the standards and resources found that, in Grades 1-3 and 6, during which the partner-language DLI teacher is responsible for social studies, Chinese cultural knowledge or learning was not explicitly emphasized within the instructional resources provided in Grades 1-3. The one possible example found was in Grade 6, which included extensive materials for lessons on ancient Chinese civilization and culture. Despite this well-developed set of resources, it was unclear whether ancient China constituted a topic unique to the Chinese DLI program social studies classes or if this was a topic that might be learned by both DLI and non-DLI students across the state. Available resources explicitly encourage Chinese DLI teachers to teach American and Utah cultural traditions, but not necessarily the partner language's cultural traditions. The lack of focus on partner-language culture raises questions for both second language learning in DLI settings and DLI teacher professional development. [ABSTRACT FROM AUTHOR]

First‐generation college students (FGCS) face unique challenges compared to non‐first‐generation peers. Lack of personal, emotional, financial, or psychological support may create difficulties adapting to college. The focus on affordability in higher education and lowering the cost of a bachelor's degree has also made the transfer process an essential part of degree completion for many, with only 41% of transfer students pursuing a bachelor's degree will achieve that goal. Research has made the connection that diminished personal support from parental figures may impact the mental health of FGCS transfer students, leading to higher dropout, lower retention, and lower degree completion rates. Students who experienced increased personal support might experience fewer mental health issues, resulting in a higher chance of degree completion. Future research implications include prioritizing support systems and mental health services to aid FGCS and transfer students lacking personal support in degree completion. [ABSTRACT FROM AUTHOR]

This instrumental case study explored non-formal educators' lay theories of adolescence using the case of the Boy Scouts of America's Scouts BSA program, a co-ed program serving youth between the ages of 11 and 17. We conducted an iterative analysis of 110 structured interviews with Scouts BSA adult volunteer leaders who served as scoutmasters or assistant scoutmasters. Results indicated that participants discussed adolescence in terms of youth characteristics as well as processes youth underwent during their adolescent years. These adults sometimes viewed adolescence as idiosyncratic, identifying differences in learning, behavior, and family situations among youth, particularly those whom they had identified as exhibiting specific challenges like autism. The results also illustrated relationships between the program and lay theories of adolescence. Namely, core Scouts BSA programmatic structures and expectations such as operating the patrol/troop method hierarchies, building leadership skills, camping or outdoor activities, and including all youth in activities influence participants' own views of adolescence, including their views of adolescence as a time to cultivate maturity and independence. The study concludes with a brief discussion of results and limitations of the study, including recommendations for training and additional research. [ABSTRACT FROM AUTHOR]

Youth purpose was investigated using a two-phase embedded design with youth participating in Scouts BSA (N = 3,943), ages 9–20 (M = 14.0, SD = 1.9). Participating Scouts were mostly White (91%) and male (98%). In Phase 1, we conducted a two-step cluster analysis on Scouts' survey responses to three purpose dimensions (personal meaning, goal-directedness, beyond-the-self orientation). Four clusters emerged: Purposeful, Explorers, Dreamers, Nonpurposeful. In Phase 2, we explored qualities of purpose within each cluster and programmatic features and relationships within the scouting context fostering youth purpose with a Scout subsample (N = 30) who completed semi-structured interviews. Results demonstrated that adults supporting scouting, inspiration from older peers, and opportunities to help others and explore new activities supported youth purpose. [ABSTRACT FROM AUTHOR]

This intrinsic case study analyzed the community-based framing of the work of Educators Rising, a nationwide organization that aims to develop a pipeline between secondary students and the teaching profession. Using TribalCrit to examine publicly available documents, videos, and websites, the study found Educators Rising primarily framed community as a place: communities are physical locations that need teachers, the original impetus for Educators Rising's existence and work. Through its partnerships with schools and districts, Educators Rising seeks to cultivate market-oriented views of knowledge and teaching in these communities. The organization's standards and activities privilege certain academic knowledge over cultural knowledge. Building from this view of certain academic knowledge, Educators Rising packages conceptions of teaching forged by external entities like the National Board for Professional Teaching Standards, which participants are expected to assimilate through their involvement in the organization. Additionally, Educators Rising attempts to enforce assimilation of external conceptions of teaching through competitions and micro-credentials. Communities, from Educators Rising's perspective, are sites to assimilate certain knowledge and narrow conceptions of teaching and teacher learning, primarily through student participation in competitive activities. Recommendations for effective partnerships are discussed. [ABSTRACT FROM AUTHOR]

Plantago princeps var. princeps is an endangered native Hawaiian plant, and part of the recovery plan includes repopulation using plants grown in a nursery. However, disease pressure from downy mildew is hindering repopulation efforts. The organism associated with the downy mildew was determined to be a Peronospora species with brown, ellipsoid conidia measuring 21 by 16 µm on average, which was morphologically different from validly described species of Peronospora that infect Plantago species, but it was morphologically similar to the invalidly published species Peronospora lanceolatae (Art. 40.1). Comparison of mitochondrial cytochrome oxidase subunit I (cox1), mitochondrial cytochrome oxidase subunit II (cox2), nuclear internal transcribed spacer (ITS), and nuclear 28S rRNA D1–D2 (28S) loci revealed the unknown Peronospora to be molecularly divergent from Peronospora alta and Peronsopora plantaginis, but very similar to Peronospora from Plantago lanceolata, the type host of P. lanceolatae. Phylogenetic trees inferred with maximum likelihood and Bayesian inference from a concatenated alignmaent and individual gene trees confirmed the divergence of the unknown Peronospora from P. alta and P. plantaginis and its similarity to P. lanceolatae. However, attempts to inoculate Plantago lanceolata with the strain from Plantago princeps var. princeps were unsuccessful, which, in conjunction with divergence in ITS, suggests that the unknown Peronospora is specific to Plantago princeps var. princeps. Herein, the Peronospora strain on Plantago princeps var. princeps is described as the new species Peronospora kuewa based on morphology, molecular phylogenetics, and host specificity. In addition, Peronospora gaponenkoae is described here to honor Nina Ivanova Gaponenko on the basis of her description of P. lanceolatae. [ABSTRACT FROM AUTHOR]

Motivation Whole-genome sequencing of uncultured eukaryotic genomes is complicated by difficulties in acquiring sufficient amounts of tissue. Single-cell genomics (SCG) by multiple displacement amplification provides a technical workaround, yielding whole-genome libraries which can be assembled de novo. Downsides of multiple displacement amplification include coverage biases and exacerbation of contamination. These factors affect assembly continuity and fidelity, complicating discrimination of genomes from contamination and noise by available tools. Uncultured eukaryotes and their relatives are often underrepresented in large sequence data repositories, further impairing identification and separation. Results We compare the ability of filtering approaches to remove contamination and resolve eukaryotic draft genomes from SCG metagenomes, finding significant variation in outcomes. To address these inconsistencies, we introduce a consensus approach that is codified in the SCGid software package. SCGid parallelly filters assemblies using different approaches, yielding three intermediate drafts from which consensus is drawn. Using genuine and mock SCG metagenomes, we show that our approach corrects for variation among draft genomes predicted by individual approaches and outperforms them in recapitulating published drafts in a fast and repeatable way, providing a useful alternative to available methods and manual curation. Availability and implementation The SCGid package is implemented in python and R. Source code is available at http://www.github.com/amsesk/SCGid under the GNU GPL 3.0 license. Supplementary information Supplementary data are available at Bioinformatics online. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Produced a phylogenetic analysis of uncultured predacious fungi using genomes generated from single cell genomic methods. • Monophyletic Zoopagales. • Ancestral state reconstructions could not resolve the trophic state of the zoopagalean ancestor. Abstract Previous genome-scale phylogenetic analyses of Fungi have under sampled taxa from Zoopagales; this order contains many predacious or parasitic genera, and most have never been grown in pure culture. We sequenced the genomes of 4 zoopagalean taxa that are predators of amoebae, nematodes, or rotifers and the genome of one taxon that is a parasite of amoebae using single cell sequencing methods with whole genome amplification. Each genome was a metagenome, which was assembled and binned using multiple techniques to identify the target genomes. We inferred phylogenies with both super matrix and coalescent approaches using 192 conserved proteins mined from the target genomes and performed ancestral state reconstructions to determine the ancestral trophic lifestyle of the clade. Our results indicate that Zoopagales is monophyletic. Ancestral state reconstructions provide moderate support for mycoparasitism being the ancestral state of the clade. [ABSTRACT FROM AUTHOR]

Previous molecular phylogenetic studies have shown that families in Zoopagales are not monophyletic. To test the monophyly of genera and species in the order, we used a single-cell approach to generate nuclear 18S rRNA (18S) sequences for 10 isolates representing nine taxa. We provide the first sequences for the genus Zoopage and additional sequences for taxa in Cocholonema, Acaulopage, and Zoophagus. Our results reveal that Zoophagus, Zoopage, and Acaulopage tetraceros are not monophyletic. We conclude that morphology alone is not sufficient to delineate genera and species in the order and encourage studies that increase genetic sampling of taxa including type species. [ABSTRACT FROM AUTHOR]

Food webs in temporary forest ponds are driven by decomposition of terrestrial inputs. Chytrid fungi are important components of the fungal community, degrading leaf litter in streams reliant on terrestrial inputs and in lake ecosystems where they may stabilize the food web. However, little is known about chytrid fungi in temporary forest ponds. We inventoried the chytrid diversity present in two temporary forest ponds via light microscopy of baited samples and ion semiconductor (Ion Torrent) sequencing of environmental DNA. We quantified trends of chytrid alpha and beta diversity as a function of spatial and temporal factors. A total of 59 chytrid taxa were detected throughout the study. Beta diversity exhibited variation across the sampled months for both the entire fungal community as well as for chytrids alone. Shifts in community composition were also apparent, although diversity metrics and composition patterns did not meet adjusted P values. The results of this study highlight the diversity of chytrid fungi in temporary forest ponds and the need for further studies on the spatial and temporal dynamics of chytrid species. [ABSTRACT FROM AUTHOR]

The internal metamorphic-plutonic zone of the middle Paleoproterozoic Wopmay orogen, northwestern Canadian Shield, exposes an oblique section through a prograde Buchan-type metamorphic sequence. New petrographic, petrologic, and geochronologic analyses of pelite and quartz arenite samples from the eastern margin of the internal zone quantify the evolving conditions and timing of metamorphism and enable the discriminant evaluation of competing tectonic models. Study of fabric development and mineral growth relationships indicates that prograde metamorphism occurred late within a craton-verging, crustal-shortening ("Calderian") deformation event. Phase equilibria modeling was used to calculate pressure-temperature (P-T) path segments and determine peak conditions from andalusite-muscovite grade at ~3.3 kbar and 575 °C to sillimanite-K-feldspar ± granitic leucosome grade at ~4.8-6.2 kbar and 670-745 °C. In situ monazite geochronology indicates that thermal peak metamorphic conditions were reached between 1878.6 ± 6.5 Ma and 1872 ± 9 Ma. Ages of detrital zircon within quartz arenite across the width of the metamorphic sequence document a diagnostic easterly Slave craton-Thelon tectonic zone derivation that links the metasedimentary rocks, including those previously considered to be "exotic" in a proposed tectonic klippe model for the internal zone, to the adjacent craton. Integration of these results with observations on the relatively low state of strain and the bracketing of a common (single) metamorphic field gradient for all garnet-bearing mineral zones confirm that the latter have preserved their prograde isogradic continuity from time of formation, and that the leading edge of a tectonic klippe consisting of rocks exotic to the Coronation margin does not traverse the study area. [ABSTRACT FROM AUTHOR]

An occurrence of diagenetic fluorapatite cement is documented within the Cambro-Ordovician Keeseville Formation, Potsdam Group, near Chateaugay in New York State. The fluorapatite cement occurs as stratiform layers within ephemeral fluvial quartz arenites, which have been reworked by aeolian processes prior to burial. The paragenetic sequence includes the following: compaction of dust-rimmed grains → quartz cementation → minor kaolinite → fluorapatite cementation followed by secondary dissolution porosity and telogenetic hematite cementation. Mesogenetic illitization of kaolinite may have taken place prior to or following fluorapatite cementation. The fluorapatite occurs as elongated bladed crystals that characteristically contain ladder-like, inclusion-rich cores running parallel to crystal length, surrounded by clearer rims, and larger blocky crystals towards the middle of interstices. In situ SHRIMP analyses of blocky fluorapatite crystals yield a U-Pb age of 486 ± 29 Ma, indicating that the cement formed during mesogenetic burial processes and (or) during fluid flow driven by Taconic orogenic events. There is no obvious source of phosphorous for the fluorapatite cement within the Potsdam Group, but phosphorous-rich lithologies are known from the adjacent basement of the Adirondack Dome. Phosphorous-rich fluids may have been derived from these basement lithologies. The occurrence of the rare fluorapatite cement in the Keeseville Formation adjacent to the Chateaugay Lake Fault raises the possibility that alkaline phosphatic fluids were focused within the fault and migrated laterally away from the fault into the host Keeseville Formation to form stratiform fluorapatite cement in the sandstone. [ABSTRACT FROM AUTHOR]

U-Pb ages of zircon from bentonites within the upper Cretaceous Bastion Ridge and Kanguk formations, Sverdrup Basin, provide constraints on sedimentation rates, biostratigraphic correlations, timing of Oceanic Anoxic Event 2 (OAE2) in the High Arctic, and the late magmatic history of the High Arctic Large Igneous Province (HALIP). A late Cenomanian to early Turonian age for the base of the Kanguk Formation is confirmed that supports correlations of the global OAE2 in the High Arctic. Sedimentation rates varied from 19 m Ma-1 between 93 and 91 Ma to 26 m Ma-1 between 91 and 83 Ma at Axel Heiberg Island. At Ellef Ringnes Island, the lower Kanguk Formation records high rates of ~70 mMa-1 between 94 and 93 Ma, which decrease to rates comparable to those of the upper Axel Heiberg section. Differences in sedimentation rates may reflect differences in setting prior to the major transgression in the latest Cenomanian to early Turonian. The timing of Arctic occurrences of the Scaphites nigricollensis and Scaphites depressus ammonite zones is shown to be broadly comparable to that of lower-latitude occurrences within the Western Interior Seaway. An eruption frequency of 0.5-2.5 Ma characterizes the late alkaline phase of HALIP magmatism. Volcanic bed thicknesses of 10-50 cm suggest ash transport distances of less than 1000 km. Long-lived volcanic centres, in the area of the Alpha Ridge, northern Ellesmere Island or northern Greenland, were the likely source of volcanic ash over a period of 10-15 Ma. [ABSTRACT FROM AUTHOR]

Paleoproterozoic metasedimentary successions of the northwestern Canadian Shield provide records of tectonic events, but the definition of depositional ages has proved elusive. Although previously poorly understood, the Montresor belt of western Nunavut yields new insight into the 2.2-1.8 Ga time window. On the basis of U-Pb analyses of detrital zircon in sedimentary rocks and igneous zircon in sills, we conclude that arenite of the lower Montresor group was deposited between 2.194 and 2.045 Ga, and arkose of the upper Montresor group after 1.924 Ga, adding constraints on the Rae cover sequence. The lower Montresor arenite yielded an older group (3.05-2.58 Ga) and a younger, more tightly constrained group (2.194 ± 0.014 Ga). Four of six zircon grains analyzed from a gabbro sill within the lower Montresor have discordant 207Pb/206Pb ages (2.71, 2.66, 2.53, and 2.39 Ga) and are considered to be inherited, whereas two grains provide an age of 2045 ± 13 Ma, interpreted to date crystallization and providing a minimum age for the lower Montresor package. Upper Montresor arkose contains detrital zircon with probability density peaks at 2.55-2.25 and 2.1-1.92 Ga, together with scattered older grains (3.8-2.65 Ga). The youngest grain yields an age of 1924 ± 6 Ma, establishing a maximum age for sandstone deposition. Provenance is inferred to have been from the west, where igneous sources of 2.5-2.3 Ga (Queen Maud block) and 2.03-1.89 Ga (Thelon orogen) are known. Collectively, the new ages suggest a minimum 120 million year gap between deposition of the pre-2045 ± 13 Ma lower and post-1924 ± 6 Ma upper parts of the Montresor group. Similar age constraints may apply to other parts of the Rae cover sequence. [ABSTRACT FROM AUTHOR]

Zoospore ultrastructural characters combined with molecular phylogenetic hypotheses have been used to revise the taxonomy of zoosporic true fungi. An example is the reclassification of Rhizophlyctis rosea-like fungal strains into four new families and three new genera within the order Rhizophlyctidales. One genus was Borealophlyctis, which included a Canadian isolate, DAOMC 229843. A recent survey of chytrid diversity in Alabama (USA) yielded additional strains (WJD 170, WJD 171) in the Borealophlyctis lineage. With light and transmission-electron microscopy we examined strains DAOMC 229843, WJD 170 and WJD 171. We also analyzed partial nuc 28S rDNA D1-D3 domains (28S) and nuc rDNA region encompassing the internal transcribed spacers 1 and 2 and 5.8S (ITS) sequences to determine the phylogenetic placement of the strains within Rhizophlyctidales. Based on molecular divergence and morphological differences from the type Borealophlyctis paxensis, we recognize DAOMC 229843, WJD 170 and WJD 171 as representatives of the new species Borealophlyctis nickersoniae. [ABSTRACT FROM AUTHOR]

Temporary forest ponds are depressions that annually cycle between non-inundated and inundated stages and are recognized as biodiversity hotspots for amphibians and other taxa. However, little is known about the microbial communities of temporary forest ponds and less is known about chytrids, an inconspicuous, early diverging lineage of fungi, present in such ponds. We sampled soil and water from a temporary forest pond in the Oakmulgee District of the Talladega National Forest. Chytrids were isolated from the samples using baits and standard isolating techniques. Isolated strains were identified using the monophyletic-species concept based on a molecular phylogeny inferred from an alignment of the nuclear large subunit rDNA. A total of 30 strains were isolated, which represented 7 species. Due to the limitations of a culture-based method in being able to culture all chytrids that are present, we have described only a portion of the chytrid community. This study, however, is foundational to future inventories that apply a multiphasic approach to further reveal chytrid diversity in this understudied and variable habitat. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic Hottah terrane is the westernmost exposed bedrock of the Canadian Shield and a critical component for understanding the evolution of the Wopmay Orogen. Thirteen new high-precision U-Pb zircon crystallization ages are presented and support field observations of a volcano-plutonic continuum from Hottah terrane through to the end of the Great Bear magmatism, from >1950 to 1850 Ma. The new crystallization ages, new geochemical data, and newly published detrital zircon U-Pb data are used to challenge hitherto accepted models for the evolution of the Hottah terrane as an exotic arc and microcontinent that arrived over a west-dipping subduction zone and collided with the Slave craton at ca. 1.88 Ga. Although the Hottah terrane does have a tectonic history that is distinct from that of the neighbouring Slave craton, it shares a temporal history with a number of domains to the south and east - domains that were tied to the Slave craton by ca. 1.97 Ga. It is interpreted herein that Hottah terrane began to the south of its current position and evolved in an active margin over an always east-dipping subduction system that began prior to ca. 2.0 Ga and continued to ca. 1.85 Ga, and underwent tectonic switching and migration. The stratigraphy of the ca. 1913-1900 Ma Hottah plutonic complex and Bell Island Bay Group includes a subaerial rifting arc sequence, followed by basinal opening represented by marginal marine quartz arenite and overlying ca. 1893 Ma pillowed basalt flows and lesser rhyodacites. We interpret this stratigraphy to record Hottah terrane rifting off its parental arc crust - in essence the birth of the new Hottah terrane. This model is similar to rapidly rifting arcs in active margins - for example, modern Baja California. These rifts generally occur at the transition between subduction zones (e.g., Cocos-Rivera plates) and transtensional shear zones (e.g., San Andreas fault), and we suggest that extension-driven transtensional shearing, or, more simply, terrane translation, was responsible for the evolution of Bell Island Bay Group stratigraphy and that it transported this newly born Hottah terrane laterally (northward in modern coordinates), arriving adjacent to the Slave craton at ca. 1.88 Ga. Renewed east-dipping subduction led to the Great Bear arc flare-up at ca. 1876 Ma, continuing to ca. 1869 Ma. This was followed by voluminous Great Bear plutonism until ca. 1855 Ma. The model implies that it was the westerly Nahanni terrane and its subducting oceanic crust that collided with this active margin, shutting down the >120 million year old, east-dipping subduction system. [ABSTRACT FROM AUTHOR]

Petrological modeling and geochronology (Lu–Hf garnet, U–Pb monazite, zircon, and titanite) for seven mid-amphibolite to granulite-facies metamorphic rocks in the Thelon tectonic zone (Ttz) provide new insights into the evolution of this orogen. A Grt-Sp-Sil diatexite records 2.01–2.00 Ga garnet and monazite growth during >830 °C contact metamorphism associated with voluminous convergent margin plutonism. The most widespread, 1.96–1.90 Ga metamorphism is associated with clockwise pressure (P)–temperature (T) paths, indicating it was driven by crustal thickening. Earlier (1.96–1.92 Ga) and lower temperature (630 °C–730 °C; 6–8 kbar) metamorphism in the eastern Slave craton contrast with ∼860 °C (7.5 kbar), 1.91–1.90 Ga diatexites in the central, Paleoproterozoic plutonic rock-dominated, core of the Ttz. These differences are interpreted to reflect lower vs. upper plate settings, respectively. A contribution of mantle heat is suggested by the counter-clockwise P–T path and 885 °C (5.7 kbar) conditions recorded by diatexite associated with c. 1.9 Ga peraluminous leucogranite that dominates a corridor along the Ttz–Rae craton boundary. A tectonic model is proposed wherein the Ttz evolved at an accretionary margin after rifting of Ttz microcontinent (mTtz) off the Rae craton at c. 2.2–2.1 Ga. Voluminous plutonism at 2.01–1.98 Ga formed via east-dipping subduction under mTtz. Following 1.97 Ga collision of the Slave craton and mTtz, west-dipping subduction generated 1.96–1.95 Ga plutonism in the composite mTtz-Slave upper plate. Collision of Rae craton at 1.95–1.94 Ga led to crustal thickening, widespread 1.91–1.90 Ga high-grade metamorphism and extensive crustal melting in the central Ttz. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic Wopmay orogen is modeled as a simple arc-continent collision involving the Archean Slave craton and an enigmatic continental arc terrane termed the Hottah terrane. Hottah is a composite terrane that includes a juvenile 2.6-2.1 Ga basement and a younger 1.93-1.90 Ga continental arc. The extent and crustal age structure of the terrane is poorly known which limits interpretations as to its origin, and eventual role in the development of the orogen. Multi-isotopic (U-Pb, Hf, O) analyses of detrital zircon from rocks of the Hottah terrane and its cover sequence are used to indirectly evaluate its age and crustal characteristics. The data confirm that ca 2.6-2.1 Ga crust is an important component of the terrane but Hf isotopic data indicate mostly non-juvenile compositions consistent with recycled Neoarchean crust sources. Ages of detrital zircon are distinct from those expected of the Slave craton but are similar to adjacent 2.0-1.90 Ga Paleoproterozoic terranes of northwestern Laurentia. The similarity to terranes such as the Ksituan/Buffalo Head and Taltson-Thelon magmatic zones, south and east of the Wopmay Orogen indicate that Hottah could represent a terrane that initially evolved adjacent to the earliest assembled parts of the Nuna continent between 2.0 and 1.9 Ga, and was rifted prior to the collision with the Slave margin that produced the Calderian orogeny. [ABSTRACT FROM AUTHOR]

Field evidence, map compilation, geochemistry, geochronology, and potential field data document six intervals of Cretaceous magmatism in the central Sverdrup Basin. These are: (1) Hauterivian (ca. 130 Ma) vol-caniclastic deposition in the lower Isachsen Formation; (2) 126.6 ± 1.2 Ma (U-Pb zircon) gabbroic intrusion; (3) 120.8 ± 0.8 Ma (U-Pb baddeleyite) diabasic intrusion; (4) 105.40 ± 0.22 Ma (U-Pb detrital zircon) pyroclastic deposition at the top of the Invincible Point Member, Christopher Formation; (5) upper Albian (ca. 103 Ma) pillow and hydroclastic breccia in the upper Christopher Formation; and (6) uppermost Albian (ca. 101 Ma) volcanic breccia and scoria in the Hassel Formation. Whole-rock geochemical data show that these magmatic rocks are similar to previously documented High Arctic large igneous province tholeiitic basalts, but analyses of fresh glass in tuffs reveal evolved ferroandesite to dacite compositions not recorded in whole-rock data. Approximate ages of saucer-shaped sills inferred from the relationship of sill width to depth of emplacement suggest at least three intervals of sill emplacement between 130 and 120 Ma. The new data show that volcanism in the Sverdrup Basin was of greater spatial extent, and that magmatism occurred more frequently, than was previously recognized. Comparison of the new central Sverdrup Basin data and interpretations with other data sets from the Sverdrup Basin, Svalbard, and Franz Josef Land suggests that High Arctic large igneous province magmatism occurred over a more extended period of time in the central Sverdrup Basin than in other regions. [ABSTRACT FROM AUTHOR]

Chytriomyces is a complex genus in Chytridiales. The morphological concept of the genus expanded as new taxa were added, and studies of zoospore ultrastructure and molecular phylogenies have revealed the genus to be polyphyletic. One problematic taxon is C. spinosus Fay, a distinctive species characterized by whorls of spines on the zoosporangium and a large accumulation of vesicle material beneath the operculum. With light-, scanningelectron and transmission-electron microscopy, we examined a culture (WJD186) isolated from a muck sample collected from a temporary forest pond. We also analyzed the D1-D2 variable domains of the nuc 28S rDNA (28S) sequences to confirmthe phylogenetic placement of the species relative to the type of Chytriomyces, C. hyalinus Karling. The morphology of culture WJD186 is consistent with features Fay described for C. spinosus, and the zoospore ultrastructure is consistent with the Group I-type zoospore characters of Chytriomycetaceae (Chytridiales). In our molecular phylogeny C. spinosus does not group with the type of Chytriomyces. Consequently, we erect a new genus in Chytriomycetaceae and present the new combination Fayochytriomyces spinosus. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zircon from lower crustal xenoliths record complex crust formation histories. [•] Cores record crust formation at ca. 3.5–2.6Ga and ca. 2.0–1.9Ga thermal reworking. [•] Metamorphic rims record regional lower crustal reworking at ca. 1.75Ga. [•] Lower crustal reworking likely resulted from 1.75Ga magma underplating. [•] Intracrystalline Pb-disturbance related to 1.75Ga granulite-facies metamorphism. [Copyright &y& Elsevier]

Alabama is a biodiversity hotspot. The diversity of chytrid fungi, however, is underexplored. For this reason, we used standard bait-culturing techniques to sample habitats in Tuscaloosa County for chytrids. We cultured 100 isolates; the majority was assigned to 23 taxa belonging to 6 of the 7 recognized orders. Some could not be assigned to a currently described taxon. The majority of isolates belonged to one of three taxa: Chytriomyces hyalinus, Rhizoclosmatium globosum, and Boothiomyces macroporosum. This result demonstrates that chytrid communities in Tuscaloosa County, as elsewhere, are composed of a few common and many uncommon to rare taxa. The presence of unidentified chytrid isolates demonstrates the need for further sampling in Alabama, and the potential for this sampling to broaden our understanding of chytrid diversity. [ABSTRACT FROM AUTHOR]

The Boothia mainland region of the north-central Rae domain is underlain by remnants of a Neoarchean volcano sedimentary sequence dismembered by two regionally extensive Neoarchean high-potassium granitoid suites with rare occurrences of a structurally interleaved, Paleoproterozoic sedimentary cover sequence. The granitoids and their gneissic equivalents are dominated by variably deformed and metamorphosed I-type, metaluminous, polyphase, commonly porphyritic to augen, biotite ±hornblende monzogranite, and subordinate granodiorite, with rare tonalite. New geochronological results, the first for this area, demonstrate that the widespread Neoarchean granitoid plutonism is dominantly 2.61-2.59 Ga, with a less prominent 2.66 Ga plutonic event. The age of zircon recrystallization suggests that ca. 2.60 Ga Archean metamorphism and fabric development (S1) affected the 2.66 Ga plutons prior to or contemporaneously with intrusion of the voluminous ca. 2.6 Ga suite. εNd(t) for the ca. 2.61-2.59 Ga suite range from 1.4 to -1.9, overlapping with the ca. 2.66 Ga suite that range from 1.4 to 1.5. The Nd isotopic data, coupled with the presence of inherited ca. 2.65, 2.70, and 2.85-2.90 Ga zircon, suggests recycling of older, Neoarchean to Mesoarchean crust in the formation of these suites. Metaplutonic rocks preserve Paleoproterozoic deformation (F4 and F5) and amphibolite-facies metamorphism, sporadically recorded in zircon rims that formed at 1.81 Ga. This event strongly reoriented the Neoarchean fabrics in metaplutonic rocks, generally without the development of a new coaxial Paleoproterozoic fabric, and we attribute this strain and metamorphism to the Hudsonian orogeny. La région terrestre Boothia du domaine Rae centre-nord repose sur des vestiges d'une séquence volcano-sédimentaire datant du Néoarchéen; cette séquence est démembrée par deux suites granitoïdes d'échelle régionale, à teneur élevée en potassium et possédant de rares occurrences d'une séquence structurellement intercalée d'une couverture sédimentaire datant du Paléoprotérozoïque. Les granitoïdes et leurs équivalents gneissiques sont dominés par un monzogranite à déformation variable, métamorphisé, de type I, métalumineux, polyphasé, souvent porphyrique à oeillé et à biotite hornblende avec une granodiorite subordonnée et une rare tonalite. De nouveaux résultats géochronologiques, les premiers pour ce secteur, démontrent que le plutonisme granitoïde néoarchéen étendu date surtout de 2,61 à 2,59 Ga, avec un événement plutonique moins important vers 2,66 Ga. L'âge de la recristallisation du zircon suggère que, vers 2,60 Ga, le métamorphisme archéen et le développement de la fabrique (S1) aient affecté les plutons âgés de 2,66 Ga avant ou en même temps que l'intrusion de la volumineuse suite vers 2,6 Ga. Les valeurs εNd(t) pour la suite datant de ~ 2,61 à 2,59 Ga varient de 1,4 à -1,9, chevauchant la suite datant ~2,66 Ga, dont les valeurs εNd(t) varient de 1,4 à 1,5. Les données d'isotopes Nd, jumelées à la présence de zircons hérités dont les âges sont ~2,65, 2,70 et 2,85-2,90 Ga, suggèrent un recyclage de l'ancienne croûte néoarchéenne à mésoarchéenne pour la formation de ces suites. Des roches métaplutoniques ont préservé la déformation paléoprotérozoïque (F4 et F5) ainsi que le métamorphisme au faciès des amphibolites, retrouvé sporadiquement dans les bordures des zircons qui se sont formées à 1,81 Ga. Cet événement a grandement réorienté les fabriques néoarchéennes dans les roches métaplutoniques, généralement sans le développement d'une nouvelle fabrique coaxiale paléoprotérozoïque; nous attribuons cette déformation et ce métamorphisme à l'orogenèse hudsonienne. [ABSTRACT FROM AUTHOR]

The timing of Sveconorwegian high-grade metamorphism is evaluated in the four lithotectonic units / terranes exposed in the Sveconorwegian belt in South Norway. U-Pb, Th-Pb and Re-Os data were obtained from 21 samples of Mesoproterozoic ortho- and paragneisses. In the Bamble Terrane, SIMS monazite U-Pb data constrain peak amphibolite- to granulite-facies metamorphism between 1137 ±1 and 1127 ±6 Ma, and unroofing at 1107 ±9 Ma. In the Kongsberg Terrane, a molybdenite Re-Os date at 1112 ±4 Ma and a monazite U-Pb date at 1092 ±1 Ma bracket amphibolite-facies metamorphism. In the Idefjorden Terrane, west of the Oslo rift, a pulse of Gothian metamorphism at 1539 ±8 Ma and three pulses of Sveconorwegian metamorphism at 1091 ±18 Ma, 1052 ±4 to 1043 ±8 Ma and 1024 ±9 Ma are recorded by monazite, zircon and titanite data. Amphibolitefacies metamorphism peaked at 1052 ±4 Ma in the kyanite field (1.00-1.17 GPa, 688-780 °C). At the boundary between the Idefjorden and Telemarkia Terranes, SIMS zircon U-Pb data constrain amphibolite-facies metamorphism between 1012 ±7 and 1008 ±14 Ma and provide a maximum age for shearing along the Vardefjell Shear Zone between these two terranes. Amphibolite-facies metamorphism in the Telemarkia hanging wall of the Vardefjell Shear Zone is coeval at 1014 ±1 Ma. In the Suldal Sector of the Telemarkia Terrane, monazite data yield an age of 1005 ±7 Ma for amphibolite- facies migmatitization. In the Rogaland-Vest Agder Sector of the Telemarkia Terrane, paired U-Pb and Th-Pb ID-TIMS monazite analyses date monazite growth to have been between 1013 ±5 and 980 ±5 Ma during M1 intermediate-pressure regional metamorphism, and between 927 ±5 and 922 ±5 Ma during M2 low-pressure high- to ultrahigh-temperature metamorphism. SIMS monazite dates at 1032 ±5 and 990 ±8 Ma in a granulite, situated outside the area affected by M2 metamorphism, demonstrate granulite-facies conditions during M1 metamorphism. Available data show that the four terranes in South Norway have distinct metamorphic histories. The Bamble and Kongsberg Terranes show evidence for early-Sveconorwegian metamorphism between 1140 and 1080 Ma. The Idefjorden Terrane, though locally affected by this early metamorphism, was mainly reworked by medium to high-pressure metamorphism between 1050 and 1025 Ma. The Telemarkia Terrane was reworked later between c. 1035 and 970 Ma. A high-temperature metamorphic phase at 930-920 Ma is specific for the Telemarkia Terrane and is related to post-collisional intrusion of the Rogaland anorthosite-mangerite-charnockite (AMC) Complex. [ABSTRACT FROM AUTHOR]

Abstract: New geological and geochronological data from the MacQuoid supracrustal belt and the geometrically overlying Cross Bay plutonic complex highlight a distinct tectonothermal evolution for the northwestern part of the Hearne domain (northwestern Hearne subdomain), compared with adjacent areas in the Rae and Hearne, of the western Churchill Province, Canada. The supracrustal and intrusive rocks dominantly formed in the Neoarchean between <2.74 and 2.65Ga, with minor 2.61Ga granite, and experienced a polycyclic Neoarchean and Paleoproterozoic deformational history. The dominant tectonic fabric throughout much of the area formed between 2.56 and 2.50Ga, including the Big Lake shear zone, a granulite-facies mylonite zone that juxtaposed the Cross Bay plutonic complex over the MacQuoid supracrustal belt at 2.50Ga. The fabric transposed earlier fabrics whose age is poorly constrained. Additional tectonic events occurred during the Paleoproterozoic at 1.90Ga, and 1.84–1.81Ga. Differences between the geological histories of the northwestern part of the Hearne domain relative to the immediately adjacent Rae and Hearne areas highlight the tectonically distinct character of the northwestern Hearne subdomain. [Copyright &y& Elsevier]

In the Yathkyed Lake area the Tyrrell shear zone (TSZ) marks the boundary between the northwestern and central Hearne subdomains of the Western Churchill Province. The TSZ is dominated by Proterozoic dextral strain, but in areas of low dextral strain, older shear fabrics are consistent with an earlier thrusting event. Four syntectonic granite sheets from within low-dextral-strain zones in the TSZ and contiguous shear zones at the base of the Yathkyed belt have ages of 2636–2629, 2652 ± 8, 2665–2639, and 2644 ± 3 Ma. The Yathkyed belt occurs in the hanging wall of these shear zones and comprises a greenschist- to amphibolite-grade, overturned panel that is overlain by an upper amphibolite-grade polydeformed panel. The geometry is consistent with a thrust-imbricated stack. Two episodes of deformation in the hanging wall are bracket between ca. 2660 and 2616 +6–4 Ma and between 2616 +6–4 Ma and ca. 2.60 Ga. The Yathkyed belt is interpreted to have initially been emplaced as a thick-skinned, thrust nappe along the TSZ, during 2.66–2.62 Ga tectonism, and reactivated at ca. 2.62–2.60 Ga, causing further crustal thickening. In the Upper Panel, protracted upper amphibolite-grade metamorphism and associated anatectic melting are recorded by zircon, titanite, and monazite ages ranging from ca. 2561 to 2492 Ma. This thermal event is in part attributed to burial in response to ca. 2.62–2.60 Ga thrust reactivation. The timing and means of emplacement of the Upper Panel on top of the Lower Panel is uncertain; however, ca. 2.50 Ga thrusting elsewhere in the northwestern Hearne subdomain provides one possible mechanism. [ABSTRACT FROM AUTHOR]

Investigates the Zircon Uranium-Lead geochronology in the Bergen arc eclogites in western Norway. Implications for the pre-Scandian evolution of the Caledonides; Formation of eclogites in an orogenic belt; Evaluation of the pre-collision history of eclogite terranes.

Abstract The purpose of our research is to investigate morphology, zoospore ultrastructure, and molecular placement of six strains in the Asterophlyctis (Chytridiales) lineage. In previous molecular analyses strain JEL 186, putatively Asterophlyctis sarcoptoides , placed as basal in family Chytriomycetaceae. Recent sampling for chytrids resulted in isolation of five strains (WJD 209, MP 058, JEL 524, JEL 857, and JEL 885) molecularly related to strain JEL 186. Our morphological evaluations reveal that strains JEL 186 and WJD 209 are members of Asterophlyctis. Strain WJD 209 is considered representative of the type, A. sarcoptoides , and strain JEL 186 a new species, Asterophlyctis michiganensis. The four strains MP 058, JEL 524, JEL 857, and JEL 885 are distinct from Asterophlyctis , and we consider them as members of a new genus, Wheelerophlyctis , composed of two species, Wheelerophlyctis interior and Wheelerophlyctis interiexterior. Asterophlyctis and Wheelerophlyctis are sister taxa and we demarcate that lineage as Asterophlyctaceae. The two genera also have similar zoospore ultrastructure, which is unique among strains in Chytridiales. In consideration of their molecular position and zoospore ultrastructure, we hypothesize that Asterophlyctis and Wheelerophlyctis represent a bridge between Chytriomycetaceae and Chytridiaceae. This research expands our concepts of systematics and zoospore ultrastructural variation in Chytridiales. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Husky Creek Formation is an interlayered redbed and basalt package that overlies a ca. 2.5 km thick, regionally extensive basaltic plateau linked to the 1.27 Ga Mackenzie Large Igneous Province. This succession provides an opportunity to study the interaction between contemporaneous fluvial sedimentation and flood basalt volcanism. The Husky Creek Formation is approximately 1900 m thick, consisting predominantly of fluvial channel and subordinate floodplain and eolian strata dominated by lithic detritus intercalated with basalt flows. U–Pb dating of detrital zircon grains collected from four stratigraphic levels in the Husky Creek Formation reveals two main age groupings: (1) a 1270 Ma peak attributed to the Mackenzie Large Igneous Province; and (2) Pre-1.6 Ga detrital zircon ages, which reflect sources from a broad region of northwestern Laurentia and are interpreted to be recycled from underlying sedimentary rocks of the Hornby Bay Basin. An upsection decrease in the proportion of ca. 1270 Ma zircon grains, coupled with increasing sandstone compositional maturity, reflects the expansion of the drainage basin during burial of a volcanic pile, with recycling becoming more dominant as the Husky Creek Formation accumulated. The Husky Creek Formation was deposited in the waning stages of the Mackenzie Igneous Event by west-flowing rivers into a geographically restricted basin above an extensive mafic volcanic plateau. This paper provides insight into fluvial basin development during the aftermath of one of Earth's largest igneous events. [ABSTRACT FROM AUTHOR]

The origin and nature of fluids responsible for U deposits of the Athabasca Basin have been in debate. This study presents the trace element abundances and stable isotope ratios (D/H and 11 B/ 10 B) of well characterized tourmaline samples determined by in situ analytical techniques, in order to evaluate the nature of fluids during the mineralization of the McArthur River U deposit, the world's largest high-grade U deposit. Magnesio-foitite, an alkali-deficient Mg-rich tourmaline, is abundant along the 13-km long P2 fault, a reverse structure that controls the location of the McArthur River deposit. Magnesio-foitite contains variable concentrations of rare earth elements (REEs, up to 46 ppm in total) and Y (up to 35 ppm). Chondrite normalized patterns indicate low light REEs (LREEs) relative to heavy REEs (HREEs) (Ce N < Y N , Y as a proxy for HREEs) and slight negative Eu anomalies, similar to those of uraninite from the deposit. The data combined with textural evidence suggest that magnesio-foitite and uraninite co-crystallized with LREE-rich aluminum phosphate sulfate minerals. Relatively high REE contents of magnesio-foitite in the ore zone indicates the incursion of a REE-rich basement fluid. Low values of δD (− 98 to − 41‰) for magnesio-foitite suggests that the mineralizing fluid originated from groundwater. Variably high values of δ 11 B (+ 13.1 to + 23.2‰) are explained by the dissolution of B from carbonate or evaporitic rocks and preferential removal of 10 B by the crystallization of illite and kaolinite. The results of this study support the ascent of a REE-rich basement fluid during mineralization and extensive modification of basinal fluids through the crystallization of clay minerals. [ABSTRACT FROM AUTHOR]

Iron oxide copper-gold (IOCG) and associated iron-oxide apatite (IOA) styles of metallic mineralization are recognized throughout the Paleoproterozoic Great Bear magmatic zone of the northwest Canadian Shield. The Great Bear magmatic zone was constructed between ca. 1876 and 1855 Ma on top of the older Hottah terrane, which preserves continental arc magmatism that began around ca. 2.0 to 1.97 Ga and continued between ca. 1.93 and 1.89 Ga. The Great Bear represents the final stages of ca. 150 million years of intermittent and pulsed magmatism related to an evolving continental orogenic belt. The preserved geology supports a dramatic geodynamic change in the subduction zone process at ca. 1875 Ma, a key driving mechanism for magma and metal mobilization, and was rapidly followed by a large-scale introduction of felsic-intermediate plutons. The overall tectonic setting is partially constrained from new and previously published geochemical data that show that the volcanic and plutonic rocks are high-K calc-alkaline to shoshonitic in nature (e.g., high K 2 O, Th/Yb, and Ce/P 2 0 5 ). They also have suprasubduction-zone geochemical signatures, including primitive mantle normalized positive Th and negative Nb, P, and Ti anomalies. The data support the primary melts were derived from a GLOSS-modified mantle wedge. Three-dimensional rendering of geophysical datasets suggest that two (of four) preserved surfaces within the upper mantle lithosphere, at 70 to 120 km depths, represent frozen, subducted oceanic slabs, and likely were the drivers for the bulk of Hottah and Great Bear arc magmatism. The older slab is northwest-striking and dips 12° to 15° northeast, whereas the younger is deeper and north-striking, dipping 13° east. The geometry of the surfaces are comparable with 4D modeling, where a subduction zone is temporarily shut down due to plateau collision, and then steps oceanward and re-initiates; there is no need for polarity reversal of the subduction system. This new geometry and the related inferences about process should be the focus of future research in the region, but for the time-being it can be stated that these subduction and collisional processes were the first order control on lithospheric evolution, and therefore metallic mineralization. Overall, the Great Bear magmatic zone IOCG and related mineralization is not comparable to other Proterozoic IOCG belts, such as those in Australia. However, the complexity of mineralization styles, the spatial-temporal relationship between IOA and IOCG mineralization, the suprasubduction zone environment, and a major change in tectonic regime are features similar to Andean-type IOCG mineralization, as well as Cordilleran alkali porphyry Cu-Au deposits. This further establishes the linkages between subduction zone processes and IOCG formation, as well as relationships in the IOCG-porphyry deposit continuum model. [ABSTRACT FROM AUTHOR]

The Eagle Plain region, located in the northeastern Yukon Territory, Canada, forms a northern segment of the Cretaceous Western Interior Sea. Its preserved mid-Cretaceous strata (Whitestone River Formation and Eagle Plain Group) document an active structural regime, sea-level fluctuations, paleoecosystem changes and the paleogeographic evolution south of the gateway to the Polar Sea. This study integrates foraminiferal assemblages recovered from two wells (Molar P-34 and Ellen C-24) and one Late Albian bentonite age with well log signatures and previously established outcrop data. The proposed biostratigraphic framework correlates well between both wells and with the fauna observed in outcrops. Three biostratigraphic zones are recognized allowing for regional correlations; the Early Albian Gaudryina tailleuri Zone, the Middle to early Late Albian Gaudryina canadensis Zone, and the latest Albian Miliammina manitobensis Zone. A new 206 Pb/ 238 U age of 105.56 ± 0.25 Ma places the upper Whitestone River Formation into the Late Albian. Foraminiferal morphogroups and their relative proportions allow for paleoenvironmental reconstruction, including oxygen and nutrient conditions. The Ellen well represents deposition in a fully marine, well oxygenated proximal shelf setting during the Early to early Late Albian, resulting in the Whitestone River Formation. The Molar well represents a deep water, offshore setting with increased accommodation space marked by an increase in tubular suspension feeders, demonstrating a northwestward deepening of the basin. Foraminiferal assemblages of the Albian Whitestone River Formation reflect the widely recognized depositional cycles of the Western Interior Sea (Moosebar, Hulcross, Joli Fou and Mowry seas). During Albian time the northern gateway between the Polar and Western Interior seas was widely inundated, contrasting with an either short lived closure or severely restricted phase during the Albian/Cenomanian boundary interval. [ABSTRACT FROM AUTHOR]

The Wopmay orogen is a Paleoproterozoic accretionary belt preserved to the west of the Archean Slave craton, northwest Canada. Reworked Archean crystalline basement occurs in the orogen, and new bedrock mapping, U-Pb geochronology, and Sm-Nd isotopic data further substantiate a Slave craton parentage for this basement. Detrital zircon results from unconformably overlying Paleoproterozoic supracrustal rocks also support a Slave craton provenance. Rifting of the Slave margin began at ca. 2.02 Ga with a second rift phase constrained between ca. 1.92 and 1.89 Ga, resulting in thermal weakening of the Archean basement and allowing subsequent penetrative deformation during the Calderian orogeny (ca. 1.88-1.85 Ga). The boundary between the western Slave craton and the reworked Archean basement in the southern Wopmay orogen is interpreted as the rifted cratonic margin, which later acted as a rigid backstop during compressional deformation. Age-isotopic characteristics of plutonic phases track the extent and evolution of these processes that left penetratively deformed Archean basement, Paleoproterozoic cover, and plutons in the west, and 'rigid' Archean Slave craton to the east. Diamond-bearing kimberlite occurs across the central and eastern parts of the Slave craton, but kimberlite (diamond bearing or not) has not been documented west of ∼114°W. It is proposed that while the crust of the western Slave craton escaped thermal weakening, the mantle did not and was moved out of the diamond stability field. The Paleoproterozoic extension-convergence cycle preserved in the Wopmay orogen provides a reasonable explanation as to why the western Slave craton appears to be diamond sterile. [ABSTRACT FROM AUTHOR]