bluuebunny/crossref_metadata_2025 huggingface dataset:
Skinfold Prediction Equations Fail to Provide an Accurate Estimate of Body Composition in Elite Rugby Union Athletes of Caucasian and Polynesian Ethnicity
Authors: Zemski Adam J. , Broad Elizabeth M. , Slater Gary J.
Published: October 2017

Body composition in elite rugby union athletes is routinely assessed using surface anthropometry, which can be utilized to provide estimates of absolute body composition using regression equations. This study aims to assess the ability of available skinfold equations to estimate body composition in elite rugby union athletes who have unique physique traits and divergent ethnicity. The development of sport-specific and ethnicity-sensitive equations was also pursued. Forty-three male international Australian rugby union athletes of Caucasian and Polynesian descent underwent surface anthropometry and dual-energy X-ray absorptiometry (DXA) assessment. Body fat percent (BF%) was estimated using five previously developed equations and compared to DXA measures. Novel sport and ethnicity-sensitive prediction equations were developed using forward selection multiple regression analysis. Existing skinfold equations provided unsatisfactory estimates of BF% in elite rugby union athletes, with all equations demonstrating a 95% prediction interval in excess of 5%. The equations tended to underestimate BF% at low levels of adiposity, whilst overestimating BF% at higher levels of adiposity, regardless of ethnicity. The novel equations created explained a similar amount of variance to those previously developed (Caucasians 75%, Polynesians 90%). The use of skinfold equations, including the created equations, cannot be supported to estimate absolute body composition. Until a population-specific equation is established that can be validated to precisely estimate body composition, it is advocated to use a proven method, such as DXA, when absolute measures of lean and fat mass are desired, and raw anthropometry data routinely to derive an estimate of body composition change.
Improving Mobility Performance in Wheelchair Basketball
Authors: Veeger Thom T.J. , de Witte Annemarie M.H. , Berger Monique A.M. , van der Slikke Rienk M.A. , Veeger Dirkjan (H.E.J.) , Hoozemans Marco J.M.
Published: October 2017

Objective: This study aimed to investigate which characteristics of athlete, wheelchair and athlete-wheelchair interface are the best predictors of wheelchair basketball mobility performance. Design: A total of 60 experienced wheelchair basketball players performed a wheelchair mobility performance test to assess their mobility performance. To determine which variables were the best predictors of mobility performance, forward stepwise linear regression analyses were performed on a set of 33 characteristics, including 10 athlete, 19 wheelchair, and 4 athlete-wheelchair interface characteristics. Results: A total of 8 of the characteristics turned out to be significant predictors of wheelchair basketball mobility performance. Classification, experience, maximal isometric force, wheel axis height, and hand rim diameter—which both are interchangeable with each other and wheel diameter—camber angle, and the vertical distance between shoulder and rear wheel axis—which was interchangeable with seat height—were positively associated with mobility performance. The vertical distance between the front seat and the footrest was negatively associated with mobility performance. Conclusion: With this insight, coaches and biomechanical specialists are provided with statistical findings to determine which characteristics they could focus on best to improve mobility performance. Six out of 8 predictors are modifiable and can be optimized to improve mobility performance. These adjustments could be carried out both in training (maximal isometric force) and in wheelchair configurations (eg, camber angle).
‘Once My Relatives See Me on Social Media… It Will be Something Very Bad for My Family’: The Ethics and Risks of Organizational Representations of Sporting Girls From the Global South
Authors: Thorpe Holly , Hayhurst Lyndsay , Chawansky Megan
Published: October 2017

This paper explores the ethics of representing girls and young women from the global South in Sport for Development (SfD) organizational campaigns via the case of Skateistan—an international SfD organization with skateboarding and educational programs in Afghanistan, Cambodia, and South Africa. Focusing particularly on Skateistan’s representations of skateboarding girls and young women in Afghanistan, we draw upon interviews with staff members as well as digital observations and organizational curriculum materials, to reveal some of the nuanced power relations within such media portrayals. In so doing, we also draw attention to some of the unintended risks of “positive” representations of sporting girls from the global South, and some of the strategies employed by Skateistan to navigate such issues.
The Intersections of Dance and Sport
Authors: Markula Pirkko
Published: October 2017

Is sport art? Is dance a sport? Such questions are asked on the pages of social media as well as on the pages of research journals. Debating whether dancers are athletes or sport has aesthetic qualities can reveal broader issues regarding the current health conscious, competitive, and commercialized (neo-liberal) culture: What do dance and sport do when they intersect in the larger operations of power that currently favor particular kinds of physical activity participation and representation? In this paper, I map various intersections of sport and dance first through sport philosophical debates about the aesthetic qualities of sport. Second, I examine what happens when competition is introduction to ballroom dance in the formation of DanceSport. Finally, I depict how dance and sport become intertwined as entertainment in reality television showsDancing with the StarsandSo You Think You Can Dance.
“You Have to Play Like a Man, But Still be a Woman”: Young Female Colombians Negotiating Gender Through Participation in a Sport for Development and Peace (SDP) Organization
Authors: Oxford Sarah , McLachlan Fiona
Published: October 2017

Colombian girls are not encouraged from playing sport due to gendered roles that idealize girls as “delicate” and reserve sport as an activity for boys. Since the early and mid-2000s girls living in two marginalized communities in Colombia have had the unique opportunity to participate in a sport for development and peace organization. Drawing on six months of ethnographic research, this paper explores how these young women are negotiating gender through their complex and limited participation in the organization. We argue these young women display an ambivalent position towards femininity and practice implicit feminism, which challenges gender norms. However, despite their feelings of agency and a creation of a “new” normal within their social bubble, evidence reveals traditional social structures continue to maintain the gender status quo.
Walking Multiple Paths of Supervision in American Sport Psychology: A Qualitative Tale of Novice Supervisees’ Development
Authors: Fogaca Janaina Lima , Zizzi Sam J. , Andersen Mark B.
Published: October 2017

There is limited evidence for what characteristics of supervision delivery facilitate novice supervisees’ development. The aim of this study was to investigate the relationship between supervision-delivery approaches and the perceptions of service-delivery competence development in novice practitioners. The authors interviewed 9 supervisor–supervisee dyads before and after the academic term in which the supervisees had their first applied experiences. Supervisees also completed reflective journal entries regarding their supervisory experiences and development. Data analysis included constant comparative analysis and triangulation of qualitative results with a practitioner-skills inventory. Different approaches to supervision delivery seemed to contribute similarly to novice supervisees’ development. Supervisees developed in more areas when the dyads had consistent meetings, close supervisory relationships, feedback, and frequent opportunities for self-reflection and when supervisors adapted the delivery to the supervisees’ developmental levels. In addition, factors in supervisees’ background, practice, and supervision that contributed to perceptions of service-delivery competence are discussed.
Structure of the TAPBPR–MHC I complex defines the mechanism of peptide loading and editing
Authors: Thomas Christoph , Tampé Robert
Published: October 2017

Two snapshots of the TAPBPR-MHC I complex

Cytotoxic CD8
+
T cells recognize infected and cancerous cells by scrutinizing the antigenic peptides presented by the major histocompatibility complex class I (MHC I). Peptide binding and exchange occurs in the endoplasmic reticulum in a sequence of events mediated by the chaperones tapasin and TAPBPR (see the Perspective by Cresswell). Thomas and Tampé resolved the crystal structure of the TAPBPR-MHC I editing complex by using a photocleavable high-affinity peptide to stabilize the MHC molecule. Jiang
et al.
crystalized MHC I molecules inhabited by truncated disulfide-linked peptides that still permit TAPBPR to bind. These complimentary snapshots elucidate the dynamic process by which chaperones stabilize the groove of peptide-free MHC I molecules. This helps MHC I sample peptide candidates and facilitates the generation of peptide repertoires enriched with high-affinity antigenic peptides.

Science
, this issue p.
1060
, p.
1064
; see also p.
992
Illuminating gravitational waves: A concordant picture of photons from a neutron star merger
Authors: Kasliwal M. M. , Nakar E. , Singer L. P. , Kaplan D. L. , Cook D. O. , Van Sistine A. , Lau R. M. , Fremling C. , Gottlieb O. , Jencson J. E. , Adams S. M. , Feindt U. , Hotokezaka K. , Ghosh S. , Perley D. A. , Yu P.-C. , Piran T. , Allison J. R. , Anupama G. C. , Balasubramanian A. , Bannister K. W. , Bally J. , Barnes J. , Barway S. , Bellm E. , Bhalerao V. , Bhattacharya D. , Blagorodnova N. , Bloom J. S. , Brady P. R. , Cannella C. , Chatterjee D. , Cenko S. B. , Cobb B. E. , Copperwheat C. , Corsi A. , De K. , Dobie D. , Emery S. W. K. , Evans P. A. , Fox O. D. , Frail D. A. , Frohmaier C. , Goobar A. , Hallinan G. , Harrison F. , Helou G. , Hinderer T. , Ho A. Y. Q. , Horesh A. , Ip W.-H. , Itoh R. , Kasen D. , Kim H. , Kuin N. P. M. , Kupfer T. , Lynch C. , Madsen K. , Mazzali P. A. , Miller A. A. , Mooley K. , Murphy T. , Ngeow C.-C. , Nichols D. , Nissanke S. , Nugent P. , Ofek E. O. , Qi H. , Quimby R. M. , Rosswog S. , Rusu F. , Sadler E. M. , Schmidt P. , Sollerman J. , Steele I. , Williamson A. R. , Xu Y. , Yan L. , Yatsu Y. , Zhang C. , Zhao W.
Published: October 2017

GROWTH observations of GW170817

The gravitational wave event GW170817 was caused by the merger of two neutron stars (see the Introduction by Smith). In three papers, teams associated with the GROWTH (Global Relay of Observatories Watching Transients Happen) project present their observations of the event at wavelengths from x-rays to radio waves. Evans
et al.
used space telescopes to detect GW170817 in the ultraviolet and place limits on its x-ray flux, showing that the merger generated a hot explosion known as a blue kilonova. Hallinan
et al.
describe radio emissions generated as the explosion slammed into the surrounding gas within the host galaxy. Kasliwal
et al.
present additional observations in the optical and infrared and formulate a model for the event involving a cocoon of material expanding at close to the speed of light, matching the data at all observed wavelengths.

Science
, this issue p.
1565
, p.
1579
, p.
1559
; see also p.
1554
Permanent Draft Genome Sequences for
Mesorhizobium
sp. Strains LCM 4576, LCM 4577, and ORS3428, Salt-Tolerant, Nitrogen-Fixing Bacteria Isolated from Senegalese Soils
Authors: Diagne Nathalie , Swanson Erik , Pesce Céline , Fall Fatoumata , Diouf Fatou , Bakhoum Niokhor , Fall Dioumacor , Faye Mathieu Ndigue , Oshone Rediet , Simpson Stephen , Morris Krystalynne , Thomas W. Kelley , Moulin Lionel , Diouf Diegane , Tisa Louis S.
Published: October 2017

The genus
Mesorhizobium
contains many species that are able to form nitrogen-fixing nodules on plants of the legume family. Here, we report the draft genome sequences for three
Mesorhizobium
strains. The genome sizes of strains LCM 4576, LCM 4577, and ORS3428 were 7.24, 7.02, and 6.55 Mbp, respectively.
Transmission in the Origins of Bacterial Diversity, From Ecotypes to Phyla
Authors: Cohan Frederick M.
Published: October 2017

Any two lineages, no matter how distant they are now, began their divergence as one population splitting into two lineages that could coexist indefinitely. The rate of origin of higher-level taxa is therefore the product of the rate of speciation times the probability that two new species coexist long enough to reach a particular level of divergence. Here I have explored these two parameters of disparification in bacteria. Owing to low recombination rates, sexual isolation is not a necessary milestone of bacterial speciation. Rather, irreversible and indefinite divergence begins with ecological diversification, that is, transmission of a bacterial lineage to a new ecological niche, possibly to a new microhabitat but at least to new resources. Several algorithms use sequence data from a taxon of focus to identify phylogenetic groups likely to bear the dynamic properties of species. Identifying these newly divergent lineages allows us to characterize the genetic bases of speciation, as well as the ecological dimensions upon which new species diverge. Speciation appears to be least frequent when a given lineage has few new resources it can adopt, as exemplified by photoautotrophs, C1 heterotrophs, and obligately intracellular pathogens; speciation is likely most rapid for generalist heterotrophs. The genetic basis of ecological divergence may determine whether ecological divergence is irreversible and whether lineages will diverge indefinitely into the future. Long-term coexistence is most likely when newly divergent lineages utilize at least some resources not shared with the other and when the resources themselves will coexist into the remote future.
Intracavitary ultrasound (ICARUS): a neuroendoscopic adaptation of intravascular ultrasound for intracerebral hemorrhage evacuation
Authors: Chartrain Alexander G , Hom Danny , Bederson Joshua B , Mocco J , Kellner Christopher Paul
Published: October 2017

Neurosurgeons performing intracerebral hemorrhage evacuation procedures have limited options for monitoring hematoma evacuation and assessing residual hematoma burden intraoperatively. Here, we report the successful neuroendoscopic adaptation of intravascular ultrasound, referred to here as intracavitary ultrasound (ICARUS), in two patients. Pre-evacuation ICARUS demonstrated dense hematomas in both patients. Post-evacuation ICARUS in patient 1 demonstrated significant reduction in clot burden and two focal hyperechoic regions consistent with pockets of hematoma not previously seen with the endoscope or burr hole ultrasound. These areas were directly targeted and resected with the endoscope and suction device. Post-evacuation ICARUS in patient 2 showed significant reduction of hematoma volume without indication of residual blood. ICARUS findings were confirmed on intraoperative DynaCT and postoperative CT 24 hours later. ICARUS is feasibly performed in a hematoma cavity both before and after hematoma aspiration. ICARUS may provide additional information to the operating surgeon and assist in maximizing hematoma removal.
Appropriateness of cases presenting in the emergency department following ambulance service secondary telephone triage: a retrospective cohort study
Authors: Eastwood Kathryn , Smith Karen , Morgans Amee , Stoelwinder Johannes
Published: October 2017

Objective

To investigate the appropriateness of cases presenting to the emergency department (ED) following ambulance-based secondary telephone triage.

Design

A pragmatic retrospective cohort analysis of all the planned and unplanned ED presentations within 48 hours of a secondary telephone triage.

Setting

The secondary telephone triage service, called the Referral Service, and the hospitals were located in metropolitan Melbourne, Australia and operated 24 hours a day, servicing 4.25 million people. The Referral Service provides an in-depth secondary triage of cases classified as low acuity when calling the Australian emergency telephone number.

Population

Cases triaged by the Referral Service between September 2009 and June 2012 were linked to ED and hospital admission records (N=44,523). Planned ED presentations were cases referred to the ED following the secondary triage, unplanned ED presentations were cases that presented despite being referred to alternative care pathways.

Main outcome measures

Appropriateness was measured using an ED suitability definition and hospital admission rates. These were compared with mean population data which consisted of all of the ED presentations for the state (termed the ‘average Victorian ED presentation’).

Results

Planned ED presentations were more likely to be ED suitable than unplanned ED presentations (OR 1.62; 95% CI 1.5 to 1.7; p<0.001) and the average Victorian ED presentation (OR 1.85; 95% CI 1.01 to 3.4; p=0.046). They were also more likely to be admitted to the hospital than the unplanned ED presentation (OR 1.5; 95% CI 1.4 to 1.6; p<0.001) and the average Victorian ED presentation (OR 2.3, 95% CI 2.24 to 2.33; p<0.001). Just under 15% of cases diverted away from the emergency care pathways presented in the ED (unplanned ED attendances), and 9.5% of all the alternative care pathway cases were classified as ED suitable and 6.5% were admitted to hospital.

Conclusions

Secondary telephone triage was able to appropriately identify many ED suitable cases, and while most cases referred to alternative care pathways did not present in the ED. Further research is required to establish that these were not inappropriately triaged away from the emergency care pathways.
Sociodemographic variations in the amount, duration and cost of potentially preventable hospitalisation for chronic conditions among Aboriginal and non-Aboriginal Australians: a period prevalence study of linked public hospital data
Authors: Banham David , Chen Tenglong , Karnon Jonathan , Brown Alex , Lynch John
Published: October 2017

Objectives

To determine disparities in rates, length of stay (LOS) and hospital costs of potentially preventable hospitalisations (PPH) for selected chronic conditions among Aboriginal and non-Aboriginal South Australians (SA), then examine associations with area-level socioeconomic disadvantage and remoteness.

Setting

Period prevalence study using linked, administrative public hospital records.

Participants

Participants included all SA residents in 2005–2006 to 2010–2011. Analysis focused on those individuals experiencing chronic PPH as defined by the Australian Institute of Health and Welfare.

Primary outcome measures

Number and rates (unadjusted, then adjusted for sex and age) of chronic PPH, total LOS and direct hospital costs by Aboriginality.

Results

Aboriginal SAs experienced higher risk of index chronic PPH compared with non-Aboriginals (11.5 and 6.2 per 1000 persons per year, respectively) and at younger ages (median age 48 vs 70 years). Once hospitalised, Aboriginal people experienced more chronic PPH events, longer total LOS with higher costs than non-Aboriginal people (2.6 vs 1.9 PPH per person; 11.7 vs 9.0 days LOS; at $A17 928 vs $A11 515, respectively). Compared with population average LOS, the standardised rate ratio of LOS among Aboriginal people increased by 0.03 (95% CI 0.00 to 0.07) as disadvantage rank increased and 1.04 (95% CI 0.63 to 1.44) as remoteness increased. Non-Aboriginal LOS also increased as disadvantage increased but at a lower rate (0.01 (95% CI 0.01 to 0.01)). Costs of Aboriginal chronic PPH increased by 0.02 (95% CI 0.00 to 0.06) for each increase in disadvantage and 1.18 (95% CI 0.80 to 1.55) for increased remoteness. Non-Aboriginal costs also increased as disadvantage increased but at lower rates (0.01 (95% CI 0.01 to 0.01)).

Conclusion

Aboriginal people’s heightened risk of chronic PPH resulted in more time in hospital and greater cost. Systematic disparities in chronic PPH by Aboriginality, area disadvantage and remoteness highlight the need for improved uptake of effective primary care. Routine, regional reporting will help monitor progress in meeting these population needs.
Geometrical effects on the load transfer mechanism of pile groups: three-dimensional numerical analysis
Authors: Lv Yaru , Zhang Dongdong
Published: October 2017

This paper investigates geometrical effects on the load transfer mechanism of off-ground capped pile groups subjected to vertical load by four three-dimensional numerical simulations, including a circular single pile, an X-shaped cross-sectional concrete (XCC) single pile, a 4 × 4 circular pile group, and a 4 × 4 XCC pile group. The ultimate bearing capacities of the XCC and circular piles within pile groups are approximately 0.86 and 0.74 times that of the XCC and circular single piles, respectively. The group efficiency of the XCC pile group is mainly improved by its side resistance. Comparing the XCC pile group to the circular pile group, the increment in side resistance is almost larger than the increment in pile perimeter, indicating that the pile geometry alters the load transfer mechanism via stress concentration and lateral stress arching. A nonuniform load distribution on piles within a capped pile group causes a bending moment along the pile shafts. The bending moment of XCC piles is smaller than that of circular piles because the raft stiffness of an XCC pile group is increased by its larger circumscribing pile diameter.
Influence of strain energy released from a test machine on rock failure process
Authors: Xu Y.H. , Cai M.
Published: October 2017

Rock instability occurs if the energy supplied to the rock failure process is excessive. The theoretical analysis on the energy transfer in the process of rock failure revealed that the rock failure process is a result of the strain energy released from the test machine or the surrounding rock masses of wall rock, plus the additional energy input from an external energy source if the deformation of the rock is continued and driven by the external energy source. The strain energy released from the test machine is the focus in this study because it is responsible for some of the unstable rock failures in laboratory testing. A finite element method (FEM)-based numerical experiment was carried out to study the strain energy released from test machines under different loading conditions of loading system stiffness (LSS). The modeling results demonstrated that depending on the LSS of a test machine, the strain energy released from the test machine alone without additional energy supply can drastically affect the rock failure process. The insight gained from this study can explain unstable rock failure in laboratory tests and the mechanism of some delayed rockbursts that occurred sometime after the excavation of the openings.
La zonation structurale des dômes gneissiques. Un exemple : le massif de Saint-Malo (Massif armoricain, France)
Authors: Brun Jean-Pierre
Published: October 2017

The Saint-Malo massif provides an example of a gneiss dome with a migmatitic core. The results of a structural analysis are used to describe a structural zonation around the migmatitic core, and a dynamic model of the massif is proposed. A comparison of these results with experimental models of gneiss domes shows that this zonation is the product of diapirism.
Chronology of the Red Wine alkaline province, central Labrador
Authors: Blaxland Alan B. , Curtis Laurence W.
Published: October 2017

An 11-point Rb–Sr whole-rock isochron for the regionally metamorphosed Red Wine alkaline province gives an age of intrusion of 1345 ± 75 Ma (errors quoted at 2σ) and an initial 87Sr/86Sr ratio of (1.7021 ± 0.0103. Two 5-point mineral isochrons give ages of ~1000 Ma that represent metamorphic 'resetting' of the alkaline rocks. The whole-rock intrusion age compares closely with the early stage of magmatism in the Gardar Province of south Greenland where un-metamorphosed agpaitic igneous rocks, similar to those of the Red Wine Province, occur. In both provinces, alkaline plutonic rocks are associated, both spatially and chronologically, with thick sequences of continental sediments and basaltic lavas, and the new age data lend strong support to the supposition that the Gardar and Red Wine rocks are parts of the same pre-drift magmatic province and inferred rift system. The Gardar Province has, however, escaped the effects of the Grenville regional metamorphism which severely affected the Red Wine rocks.
Stress orientations from borehole wall fractures with examples from Colorado, east Texas, and northern Canada
Authors: Gough D. I. , Bell J. S.
Published: October 2017

Azimuthally aligned breakouts in oil wells are explained as shear fractures in the zone of amplified stress difference near the borehole, in a stress field having unequal horizontal principal stresses. Brittle fracture theory, on the Mohr–Coulomb failure criterion, shows that the fractures will propagate from the wall and cause wide spalled zones observable with the four-arm dipmeter. In homogeneous rock, breakouts formed in this way should lengthen the diameter by no more than 8–10%. The breakouts occur near the ends of the diameter parallel to the smaller horizontal stress. Tensile fractures may occur in the orthogonal azimuth, but are unlikely to be seen by the four-arm dipmeter calipers.Three examples are given of principal stress orientations inferred from borehole breakouts. At Rangely, Colorado, breakout azimuths suggest an approximately east–west principal compression in agreement with results obtained previously from direct stress measurements, hydrofracture, and earthquake mechanism analysis. In the east Texas Basin, north-northwest to northwest aligned breakouts suggest maximum horizontal stresses oriented at right angles to these directions. This is consistent with inferences from recent extensional faulting and one hydraulic fracture determination. In the Norman Wells area of northern Canada, northwest–southeast aligned breakouts suggest a contemporary horizontal principal compression closely parallel to natural, probably hydraulic fractures of Laramide age in a subsurface limestone reservoir. The inferred principal stress axes are consistent with the structural evolution of this area, and extend the evidence for coherent stress orientation in western Canada from southern Alberta to Norman Wells, a distance of 1900 km.
The geochronology of uranium deposits in the Great Bear batholith, Northwest Territories
Authors: Miller Richard G.
Published: October 2017

The oldest uranium mineralisation found in the Great Bear batholith during this study may be hydrothermal pitchblende–hematite veins at Hottah Lake. Their apparent age of 2058 ± 34 Ma can also be explained by the contamination of deposits only 440 ± 57 Ma old, which is the age of pitchblende veins nearby. Numerous pendants of metamorphosed, uraninite-bearing "black sand" placers in a north-trending belt west of the Wopmay Fault are 1860 ± 20 Ma old, the age of the granites that intrude them. Mineralisation at Echo Bay is from 1500 ± 10 to 1424 ± 29 Ma old, and extends up to 30 km north and 40 km south of Echo Bay. The JD claims contain small quartz vein deposits dated at 535 ± 164 and 1092 ± 115 Ma. At Mountain Lake, pitchblende in Helikian sandstones overlying the batholith is 1076 ± 96 Ma old. Polymetallic veinlets at Mazenod Lake are 457 ± 26 Ma old. Pitchblende in a giant quartz vein at the Rayrock mine is 511 ± 86 Ma old. Small pitchblende veins east of the batholith along the Coppermine River are between 400 and 660 Ma old.All the deposits are either between ~395 and 660 Ma old, or indicate remobilization during this interval. These events may be related to a marine transgression and regression approximately 600 and 350 Ma ago, respectively.
Late Precambrian marbles of unusual carbon-isotope composition, southeastern British Columbia
Authors: Ghent Edward D. , O'Neil James R.
Published: October 2017

Carbon- and oxygen-isotope analyses were made of both carbonates and graphites from several Precambrian metamorphic samples from British Columbia. The carbon-isotope data are unusual in that the δ13C values of many marbles are very high, up to 9.9, and the most positive values occur in the sillimanite-zone rocks. The δ13C values of graphite are also relatively high, and the 13C fractionations between calcite and graphite suggest that (1) the rocks attained and retained carbon-isotope equilibrium during metamorphism, and (2) the temperature of graphite equilibration in marbles from the sillimanite zone is 650–690 °C, in agreement with temperatures estimated from mineralogical phase equilibria.Possible precursor carbonates for the 13C-rich marbles in British Columbia include (1) Precambrian carbonate-secreting organisms such as algae that participate in reactions with large kinetic isotope effects, (2) carbonates that exchanged carbon isotopes with a large reservoir of organic material prior to metamorphism, and (3) travertines.
Conductive structures under the Canadian Rocky Mountains
Authors: Bingham D. K. , Gough D. I. , Ingham M. R.
Published: October 2017

The paper reports results from an array of 33 three-component magnetometers that recorded time-varying fields in 1981 over an area of some 56 000 km2 in the Canadian Cordillera. The array was centred at Tête Jaune Cache in the Rocky Mountain Trench, where a large magnetovariation anomaly had been located in an earlier array study. It was bisected by the trench and extended to the northeast across the Rocky Mountains to the Alberta Foothills and to the southwest across the Cariboo and Monashee mountains. Magnetograms and Fourier transform maps covering the period range 10–91 min show strong attenuation of the vertical component, Z, southwest of the Rocky Mountain Trench, with very large Z amplitudes in the Main Ranges of the Rockies. The horizontal components show an elongated anomaly along the Rocky Mountains Main Ranges and Trench, with three-dimensional features superimposed. The conductive structures include a highly conductive layer, probably in the lower crust, southwest of the trench and a conductive ridge rising into the upper crust near the edge of that layer. Current models have been fitted to observed vertical -and horizontal-component anomalies and show that both layer and ridge are necessary for a fit and that the ridge is 50–80 km wide. Single-station transfer functions at periods of 10 and 22 min have been calculated from a number of variation events of various polarizations, to reduce any displacement of the anomalies by auroral-zone source currents. Artificial-event analysis, with these transfer functions, shows that the conductive ridge lies under the Main Ranges of the Rockies and not under the trench. Its great width indicates a structure of major tectonic significance, which will be considered in another paper.
Relations entre dynamismes éruptifs et réalimentations magmatiques d'origine profonde au Popocatépetl
Authors: Boudal Christian , Robin Claude
Published: October 2017

The modern volcano Popocatépetl is 30 000 – 50 000 years old. Until 5000 years BP, its volcanic activity led to the construction of a 2000 m high cone, the El Fraile volcano. This edifice was later topped by the Popocatépetl summit. The volcanic activity was characterized by long-term construction by lava flows, alternating with periods of 1000–2000 years of mixed explosive and effusive activity. The El Fraile volcano experienced three periods of this type, marked by back-falling pyroclastic flows with heterogeneous magma products and thick air-fall deposits (ash and scoria). The first one occurred more than 10 000 years BP; the second, between 10 000 and 8000 years BP; the third, from 5000 to 3800 years BP. Each of these periods showed violent explosive episodes alternating with lava flows in cycles of 100 to several hundreds of years in duration. Whenever the explosive activity occurred, it destroyed the upper part of the volcano, opening large craters. After a ~ 2500 year period of lava-flow construction (from ~ 3800 to 1200 years BP), the Popocatépetl summit began a similar activity. The last event, producing pyroclastic flows, occurred just before me Hispanic Conquest, and since that time the activity has been effusive and Plinian.Heterogeneous to subhomogeneous pyroclastic flow products exhibit a complex mineralogy: Fe clinopyroxene, Mg clinopyroxene, Fe orthopyroxene, Mg orthopyroxene, plagioclase in equilibrium or disequilibrium, and scarce olivine. All lava flows show a similar paragenesis, suggesting magma-mixing processes. A model in which a basaltic magma is periodically injected in a differentiated chamber at the beginning of each explosive period (or each cycle?) is proposed to explain the heterogeneous products. However, calculations of mixing models do not agree with the high Mg and Ni values observed in some hybrid lavas. This excess is probably due to the remobilization of cumulative olivine by basic magma supplies in the lower part of the reservoir. On the other hand, lava flows emitted during the long phases of effusive activity correspond to evolution in a closed and zoned chamber, partly affected by convective movements. The convection explains the complex mineralogy of these lavas, which result from differentiation of a previously homogenized magma rather than directly from magma mixing.
Sedimentation in an esker system influenced by bedrock topography near Kingston, Ontario
Authors: Henderson Penny J.
Published: October 2017

Late Wisconsinan sand and gravel deposits on the Frontenac Arch, Ontario, record a major meltwater drainage system developed subglacially and subaqueously in one or more glacial lake phases of the Lake Ontario basin during retreat of the Laurentide Ice Sheet. Factors influencing channel location, morphology, and sediment deposition are ice flow direction and the Precambrian bedrock topography, in turn dependent upon bedrock structure and composition. Meltwater drainage across the Frontenac Arch is localized within a broad depression oriented approximately parallel to glacial flow. Sediment deposition within the regional depression follows ice-flow direction despite irregular bedrock relief, indicating formation of the meltwater system and associated sediments in three stages: (i) establishment of a continuous meltwater system subglacially under high hydrostatic pressure with minor erosion of underlying Precambrian bedrock; (ii) deposition of poorly sorted, coarse-grained sediment in cavities or channels associated with irregular bedrock topography; and (iii) deposition of several coalescing subaqueous outwash fans at the ice margin as the glacier receded from the area. The discontinuous nature of the deposits and the association of proximal to distal outwash fan facies within a deposit suggest that esker sedimentation occurred during periodic stabilization of the ice front during deglaciation.
Ductile thrusting at mid-crustal level, southwestern Grenville Province
Authors: Hanmer Simon
Published: October 2017

The northwestern boundary zone of the Central Metasedimentary Belt (Grenville Province) in the Haliburton area (Ontario) is a stack of alternating tonalitic and syenitic crystalline thrust sheets, transported toward the northwest on out-of-sequence, upper amphibolite facies, ductile thrust zones during the Grenvillian Orogeny, at 1060 Ma, approximately 100 Ma after the initiation of thrusting in the underlying Central Gneiss Belt. Kinematics of the deformation are complex. Predominant northwestward thrusting was, at least partly, coeval with subordinate northeastward thrusting. Late synmetamorphic extensional shears cut both thrusts and thrust sheets. Minor late thrusting on discrete ductile shear zones postdates the extensional structures. Belts of mechanically weak pelite(?) appear to have localised the thrust sheets. Highly mobile marble behaved as a relatively low viscosity fluid during transport, able to intrude and erode more competent wall rock.
U–Pb ages of early and middle Proterozoic volcanism and metamorphism in the Makkovik Orogen, Labrador
Authors: Schärer U. , Krogh T. E. , Wardle R. J. , Ryan B. , Gandhi S. S.
Published: October 2017

Zircon U–Pb dating on rhyolites from three different localities in the upper Aillik group, a volcano-sedimentary sequence of the Makkovik Orogen in Labrador, indicates two distinct pulses of volcanic activity at about 1860 and 1807 Ma. The individual rhyolite ages of [Formula: see text], 1856 ± 2, and 1807 ± 3 Ma are 40–150 Ma older than Rb–Sr ages determined previously on the same rocks. A slight scatter of zircon data observed for one of the rhyolites and the presence of old zircon cores suggest that the felsic magmas were derived in part from older continental material. Analyses of monazite and titanite from two anatectic rocks, a migmatite and leucogranite from a gneiss terrain adjacent to the supracrustals, document a period of high-grade metamorphism in the interval 1794 ± 2 to 1761 ± 2 Ma. This period is considered the terminal phase of the Makkovikian Orogeny. Zircons in the migmatite yield minimum ages ranging from about 1800 to 2340 Ma, indicating a derivation from latest Archean to early Proterozoic basement rocks.Zircon dating on a rhyolite from the Bruce River Group within the ~1650 Ma old Trans-Labrador batholith yields an age of 1649 ± 1 Ma. This age suggests that Bruce River acid volcanism was related to Trans-Labrador batholith emplacement.
Lead- and strontium-isotope geochemistry of the Tertiary Catface intrusions and related mineralization, Vancouver Island, British Columbia
Authors: Andrew Anne , Godwin Colin I.
Published: October 2017

Lead- and strontium-isotope ratios from the Catface Tertiary intrusions in Vancouver Island occupy a narrow range of values, indicating a homogeneous or well-mixed source. Within this range, the lead-isotope data fall into two distinct clusters centred about initial 206Pb/204Pb of 18.70 and 18.95. These two clusters correlate, respectively, with the eastern and western belts of Catface intrusions. Initial strontium ratios for these intrusions show little variation about a mean value of 0.7039.The source of these intrusions cannot be identified uniquely using lead- and strontium-isotope data alone, but two possibilities can be ruled out. 207Pb/204Pb, 208Pb/204Pb, and initial strontium ratios are all too high to be solely from mantle-derived magmas. Initial strontium ratios are too low and the 208Pb/204Pb and 232Th/238U ratios are too high for the Catface intrusions to be the products of melting of pre-existing Sicker Group rocks.Galena from quartz-gold veins related to the Zeballos pluton has a lead isotopic composition similar to that of the Zeballos pluton. Consequently, if lead and gold have the same origin, the source of the gold is the intrusion, rather than the host rocks.
Possibly diamond-bearing mantle peridotites and podiform chromitites in the Luobusa and Donqiao ophiolites, Tibet
Authors: Bai Wen-Ji , Zhou Mei-Fu , Robinson Paul T.
Published: October 2017

The Luobusa ophiolite of the Yarlung–Zangbo (southern Tibet) suture zone and the Donqiao ophiolite of the Bangong–Nujiang (northern Tibet) suture zone are allochthonous bodies that contain possibly diamond-bearing mantle peridotites and podiform chromitites. The mantle sections in both massifs consist chiefly of harzburgite and diopside-bearing harzburgite with abundant lenses of dunite and chromitite. These ultramafic rocks are more strongly depleted than typical abyssal peridotites and their whole-rock and mineral chemistries suggest formation above a subduction zone. An unusual mineral association (diamond, SiC, graphite, native chromium, Ni–Fe alloy, Cr2+-bearing chromite), indicating a high-pressure, reducing environment, occurs in both the peridotites and chromitites. We suggest that these ophiolites were generated originally in a suprasubduction zone environment and were later carried deep into the mantle along a second subduction zone, at which time the diamonds and other high-pressure minerals were formed. It is not yet clear whether the diamonds formed by high-pressure metamorphism of the oceanic crust or by crystallization from mantle melts, but their occurrence in chromitites and harzburgites suggests a metamorphic origin. During the collision of India with the Eurasian plate, the mantle sections were tectonically emplaced at shallow crustal levels rapidly enough to preserve the diamonds.
The stratigraphy of the Nicola Group in the Hedley district, British Columbia, and the chemistry of its intrusions and Au skarns
Authors: Ray G. E. , Webster I. C. L. , Dawson G. L.
Published: October 2017

The Nicola Group at Hedley, British Columbia, is a late Carnian to late Norian (Late Triassic) sequence of calcareous sedimentary and arc-related volcaniclastic rocks. It was deposited on a tectonically active paleoslope that marked either the rifted eastern margin of the shallow-marine Nicola basin or the faulted edge of an intrabasinal platform. The lower part of the Nicola Group comprises a succession of four essentially coeval sedimentary facies. From east to west across the district, these are informally named the thin (approx. 200 m), shallow-marine, limestone-dominant French Mine formation; the thicker, calcareous siltstone-dominant Hedley and Chuchuwayha formations in the central part of the district; and the thick (up to 2200 m), deeper water and argillite-dominant Stemwinder formation. These facies are all blanketed by the Whistle formation, a 1200 m thick unit of basaltic tuff and tuffaceous sediment whose base is marked by a gravity-slide megabreccia, the Copperfield breccia. The Nicola arc at Hedley was associated with two plutonic episodes. Oldest are the Hedley intrusions, which are related to economic Au skarns, including the Nickel Plate deposit, which has produced over 71 t of gold from 13.4 Mt of ore. The Hedley intrusions are similar in composition (quartz gabbro to quartz diorite) and overall metaluminous chemistry to other island-arc-generated plutons related to many Cu and Fe skarns in British Columbia, although they are less evolved. They also differ in having lower Fe2O3/FeO ratios (avg. 0.23), indicating a reduced oxidation state, and higher Ba/La and Sc/Nb ratios. A slightly younger plutonic episode produced the 193 Ma (Early Jurassic) Bromley batholith and the 194 Ma Mount Riordan stock; the latter is associated with the Mount Riordan (Crystal Peak) industrial garnet skarn. Gold skarns are preferentially developed in areas where the Hedley intrusions cut the Hedley and French Mine formations. The Au skarn ore is marked by anomalous As, Bi, Te, and Co values, and by high pyrrhotite/pyrite and pyroxene/garnet ratios. It is distinct from the ore of Fe, Cu, Mo, Pb–Zn, W, and Sn skarns by its very low Cu/Au, Zn/Au, and Ag/Au ratios (avg. 97, 18, and 12, respectively).
Fauna of the lower Beauharnois Formation (Beekmantown Group, Lower Ordovician), Grande-Île, Quebec
Authors: Desbiens Sylvain , Bolton Thomas E. , McCracken Alexander D.
Published: October 2017

Lenses of bioclastic packstone and grainstone within the lower dolomite sequence of the Ogdensburg Member, Beauharnois Formation (Beekmantown Group, Lower Ordovician), in the Valleyfield region, Quebec, bear a distinct diverse faunal assemblage. This Isoteloides–Goniotelina–Ribeiria assemblage is characterized by brachiopods Finkelnburgia armanda (Billings) and Finkelnburgia cullisoni Ulrich and Cooper, molluscs Ribeiria calcifera Billings, "Maclurites" affinis (Billings), and Ceratopea canadensis (Billings), and trilobites Isoteloides canalis (Whitfield), Isoteloides peri Fortey, Bolbocephalus convexus (Billings), Goniotelina subrectus (Bradley), Strigigenalis caudata (Billings), and Hystricurus conicus (Billings). Precise correlation of this lower Beauharnois megafauna is with the Strigigenalis caudata Zone of the Catoche Formation, Cassinian Stage, of western Newfoundland, the Oxford Formation of southeastern Ontario, the Fort Cassin Formation, Cassinian Stage, Canadian Series of New York–Vermont, and the Ross–Hintze trilobite Zone G2 of Utah, Upper Ibexian Series (Tulean Stage). Conodonts include Acodus comptus (Branson and Mehl), Acodus delicatus (Branson and Mehl), Colaptoconus emarginatus (Barnes and Tuke), Colaptoconus quadraplicatus (Branson and Mehl), Scolopodus subrex Ji and Barnes, Drepanoistodus angulensis (Harris), and Oepikodus communis (Ethington and Clark). This fauna corresponds to the Oepikodus communis–"Microzarkodina" marathonensis Zone, which has its lowest limit above the middle of Zone G2 in the Ibex area of Utah. In western Newfoundland, the fauna correlates with the Oepikodus communis – Protoprioniodus simplicissimus Assemblage Zone of the Catoche Formation, and the Prioniodus elegans and Oepikodus evae zones in the Cow Head Group.
Laurentide subgiacial outburst floods: landform evidence from digital elevation models
Authors: Shaw John , Rains Bruce , Eyton Ronald , Welssling Lee
Published: October 2017

Various lines of landform evidence in many parts of Canada are comprehensively explicable as products of subglacial sheetfloods–outburst floods. In the Northwest Territories, northern Saskatchewan, and Alberta, landform associations such as scoured bedrock tracts, cavity-fill drumlins, erosional drumlins, erosional giant flutes–remnant ridges, tunnel channels, channeled scabland, and hummocky terrain with upstanding moraine plateaus reflect primary glaciofluvial erosional processes and secondary depositional activities. The Livingstone Lake event major sheetfloods path arcs obliquely upslope from the Keewatin District, Northwest Territories, through northern Saskatchewan and much of Alberta into Montana, U.S.A. Hill-shaded maps generated from digital elevation models, at widely varying scales, are used to illustrate regional to local examples of megaflood landform suites. Complementary maps and diagrams are derived from more conventional data sources. Speculations regarding extraglacial implications of the outburst floods in the Missouri–Mississippi basins, Mississippi Delta, and Gulf of Mexico are offered for testing by others.