bluuebunny/crossref_metadata_2025 huggingface dataset:
Human α-Defensins Inhibit Hemolysis Mediated by Cholesterol-Dependent Cytolysins
Authors: Lehrer Robert I. , Jung Grace , Ruchala Piotr , Wang Wei , Micewicz Ewa D. , Waring Alan J. , Gillespie Eugene J. , Bradley Kenneth A. , Ratner Adam J. , Rest Richard F. , Lu Wuyuan
Published: July 2009

Many pathogenic gram-positive bacteria release exotoxins that belong to the family of cholesterol-dependent cytolysins. Here, we report that human α-defensins HNP-1 to HNP-3 acted in a concentration-dependent manner to protect human red blood cells from the lytic effects of three of these exotoxins: anthrolysin O (ALO), listeriolysin O, and pneumolysin. HD-5 was very effective against listeriolysin O but less effective against the other toxins. Human α-defensins HNP-4 and HD-6 and human β-defensin-1, -2, and -3 lacked protective ability. HNP-1 required intact disulfide bonds to prevent toxin-mediated hemolysis. A fully linearized analog, in which all six cysteines were replaced by aminobutyric acid (Abu) residues, showed greatly reduced binding and protection. A partially unfolded HNP-1 analog, in which only cysteines 9 and 29 were replaced by Abu residues, showed intact ALO binding but was 10-fold less potent in preventing hemolysis. Surface plasmon resonance assays revealed that HNP-1 to HNP-3 bound all three toxins at multiple sites and also that solution-phase HNP molecules could bind immobilized HNP molecules. Defensin concentrations that inhibited hemolysis by ALO and listeriolysin did not prevent these toxins from binding either to red blood cells or to cholesterol. Others have shown that HNP-1 to HNP-3 inhibit lethal toxin ofBacillus anthracis, toxin B ofClostridium difficile, diphtheria toxin, and exotoxin A ofPseudomonas aeruginosa; however, this is the first time these defensins have been shown to inhibit pore-forming toxins. An “ABCDE mechanism” that can account for the ability of HNP-1 to HNP-3 to inhibit so many different exotoxins is proposed.
Complement C3 Plays an Essential Role in the Control of Opportunistic Fungal Infections
Authors: Tsoni S. Vicky , Kerrigan Ann M. , Marakalala Mohlopheni J. , Srinivasan Naren , Duffield Maureen , Taylor Philip R. , Botto Marina , Steele Chad , Brown Gordon D.
Published: July 2009

The innate recognition of fungal pathogens is a crucial first step in the induction of protective antifungal immunity. Complement is thought to be one key component in this process, facilitating fungal recognition and inducing early inflammation. However, the roles of the individual complement components have not been examined extensively. Here we have used mice lacking C3 to examine its role in immunity to opportunistic fungal pathogens and show that this complement component is essential for resistance to infections with
Candida albicans
and
Candida glabrata
. We demonstrate that the absence of C3 impairs fungal clearance but does not affect inflammatory responses. We also show that the presence of C3 contributes to mortality in mice challenged with very high doses of
Saccharomyces cerevisiae
, although these effects were found to be mouse strain dependent.
Gr1+Cells Control Growth of YopM-NegativeYersinia pestisduring Systemic Plague
Authors: Ye Zhan , Kerschen Edward J. , Cohen Donald A. , Kaplan Alan M. , van Rooijen Nico , Straley Susan C.
Published: July 2009

YopM, a protein toxin ofYersinia pestis, is necessary for virulence in a mouse model of systemic plague. We previously reported YopM-dependent natural killer (NK) cell depletion from blood and spleen samples of infected mice. However, in this study we found that infection withY.pestisKIM5 (YopM+) caused depletion of NK cells in the spleen, but not in the liver, and antibody-mediated ablation of NK cells had no effect on bacterial growth. There was no YopM-associated effect on the percentage of dendritic cells (DCs) or polymorphonuclear leukocytes (PMNs) in the early stage of infection; however, there was a YopM-associated effect on PMN integrity and on the influx of monocytes into the spleen. Ablation of Gr1+cells caused loss of the growth defect of YopM−Y.pestisin both the liver and spleen. In contrast, ablation of macrophages/DCs inhibited growth of both parent and mutant bacteria, accompanied by significantly fewer lesion sites in the liver. These results point toward PMNs and inflammatory monocytes as major cell types that control growth of YopM−Y.pestis. Infection with fully virulentY.pestisCO92 and a YopM−derivative by intradermal and intranasal routes showed that the absence of YopM significantly increased the 50% lethal dose only in the intradermal model, suggesting a role for YopM in bubonic plague, in which acute inflammation occurs soon after infection.
Adhesion of
Candida albicans
to Endothelial Cells under Physiological Conditions of Flow
Authors: Grubb Sarah E. W. , Murdoch Craig , Sudbery Peter E. , Saville Stephen P. , Lopez-Ribot Jose L. , Thornhill Martin H.
Published: July 2009

Candida albicans
is a commensal organism that under certain circumstances can become pathogenic. During systemic infection
C. albicans
is disseminated via the circulation to distant organs, where it causes multiple organ failure. Despite the severity of systemic
C. albicans
infection, little is known about the mechanisms involved in the adhesion of this organism to the endothelium lining blood vessels. Previous studies have used static assays to examine adhesion. However, these do not realistically model blood vessels, where circulating
C. albicans
cells must adhere to the endothelium under conditions of flow and shear stress. Furthermore, there is conflicting evidence concerning the role played by yeast, pseudohyphal, and hyphal forms of
C. albicans
in adhesion to endothelium. To test the hypothesis that there may be differences in the abilities of these three morphogenic forms of
C. albicans
to adhere to endothelium under conditions of flow, we developed an in vitro flow adhesion assay. We found that all three forms of
C. albicans
rapidly bound to confluent endothelial cells under conditions of flow. Maximum adhesion was found at low shear stress levels similar to that found in postcapillary venules. Moreover, yeast forms bound in significantly greater numbers than did pseudohyphal and hyphal forms, respectively, contrasting with previous findings from static assays. These findings are consistent with recent in vivo data suggesting that yeast forms may be capable of adhering to the endothelium and migrating into the tissues before undergoing morphogenic change to cause tissue damage.
The CheZ Binding Interface of CheA
S
Is Located in α-Helix E
Authors: O'Connor Christopher , Matsumura Philip , Campos Andres
Published: July 2009

Specific CheA-short (CheA
S
) residues, L123 and L126, were identified as critical for CheZ binding. In the CheA
S
′P1-CheZ nuclear magnetic resonance structure, these residues form an interaction surface on α-helix E in the ′P1 domain. Both L123 and L126 are buried in CheA-long (CheA
L
), providing an explanation for why CheA
L
fails to bind CheZ.
Selection, Recombination, and Virulence Gene Diversity among Group B Streptococcal Genotypes
Authors: Springman A. Cody , Lacher David W. , Wu Guangxi , Milton Nicole , Whittam Thomas S. , Davies H. Dele , Manning Shannon D.
Published: July 2009

Transmission of group BStreptococcus(GBS) from mothers to neonates during childbirth is a leading cause of neonatal sepsis and meningitis. Although subtyping tools have identified specific GBS phylogenetic lineages that are important in neonatal disease, little is known about the genetic diversity of these lineages or the roles that recombination and selection play in the generation of emergent genotypes. Here, we examined genetic variation, selection, and recombination in seven multilocus sequence typing (MLST) loci from 94 invasive, colonizing, and bovine strains representing 38 GBS sequence types and performed DNA sequencing and PCR-based restriction fragment length polymorphism analysis of several putative virulence genes to identify gene content differences between genotypes. Despite the low level of diversity in the MLST loci, a neighbor net analysis revealed a variable range of genetic exchange among the seven clonal complexes (CCs) identified, suggesting that recombination is partly responsible for the diversity observed between genotypes. Recombination is also important for several virulence genes, as some gene alleles had evidence for lateral gene exchange across divergent genotypes. The CC-17 lineage, which is associated with neonatal disease, is relatively homogeneous and therefore appears to have diverged independently with an exclusive set of virulence characteristics. These data suggest that different GBS genetic backgrounds have distinct virulence gene profiles that may be important for disease pathogenesis. Such profiles could be used as markers for the rapid detection of strains with an increased propensity to cause neonatal disease and may be considered useful vaccine targets.
The Germination-Specific Lytic Enzymes SleB, CwlJ1, and CwlJ2 Each Contribute to
Bacillus anthracis
Spore Germination and Virulence
Authors: Giebel Jonathan D. , Carr Katherine A. , Anderson Erica C. , Hanna Philip C.
Published: July 2009

The bacterial spore cortex is critical for spore stability and dormancy and must be hydrolyzed by germination-specific lytic enzymes (GSLEs), which allows complete germination and vegetative cell outgrowth. We created in-frame deletions of three genes that encode GSLEs that have been shown to be active in
Bacillus anthracis
germination:
sleB
,
cwlJ1
, and
cwlJ2
. Phenotypic analysis of individual null mutations showed that the removal of any one of these genes was not sufficient to disrupt spore germination in nutrient-rich media. This finding indicates that these genes have partially redundant functions. Double and triple deletions of these genes resulted in more significant defects. Although a small subset of Δ
sleB
Δ
cwlJ1
spores germinate with wild-type kinetics, for the overall population there is a 3-order-of-magnitude decrease in the colony-forming efficiency compared with wild-type spores. Δ
sleB
Δ
cwlJ1
Δ
cwlJ2
spores are unable to complete germination in nutrient-rich conditions in vitro. Both Δ
sleB
Δ
cwlJ1
and Δ
sleB
Δ
cwlJ1
Δ
cwlJ2
spores are significantly attenuated, but are not completely devoid of virulence, in a mouse model of inhalation anthrax. Although unable to germinate in standard nutrient-rich media, spores lacking SleB, CwlJ1, and CwlJ2 are able to germinate in whole blood and serum in vitro, which may explain the persistent low levels of virulence observed in mouse infections. This work contributes to our understanding of GSLE activation and function during germination. This information may result in identification of useful therapeutic targets for the disease anthrax, as well as provide insights into ways to induce the breakdown of the protective cortex layer, facilitating easier decontamination of resistant spores.
Smoking uptake and prevalence in Ghana
Authors: Owusu-Dabo E , Lewis S , McNeill A , Gilmore A , Britton J
Published: July 2009

Background:

Developing countries are at high risk of epidemic increases in tobacco smoking, but the extent of this problem is not clearly defined because few collect detailed smoking data. We have surveyed tobacco smoking in the Ashanti region of Ghana, a rapidly developing African country with a long-established tobacco industry.

Methods:

We took a random sample of 30 regional census enumeration areas, each comprising about 100 households, and a systematic sample of 20 households from each. These were visited, a complete listing of residents obtained and questionnaire interviews on current and past smoking, age at smoking uptake, sources of cigarettes and other variables carried out in all consenting residents aged 14 or over.

Results:

Of 7096 eligible individuals resident in the sampled households, 6258 (88%; median age 31 (range 14–105) years; 64% female) participated. The prevalence of self-reported current smoking (weighted for gender differences in response) was 3.8% (males 8.9%, females 0.3%) and of ever smoking 9.7% (males 22.0%, females 1.2%). Smoking was more common in older people, those of Traditionalist belief, those of low educational level, the unemployed and the less affluent. Smokers were more likely to drink alcohol and to have friends who smoke. About 10% of cigarettes were smuggled brands. About a third of smokers were highly or very highly dependent.

Conclusions:

Despite rapid economic growth and a sustained tobacco industry presence, smoking prevalence in Ghana is low, particularly among younger people. This suggests that progression of an epidemic increase in smoking has to date been avoided.
Metamorphism of the Settler Schist, southwest of Yale, British Columbia
Authors: Pigage Lee C.
Published: July 2009

Pelitic metasediments immediately southwest of Yale, British Columbia contain mineral assemblages characteristic of staurolite through sillimanite zones of the Barrovian facies series. Microprobe analyses of major constituent phases in the pelites are combined with linear regression techniques to formulate probable kyanite- and sillimanite-forming reactions.A zone some 3 km wide contains the assemblage staurolite–kyanite–garnet–biotite–muscovite–quartz–plagioclase-ilmenite-rutile, which is univariant in AFM projection. Within precision limits of microprobe analysis, this assemblage is also univariant using linear regression techniques. Univariant relations are possible if [Formula: see text] with the composition of the fluid phase being buffered by the progressing reaction. This assemblage emphasizes the need for precise analyses when using the regression method, since minor components are often within permissible error limits rather than being balanced.Pelitic and calc-silicate assemblages from the metasediments restrict estimates of pressure–temperature conditions during regional metamorphism to 6–8 kbar and 550–770 °C. Pseudomorphs after andalusite indicate that contact metamorphism preceded regional upgrading of the pelites.
Contrasting types of bladed olivine in ultramafic rocks from the Archean of Labrador
Authors: Collerson Kenneth D. , Jesseau C. Wayne , Bridgwater David
Published: July 2009

Exceptionally coarse grained, interlocking olivine crystals up to 1 m long occur in small lenticular ultramafic bodies within the Nain Province of Labrador. The ultramafic rocks occur in association with Archean gneisses that vary in metamorphic grade from amphibolile fades to granulite facies. Some of the interlocking textures (i.e. near Hopedale) are interpreted as relict cumulate or harrisitic growths, mimicked by olivine regrowlh during metamorphism and preserved in structurally isotropic enclaves in their host rocks. Others (e.g. near Saglek) are regarded as solely of metamorphic origin. None of the olivine growths resemble spinifex textures reported in Archean ultramafic rocks elsewhere.
A possible volcanic-exhalative origin for lenticular nickel sulfide deposits of volcanic association, with special reference to those in western Australia
Authors: Lusk J.
Published: July 2009

Archean lenticular nickel sulfide deposits of volcanic association bear a striking resemblance lo volcanic-exhalative Cu–Zn massive sulfide deposits. They have similar morphologies, show well developed mineralogical layering, and exhibit close stratigraphic relationships with intimately associated volcanics and intra-volcanic sediments of greenstone belts. The nickel sulfide deposits are associated with early ultramafic/mafic volcanics. and massive Cu–Zn sulfide deposits with intermediate to silicic volcanics that formed later in volcanic-sedimentary cycles.It is suggested that a magmatic volcanic-extrusive origin does not explain features of massive nickel sulfide deposits as well as an alternative volanic-exhalative origin, which provides a direct link between sulfide ores and intimately associated exhalative sediments. It also satisfactorily accounts for a number of important features, including mineralogical layering, a relative enrichment in pyrite, and the local abundance of millerite.Outpouring of extremely hot ultramafic lavas across top surfaces of deposits would partially melt the Ni–Cu sulfides, thereby generating the igneous textures observed. Later regional metamorphism has modified these earlier features.
New gravitational evidence for the subsurface extent of oceanic crust in north-central Newfoundland
Authors: Miller H. G. , Deutsch E. R.
Published: July 2009

Gravity has been measured at 226 locations having a mean spacing of 2.5 km in the area of western Notre Dame Bay, in north-central Newfoundland. The data reveal that the observed steep seaward positive gradients of the Bouguer anomalies previously found on eastern Notre Dame Bay continue to coastal areas of western Notre Dame Bay. This belt of large gradients correlates spatially with the trace of the Chanceport – Lobster Cove Fault, which is the southern boundary of this belt of ophiolitic and island arc rocks (Belts Cove Ophiolite Complex) on the Burlington peninsula, which forms the basement of this belt. The observed anomalies may represent the gravity signature of a Paleozoic lithospheric plate margin, but a test of this possibility must await data from the bay itself.Interpretation of four profiles, using density data from rock samples and two-dimensional models, leads to the conclusion that oceanic crustal material similar to that found on Notre Dame Bay, zone D, continues inland beneath parts of zones C and E to 5–10 km maximum depth. The interpretation also suggests the desirability of establishing a subzone on the Burlington peninsula.
Polyphase magnetization of the Big Spruce Complex, Northwest Territories
Authors: Irving E. , McGlynn J. C.
Published: July 2009

The Big Spruce alkaline complex has yielded a Rb–Sr isochron of 2111 ± 40 m.y. The rocks are unmetamorphosed, but the local geochronological evidence indicates that they have had a complicated thermal history. The complex has four magnetizations, which can be separated by a two-stage demagnetization procedure. The D magnetization (19 sites; 022, +88; α95 = 8°; pole 67 °N 113 °W) is considered to have been acquired at the time of emplacement because it generally has the highest blocking temperatures (500 to 650 °C). The X, Y, and Z magnetizations are believed to be later overprints, as they generally have lower blocking temperatures and have directions that are comparable to those found in younger rocks in the interval of approximately 2000 to 1400 m.y. Most of the overprints seem to have been acquired at times of mild reheating during this interval.
Whole-rock Rb/Sr and zircon U/Pb ages of metamorphic rocks from northern Ellesmere Island, Canadian Arctic Archipelago. II. The Cape Columbia Complex
Authors: Sinha A. K. , Frisch Thomas
Published: July 2009

Although not clearly separable on field and petrographic criteria, the gneisses of the Cape Columbia Complex, one of the two major crystalline terrains in the Northern Ellesmere Fold Belt, fall into two Rb/Sr age groups: nine samples define an isochron corresponding to an age of 1083 ± 18 m.y., Sr0 = 0.7057, while six samples show more scatter at 512 ± 90 m.y.,Sr0 = 0.7189. Zircons from two gneisses have 207Pb/206Pb, i.e. minimum, ages of 926 and 980 m.y. These data are interpreted as indicating that the rocks were recrystallized in the amphibolite facies about 1000 m.y. ago; little significance is attached to the younger Rb/Sr age. However, the possibility that the rocks are orthogneisses emplaced about 1000 m.y. ago and subsequently metamorphosed ~500–600 m.y. ago, cannot be excluded. In any event, the Cape Columbia Complex becomes the latest addition to the growing list of occurrences of 900–1200 m.y.-old ('Grenville-Sveco-Norwegian') rocks in the North Atlantic craton and environs.
Large scale magnetic anomalies over western Canada and the Arctic: a discussion
Authors: Coles R. L. , Haines G. V. , Hannaford W.
Published: July 2009

A contoured map of vertical magnetic field residuals (relative to the IGRF) over western Canada and adjacent Arctic regions has been produced by amalgamating new data with those from previous surveys. The measurements were made at altitudes between 3.5 and 5.5 km above sea level. The map shows the form of the magnetic field within the waveband 30 to 5000 km. A magnetic feature of several thousand kilometres wavelength dominates the map, and is probably due in major part to sources in the earth's core. Superimposed on this are several groups of anomalies which contain wavelengths of the order of a thousand kilometres. The patterns of the short wavelength anomalies provide a broad view of major structures and indicate several regimes of distinctive evolutionary development. Enhancement of viscous magnetization at elevated temperatures may account for the concentration of intense anomalies observed near the western edge of the craton.
Quadra Sand and its relation to the late Wisconsin glaciation of southwest British Columbia
Authors: Clague J. J.
Published: July 2009

Quadra Sand is a late Pleistocene lithostratigraphic unit with widespread distribution in the Georgia Depression, British Columbia and Puget Lowland, Washington. The unit consists mainly of horizontally and cross-stratified, well sorted sand. It is overlain by till deposited during the Fraser Glaciation and is underlain by fluvial and marine sediments deposited during the preceding nonglacial interval.Quadra Sand was deposited progressively down the axis of the Georgia–Puget Lowland from source areas in the Coast Mountains to the north and northeast. The unit is markedly diachronous; it is older than 29 000 radiocarbon years at the north end of the Strait of Georgia, but is younger than 15 000 years at the south end of Puget Sound.Aggradation of the unit occurred during the climatic deterioration at the beginning of the Fraser Glaciation. Thick, well sorted sand was deposited in part as distal outwash aprons at successive positions in front of, and perhaps along the margins of, glaciers advancing from the Coast Mountains into the Georgia–Puget Lowland during late Wisconsin time.The sand thus provides a minimum age for the initial climatic change accompanying the Fraser Glaciation. This change apparently occurred before 28 800 y BP, substantially earlier than glacial occupation of the southern Interior Plateau of British Columbia. Thus, several thousand years may have intervened between the alpine and ice-sheet phases of the Fraser Glaciation.
Deformation of the Isua block, West Greenland: a remnant of the earliest stable continental crust
Authors: James Patrick R.
Published: July 2009

The Isua block of West Greenland is composed of a belt of supracrustal rocks and surrounding granitic gneisses, both of which yield dates of approximately 3750 m.y. This age is equivalent to that of the Amitsoq gneisses of the nearby Godthaabsfjord area. From the lilhological variation and structural style, two major deformalional events are recognised in both the supracrustals and the gneisses: D1, a phase of fabric formation caused by a vertical simple shear mainly affecting rocks of the supracrustal belt; and D2. a phase of major and minor folding of the earlier structures probably caused by an ENE–WSW ductile dextral simple shear movement. Measurements of the amount of strain from a distinctive conglomeratic unit yield strain paths for the two deformations and a value of vertical displacement of approximately 7 km for D1. Two dyke sets invade the supracrustals and gneisses, a tangential set during D2 and a radial set after D2.
A new astrobleme: Ile Rouleau structure, Lake Mistassini, Quebec
Authors: Caty Jean-Louis , Chown E. H. , Roy Denis W.
Published: July 2009

Ile Rouleau (50° 41′ N, 73 °53′ W) in Lake Mistassini has a circular shape, 1 km in diameter, with a glacial tail pointing southwest. The island is formed of argillaceous and micritic dolomite of the Mistassini Group and shows extensive tectonic disturbances, in contrast to the very slight regional deformation. The distortion of the bedding appears to reflect both solid rotation and internal deformation of tectonic blocks. Dikes and irregular masses of polymictic breccia with a matrix of finely comminuted rock particles cut the beds. Shatter cones are conspicuous all around the island. A few silty quartz grains in some breccia fragments show multiple sets of planar features. The size of the shatter cones is limited by the thickness of the beds in which they occur. Their average apical angle is 94°, and the bedding to cone axis angle appears to be between 45°and 70°. The cones point upward and towards the center of the island. These features suggest that the Ile Rouleau structure is an astrobleme (scar left by the impact of a large cosmic body). The age of the structure is unknown within wide limits; the Mistassini group in which it occurs is upper Aphebian (1.8 b.y.) and it is covered by Pleistocene Glacial deposits. The small size and good preservation suggest that the structure is fairly recent.
The paleomagnetism of the Helikian Mistastin pluton, Labrador, Canada
Authors: Fahrig W. F. , Jones D. L.
Published: July 2009

A paleomagnetic study was carried out on 70 cores from 11 sites on the Helikian (1346 ± 30 m.y.) Mistastin pluton, which lies in the Churchill Province about 120 km north of the Grenville Front. Primary magnetization could not be recovered from four of the sites, which were very weakly magnetized. The magnetization of three of these was dominated by a steeply-dipping down direction, which is thought to reflect the recent earth's field direction and may have originated during the process of recent weathering. The primary magnetization was isolated from the remaining seven sites, with a mean direction of D = 93.5°, I = 7.0° and α95 = 8.8°. One site was reversely magnetized relative to the rest. The Pacific pole lies at 158.5 °Wand 1.0°S, with A95 = 7.6°. This pole position supports the concept of a clockwise rotation (30° ± 5°) of the northeastern Grenville Orogen during the Helikian.
Geocryological terminology
Authors: Everdingen R. O. van
Published: July 2009

Ambiguity and inconsistent use of the word frozen and a number of related terms present problems in terminology describing permafrost and seasonal frost. To overcome some of these problems, the author proposes that use of the word 'frozen' be reserved exclusively for cases where at least some ice is present in the soil/water system. A new term, cryotic, is proposed to indicate that the temperature of the soil/water system is below 0 °C, without implying any phase conditions. Other terms dealt with are liquid water content, ice-rich, frost-sensitive, thaw-sensitive, frost-stable, and thaw-stable. A partially genetic terminology is proposed to describe various types of nonfrozen zones in permafrost areas.
The Indian Bay Formation: fossiliferous Early Ordovician volcanogenic rocks in the northern Gander Terrane, Newfoundland, and their regional significance
Authors: Wonderley Patricia F. , Neuman Robert B.
Published: July 2009

The first reported fossiliferous rocks in the northern Gander Terrane of the Newfoundland Appalachians occur at Indian Bay Big Pond, in an area previously mapped as unfossiliferous quartzose sedimentary rocks of the Gander Group. Brachiopods, trilobites, and bryozoans in argillaceous tuff indicate a late Arenigian (late Early Ordovician) age. The rocks associated with the fossils are similar to coeval rocks of the Dunnage Terrane in Newfoundland, but are atypical of the Gander Terrane. The sequence that includes the fossiliferous rocks at Indian Bay Big Pond is here named the Indian Bay Formation. The Indian Bay Formation may overlie the Gander Group stratigraphically, but structural, geophysical, and geochemical data suggest that the rocks of the Indian Bay Formation are contained in a klippe thrust onto the Gander Terrane.
Crustal electrical conductivity in north-central Saskatchewan: the North American Central Plains anomaly and its relation to a Proterozoic plate margin
Authors: Handa S. , Camfield P. A.
Published: July 2009

Seven recording magnetometers monitored time-varying fields at points on a northwest–southeast line 280 km long in north-central Saskatchewan during July 1981. The experiment was designed to test the hypothesis advanced in 1975 by Alabi, Camfield, and Gough that the electrical conductivity anomaly in the North American Central Plains links with the Wollaston Domain in the exposed Precambrian Shield of Saskatchewan. From clear reversals in the phase of vertical variations, it is evident that the conductor passes between two stations straddling the Rottenstone–La Ronge Magmatic Belt, to the immediate east of the Wollaston Domain. Enhanced horizontal variations transverse to the belt at a third, intermediate, station reinforce this interpretation. Vertical-field response arrows obtained from daytime events in the period range 1–40 min clearly indicate the existence of a major conductor that extends to lower crustal depths beneath the belt. To the northwest across the Cree Lake Zone, reversals in the direction of response arrows at short periods (up to 4 min) imply complex electrical structures in the shallow part of the crust.Lewry termed the Rottenstone–La Ronge Belt a Hudsonian "Cordillera-type" arc massif, and described strong geological evidence for collisional suturing and microplate interaction in this part of the Churchill Province. A similar scenario seems to apply in Wyoming, from the work of Hills and Houston. Thus the conductor appears to trace a Proterozoic plate margin 1500 km from a subduction zone in Wyoming along a transform fault to a subduction zone in northern Saskatchewan.
Brittle deformation in the Columbia River fault zone near Revelstoke, southeastern British Columbia
Authors: Lane Larry S.
Published: July 2009

The brittle Columbia River fault zone forms part of the eastern margin of the Shuswap Metamorphic Complex, and for much of its 230 km length it coincides with the eastern exposure of the ductile Monashee décollement. The Eocene brittle fracturing and displacement are broadly parallel with, but cut and disrupt the middle Jurassic ductile mylonite zone. Excavations for a hydroelectric dam and a highway have facilitated a detailed analysis of fracture patterns at several localities along the fractured zone.Regionally, the brittle fault zone strikes 350° (locally 310–030°) and dips shallowly eastward. Over most of the studied part of the zone, the distributions of subsidiary fractures and displacement vectors demonstrate a normal dip-slip displacement consistent with subhorizontal east–west extension within the fractured zone, irrespective of the local trend of the zone. At Revelstoke damsite, where the zone trends 030° for 2 km, motion was towards the southeast, possibly indicating a localized clockwise rotation postdating dip-slip displacement.Fractures preserving both early dip-slip vectors and later strike-slip vectors demonstrate that minor north–south, strike-slip motion was superimposed on all parts of the zone, though no throughgoing strike-slip fault formed.In the damsite excavation, the fractured zone is largely confined to mylonites derived from footwall terrane. The Tertiary brittle offset was minor by comparison with the Jurassic ductile displacement.
Geothermal measurements in northern British Columbia and southern Yukon Territory
Authors: Jessop Alan M. , Souther J. G. , Lewis Trevor J. , Judge A. S.
Published: July 2009

Measurements at seven sites in the Intermontane region of northern British Columbia and southern Yukon show heat flow of 63–100 mW/m2 and heat generation, obtained from intrusive rocks at three of these sites, of 1.8–6.5 μW/m1. These few data cannot define a linear relation between heat flow and heat generation for this region, but the plotted points lie between the lines of the stable crust of the eastern United States and of the Basin and Range Province. Conductive thermal models of the crust, assuming a basalt composition for the lower crust, predict at 35 km depth a heat flow of 30 mW/m2 and temperatures between 645 and 775 °C at most sites.At two sites conductive models based on reasonable properties do not yield reasonable temperatures. The site on the axis of the Stikine Volcanic Belt shows a probable component of convectively enhanced heat flow or the presence of a young intrusion at depth. The site in the Bowser Basin shows the probable effect of water movement in the sediments.
A conulariid from the Mississippian of Manitoba
Authors: Lammers George E. , Young Harvey R.
Published: July 2009

Diconularia sp., from the Kinderhookian Virden Member of the Lodgepole Formation, is the youngest conulariid reported from Manitoba, and is the first Mississippian conulariid reported from western Canada
Horizontal shortening of upward-facing greenstone structures in the southern Superior Province, Canadian Shield
Authors: Borradaile Graham John , Schwerdtner W. M.
Published: July 2009

Metavolcanics and clastic metasediments in parts of the Wabigoon and Shebandowan–Wawa subprovinces have been folded into tight upward-facing structures. Although the principal compressive strain is locally greater than 70%, the maximum value obtained for the overall horizontal shortening in a north–south direction is in the range of 40–60%. The actual horizontal shortening may be much less than this range unless there are large reverse faults or thrusts that have not been recognized to date.
Folds and folding in the Beardmore–Geraldton fold belt
Authors: Kehlenbeck M. M.
Published: July 2009

The Beardmore–Geraldton fold belt forms a transitional crustal segment between the Quetico and Wabigoon subprovinces of the Canadian Shield.Bedding surfaces (So) and a bedding-plane schistosity (S1) were folded into asymmetrical to recumbent early folds. These folds were refolded by a later F2 folding episode. The F2 folds possess a penetrative axial-planar schistosity (S2) that is subvertical and generally strikes east–west. F2 hinge lines coincide closely with the axial direction of the early folds.The "structural facing direction (sensu Borradaile)" of F2 folds is either east or west. Folds with consistent facing directions are confined to distinct panels. Panels containing F2 folds with opposing facing directions are in sharp contact with each other. In several panels F2 folds face upward through sideways to downward.Modification of F2 buckle folds by homogeneous compressive strain components produced flattened flexure folds that closely approach folds of the similar fold model class.Further modification of fold shapes occurred in response to shear discontinuities that pervade the fold belt. Sheared F2 fold limbs commonly bind segments containing displaced F2 hinge zones of formerly adjacent folds. Zones of intense shearing show evidence of transposition of earlier fabric elements into the S2 schistosity. These zones of intense shear also form the boundaries of juxtaposed panels in which folds of variable orientation occur.The Beardmore–Geraldton fold belt is a terrain in which displacements along pervasive shear discontinuities of refolded folds and transposition of earlier fabric elements into the S2 schistosity have resulted in a pseudostratigraphy composed of disrupted and rotated segments of a pre-existing sequence of layered rocks.
Petrology and geochemistry of the early Mesozoic Caraquet dyke, New Brunswick, Canada
Authors: Greenough John D. , Papezik V. S.
Published: July 2009

The Caraquet dyke of New Brunswick is one of three early Mesozoic dykes recognized in Atlantic Canada. It has a quartz-normative tholeiitic composition intermediate in character between "low-Ti" and "high-Ti" Appalachian diabase. Major-element (e.g., MgO, SiO2) and trace-element concentrations (e.g., Ba, Zr) suggest that the dyke is less evolved than the Shelburne dyke but slightly more evolved than the Avalon dyke. Although related to continental rifting and opening of the Atlantic Ocean, the dykes of the Atlantic Provinces show little in common with continental rift volcanic rocks. They resemble MORB except that their K, Rb, and Ba concentrations are much higher. Semi-quantitative modelling suggests that the elevated large-ion lithophile-element concentrations reflect assimilation of continental crust. Differences in composition among the three dykes may be due to variations in the quantity and composition of assimilated material as well as the degree of differentiation. As with other early Mesozoic dykes of eastern North America, the emplacement of these rocks was structurally controlled: (1) their orientations reflect a rift-induced stress field and (2) their location reflects control by Paleozoic lithotectonic terranes of the Applachian Orogen.
New ptychaspidid trilobites from the Upper Cambrian Mistaya Formation of southern Alberta
Authors: Westrop Stephen R.
Published: July 2009

Three new ptychaspidid genera are described from the Upper Cambrian (Sunwaptan Stage) Mistaya Formation of Banff and Jasper national parks, southern Alberta. Proricephalus gen. nov. is represented by two species and is placed in the subfamily Ptychaspidinae. Both Sunwaptia gen. nov. and Wilcoxaspis gen. nov. are monotypic. They are assigned to a new ptychaspidid subfamily, the Macronodinae, which also includes Macronoda Lochman. New species described are Proricephalus wilcoxensis, Sunwaptia carinata, and Wilcoxaspis bulbosa.
Vitrinite reflectances from Eocene rocks of southern British Columbia, a regional reconnaissance
Authors: Mathews W. H. , Bustin R. M.
Published: July 2009

Reflectances of Eocene vitrinite from a wide selection of sites in southern British Columbia show a concentration between 0.45 and ~1.0%. Localities with reflectances less than 0.45% may be less deeply buried (Kamloops at 0.25%) than most of the others, younger (Hat Creek), or perhaps associated with an abnormally low geothermal gradient (Princeton?). Localities with abnormally high reflectances (>1.0%) include sites with local heat sources, such as an intrusion (Afton mine near Kamloops), a coal fire (Hat Creek), or a hot, pyroclastic flow (south of Princeton). Other occurrences with high reflectances are those that may have been blanketed by an overthrust sheet (Big Bar), deposited on crustal rocks shortly after they had been tectonically stripped and while they were still warm (Enderby), or otherwise juxtaposed against such deep crustal rocks (White Lake area). Measurement of reflectance plays a useful role in calling attention to abnormal geothermal conditions once the regional pattern is determined.
The trace fossil Yakutatia emersoni from the Cretaceous Kodiak Formation of Alaska
Authors: McCann T. , Pickerill R. K.
Published: July 2009

The enigmatic trace fossil Yakutatia emersoni has previously only been briefly described from the Cretaceous Kodiak Formation of Kodiak Island, Alaska. Herein we examine the trace fossil in detail, confirm that it is indeed a graphoglyptid, note the associated trace fossils, interpret the depositional environment of the strata in which it occurs as most probably a lobe fringe environment in the distal part of a large submarine fan, and designate a lectotype.
Sulphur-isotope geochemistry of silver–selpnarsenide vein mineralization, Cobalt, Ontario
Authors: Goodz M. D. , Watkinson D. H. , Smejkal V. , Pertold Z.
Published: July 2009

The silver–sulpharsenide vein deposits of Cobalt, Ontario, crosscut basement Archean metavolcanic rocks, Proterozoic strata, and younger Proterozoic diabase sills. A petrographic and sulphur-isotope study of the metallic minerals was initiated to assess possible genetic models of vein formation. Discrete differences exist between the sulphur-isotope compositions of basement sulphides (δ34S = + 4.0‰), brecciated wall-rock sulphides (+ 3.5‰), and vein sulphides (+ 2.3‰). The δ34S values consistently increase with distance from the vein centres. Sulphur-isotope fractionation trends are similar for all the vein deposits studied. Sulphur-isotope data suggest that sulphides were deposited between 130 and 254 °C. Based on the assumption of equilibrium between chalcopyrite and galena, the initial δ34S of the fluid was between + 5.0 and + 11.0‰. The release of sulphur during the reaction of Archean pyrite with Proterozoic formational brines to form pyrrhotite is proposed to explain the heavy sulphur isotopic composition of the fluid. This process could also have provided the Ni, Co, and As, known to be concentrated in some pyrite, that was deposited in the silver veins. Interpretation of mineral paragenesis and geothermometry indicate that temperature decreased and aS2 increased as deposition proceeded.
Silver deposits associated with the Proterozoic rocks of the Thunder Bay District, Ontario
Authors: Franklin J. M. , Kissin S. A. , Smyk M. C. , Scott S. D.
Published: July 2009

The silver deposits to the immediate north and west of Lake Superior are divided into three groups. The Mainland veins, the largest group, occur along a zone of normal faults near the western margin of the Proterozoic rocks of the Southern Province. The most economically productive deposits, the Island group, arc in or very near a northeast-trending swarm of gabbro dykes lying immediately offshore the northwestern shore of Lake Superior. The third group occurs near the western margin of the Port Coldwell alkalic complex; these veins are in a shear zone that cuts both Archean metasedimentary rocks and a Proterozoic diabase dyke. The Mainland deposits occur in the Rove shale, immediately below the contact with Logan diabase sills. The veins locally extend upwards into the sills, but the silver-bearing portions, consisting of acanthite and native silver associated with base-metal sulphides, fluorite, barite, quartz, and calcite, are largely bounded by locally silicified shale. The Island veins, typified by the Silver Islet mine, are in fractures perpendicular to the gabbro-dyke host rocks. These veins contain both native silver and acanthite, associated with a Ni–Co sulpharsenide suite and the same mineral assemblage as the Mainland deposits. The veins near Coldwell are rich in sphalerite and galena.Lead-isotope data indicate that the Mainland and Island veins are genetically related and that the Mainland veins formed from an inhomogeneous fluid. Two-stage calculations indicate an early Proterozoic source rock, possibly the Rove shale. The Island veins are more isotopically homogeneous, and their metals may have been derived partially from the gabbro. The Coldwell veins contain lead that is less radiogenic than that of the other two groups and is possibly derived from the adjacent Archean rocks. All three groups of deposits have isotopic compositions that are much less uranogenic and more thorogenic than the nearby Pb–Zn–Ba veins of the Dorion area. Preliminary fluid-inclusion data from the Mainland veins indicate that deposition occurred from a fluid whose temperature varied from approximately 200 °C to more than 400 °C; deposition occurred during boiling induced by adiabatic expansion of the fluid at relatively shallow crustal depths. The Mainland veins developed in the shale (rather than the diabase), as its high fissility, and hence permeability, made it susceptible to intense fracturing by the expanding fluid. Both the Mainland and Island groups were deposited in structures formed dominantly by listric normal faulting during late stages of intracontinental rifting. Heat was supplied by abundant mafic intrusions that formed coincident with rifting. The ore fluid was probably formed as a result of metamorphic dewatering, with metals released to the fluid because of silicate and sulphide recrystallization.
Quantitative coal mineralogy of the Sydney Coalfield, Nova Scotia, Canada, by scanning electron microscopy, computerized image analysis, and energy-dispersive X-ray spectrometry
Authors: Birk Dieter
Published: July 2009

Automated image and X-ray analysis, with a scanning electron microscope, has been used to "fingerprint" mineral particles in bituminous coals of the Sydney Coalfield and catalogue their chemical class and size distribution. Four seams (Hub, Harbour, Phalen, and Gardiner) were analyzed quantitatively for some 32 000 mineral particles; these analyses revealed particle-size and weight distributions for 27 chemical classes. Manual searches augmented the computer-automated scans, covering eight seams and recording a total of 35 mineral species, their paragenesis, and sites for 28 elements.Sydney seam mineralogy is dominated by pyrite and kaolinite, but illite, chlorite, siderite, ankerite, and quartz are locally prominent; these are accompanied by a large variety of accessory minerals (zircon, rutile, apatite, barite, gypsum, rare-earth phosphates, and ore minerals) and alteration products (goethite and hydrated sulphates). Individual column benches show geochemical fades with different mineral suites resulting from cyclic sedimentation, hydrologie conditions, and changes in pore-water chemistry during peat accumulation, coalification, and diagenesis. A sulphide facies and a siderite–chlorite facies are recognized within one seam (Harbour); these facies change vertically and laterally within lithotype bands.Stratigraphic correlation is precluded, but quantitative mineralogy can elucidate paleoenvironments and be applied to coal-cleaning technology (beneficiation) or environmental studies.
The evolution and tectonic consequences of a tonalitic magma layer within Archean continents
Authors: Ridley J. R. , Kramers J. D.
Published: July 2009

The petrological and tectonic consequences of early continent formation by localized open-system fractional crystallization of an almost global shallow-level tholeiitic magma layer are investigated. A near-surface tonalitic–trondhjemitic–granodioritic (TTG) magma "ocean", evolved by such a process near mantle sinks, would rapidly crystallize a stably floating solid upper crust several kilometres thick and could therefore be a long-lived feature of Archean geology. Given likely mantle heat fluxes, crystallization of the molten layer resulting from secular cooling and movement from mantle-upwelling to -downwelling regions would normally be from the top downward. In areas of extremely low mantle heat flow, crystallization from the base upward is also possible.The partially molten layer will convect with cells on a much smaller scale than those in the underlying mantle. This convection will influence tectonic patterns in the overlying solid crust, the history of which will be largely independent of specific mantle convection patterns. Small-amplitude surface topography is predicted. Intrusion of mafic or ultramafic magmas to high levels would not be possible through tonalite with a melt proportion greater than about 40% and is likely therefore to be concentrated at cooler, downwelling zones of the small-scale convection system. These two predictions together suggest that Archean greenstone belts form over local downwarping zones of TTG crust. Early, shelf-facies sedimentation is related to convection-induced topographic relief, whereas later, higher energy sedimentation is related to gravitational instability resulting from localized loading of the crust.So long as a continental magma layer is continually replenished by tholeiite melt, its composition remains essentially tonalitic. When it ceases to be replenished, fractionation will give rise to granitic melts that through their lower density will increase the gravitational instability of the Archean crust.