bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultradeep Pyrosequencing Detects Complex Patterns of CD8
+
T-Lymphocyte Escape in Simian Immunodeficiency Virus-Infected Macaques
Authors: Bimber Benjamin N. , Burwitz Benjamin J. , O'Connor Shelby , Detmer Ann , Gostick Emma , Lank Simon M. , Price David A. , Hughes Austin , O'Connor David
Published: June 2009

Human and simian immunodeficiency viruses (HIV/SIV) exhibit enormous sequence heterogeneity within each infected host. Here, we use ultradeep pyrosequencing to create a comprehensive picture of CD8
+
T-lymphocyte (CD8-TL) escape in SIV-infected macaques, revealing a previously undetected complex pattern of viral variants. This increased sensitivity enabled the detection of acute CD8-TL escape as early as 17 days postinfection, representing the earliest published example of CD8-TL escape in intrarectally infected macaques. These data demonstrate that pyrosequencing can be used to study the evolution of CD8-TL escape during immunodeficiency virus infection with an unprecedented degree of sensitivity.
Immune-mediated and chronic inflammatory disease in people with sarcoidosis: disease associations in a large UK database
Authors: Rajoriya N , Wotton C J , Yeates D G R , Travis S P L , Goldacre M J
Published: June 2009

Background

Sarcoidosis is a multi-system disorder characterised by non-caseating granulomas. Coexistence of sarcoidosis with immune-mediated and chronic inflammatory diseases has been described in case series. However, the coexistence of two different diseases in individuals can occur by chance, even if each of the diseases is rare.

Aim

To determine whether sarcoidosis necessitating hospital admission or day-case care coexists with a range of immune-mediated and chronic inflammatory diseases more commonly than expected by chance.

Design

Analysis of an epidemiological database of hospital admission and day-case statistics, spanning 30 years.

Results

1510 patients with sarcoidosis were identified (mean age 44 years, median follow-up 19 years) who had been admitted to hospital or day-case care. Significant associations in the sarcoidosis cohort were identified with systemic lupus erythematosus (odds ratio (OR) 8.3; 95% CI 2.7 to 19.4), autoimmune chronic hepatitis (OR 6.7; 95% CI 1.8 to 17.1), multiple sclerosis (OR 3.3; 95% CI 1.7 to 5.6), coeliac disease (OR 3.1; 95% CI 1.01 to 7.3), thyrotoxicosis (OR 2.5; 95% CI 1.4 to 4.0), myxoedema (OR 2.2; 95% CI 1.2 to 3.7) and ulcerative colitis (OR 2.1; 95% CI 1.1 to 3.7). Weaker associations were found for diabetes mellitus with a first admission aged 30–49 years (OR 2.9; 95% CI 2.1 to 4.0) or age >50 (OR 1.7; 95% CI 1.2 to 2.3), but not for people age <30. No significant association with Crohn’s disease (OR 1.52; 95% CI 0.61 to 3.14) or primary biliary cirrhosis (OR 3.75; 95% CI 0.77 to 11.0),was found. When all immune-mediated and chronic inflammatory diseases for which associations were sought were combined, the overall rate ratio associated with sarcoidosis was 2.2 (95% CI 1.9 to 2.6).

Conclusion

This study adds epidemiological evidence to information from clinical reports that there is a connection between sarcoidosis and other immune-mediated and chronic inflammatory diseases.
New insulins and new insulin regimens: a review of their role in improving glycaemic control in patients with diabetes
Authors: Crasto W , Jarvis J , Khunti K , Davies M J
Published: June 2009

Effective glycaemic control can reduce and potentially prevent the microvascular and macrovascular complications of diabetes. Insulin is the mainstay of treatment for type 1 diabetes and is indicated in patients with type 2 diabetes who do no achieve optimal glycaemic control despite the use of oral hypoglycaemic agents. The advent of the so-called “designer” insulins, the insulin analogues, has offered new opportunities in the clinical management of diabetes. This review examines the efficacy of the different analogue insulins introduced thus far and goes on to explain their pharmacodynamics and pharmacokinetics. The review also examines the different types of insulin regimen currently used in clinical practice and discusses some of the factors that influence the choice of a particular insulin regimen. Further, irrespective of the insulin regimen used, the importance of prompt initiation and ongoing titration of insulin treatment to achieve optimal glycaemic targets is emphasised.
Causes of mortality in diabetes mellitus: data from a tertiary teaching hospital in India
Authors: Zargar A H , Wani A I , Masoodi S R , Bashir M I , Laway B A , Gupta V K , Wani F A
Published: June 2009

Background

Mortality studies can show the relative contribution of diabetes to mortality in the total population, and they can provide important descriptions of the changes in causes and frequency of diabetes mortality over time.

Objective

To find the mortality pattern in people with diabetes admitted to a tertiary care hospital in a developing country, using underlying/contributory causes of death.

Methods

In this retrospective study, mortality trends among people with diabetes admitted to Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Kashmir, India were reviewed by screening the hospital records of all people with diabetes who died over the last 9 years, carrying forward earlier observations from the same centre.

Results

Of 234 776 people admitted to the centre during the review period, 16 690 (7.11%) died; 741 (383 men) of these had diabetes mellitus mentioned on the death certificate. The mean (SD) age at death for people with diabetes was 60.07 (13.62) years in men and 57.36 (13.40) years in women. The leading contributory causes of death were infections (40.9%), chronic renal failure (33.6%), coronary artery disease (16.9%), cerebrovascular disease (13.2%), chronic obstructive pulmonary disease (6.9%), acute renal failure (6.2%), malignancy (4.2%), hypoglycaemia (3.5%) and diabetic ketoacidosis (3.4%). The cause of death could not be ascertained in 2.8% of cases; in 52.9%, 36.3% and 8.0% cases one, two and three or more causes, respectively, were recorded as the cause of death.

Conclusions

The aetiological spectrum of mortality in people with diabetes at this Indian centre continues to be dominated by infections and renal failure, which is different from that in the developed world, where coronary artery disease and cerebrovascular disease are the principal causes of death in people with diabetes.
CRETACEOUS VERTEBRATES FROM THE ANDERSON RIVER N.W.T.
Authors: Russell Dale A.
Published: June 2009

Vertebrate remains have been recovered from two horizons in late Cretaceous strata along the east bank of the Anderson River at latitude 69 °N. The lower horizon has produced a fauna very similar to that of the Niobrara Chalk in western Kansas, including mosasaurs, plesiosaurs, and abundant toothed birds. The upper horizon has yielded a moderately short-necked plesiosaur of cimoliasaurian affinities. These vertebrates lived in or near a strait linking the Arctic Ocean with the interior sea in very late Cretaceous time.
CHROMIAN SPINEL AS A PETROGENETIC INDICATOR: PART 2. PETROLOGIC APPLICATIONS
Authors: Irvine T. N.
Published: June 2009

The crystallization of chromium-bearing spinel from silicate magmas is first examined, and then an attempt is made to apply the theory developed in Irvine (1965) to the principal occurrences of the mineral for which data are available. It is concluded that the chromium-rich varieties commonly known as chromite have generally formed simultaneously with olivine, and that their crystallization has in many occurrences been terminated by a peritectic (reaction) relation leading to formation of a pyroxene. The origin of the aluminium-rich varieties is more problematical and perhaps more varied; however, they evidently occur only in alpine-type peridotite bodies and peridotite "nodules" in basaltic volcanic rocks, and their formation may generally have involved high pressures. It is found that there is a rough correlation between the Mg/Fe++ ratios of chromian spinels, olivines, and pyroxenes occurring in the same rock bodies, and there is some evidence that the Mg–Fe++ distribution coefficients of spinel–silicate pairs may significantly be sensitive to temperature. The chromites of stratiform intrusions reflect an appreciable range of oxygen fugacities, whereas the spinels of alpine- type peridotite bodies seem generally to have formed at about the same relatively low oxygen fugacity. Chromites from ultra mafic bodies of the type common to southeastern Alaska have exceptionally high Fe+++/Cr + Al + Fe+++ ratios, probably because the bodies crystallized from magma that was extremely poor in silica.
BRIDGE RIVER ASH AND SOME OTHER RECENT ASH BEDS IN BRITISH COLUMBIA
Authors: Nasmith H. , Mathews W. H. , Rouse G. E.
Published: June 2009

The character, distribution, and age of the Bridge River ash from postglacial sites in British Columbia and Alberta are discussed. The ash consists of dust-sized shards with ellipsoidal fragments of pumice. With a source in the region of the upper Lillooet River, the ash both, thins and fans out east-northeasterly as far as westernmost Alberta in the vicinity of the North Saskatchewan River. Peat immediately below the ash in a bog near Jesmond, British Columbia, was dated by radiocarbon at 2 440 ± 140 years before present (B.P.). The track of the Bridge River ash overlaps that of the Mazama ash of about 6 600 years, but lies north of the presently known distribution of St. Helens Y ash of approximately 3 200 years B.P. It is suggested that with a distinctive character and limited distribution, the Bridge River ash is potentially valuable as a postglacial marker horizon in southcentral British Columbia.
THE THICK-HEADED CERATOPSIAN DINOSAUR PACHYRHINOSAURUS (REPTILIA: ORNITHISCHIA), FROM THE EDMONTON FORMATION NEAR DRUMHELLER, CANADA
Authors: Langston Jr. Wann
Published: June 2009

Pachyrhinosaurus, hitherto known from the lower Edmonton facies of the Lethbridge district in Alberta, Canada, has recently been discovered in correlative rocks in the Red Deer River valley, near Drumheller. An incomplete skull referred to Pachyrhinosaurus of. P. canadensis Sternberg is better preserved than others previously described. It reveals basic resemblances between this genus and certain ceratopsids (Centrosaurus: Styracosaurus) with short squamosals, deep faces, and wide uncomplicated narial apertures; the frill was fenestrated. Packyrhinosaurus is best placed in the Ceratopsidae, where it is unique in the possession of a massive nasofrontal boss in place of the usual nasal horn.
Cordilleran and Laurentide Multiple Glaciation West-Central Alberta, Canada
Authors: Roed Murray A.
Published: June 2009

Informal rock stratigraphic units have been established for the area. They consist of the Marlboro, Raven Creek, Obed, and Drystone Creek tills of Cordilleran provenance, and the Marsh Creek, Edson, and Mayberne tills of Canadian Shield or Laurentide source. Three different gravel units of Tertiary–Quaternary age underlie glacial deposits of the area and are here called the Tableland, Lowland, and Buried Valley gravel, in order of decreasing age.Evidence for four and possibly five glacier advances has been recognized. The oldest is inferred by fragmentary evidence of an 'Early' Cordilleran till. The second, represented by the Marsh Creek till, is the initial and greatest advance of Laurentide ice into the area. In the third both Cordilleran and Laurentide glaciers advanced and met. The Cordilleran ice is recorded by the Marlboro and Raven Creek tills, and the Laurentide by the Edson and Mayberne tills. The fourth glacial advance is documented by the Obed till of Cordilleran source. The Hinton terraces were formed during retreat of this glacier. The last glacier advance is indicated by the Drystone Creek till present in small valleys at the mountain front.Although radiocarbon dates are not available, the Marlboro, Obed, and Drystone Creek Cordilleran ice advances may represent the Early, Middle, and Late Stages of the Pinedale Glaciation (classical Wisconsin) of the Rocky Mountain area of the United States of America. Broadly correlative Cordilleran glacial advances occurred in the Banff area and the Williston Lake area of British Columbia.
Role of Fluid State Mobilization during Metamorphism of the Henderson Ore Bodies, Chibougamau, Quebec, Canada
Authors: Guha Jayanta , Koo Jahak
Published: June 2009

The Henderson Cu-Au deposit occurs in discordant structures within the anorthosite zone of the Doré Lake Complex. The Doré Lake Complex is intruded into volcanic rocks of the Chibougamau greenstone belt on the southeastern side of the Superior Province. Massive to disseminated sulfide ores are associated with sericite, carbonate, chlorite and/or chloritoid schists within a large 'shear zone'. These ores show structural and textural evidence of intense deformation, recrystallization, and metamorphic mobilization.The deposit comprises not only sulfide schist ore with alternating sulfide and schist layers, but also 'hydrothermal' vein-type segregation ore. The latter is characterized by sulfide-bearing quartz-calcite veins that occur in the 'shear zone' and in the subsidiary fractures adjacent to it.The sulfide schist and vein types of ores can be attributed to partly solid state mobilization combined with fluid state mobilization from a pre-existing ore, and is an excellent example of extensive fluid state mobilization of sulfides under relatively low-grade regional metamorphism. It is suggested that fluid state mobilization can play an important role during the metamorphism of a pre-existing sulfide body, especially in the presence of differential stress accompanied with rupture. The deformational features of the ore are the important indication for syn- and/or pre-metamorphic origin of the ore.
New Silurian Gastropods from Nova Scotia and Britain
Authors: Peel John S.
Published: June 2009

Eight Silurian gastropod species are described from the Arisaig Group of Nova Scotia and equivalent strata in Britain. Mimospira, Haplospira, and Brachytomaria are recorded from the Silurian for the first time. The following new species are described: Pharetrolites bambachi, Mimospira abbae, Haplospira sibeliuxeni, Naticonema kauffmani, Cyclonema (C.) lydiamariarum, Naticopsis trevorpatriciorum, Morania (?) boltoni.
Dispersion Trends of Elements and Indicator Pebbles in Glacial Till around Mt. Pleasant, New Brunswick, Canada
Authors: Szabo N. L. , Govett G. J. S. , Lajta E. Z.
Published: June 2009

Studies on the composition of glacial till around the Mt. Pleasant Mo-W-Bi-Cu-Sn-Zn mineralization show that the host rock at Mt. Pleasant, which can be regarded as a point source, can be detected by pebble counts in the till 7 km down-ice from Mt. Pleasant. Analysis of various size fractions of glacial till demonstrate that glacial transport can, in some situations, actually be an advantage in the use of exploration geochemical techniques. Whereas dispersion trains of Cu, Pb, and Zn in the fine fractions of till can be traced for only 2 to 5 km from the mineralized source, they extend for more than 16 km in the coarse fraction of the till. Analysis of the coarse fraction of glacial till is clearly a potentially powerful reconnaissance-scale exploration technique.
The Petrochemistry and Paleomagnetism of the Molson Dikes, Manitoba
Authors: Ermanovics I. , Fahrig W. F.
Published: June 2009

Northeasterly trending, tholeiitic, low-alkali basaltic dikes which cut the Archean rocks of northeastern Manitoba have yielded a paleomagnetic pole at 114°W, 28°N, α95 = 12°. The material from nine sites was normally magnetized, and from one site, reversely magnetized. Potassium–argon age determinations suggest that the dikes were magnetized during late Aphebian. They may have been magnetized at the time of intrusion. Strongly differentiated dikes show intense and variable deuteric alteration, which is interpreted to be the cause of within-site dispersion of NRM. However, strong NRM is related to high contents of opaques regardless of the degree of alteration. Aphanitic dikes of low magnetite content and exhibiting minimal magmatic differentiation usually record moderate magnetic intensities and good groupings.
The Ceratopsian Dinosaurs and Associated Lower Vertebrates from the St. Mary River Formation (Maestrichtian) at Scabby Butte, Southern Alberta
Authors: Langston Jr. Wann
Published: June 2009

Scabby Butte, a limited exposure of late Cretaceous sediments in southern Alberta, Canada, is an important source for the large ceratopsian dinosaur Pachyrhinosaurus Sternberg. New cranial material confirms this taxon's place among short-faced ceratopsids, and circumstantial evidence suggests that it possessed a spiked frill reminiscent of Styracosaurus. Postcranial bones associated with Pachyrhinosaurus skulls in a bonebed deposit probably belong to the genus and indicate a massive body approaching Triceratops dimensions. Another ceratopsian, Anchiceratops, is sparsely represented.All classes of gnathostomes, except birds, are represented by fragmentary material at Scabby Butte. Of 21 lower vertebrate taxa, fourteen are new to the St. Mary River Formation (Squatirhina, Squatina, Amia, Belonostomus, Paralbula, Platacodon, Opisthotriton, Boremys, Plioplatecarpus, a tyrannosaur, a coelurosaur, an ornithomimid, Troödon, Edmontosaurus, Edmontonia).
Paleomagnetism of the Contact Aureole and Late Dikes of the Otto Stock, Ontario, and its Application to Early Proterozoic Apparent Polar Wandering
Authors: Pullaiah G. , Irving E.
Published: June 2009

The Otto Stock consists mainly of syenite. Except for some mafic phases the syenites are magnetically unstable, but late-stage lamprophyre dikes and basic rocks in the contact aureole contain abundant stable material. Their mean direction of magnetization is 330°, +71 °(18 sites, 84 samples, α95 = 3°) with a corresponding pole at 69°N, 133°W (A95 = 5°). A subordinate later magnetization also occurs in three lamprophyre dikes. Using these and previous results a path of apparent polar wander for Laurentia for the interval 2200 to 1800 m.y. of simple form is constructed. The fact that a single simple polar path can be constructed, which is consistent with data from localities spread widely over the Laurentian Shield, indicates that the Hudsoni orogeny may not have been accompanied by very large relative motions of the bordering Archean cratons.
Archean Stromatolites in the Northern Slave Province, Northwest Territories, Canada
Authors: Henderson John B.
Published: June 2009

Archean stromatolites occur in a discontinuous dolomite unit at the contact between a major felsic volcanic buildup and a thick sequence of greywacke–mudstone turbidites in the vicinity of Snofleld Lake (67°18′N, 110°45′W). The stromatolitic unit is intimately associated with black carbonaceous mudstones that may also be of biogenic origin. The most common stromatolitic form is a generally flat variety with wavy to corrugated laminations, and contains small local convexities with relief of about 1 cm. A few small stromatolitic heads to low mounds that are formed from similar, even to corrugated, laminae also occur. Minor intraformational breccia layers are present, which in some cases contain larger clasts that have formed oncolites. Although Archean stromatolites are very rare, similar, more deformed and metamorphosed carbonate units occur at similar stratigraphie positions between felsic volcanic sequences and the turbidites elsewhere in the Slave Province. Thus, in an otherwise unstable, inhospitable Archean world, the development of stromatolites around emergent felsic volcanic islands was favored. This was due to a temporary environment with the right light conditions for photosynthesis and perhaps an abundant nutrient supply provided by local volcanic fumarolic activity, as indicated by the occurrence of several base-metal mineral deposits in the Slave Province at this same horizon.
The Closing of Ice-wedge Cracks in Permafrost, Garry Island, Northwest Territories
Authors: Mackay J. Ross
Published: June 2009

The closing of thermal contraction (ice-wedge) cracks at Garry Island, N.W.T., 150 km northwest of Inuvik, N.W.T., has been measured by means of gauge probes inserted into the cracks and by precise taping between bench marks across ice-wedge troughs. The results show that a simple elastic model fails to explain the time of cracking, the depth of cracking, the crack spacing, and the time of closing. The mean annual ice vein increment, at Garry Island, is probably less than 20% of the mean winter crack width. Thermal contraction cracks are of potential engineering interest, because they may affect underground cables, reservoirs, and other man-made structures.
Pollen and Seed Analysis of the Titusville Section (Mid-Wisconsinan), Titusville, Pennsylvania
Authors: Berti Albert A.
Published: June 2009

Wisconsinan interstadial sediments, consisting mainly of moss peat, peaty silt and sand, are exposed near Titusville in northwestern Pennsylvania. They lie beneath the Titusville Till, south of the margin of the Late Wisconsinan Kent Till. Radiocarbon dates obtained range from 35 000 to 40 000 years BP, indicating that the sediments are of late Port Talbot II age (Mid-Wisconsinan).A pollen diagram from the section is divided into the three informal lower, middle and upper zones. Macrofossils of dwarf birch Betula glandulosa var. glandulosa, the only subarctic taxon recovered, characterize the lower dated peat layer (lower zone). The presence of dwarf birch is indicative of a forest–tundra environment during deposition of this peat. In the upper dated peat layer (upper zone) low numbers of Cyperaceae seeds, along with relatively high percentages of Cyperaceae pollen, imply that at least part of the sedge pollen was derived from plants growing on the uplands in an even more open spruce parkland. These data outweigh the implication that the climate was ameliorating as suggested by the marked rise in Pinus pollen in the upper zone. The pine pollen are attributed to the relatively increased effect of long distance transport as the local tree pollen production decreased.
40Ar/39Ar Ages from the Bay of Islands Metamorphic Aureole: Their Bearing on the Timing of Ordovician Ophiolite Obduction
Authors: Dallmeyer R. D. , Williams Harold
Published: June 2009

40Ar/39Ar age spectra of hornblendes from the metamorphic aureole of the allochthonous Bay of Islands ophiolite complex yield similar dates, which overlap at 460 ± 5 m.y. Recent models indicate that the aureole developed during obduction of the ophiolite suite, and it is suggested that the 460 m.y. age dates this tectonic event. Well-documented paleontological control brackets ophiolite obduction to the late Arenigian, and the 460 m.y. date is an important reference point in the calibration of an absolute Ordovician time-scale.
On the Age of the Sudbury Dike Swarm
Authors: Schmus W. R. Van
Published: June 2009

Review of existing geochronologic and paleomagnetic data indicates that an age of 1250 ± 50 m.y. (1σ) is currently the most reasonable estimate for the Sudbury dike swarm.
Rb–Sr geochronometry of the Ecstall, Kitkiata, and Quottoon plutons and their country rocks, Prince Rupert region, Coast Plutonic Complex, British Columbia
Authors: Armstrong Richard Lee , Runkle Dita
Published: June 2009

The minimum age of the Ecstall pluton is 78–79 Ma, based on Rb–Sr mineral isochrons for two pegmatites. At that time the entire body of the pluton, zoned concentrically from quartz monzonite to diorite, was Sr rich – Rb poor, relatively homogeneous in Rb/Sr ratio (0.024–0.061), and somewhat variable in initial Sr isotopic composition (87Sr/86Sr = 0.7044 to 0.7048). Late-stage leucocratic dikes contain radiogenic Sr that is probably derived from old and Rb-rich country rocks. Pegmatite dikes from two different localities are similar to one another in Rb/Sr and 87Sr/86Sr and either have high initial ratios (0.7055 and 0.7058), like the leucocratic dikes (0.7051 and 0.7059), or the pluton and its pegmatite dikes are very much older (~190 Ma) than the 78–79 Ma pegmatite mineral isochrons. Sr isotopic data do not resolve this ambiguity. The Kitkiata pluton has an initial 87Sr/86Sr ratio of 0.7042–0.7043, depending on its age. One radiogenic Sr-rich sample gives a model date of 165 ± 11 Ma, but the possibility of anomalous initial ratio makes this result highly uncertain.The Quottoon pluton, which lies a bit farther east of the Ecstall pluton, gives a whole-rock isochron of 51 ± 2 Ma with 0.7045 ± 1 initial ratio and somewhat older, near concordant, U–Pb zircon dates of 60 Ma. The low initial ratios indicate a preponderance of mantle-derived magma of Mesozoic or early Cenozoic age in the plutons studied.Radiogenic Sr in schists near Prince Rupert suggests an age on the order of 524 Ma, and correlation with upper Precambrian and lower Paleozoic rocks of the Alexander Terrane of the Alaska Panhandle.Sr isotopic composition of the Central Gneiss Complex is compatible with late Paleozoic – early Mesozoic ages for precursor detrital and volcanic strata and local presence of marine carbonate with moderately enriched 87Sr/86Sr. The generally low radiogenic Sr content of these core gneisses rules out an origin by remobilization of greatly older rocks.
A model of the thermal effects of igneous intrusion and uplift as applied to Quottoon pluton, British Columbia
Authors: Harrison T. Mark , Clarke Garry K. C.
Published: June 2009

A recently obtained isotopic cooling curve for the Quottoon pluton, near Kitimat, British Columbia, has allowed resolution of its thermal history. Our analysis is based on a time-dependent mathematical model of the cooling of a two-dimensional pluton with rectangular cross section. The pluton is assumed to be intruded into a medium initially in equilibrium with a constant geothermal flux and evenly distributed radioactive heat sources. A complicated history of regional uplift can be assumed. Model input parameters constraining dimensions, thermal properties, thermal flux from the mantle, heat production, uplift rate, and initial temperature were either measured or estimated independently of the numerical simulation. The cooling curve generated by our model agrees closely with the experimental curve derived from nine mineral dates and previously assigned values for closure temperatures of the radiometric systems. This approach appears to provide a valuable tool for calculating thermal effects of intrusion and for testing the physical soundness of geological interpretations.
Archaean precious-metal hydrothermal systems, Dome Mine, Abitibi Greenstone Belt. I. Patterns of alteration and metal distribution
Authors: Fryer B. J. , Kerrich R. , Hutchinson R. W. , Peirce M. G. , Rogers D. S.
Published: June 2009

The Porcupine District, Abitibi Greenstone Belt is one of the most extensive areas of Archaean auriferous mineralization. At least two stages of lode gold emplacement may be recognized. The first involves gold-bearing ferroan dolomite layers with subordinate chert, sulphides, and graphite deposited as laterally extensive chemical sediments at interflow horizons within the mafic volcanic sequence. The second stage is represented by major gold-bearing hydrothermal quartz–albite–dravite veins which transect diverse host rocks including the carbonate chemical sediments. Differences between gold-bearing chemical sediment and auriferous hydrothermal veins, in terms of texture, mineralogy, and nature of inclusions, together with considerations of chemistry are not compatible with local derivation of veins from enveloping chemical sediments or adjacent host rocks. The chemical sediments display slump structures and predate all tectonic deformation. In general, auriferous hydrothermal quartz veins transect bedding and/or schistosity, and are at a low state of internal strain. They appear to have been emplaced late during the second regional fold episode.Au, Ag, and Pd average 10, 2, and 0.1 ppm respectively in ore types at the Dome mine; representing concentration factors of 10 000,40, and 10 times background values in unmineralized metabasalt, and primary igneous rocks worldwide. Au and Ag are inhomogeneously distributed.Mineralized metabasic rocks adjacent to vein stockworks have Ti/Zr and Ti/Al2O3 ratios comparable to tholeiitic basalts, but display variable enrichment or depletion of silica, systematic depletion in Na2O, and where intensely altered significant extraction of calcium. The low Ni and Cr contents of the carbonate layers, together with low Ti/Zr ratios (43–78) of the carbonates and their enveloping mafic schists, are not consistent with the hypothesis that these auriferous rocks are carbonated ultramafics. Massive banded quartz–fuchsite–dravite veins have Cr and Ni abundances averaging 350 ppm, implying hydrothermal transport of these elements. Ti/Zr ratios of 120, together with high Mg, Cr, and Ni abundances in magnesite–dolomite–quartz– chlorite schists which host the banded veins are compatible with a primary komatiitic composition. Mineralized metabasic rocks are reduced (Fe2+/ΣFe = 0.9) relative to rocks with primary background abundances of precious metals (Fe2+/ΣFe = 0.7). This change of oxidation state implies that large volumes of reducing hydrothermal solutions were involved in vein mineralization.
Uranium and thorium in the Precambrian basement of western Canada. II. Petrologic and tectonic controls
Authors: Burwash R. A.
Published: June 2009

Analyses of 182 basement cores, when plotted as log U and log Th, show bimodal frequency distributions. Cumulative frequency plots indicate an approximate 35–65% split between the two populations. Histograms of numbers of samples in various rock classes vs. log U fail to explain the bimodal distribution.A plot of log K vs. log U provides easy visual separation of rocks with varying K/U ratios and U contents. K/U values greater than 3 × 104 are ascribed principally to granulite facies metamorphism. K/U values less than 5 × 103 represent U-enrichment either in granitic melts or K-metasomatized gneisses. Factor analysis indicates a strong correlation between U, Th. Rb, Pb, and K.The geographic distribution of samples with K/U values greater than 3 × 104 can be related to relict Kenoran granulite facies terranes in the subsurface of northeastern Alberta and west central Saskatchewan similar to those mapped on the exposed Shield in northwestern Saskatchewan. These relict granulites could account for most of the samples in the smaller of the two sample populations.The U-enriched rocks are concentrated in three areas: (1) the epizonal, porphyritic granitic plutons of southwestern Saskatchewan, (2) linear quartz monzonite batholiths along the Kasba Lake – Edmonton gravity low, and (3) K-rich gneisses in the Peace River High of northwestern Alberta. In none of these areas is assimilation of large volumes of Aphebian sedimentary rocks indicated.
The relationship between morphology, microstructure, and microbiota in three vertically intergrading stromatolites from the Gunflint Iron Formation
Authors: Awramik Stanley M. , Semikhatov M. A.
Published: June 2009

The microstructure in three silicified morphologically distinct and vertically intergrading stromatolites from the Aphebian (~2 Ga old) Gunflint Iron Formation of Ontario, Canada was found to be different for each stromatolite morphology studied; each in turn has a characteristic microbial composition. Non-columnar stromatolites that comprise the middle zone of the intergrading sequence contain a microstructure characterized by relatively thin laminae composed of a cyanophytic community dominated by the coccoid Huroniospora Barghoorn while the columnar stromatolites of the lower (small, frequently divergent branching columns) and upper zone (large, infrequently α- to β-parallel branching columns) have thicker laminae differing in shape and continuity, which were built by a filamentous cyanophyte-dominated community. 'Microstromatolites' referable to Frutexites Maslov are found in the middle non-columnar and occasionally in the lower parts of the upper columnar zone.In the stromatolites thus far examined from the Gunflint formation, the microbiota, microstructure, and macrostructure are all interrelated, the composition of the microbiota, the nature of the microstructure, and the resulting gross morphology of the stromatolite presumably were influenced or controlled by the microbiota.
Glacial Lake Whittlesey: the probable ice frontal position in the eastern end of the Erie basin
Authors: Barnett Peter J.
Published: June 2009

Glacial Lake Whittlesey is related to the glacial advance during the Port Huron Stadial, approximately 13 000 radiocarbon years BP. This episode has previously been thought to be represented, in the eastern end of the Lake Erie basin, by the Paris and Galt Moraines and the deposition of the Wentworth Till in southern Ontario.However, the location of Whittlesey shoreline features suggests that this lake existed during the subsequent advance which deposited the Halton Till. A 'Halton' ice-contact delta, at Summit, Ontario, coincides with the Lake Whittlesey water plane curve constructed from 72 data points around Lakes Huron and Erie.It is suggested, therefore, that the glacial ice advance represented by the Halton Till, based on its relationship to Lake Whittlesey, has an age of about 13 000 radiocarbon years BP (Port Huron Stadial) and that the Wentworth Till (Paris and Galt Moraines) is of Port Bruce Stadial age.
Geotechnical implications of diagenetic iron sulfide formation in Champlain Sea sediments
Authors: Donovan Joseph J. , Lajoie Ginette
Published: June 2009

It has been proposed that iron hydroxides act as cementing agents in Champlain Sea clays, causing brittle behaviour and high sensitivities. Study of interbedded turbiditic sandy and clayey strata of the Champlain Sea disputes this contention. Ground waters flowing through these sandy interbeds have high pH and are sodium bicarbonate dominant and strongly reduced, with a calculated Eh of −276 to −343 mV, using the sulfate–sulfide redox couple. During movement from recharge to discharge, sulfate is reduced by bacterial decomposition of organic matter in the clays, producing high sulfide and bicarbonate activities. In terms of Eh and pH, these waters fall within the stability fields of Fe2+ and FeS2.No pyrite was detected in the sediments, but in borehole samples and very fresh exposures of both clay and sand lithologies a very finely-disseminated black mineral phase, interpreted as iron monosulfides, was observed which is highly unstable in an aerobic environment, oxidizing rapidly to red-brown ferric hydroxide. The presence of these monosulfides, along with the aqueous geochemical data, indicate strongly reducing conditions in the clay strata, in which iron hydroxides are not a stable phase. Ferric hydroxides can therefore not be called upon as cementing agents; past studies which identified these ferric compounds as such cementing agents based their conclusions on samples out of equilibrium with their natural environment and are not directly relevant to the behaviour of the clay under natural conditions. The effects of these iron monosulfides and associated organic material on clay behaviour have not yet been studied.
The age of the Roberts Arm Group, north-central Newfoundland
Authors: Bostock H. H. , Currie K. L. , Wanless R. K.
Published: June 2009

Felsites from the Roberts Arm Group have yielded a Rb–Sr isochron age of 447 ± 7 Ma, with an initial 87Sr/86Sr of 0.7063, and a genetically related granite pluton has yielded an isochron age of 464 ± 13 Ma, with an initial ratio of 0.7064. The Mansfield Cove oceanic plagiogranite complex, which is in fault contact with the Roberts Arm Group, has yielded a minimum zircon 207Pb/206Pb age of 594 ± 10 Ma. This plagiogranite, and basaltic rocks of the Hall Hill complex which partly surround it, thus provide a basement of suitable age upon which the Roberts Arm Group may have been deposited. The age of this basement corresponds to that of the opening of the lapetus Ocean.The stratigraphic age of the Roberts Arm Group, indicated by these ages, is Middle or possibly Late Ordovician. The volcanics were deposited either before or slightly after the Caradocian black shales of the Notre Dame Bay region. In the former case, Ordovician volcanism around western Notre Dame Bay ceased at about the time of obduction of the allochthons of western Newfoundland. In the latter, volcanism of the Roberts Arm Group marks a north to westward shift of volcanism within the central mobile belt of Newfoundland that occurred in late Middle or early Late Ordovician time. If the Buchans Group is of Silurian age and correlative with the Roberts Arm Group then this lithostratigraphic unit is probably diachronous, younging to the south.
A positive contact test between Nipissing diabase and Gowganda argillites
Authors: Morris W. A.
Published: June 2009

A positive contact test between Gowganda argillites and Nipissing diabase indicates the shallowly inclined and southerly directed Nipissing remanence records a primary intrusive event. Contact tests on the steeply inclined Nipissing direction are also positive. Together these tests conclusively indicate there were two distinct phases of Nipissing intrusion. Limited evidence suggests that the sequence between these two events should be from the shallow to the steeply inclined direction, giving a pole path from south to north. This is in direct conflict with the presently accepted north to south trending Track 5.
Global geodynamics in Canada 1971–79
Authors: Rochester M. G.
Published: June 2009

This paper reviews Canadian contributions to global geodynamics during the International Geodynamics Project, including: the decisive demonstration that great earthquakes can excite the Chandler wobble; the use of inland Earth-tide observations to infer the tides in the open ocean; a new upper limit on the temporal decrease of the gravitation constant, set by the absence of tensional features on Mercury, the refinement of Earth models, particularly of the lower mantle and core, using array-recorded multiply-reflected core phases; development of the mathematical machinery for modelling postglacial rebound on a viscoelastic Earth (with self-gravitation and redistribution of meltwater), the evolution of sedimentary basins, and the migration of phase transitions in depth in response to surface loading; discovery of a high degree of organization in lithospheric plate geometry over the entire Phanerozoic, and its interpretation in terms of an evolving mantle-wide convection pattern; incorporation of whole-mantle convection and a vis-cosity profile in a model for the Earth's thermal history; resolution of the 'core paradox' by improved estimates of the Gruneisen parameter using liquid metals theory; pioneering theoretical studies of long-period oscillations of the rotating liquid core, and development of a high-precision gravimeter to search for such modes and the information they should provide on the thermal state of the core; palaeomagnetic confirmation of the centred dipole hypothesis; and proof that laminar precession-driven flow in the core is incapable of sustaining the geomagnetic dynamo.
Paleopoles and paleolatitudes of North America and speculations about displaced terrains
Authors: Irving E.
Published: June 2009

A statistically determined path of apparent polar wander for the past 300 Ma for North America is given. It has a zigzag form, the bends corresponding to important changes in the drift of North America. Many Mesozoic and Early Tertiary paleopoles from the Western Cordillera do not conform to this path, and they are best explained by motions of miniblocks within the Cordillera. Especially notable is the displacement of Vancouver Island and associated Alaskan terrains (Wrangellia) in the early Mesozoic, and the clockwise rotation of the Coast Range of Oregon and Washington (Siletzia) in the Cenozoic. Limited evidence indicates that part at least of the Northern Appalachian region could have been about 10° south of its present position relative to North America in Late Devonian and Early Carboniferous times, and that it achieved its present position by Late Carboniferous time. Displaced terrains of early and middle Paleozoic age may also be present in the Appalachians. Displacements in the Appalachians and Cordillera could have been caused by the exchange of fragments of continental crust across transcurrent plate junctures. Apparent polar wandering paths for the Precambrian are tentative, but a fairly simple single path can be constructed for all structural provinces of the Laurentian Shield. This reconstruction of a single Precambrian path is supported by agreement among approximately contemporaneous paleopoles from widespread localities. It implies that movements amongst the structural provinces of the shield during the Hudsonian and Grenvillian Orogenies have been modest, and perhaps not in excess of about 1000 km in a latitude sense. This idea has been disputed by those who would apply conventional ideas of plate-tectonics to the Proterozoic, but it has the merit of explaining all the paleopoles and their geological relationships in a comparatively simple unified scheme. Rates of latitude change in the Precambrian may have been over twice as great as in the Phanerozoic.
Geophysical review of the continental margins of eastern and western Canada
Authors: Keen C. E. , Hyndman R. D.
Published: June 2009

The evolution and geophysical features of the continental margins of eastern and western Canada are reviewed in light of recent plate-tectonic concepts. The two margins are very different in age, structure, and origin. The eastern margins were formed either by rifting or by transform motion during the latest separation of the continents around the Atlantic that occurred from Jurassic to Tertiary times. Studies of these margins centre around a reconstruction of plate motions, the inception of which occurred over 70 Ma ago, and on subsequent processes such as subsidence and sedimentation. The subsidence of the margin is explicable in terms of cooling of the lithosphere and sediment loading. Deep crustal features are inferred from seismic, gravity, and magnetic data. The recognition of the ocean–continent boundary at these margins involves consideration of edge effects, magnetic quiet zones and rifting mechanisms. The western Canadian margins are present active plate boundaries. Recent geophysical studies of these margins centre around the detailed definition of the present plate boundaries and relative plate motions, and those of the recent past (about the past 10 Ma), and involve spreading ridges, transform faults, and subduction zones. The plate convergence predicted by offshore geophysical data has a pronounced effect on the continental crust and upper mantle extending several hundred kilometres inland from the coast. In southwestern Canada patterns characteristic of subduction zones are seen in seismic structure, the gravitational and magnetic fields, heat flow, and deep electrical structure.
Contributions to the tectonic history of the Innuitian Province, Arctic Canada
Authors: Trettin H. P. , Balkwill H. R.
Published: June 2009

The Innuitian Tectonic Province contains the record of a Phanerozoic mobile belt in northern Greenland and the Canadian Arctic Archipelago. Two fundamentally different phases in its development were separated by the Devonian–Carboniferous Ellesmerian Orogeny. The first contribution focuses on the early Paleozoic history of a key area, the second summarizes the Carboniferous to Cenozoic history of most of the Canadian part of the province.(1) The early Paleozoic architecture of the mobile belt is apparent only in Ellesmere Island, where exposures extend from the Canadian Shield through Arctic Platform and Franklinian basin into the Pearya orogenic welt. The Franklinian basin comprised the deep but ensulic Hazen Trough and two unstable shelves bordering it on the northwest and southeast. The northwestern shelf was a site of felsic to intermediate volcanism, mainly in the Ordovician Period. Pearya, a site of granitic plutonism in the Devonian Period, supplied much of the clastic basin fill. Its core consisted of a metamorphic complex, about 1.0 Ga old, exposed in basement uplifts in nor thernmost Ellesmere Island. Both basin and welt essentially formed part of the North American Plate, although rifting, evident from mafic and ultramafic intrusions, probably occurred in Early Devonian (or latest Silurian) time. The history of this part of the province is tentatively interpreted as response to the opening and closure of an ocean, connected with lapetus, that separated northern Ellesmere Island and Greenland from the sialic crust of the present Lomonosov Ridge and Barents Shelf. The Lomonosov Ridge still seems to be attached to the shelf off northeasternmost Ellesmere Island.(2) Deep subsidence and filling of Sverdrup Basin dominated the Innuitian region from Early Carboniferous through Late Cretaceous time. Large halokinetic diapirs and mafic dikes and sills intruded axial parts of the basin succession through Mesozoic time. Steep faults along the northwestern margin of the basin are Middle Cretaceous and older. Part of the northwestern rim of Sverdrup Basin sagged in latest Cretaceous time, becomingpart of the Arctic continental terrace. In the Late Cretaceous and early Tertiary a system of large grabens developed through the southern part of the Innuitian region, linking Canada Basin with Baffin Bay; about the same time, uplift formed some large arches in the northeastern part of the region. Middle Eocene and older rocks were laterally compressed by a phase of pre-Miocene folding and faulting. Some uplift took place in Oligocene or Miocene time on Axel Heiberg Island. The distribution of recent earth quakes does not indicate the presence of modern active plate margins.