摘要:

Iron oxide compounds in 12 selected Canadian soil samples have been characterized by Mössbauer, X-ray, chemical, infrared absorption, and differential thermal methods. Chemical differentiation provides useful information about the forms of iron compounds present such as crystalline, amorphous, inorganic, and organic complexed iron compounds. X-ray diffraction methods can generally identify mineral species of crystalline iron compounds. However, detection limits of goethite and hematite, which are iron oxide minerals commonly present in soils, are about 7% and 10%, respectively. The Mössbauer method is especially useful for identification of small amounts of these iron oxide compounds which are far beyond X-ray detection limits. In addition, information about grain size of hematite and goethite, the Fe3+/Fe2+ratio and characterization of the 'amorphous' fraction are also available from Mössbauer spectra. Infrared absorption and differential thermal analyses provide supplementary data concerning organic complexed iron compounds.Hematite content in the soils examined is always lower than 10%, but goethite content varies widely and coexistence of both minerals appears to be common.

ISSN:0008-4077    

DOI:10.1139/e77-001

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The resistivity, dielectric constant, and loss tangent of natural clay permafrost samples that have never been thawed have been measured as functions of temperature, applied uniaxial confining load, and applied electric field strength. DC resistivities are on the order of 105ohm-m at −10 °C, with the complex resistivity becoming strongly frequency dependent within and above the range of 10 to 103 Hz (resistivity decreasing with increasing frequency). Below 103 Hz, the electrical properties are slightly dependent upon applied electric held, and below 105 Hz, the electrical properties are very strongly dependent upon applied uniaxial confining load. Several different mechanisms are responsible for the observed properties, including ionic conduction, a colloidal response that is similar to a Maxwell-Wagner type of effect, the relaxation of Bjerrum defects in ice, the relaxation of the unfrozen water molecules, and a possible relaxation of organic molecules in the unfrozen water sheath surrounding clay particles.

ISSN:0008-4077    

DOI:10.1139/e77-002

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

One of three explanations of a prominent time delay in the 6.5 km/s branch of a recent seismic refraction survey in the Rocky Mountain Trench suggested a high-angle crustal fault crossing the trench near Radium, British Columbia. If the density contrast between basement and cover rocks is 0.1 g/cm3, a gravity anomaly of approximately 18 mGal should be observed. To test the fault hypothesis, a gravity survey has been carried out in and adjacent to the trench in the Radium area. The resultant data are not consistent with the proposed fault model. The principal feature of the data is a pronounced low, which coincides with the trench throughout the survey area. The low is due to Cenozoic fill and interpretation by two-dimensional modelling indicates the thickness of fill is about 550 m to the north and 420 m to the south of Radium. As a result of this survey, the two alternative hypotheses to explain the seismic data must be reconsidered. These are (1) the existence of a crustal low velocity zone, and (2) a major deformation of the basement and overlying rocks due to the trench being an ancient zone of weakness, which coincides with the western limit of the continental Precambrian craton. As reflections from the top of a low velocity zone are not observed, the second alternative is preferred.

ISSN:0008-4077    

DOI:10.1139/e77-003

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Near Pinchi Lake, central British Columbia, a fault-bounded alpine peridotite occurs within the Cache Creek Group. It comprises massive harzburgite, dunite, and pyroxenite, all of which display tectonite fabrics. Near isoclinal folds (F1), outlined by dunite, pyroxenite, and spinel layers (compositional layering) constitute the earliest recognizable penetrative deformation. A second set of near-coaxial open folds (F2) refolds the earlier set; both are cut by a later fracture cleavage (F3). Flattened, elongate olivine and orthopyroxene grains within the harzburgite outline foliations and lineations parallel with axial surfaces and minor fold axes of both fold sets. Narrow zones of mylonitization within the isoclinally folded dunites transect the composition layering, are parallel with the axial surfaces of the F1isoclines, and appear to be related to refolding of F1by F2. Relic olivines are kinked along {OKL}:[100], have pronounced α-maxima perpendicular to F1and γ-axes maxima parallel to fold axis L1. Orthopyroxene, kinked on (100):[001] shows weaker fabric, but is symmetric with earliest composition layering, some 15°–20° away from F1. Asymmetry of fabrics results from olivine recrystallizing under conditions where orthopyroxene only kinks.It is speculated that the peridotite is a fragment of Paleozoic oceanic lithosphere. F1and F2are believed to be mantle transport fabrics resulting from a northerly driven plate, whereas F3fractures are high-level emplacement features produced during late Paleozoic time.

ISSN:0008-4077    

DOI:10.1139/e77-004

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The Labrador Trough is the best preserved and exposed of several Aphebian (lower Proterozoic) fold belts which surround the Archaean Ungava Craton of northern Quebec and is characterised by three longitudinal facies zones: predominantly meta-sedimentary rocks in the west and east and predominantly basic meta-igneous rocks in the centre. The results of a detailed gravity survey of the central part of the Labrador Trough between latitudes 55° 45′ and 57° 30′ and longitudes 66° 30′ and 70° are presented. Over 1500 rock samples provide density control for the interpretation of four residual gravity anomaly profiles in terms of the surface geology.In the eastern part of the Labrador Trough positive gravity anomalies correlate with outcrops of basic meta-igneous rocks. Their causative bodies extend subsurface to the east and reach depths of up to 9 km in the central part of the area, but are considerably thinner to the north and south. This interpreted depth is considerably less than the 15–20 km that has been inferred by other workers from surface geological investigations. Small positive gravity anomalies are associated with iron formation. A persistent depression in the observed gravity field over the centre of the trough in the south coincides with deposits of the basal sedimentary unit. Uncertainty in the location of the regional level prohibits accurate thickness determinations of the causative bodies of negative anomalies in this area, but the approximate values of 2–3 km obtained for the basal unit are of the same order as estimates based on geological investigations. In the northern part of the area the causative bodies of the negative anomalies are probably elevated areas of granitic basement. These elevated basement features may be related to a ridge that controlled sedimentation during much of the trough's history.

ISSN:0008-4077    

DOI:10.1139/e77-005

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Lead-isotope ratios have been determined for a preliminary set of 16 galenas from the Grenville and some adjacent Palaeozoic formations in southern Ontario and Quebec. The206Pb/204Pb ratios of the Grenville-hosted deposits range from 16.24 to 20.20. Six of the Grenville-hosted samples have a post-Ordovician age of mineralization, but may represent re-mineralized Grenville lead. With the five 'true' Grenville samples they can be used to define a Grenville 'secondary isochron' on a207Pb/204Pb–206Pb/204Pb plot. The trend of this isochron appears to be consistent with published feldspar- and marble-lead data for nearby sections of the Grenville. Its slope (.120 ±.015) is compatible with a time of ~1300 Ma ago for inclusion of uranium in the sediments of the Grenville supergroup, followed by lead mineralization at ~1000 Ma. Calculations based on a simple lead-isotope evolution model give a similar age (1280 ± 15 Ma) for the stratabound Tétrault Pb–Zn deposit.The geologically similar New Calumet deposit has a quite different model age of 1115 ± 20 Ma. This is similar to the model age of the Balmat, New York ore deposits and it appears that New Calumet and Balmat may be members of a contemporaneous mantle (volcanic)–continental sequence.An apparent correspondence of the isotopic ratios of the Palaeozoic samples with the Grenville secondary isochron raises some critical questions regarding the development and migration of the Pb in these deposits.

ISSN:0008-4077    

DOI:10.1139/e77-006

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The natural remanent magnetizations of Beltian argillites from the Spokane Formation (formerly Grinnell Formation) have been analyzed with alternating field and thermal demagnetization techniques. Two groups of magnetic directions have been observed. One is assumed to be the primary magnetization, representative of the Helikian (approx. 1300 Ma) geomagnetic field:D = 201.5°;I = +40°;k = 61; and α95 = 5.1° forN = 14 sites (51 samples), yielding a pole position at 15.5 °S. 134.5 °W, dp = 3.7°, dm = 6.2°. Comparisons with contemporaneous pole positions reveal good agreement. The other direction of magnetization corresponds to a Late Hadrynian age (approx. 600 to 750 Ma) and resulted from low-grade metamorphism. It is speculated that this thermal event resulted from enhanced heat flow during continental breakup in the Late Hadrynian. This direction (D = 267.5°;I = +17;k = 10; α95 = 9.1° forN = 28 specimens) yields a pole position at 5°N, 163.5°E, with dp = 4.9°, dm = 9.4°. Both groups of directions of magnetization are pre-folding, which occurred during the Laramide orogeny. Laramide deformation was only moderate, however, and the eastward thrusting of the Beltian sediments over the Lewis thrust was probably not accompanied by significant structural rotation.

ISSN:0008-4077    

DOI:10.1139/e77-007

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The Charlevoix structure, Quebec, Canada, is generally accepted as a Paleozoic meteorite impact site. Plagioclase grains from samples in and around this structure were examined via X-ray (oscillation) techniques to determine the maximum range of angular misorientation between crystal subdomains (mosaicism) within a given sample (ηmax), and its usefulness as an index of shock metamorphism at Charlevoix. The complex morphological character of the impact crater can be divided into five concentric zones, which exhibit alternately high and low values of ηmax. This distribution appears to be the result of differential uplift and subsidence that followed the impact event, in that blocks which have undergone different shock histories during the impact event have been brought into juxtaposition. The wide range in ηmaxwithin as well as between samples attests to the complex nature of the shock process and the hazards of using mosaicism as the sole index of shock metamorphism.

ISSN:0008-4077    

DOI:10.1139/e77-008

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Forty-four oriented drill cores were collected from a 65 m thick northwest-trending olivine diabase dyke (1250 Ma) and the norite (1900 Ma) with which the dyke is in contact. Thermal and alternating field treatments show that the magnetic direction of the dyke and that of the norite up to 45 m from the contact are parallel and conform to directions reported by others for the diabase dyke swarm near Sudbury. Between 45 m and 70 m (end of outcrop) hybrid directions are observed intermediate between that of the dyke and that reported by others for the norite. The NRM unblocking temperature spectrum and the inferred acquisition of VRM at higher temperatures in the norite suggest that a maximum temperature of 450 °C was attained in the hybrid zone at about 50 m from the dyke. Calculation of the thermal effect of the diabase intrusion on the norite in the hybrid zone indicates a temperature increase of 270 °C. Consequently, the ambient temperature of the norite at the time of intrusion was 450 – 270 = 180 °C (± 30). Taking the contemporary geothermal gradient at 20 to 25 °C/km the present erosion level of the norite is estimated to have been at a depth of 7 km (± 25%) about 1250 Ma ago. This suggests that a 7 km thick layer of the pre-Grenvillian part of the Canadian Shield has been removed by erosion during the past 1250 Ma if the Shield can be regarded as a single block that has not been tilted. Similar work elsewhere in the Shield may show the extent of these vertical movements.

ISSN:0008-4077    

DOI:10.1139/e77-009

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The Lower Jurassic Hettangian Stage is documented with certainty for the first time in the Canadian Arctic. It is represented by a basal Jurassic sandstone unit in the Bonnet Lake area of northern Yukon Territory. The two subzones of the Early Hettangian Planorbis Zone,i.e., the Planorbis Subzone and the Johnstoni Subzone, are indicated by poorly preservedPsilocerassp. indet. andPsiloceras(Caloceras) cf.P. (C.)johnstoni(J. de C. Sowerby), respectively. The varied but poorly preserved bivalve fauna associated withP. (C.) cf.P. (C.)johnstoniincludesProsogyrotrigonia(?) sp. cf.P.inouyei(Yehara),Cardiniasp. cf.C.hybrida(J. Sowerby),C. sp. aff.C.concinna(J. Sowerby),Pleuromya(?) sp.,Meleagrinella(?) sp.,Oxytoma(Oxytoma) sp., andParallelodon(?) sp. The bivalves closely resemble approximately coeval forms described from Japan. The above-mentioned faunas are figured as is a specimen ofPsilocerascf.P.erugatum(Phillips), which was previously described from the Hettangian of southern Yukon. Other occurrences of the Hettangian in Canada and Alaska are reviewed.

ISSN:0008-4077    

DOI:10.1139/e77-010

出版商:NRC Research Press    

年代:1977

数据来源: NRC