加拿大Sullivan超大型Pb-Zn-Ag矿床中几个指示成矿环境的特征矿物研究   总被引：2，自引：1，他引：1  

蒋少涌 《高校地质学报》2000,6(2):173-177

加拿大Sullivan矿床是世界上最典型的SEDEX型Pb-Zn-Ag矿床。对该矿床中产出的几个特征矿物,如硼矿物电气石,富氯的方柱石和黑云母,富钡的钾长石和白云母,及富锰的石榴子石、绿泥石、碳酸盐和钛铁矿进行了研究。指出这些矿物的存在反映了该矿床产出的物理化学环境。提出成矿流体可能淋滤了深部存在的非海相蒸发岩层,层状硫化物矿石可能形成于海底高盐度热卤水池中。  相似文献   

Age and Origin of Upland block Fields on Melville Peninsula, Eastern Canadian Arctic     

Lynda A. Dredge 《Geografiska Annaler: Series A, Physical Geography》2000,82(4):443-454

Block fields have developed on gently graded uplands of granite and gneiss on central and southern Melville Peninsula. The location of block fields is not controlled by elevation, but rather by areas covered by cold–based ice during the last glaciation. Block fields consist either of angular boulders, sorted circles 3–4 m across having blocky rims and central areas of weathered grus, concentrations of openwork boulders, or in the southeast, of immature bouldery till. The block fields are primarily relict features predating the last glaciation, produced by weakening of bedrock by weathering along joints, followed by frost heave, although some block fields have been modified by meltwater from regional glacier down–wasting. Frost processes are active in the modern environment but the extent of riven bedrock and the size of recent patterned ground forms on postglacial surfaces are insufficient to account for the forms in the block fields.  相似文献   

Magnetotelluric Soundings In the Canadian Rocky Mountains     

V. R. S. Hutton  D. I. Gough†  G. J. K. Dawes  J. Travassos 《Geophysical Journal International》1987,90(1):245-263

Summary. Magnetotelluric soundings have been made at 25 stations in the Rocky Mountain Trench (RMT) and Main Ranges near 53° N, close to the centre of a major conductivity anomaly which had been mapped in a magnetovariation array study. Most stations covered the frequency range 0.01–500 Hz and three stations 0.0002–500 Hz. the resistivity tensor shows low to moderate anisotropy in the RMT, but is strongly 2-D or 3-D in the Rocky Mountains. Apparent resistivities as a function of frequency are displayed in pseudosections along the Trench and along a transverse profile across the RMT and into the Main Ranges. In preparation for 2-D modelling, 1-D inversions have been used to construct resistivity-depth sections satisfying both magnitudes and phases of the MT responses. These show very low resistivities, in the range 1—10Ωm, in the upper crust under the RMT and even lower values under the Main Ranges. the latter values give strong confirmation of the Northern Rockies conductor reported by Bingham, Cough & Ingham and are in agreement with models of the conductors fitted to long-period magnetovariation fields by Ingham, Gough & Parkinson. the MT results here reported add some essential depth and resistivity information. It is suggested that the conductors beneath the Rocky Mountains Main Ranges and Trench constitute a thickening at the edge of the Canadian Cordilleran Regional (CCR) conductor. Gough has argued that a wide variety of geophysical and geological parameters indicate high temperatures and partial melting in the mantle under the CCR conductor. At the upper crustal depths penetrated in this magnetotelluric study, it is considered more probable that the high conductivity is caused by hot, saline water of mantle origin rather than silicate melt. the CCR in general may have two layers of fluid producing its high conductivity, silicate melt below and saline hot water above.  相似文献   

Implementing Canada's marine fisheries policy: Objectives,hazards and constraints     

Parzival Copes 《Marine Policy》1982,6(3):219-235

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Inferring marine distribution of Canadian and Irish Atlantic salmon (Salmo salar L.) in the North Atlantic from tissue concentrations of bio-accumulated caesium 137     

Spares  Aaron D.; Reader  Jeffery M.; Stokesbury  Michael J. W.; McDermott  Tom; Zikovsky  Lubomir; Avery  Trevor S.; Dadswell  Michael J. 《ICES Journal of Marine Science》2007,64(2):394-404

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Distribution of cytochrome P4501A (CYP1A) in the tissues of Baltic ringed and grey seals     

Hyyti OM  Nyman M  Willis ML  Raunio H  Pelkonen O 《Marine environmental research》2001,51(5):465-485

Information about the expression of CYP1A in wildlife species is essential for understanding the impact of organochlorine exposure on the health status of an exposed population. Therefore, we aimed at characterising a putative CYP1A enzyme expression in both hepatic and extrahepatic tissues of ringed and grey seals from the Baltic Sea and from less polluted waters. The cellular localisation of CYP1A was identified using a monoclonal antibody against scup P4501A1 (MAb 1-12-3). Immunohistochemical staining showed the highest level of CYP1A expression in liver hepatocytes, and the second highest level in the endothelial cells of capillaries and larger blood vessels in the liver and other organs. The most frequent and strongest staining was found in Baltic ringed seals. Although CYP1A-positive staining was observed in only a few tissues in the other seal populations, it was more intense in Baltic grey seals than in Canadian grey seals. The CYP1A enzyme activity, expressed as ethoxyresorufin O-deethylation (EROD), followed a similar tissue distribution and geographical pattern as the immunohistochemistry with clearly elevated EROD activities in most tissues of both Baltic seal populations. Immunochemical characterisation by immunoblotting confirmed the presence and elevation pattern of a putative CYP1A protein in ringed and grey seals, supporting our findings using other methods. The evenly distributed elevation of CYP1A expression among most of the tissues examined indicates that Baltic seals are exposed to CYP1A inducing agents affecting the whole body. This may result in an increased or decreased toxic potential of foreign substances, which may ultimately determine the biological effects of the contaminants.  相似文献   

Late Cenozoic sea-level changes and the onset of glaciation: impact on continental slope progradation off eastern Canada     

David J.W. Piper  William R. Normark 《Marine and Petroleum Geology》1989,6(4)

Late Cenozoic sedimentation from four varied sites on the continental slopes off southeastern Canada has been analysed using high-resolution airgun multichannel seismic profiles, supplemented with some single channel data. Biostratigraphic ties are available to exploratory wells at three of the sites. Uniform, slow accumulation of hemipelagic sediments was locally terminated by the late Miocene sea-level lowering, which is also reflected in changes in foraminiferan faunas on the continental shelf. Data are very limited for the early Pliocene but suggest a return to slow hemipelagic sedimentation. At the beginning of the late Pliocene, there was a change in sedimentation style marked by a several-fold increase in accumulation rates and cutting of slope valleys. This late Pliocene cutting of slope valleys corresponds to the onset of late Cenozoic growth of the Laurentian Fan and the initiation of turbidite sedimentation on the Sohm Abyssal Plain. Although it corresponds to a time of sea-level lowering, the contrast with the late Miocene lowstand indicates that there must also have been a change in sediment delivery to the coastline, perhaps as a result of increased rainfall or development of valley glaciers. High sedimentation rates continued into the early Pleistocene, but the extent of slope dissection by gullies increased. Gully-cutting episodes alternated with sediment-draping episodes. Throughout the southeastern Canadian continental margin, there was a change in sedimentation style in the middle Pleistocene that resulted from extensive ice sheets crossing the continental shelf and delivering coarse sediment directly to the continental slope.  相似文献   

加拿大的海洋地质灾害调查与研究     

李日辉 《海洋地质前沿》2003,19(1):11-13

简要介绍加拿大海洋地质灾害调查与研究现状。重点论述了几种主要的海洋地质灾害，并从特征、形成过程、调查手段与方法以及潜在的影响等几个方面进行了论述。  相似文献   

NODAL HETEROLOCALISM AND TRANSNATIONALISM AT THE UNITED STATES‐CANADIAN BORDER*     

SUSAN W. HARDWICK 《Geographical review》2006,96(2):212-228

ABSTRACT. Since the late 1990s Wilbur Zelinsky's theory of “heterolocalism’ has provided human geographers and other social scientists with a new approach to analyzing the spatial patterns and ethnic identities of recent immigrants in the United States. Zelinsky's heterolocal model suggests that, to a degree unknown in the past, new migrants in North American cities may choose to settle in widely dispersed places, rather than in more concentrated ethnic enclaves, while maintaining their ethnic identities. This article expands on and critiques prior work on heterolocalism in Oregon by examining the spatial patterns, ethnic and religious identities, and transnational relationships of two recent refugee groups in three urban areas in the Pacific Northwest. Using data from U.S. and Canadian census records, refugee resettlement agency files, survey questionnaires, structured and unstructured interviews, and participant observation with post‐Soviet Russians and Ukrainians in the Vancouver, British Columbia, Seattle, Washington, and Portland, Oregon metropolitan areas, I analyze the spatial patterns and related social networks that define the identities and residential and religious spaces of these groups to test the efficacy of relating heterolocalism and transnationalism across an international boundary.  相似文献   

Morphodynamics and climate controls of two aeolian blowouts on the northern Great Plains,Canada   总被引：2，自引：0，他引：2  

C. H. Hugenholtz  S. A. Wolfe 《地球表面变化过程与地形》2006,31(12):1540-1557

Blowouts are the most regionally pervasive active aeolian landform on the northern Great Plains of North America. This study reports a long‐term investigation into the morphological development of two adjacent blowouts in a continental dune field. The blowouts were monitored for a decade in the Bigstick Sand Hills of southwestern Saskatchewan, Canada. Topographic changes were determined from dense arrays of erosion pins in each blowout (1 per 4 m², n = 171; and 1 per 16 m², n = 150). Pin measurements were made 16 times between May 1994 and May 2004. Over the decade both blowouts expanded and more than doubled in volume. Differences in form–flow interactions have caused the larger of the two blowouts to deposit more than a metre of sediment within the deflation basin, and the smaller blowout to erode by more than a metre. A negative feedback effect was triggered when the larger blowout reached a critical size around 1994 (60 m × 36 m × 8·1 m, length × width × height) when sediment was no longer eroded from the deflation basin. A positive feedback in the smaller blowout continues to facilitate erosion from the deflation basin. Monthly observations since 2002 indicate that aspect plays an important role in the development of these blowouts by creating a spatial asymmetry in sediment availability. Sediment is more readily available throughout the year on south‐facing slopes, which receive greater insolation than north‐facing slopes and are often drier and more frequently thawed in this cold‐climate environment. Comparisons between climate data from a remote meteorological station 45 km to the southwest and sediment transport indices developed from the erosion pin data produced very few correlations significant at the 95 per cent confidence level. Nevertheless, the signs of the correlation coefficients indicate that sediment erosion and deposition in both blowouts respond similarly to the following climate variables recorded at the remote station: (i) the amount of precipitation, (ii) the transport capacity of the wind and (iii) transporting winds from a directional wedge between 180 and 330°. Taken altogether, the results from this study highlight the importance of climate and feedback effects in blowout development that may be extended to other blowouts in continental and coastal settings. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献