摘要:

In the Columbia Valley north of Trail, the Carboniferous Mount Roberts Formation is underlain by a mass of gneiss. This, the Trail Gneiss, consists of amphibolite, grey biotite gneiss with minor mica schist, and marble, cut by hornblende and biotite quartz diorite orthogneiss, all laced by abundant pegmatite and aplite. Siltstone, slate, and greywacke with chert pebble conglomerate and limestone lenses of the Mount Roberts Formation face away from the Trail Gneiss, separated by a recrystallized mylonite zone, which may represent an unconformity between basement and cover, tectonized during décollement of the cover. The Trail Gneiss likely is a partially reworked and possibly allochthonous piece of the Precambrian North American craton. An upper Paleozoic to Jurassic sequence of 'arc-type' clastic, andesitic volcanic, and volcaniclastic rocks accumulated on this basement and was probably over-thrust by it in the Jurassic.The Trail Gneiss and its cover pass northward through a zone of increasing metamorphic grade into augen gneiss and pegmatite incorporating slabs and sheets of Trail Gneiss. This younger complex, the Castlegar Gneiss, closely resembles the upper sheet of mixed gneiss in Valhalla Dome and is nearly continuous with it. The Trail and Castlegar Gneisses outline a broad antiform continuous with Valhalla Dome.

ISSN:0008-4077    

DOI:10.1139/e79-001

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Hydrogeologists and ground water geochemists have observed a decline in the measured (platinum electrode) potential,EH, of ground water as it migrates from upland recharge areas to lowland discharge areas under confined conditions. Such variations inEHand variations in concentrations of elements with variable oxidation states (e.g., oxygen, nitrogen, iron, manganese, sulfur, and carbon) can be accounted for by a sequence of oxidation–reduction reactions occurring in the flow systems, the sequence being based on thermodynamic principles as outlined by Stumm and the microbial catalysis of such reactions. This sequence of reactions results in the identification of three redox zones in ground water flow systems: (1) oxygen–nitrate, (2) iron–manganese, and (3) sulfide. The mobility and concentration of most transition metal and nonmetal ions vary according to zone—a matter of considerable significance in exploration geochemistry and in ground water pollution studies.

ISSN:0008-4077    

DOI:10.1139/e79-002

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The Kiglapait basic layered intrusion in northern Labrador previously has been interpreted, on geological grounds, to be a lopolith with a maximum thickness of 8.7 km. It is associated with a large (~45 mGal) positive gravity anomaly that for the most part is very similar to a theoretical anomaly computed for the proposed lopolith model, except over the southeastern part of the exposure where the theoretical anomaly is significantly more positive. Model studies of the gravity data suggest that the form and dimensions of the lopolithic model predicted on geological criteria are essentially valid and that a granitic intrusion is present in the southeastern region of the lopolith causing the discrepancy between observed and theoretical anomalies. The latter intrusion is believed to be genetically related to the Manvers granite, which occurs throughout the southeastern region as dykes and small stocks. The presence of another buried granitic mass south of the Kiglapait intrusion is also suggested by the gravity data.

ISSN:0008-4077    

DOI:10.1139/e79-003

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The sands of the Frenchman Formation (Maastrichtian) and the Ravenscrag Formation (Palaeocene) in southwestern Saskatchewan are mineralogically immature lithic arenites and wackes. Volcanic rock fragments, which in the Frenchman Formation make up to 30% of the fraction coarser than 0.0625 mm, are less common in the Ravenscrag Formation, where quartz and carbonate rock fragments are significantly more abundant in the same size fraction. Sand composition is influenced by grain size in both formations. Over the range from 0.59–0.074 mm there is, in general, a decrease in the percentage of rock fragments and an increase in the percentage of quartz, with decreasing grain size. Although the Ravenscrag sands mostly are finer grained than those of the Frenchman, compositions of the fraction coarser than 0.0625 mm fall into separate but overlapping fields in a conventional quartz – feldspar – rock fragment (QFR) diagram. Differences, in terms of QFR ratios, between the formations, are clearer if compositions of limited size ranges (six size ranges between 0.59 and 0.074 mm) are considered, but there is still overlap. Significant compositional differences are obvious only when the relative amounts of different types of rock fragment are taken into account.Grain-size distributions of different components in the sands are, for the most part, the same in both formations, and reveal trends that are anticipated by studies of sand transport in modern streams. The proportions of quartz and detrital carbonate grains increase with decreasing grain size, whereas relative amounts of nonvolcanic rock fragments and chert decrease with decrease in grain size. Volcanic rock fragments and feldspar show an irregular increase with decreasing grain size in the Frenchman sands, and an increase followed by a decrease in the Ravenscrag sands. The differences in the latter two components between the sands of the two formations are attributed to a reduction in both the abundance and the variety of volcanic detritus supplied to the area in Palaeocene times.The bulk of the volcanic material in both formations likely was derived from western Montana. In particular, the Elkhorn Mountain Volcanics (Campanian) and the Adel Mountain Volcanics (Maastrichtian to ?Palaeocene) probably were important sources. The uplift of Palaeozoic carbonate rocks and Mesozoic clastic deposits in the Front Ranges of the Rocky Mountains may account for the relative reduction in supply of volcanic rock fragments and feldspar, and the increased contribution of detrital carbonate and quartz, to the sands of the Ravenscrag Formation.

ISSN:0008-4077    

DOI:10.1139/e79-004

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Copper minerals are known from at least five stratigraphic levels above and below an angular unconformity recognized within rocks of the Rapitan Group on and near the Nite copper prospect, Mackenzie Mountains. The main showing on the prospect is structurally controlled and occurs in siliceous dolostone near the top of the folded and faulted Coppercap Formation, directly beneath an unconformity separating two local members of the Sayunei Formation (Rapitan Group). The copper was emplaced in tectonically fractured dolostone, precipitated from solutions that may have descended from copper-bearing conglomerates in the Rapitan Group above the unconformity, or ascended from weakly mineralized carbonates below. Mechanical reworking of older strata-bound copper deposits is indicated by significant copper content in clasts eroded from older rocks of the northeastern Mackenzie Mountains. The ultimate source of copper can probably be sought in basaltic dikes and flows emplaced prior to deposition of Redstone River and Coppercap formations during an early phase of crustal extension in the northern part of the Cordilleran miogeosyncline.

ISSN:0008-4077    

DOI:10.1139/e79-005

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Two alkaline igneous complexes and three lines of diatreme breccias were emplaced in the East Arm of Great Slave Lake during the lower Proterozoic. Field relationships suggest that those rocks are broadly cogenetic and were emplaced about 2.1 Ga ago.One of the intrusions, the Easter Island dyke, was rotated subsequent to emplacement such that both top and bottom are now exposed. Field and petrographic data are indicative of progressive differentiation along (i.e., up) the dyke and are substantiated by chemical data. The differentiation history of the early gabbros of the Blachford Lake complex is similar. Late differentiates of both complexes closely resemble the igneous matrices of the breccias and petrographic and chemical data support the proposal of cogenesis and contemporaneity.The field data show that there was a period of significant faulting and concomitant alkaline igneous activity in the East Arm area in the lower Proterozoic.

ISSN:0008-4077    

DOI:10.1139/e79-006

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A simple divided-bar apparatus for studying the thermal conductivity of rocks and soils at permafrost temperatures is described. The apparatus is intended also for use with permafrost specimens tested in their natural frozen state. It has been designed for low heat fluxes and consequent small temperature drops across the test specimen, while retaining a high precision of measurement.Different thicknesses of two water-saturated sandstones and a limestone have been tested as a function of changes in temperature, frozen and unfrozen. Significant corrections for the contact resistance between the specimen and divided bar were determined. The influence of the magnitude of temperature gradient across the specimen was not found to be important for the low gradients employed in these experiments.The measured thermal conductivities show a slight decrease in value with temperature increasing to 0 °C. In the neighbourhood of 0 °C, a sharp reduction in thermal conductivity was observed as the ice–water phase change occurred. It is clear that the magnitude of the thermal conductivity of the rocks depends on their mineral content; quartz, with its high thermal conductivity, plays the predominant role where it is present.

ISSN:0008-4077    

DOI:10.1139/e79-007

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The ultramafic rocks in the Shaw Dome area, southeast of Timmins, Ontario, are divided on the basis of held criteria into two groups for the purpose of comparing their chemical compositions: (1) extrusive ultramafic rocks consisting of peridotitic komatiites and (2) intrusive ultramafic rocks, consisting of dunites and lherzolites.The two groups can be distinguished on a chemical basis by graphical and statistical methods which provide accuracies of extrusive–intrusive classification of about 92 and 96% respectively. Both methods provide qualitative and quantitative aspects of discrimination.The discriminating parameters were developed using samples which show all types and degrees of alteration that are common in ultramafic rocks. Preliminary studies indicate that the genera! procedure for chemical discrimination between extrusive and intrusive ultramafic rocks may be applicable to similar Archean rocks from other areas.In addition, the separation provides an aid to exploration for minerals such as nickel sulphides, asbestos, magnesite, and gold which may be largely restricted to either extrusive or intrusive ultramafic rocks.

ISSN:0008-4077    

DOI:10.1139/e79-008

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

New mammalian fossils from the Upper Cretaceous Oldman Formation, Alberta, pertain to three species of the marsupialAlphadonSimpson. One of these species,A.praesagus(Russell), is ancestral to the LancianA.rhaisterClemens. The second, closely related but not ancestral to the LancianA.marshiSimpson, is new, and the third,A.halleyiSahni, is closely related to the LancianA.lulliClemens, as had been earlier supposed from fossils from the Judith River Formation, Montana. The phylogenetic relationships ofAlphadonare discussed.

ISSN:0008-4077    

DOI:10.1139/e79-009

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

PediomysMarsh, a primitive marsupicarnivore, is the most common therian mammal known from the Upper Cretaceous Oldman Formation, Alberta, where it is represented by at least four species. The first,P.clemensiSahni, appears closely related to the LancianP.cookiClemens; other species, poorly represented by fossils, resemble the LancianP.elegansMarsh andP.hatcherirespectively; a final species, which is new, is interpreted as the direct ancestor of the LancianP.krejciiClemens.Pediomysshows trends toward enhancement of a crushing rather than a shearing function of the postcanine dentition and, consequently, seems not ancestral to the Cenozoic 'dog-like' marsupials of Australia and South America, contrary to recent suggestions elsewhere.

ISSN:0008-4077    

DOI:10.1139/e79-010

出版商:NRC Research Press    

年代:1979

数据来源: NRC