No description available.

No description available.

The origin of diamonds, their preservation and transport to the surface have been important issues over the last decades after the acknowledgement that diamonds are xenocrysts in the host kimberlites and after the discovery of new transport media such as lamproites. Different types of diamonds -E-type diamonds, P-type diamonds- and different types of hosts - Eclogites, Peridotites- have been distinguished. Each type corresponds to particular formation criteria. Ecogitic Diamonds are mostly related to subduction processes, whereas more uncertainties remain regarding the formation of Peridotitic Diamonds. Komatiite extraction and subduction of graphite-bearing serpentinites have been proposed as the more likely processes involved in their formation. A typical mantle signature for diamonds implies a thick, cool, reduced lithosphere. The keel-shape model is the most popular. Archaean cratons are therefore the most promising exploration target and area selection will expect to follow the Clifford's Rule. However, the evidence of cratonic areas hidden under younger formations · through seismic profiles and the discovery of diamond structurally trapped outside their stability field, have increased the potential of diamondiferous areas. Preservation of diamonds inside the lithosphere requires that the mantleroot remains insulated against excessive reheating and tectonic reworking. Mantle-root friendly and mantle-root destructive structures are distinguished. Small-size cratons are usually the most promising exploration targets. Transport of diamonds to the surface is dependant on' the same criteria of preservation. Only kimberlites and lamproites have been recognized as efficient transport media. Their ascent to the surface is conditioned by a multitude of parameters, amongst them the nature of the magma, the speed of ascent, the presence of pre-existing structures in the crust and the availability of ground water in the near-surface environment. The origin of kimberlite magma probably lies near the transition zone. Mixtures of depleted asthenospheric · sources and metasomatically enriched and possibly subducted materials are likely to be at the origin of the different kimberlite magmas. Kimberlite magmatism correlates generally in time with global tectonic events, triggered by either plume activity or by subduction processes, depending of the tectonic school of thought. Kimberlite alignments have been interpreted as hotspot tracks, and kimberlite magmas as volatile-rich melts issued from the remaining plume tail. The plume head produces flood-basalts in an adjacent "thinspot" of the lithosphere, generally on the edges of the cratons. Kimberlite and lamproite ascent to the surface are unconditionally influenced by regional structures. Rift structures, ring structures, transform faults, suture zones and deep-seated faults have been mentioned as controlling or accompanying features of kimberlite magmatism. Nearsurface emplacement constraints are better understood and the ultimate shape of the intrusion(s) depends on the nature of the country rocks, the availability of ground water and the near-surface faulting pattern. The recent discovery of "fissure" kimberlites is one of the more important breakthroughs of the last decade. With a better understanding of the processes involved in diamond formation, preservation and of kimberlite emplacement, major diamond discoveries have recently increased on all the continents. Successful diamond exploration requires today an integration of all geophysical, petrologic, geochemical and structural information available. The particular study of the northwestern Australian lamproite and kimberlite fields, the Brazilian kimberlites, the easternNorth American kimberlite fields, the Lac de Gras kimberlite field, the South African rich kimberlite provinces, and the Yakutian kimberlite fields provide concrete examples of the geotectonic controls on primary diamond deposits. Area selection criteria based on the previous models and examples, are expected to yield to many more discoveries in the coming years. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in

Maps in pockets bound with piece.

Maps in portfolio.

Folded maps in pocket.

[No abstract available] / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The regional geology of the McDame Area is described briefly and a detailed description of the "Contact Group" mineral claims within this area is presented. The "Contact" vein deposit described herein is apparently unique, as far as geological literature is concerned, in its primary mineral associations. This vein, in a contact-metamorphic environment, possesses the form and textural characteristics of a mesothermal deposit. Typical high, medium and low temperature minerals are present in relationships that suggest unbroken deposition in the vein and a genetic relation to both the associated intrusive and related pyrometasomatic deposits. The occurrence and origin of native sulfur, wad, and hydrocarbon in the vein are discussed. Alabandite (MnS), which is a common constituent, is classified, on grounds of ex-solution phenomena, as having crystallized at temperatures greater than those previously assigned to it. The role of manganese in this deposit is given special attention. The conclusion is reached that the Contact Vein was formed at shallow depth under conditions of high but rapidly falling temperature and locally high pressure. Accordingly, it illustrates telescoping within the mesothermal-pyrometasomatic range of physical conditions. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Dellwood Seamount Area, an area of approximately 10,000 square km., about 185 km. west of the northern tip of Vancouver Island is located at or near the northernmost end of the Juan de Fuca plate. The main purpose of the study was to test the hypothesis that the Dellwood Knolls mark the site of a short spreading segment connected to the Explorer Spreading Segment at one end by a transform fault trending along the southwestern slope of Paul Revere Ridge; and meeting the Queen Charlotte right lateral transform fault at the other end. An analysis of more than 950 km. of continuous seismic reflection profiles, in conjunction with other geophysical data, shows that (i) the Revere -Dellwood fault zone is a dextral transform fault zone connecting the Explorer and Dellwood spreading segments. (ii) The Queen Charlotte transform fault dies out at the southeastern end of the Scott Channel near the northeastern end of the Dellwood Spreading Segment. (iii) In the channel between the Dellwood Knolls (one of two possible locations of the Dellwood Spreading Segment), the sediments and volcanic basement are cut by normal faults, a feature which is characteristic of spreading centres with median valleys. The heat flow in this channel and in the Revere - Dellwood fault zone is high. (iv) The lower continental slope sediments west of Queen Charlotte Sound is faulted and crumpled and may be the northerly extension of the Scott Islands fault, zone and a site of slow contemporaneous or recently ceased subduction. The deformation of the thick turbidite sequence in the Winona Basin may also be due to subduction. Basalt from the area is chemically intermediate between tholeiitic and alkalic types. That from the Northwest Dellwood Knolls, however, is least differentiated and less than 1 myr. old in contrast to basalt from the sediment-draped Southeast Dellwood Knolls, the latter basalt having Mn-coating up to 50 mm. thick and is thus relatively old. This suggests that spreading may be occurring at the Northwest Dellwood Knolls and not in the channel between the knolls. The texture of basalts from the Dellwood Seamount Range vary depending on size of pillow and depth below pillow surface, but the mineralogy is essentially similar. An unusual rock probably best described as a plagio-clase-olivine basalt porphyry was also recovered from the Dellwood Seamount Range. Non-volcanic rocks recovered include glacial erratics, an authigenic sandstone comprising glacial fragments in an iron-rich cement, a laminated limonitic sediment and manganese nodules. The Dellwood Spreading Segment may have originated by left lateral transcurrent offset from the Explorer Spreading Segment, the offset caused by a change in the direction of motion of the Juan de Fuca plate. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Coal measures of the Late Jurassic-Early Cretaceous Kootenay Formation are complexly deformed in the southeastern Canadian Rocky Mountains. The structural style and associated features of the coal measures are in part characteristic of the ‘Foothills Family’ of structures. In addition, by virtue of the major contrast in competency between the coal seams and adjacent strata, the structural features of the coal measures display considerable variation which, to some extent, can be correlated with the regional and local structural setting., The variation in the structural features of the coal measures have a marked influence on the mineability of the coal and both directly and indirectly on coal quality. During deformation the coal seams were the loci of interstratal slip, thrust faulting and detachment during folding.. The coal seams vary markedly in thickness; in some areas coal seams have been thickened as much as an order of magnitude in response to thrust faulting, normal faulting and folding, whereas in other adjacent areas, the seams may be completely pinched-off or faulted out. Structural thickening of the coal seams has been facilitated by cataclastic flow of the finely sheared coal along a myriad of discrete shear surfaces. The mesoscopic and microscopic fabric of the coal is cataclastic with the exception of local areas of apparently high strain where the vitrain and clarain components have behaved plastically. Shearing of the coal and adjacent strata has resulted in the introduction and dissemination of formerly discrete rock partings which in turn have produced abnormally high ash contents and poor washability characteristics and has made the coal more susceptible to oxidation. Measurement of vitrinite reflectance of coal in some major shear zones suggests, by comparisipn with samples heated in the laboratory for short durations, that frictional heating during shearing may have resulted in temperatures of up to 450°C. . Adjacent to and within other shear zones there is no evidence for frictional heating. The presence or absence of frictional heating may be the result respectively of stick-slip and stable sliding conditions during shear, which in turn may be a product of variable pore pressures. In underground mines the structural features of the roof rock and the coal seams have a pronounced effect on roof stability.. In the Vicary Creek mine, located in the hanging wall of the Coleman Fault, the Number 2 seam and some of the roof rock were pervasively sheared as a result of interstratal slip during flexure of the coal measures and possibly as a result of drag from overriding thrust faults. In such areas the coal pillars have low bearing strength and the cohesion between successive beds in the immediate roof rock has been destroyed, resulting in poor roof conditions. Slickenside striae on bedding surfaces, joints in the roof strata and some extension faults which cut the seam, define a kinematic and dynamic pattern which is consistent with the regional structure. In the Balmer North, Five Panel and Six Panel mines, located in the northern part of the Fernie synclinorium, the coal measures are only mildly deformed. A cleat system is present at all sample localities but no consistent pattern exists which can be related to the overall structure or to joints in the roof and floor.. In the Balmer North mine, young, gently west dipping, shear surfaces are present throughout which, in conjunction with slickensided bedding surfaces, have promoted roof and coal rib failure along north to northwesterly trends. In the Five Panel mine roof and coal rib failure have been facilitated by steep easterly dipping fractures. The absence of a consistent joint or cleat pattern in the Balmer North, Five Panel or Six Panel mines may be the result of mechanical anisotropy of the strata or of multiple episodes of deformation. Striated structures, many of which are conical in form, are common mesoscopic elements on fracture surfaces in the deformed coal. . Such structures, although rarely reported previously in the literature, occur at many localities in the study area. The structures are planar, conical and pyramidal in form, and are characterized by striae which radiate from a common apex and 'horsetail' to form subsidiary structures on the master surface. All three types of striated structures are considered the products of dynamic, brittle shear fracture which was possibly facilitated at failure by high inter- and/or intra-particle pore pressure. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate