The Neys Diatreme is a sharply defined structure consisting of large, subround fragments set in a finely comminuted matrix of the same material.  It is located on the west side of the Coldwell Peninsula where it is seen to cut rocks of the Coldwell Alkaline Complex.  The diatreme itself is cut by later dykes.

Detailed mapping and sampling of the diatreme and the immediate host rock have been undertaken to determine the shape, extent and lithologic relationships of the structure.  Studies of the petrography, mineralogy and geochemistry of the clasts and dyke rocks have also been made.

The Neys Diatreme contains clasts of alkali feldspar syenite, layered olivine monzo-gabbro and nepheline syenites, all of which belong to the Coldwell alkaline complex.  Minor exotic clasts of undeformed porphyritic felsite and basic volcanics are also present.  In addition basic hornfels clasts are found which are believed to originate from the contact aureole of the Coldwell intrusion.

The shape of the diatreme suggests structural control of its emplacement.  Turbulent flow, the result of high velocities achieved by a gas-solid phase of a volatile-rich magma, is postulated as generating the diatreme breccia.  Block faulting is interpreted to have occurred in the Coldwell Complex.  This may be assumed to have initiated the intrusion of this type of structure.

The thesis area is located in the Keewatin District of the Northwest Territories on the east shore of Smiling Ghost Lake.  An approximate 1.2 km² area of metamorphosed Archean volcanic and sedimentary rocks of the Henik Group was studied in detail.  The rocks vary in metamorphic grade from greenschist to epidote-amphibolite facies.  Pillowed and massive basic flows are the major lithology in the thesis area and form the upper and lower volcanic units.  Medium grained porphyritic rocks of andesitic composition occur as irregular shaped bodies throughout the sequence. 

Volcaniclastic rocks vary from tuffaceous to breccia textures and are both oligomict and polymict.  These rocks interlayer the basic flows in the central portion of the thesis area.  Macroscopic and microscopic examination of the volcaniclastic breccias combined with geochemical whole rock analyses indicates derivation from a multicompositional source area.  Therefore it is postulated that the Smiling Ghost Lake area is a section of the epiclastic rocks represent reworked units.  Gravity sliding and slumping in a subaqueous environment are suggested as possible methods of deposition, and were likely similar to a laharic type deposition present in the cone-complex facies.

Strike-slip faults caused by compressive forces are present throughout the thesis area and have developed well defined shear zones, jointing and minor folds.  Shearing and metamorphism cause variable amounts of deformation and foliation in the rocks, which have been subjected to several periods of deformation.

Sulphide mineralization is present in a fracture filled shear zone found in basic volcanic rocks.  Chalcopyrite, sphalerite, pyrite and iron oxides are found with deformed and foliated quartz-sericitic rocks.  Cataclastic textures in both the ore minerals and the fracture filling material indicate that deformation along the shear zone was intense.  Likely the fracture filling itself was sheared and brecciated by later movements along the fault.

Early Precambrian metavolcanic and metasedimentary rocks of the Schreiber-White River greenstone terrain have been intruded by rocks of the Coldwell alkaline complex.  A thermal metamorphic aureole produced by the complex attains pyroxene hornfels facies in adjacent country rocks.

The earliest magmatism, center 1, is exposed at the western margin of the complex and consists of gabbro and ferroaugite syenite.  Younger, center 2, silica-undersaturated syenites intrude both the gabbro and ferroaugite syenite.

The gabbro is characterized by igneous layering and evidence of deformation, in the form of cataclasis and recrystallization of the feldspar.  Ferroaugite syenite intrudes the gabbro and contains inclusions of an ilmeno-magnetite bearing cumulate rock and country rock xenoliths.

The principal rock units are crosscut by a dyke suite exhibiting a complex intrusive history.  The most common dyke type is lamprophyre.

In a north-south traverse of the Quetico Subprovince (of the Superior Province, Canadian Shield) a metasedimentary sequence and a migmatitic sequence are exposed.  The metasedimentary sequence consists of slates and turbiditic greywackes.  Interbedded with these are calc-silicate rich horizons and nodules.  The metasediments are folded into a major F₁ antiform and synform which are probably downward facing on the schistosity.  In the northern part of the study area a schistose migmatitic sequence is exposed separated from the metasediments by intrusive rocks.

Grade of the syn and post-tectonic metamorphism increases from south to north.  Low grade (chlorite, biotite), middle grade (staurolite, cordierite) and high grade (sillimanite) zones are defined.  A somewhat higher pressure assemblage, including staurolite, is probably post dated by a lower pressure assemblage, including cordierite.

A zone of largely ductile dislocation metamorphism in a zone known as the Quetico Fault, post dates the regional metamorphism.

In the summer of 1980, during reconnaissance mapping with the Geological Survey of Canada a succession of mafic flows and volcaniclastic sediments, subsequently named the Ingrid group, was discovered about 2500 metres west of the Nain-Churchill Province's boundary.

The group consists of basalt, porphyritic basalt, conglomerates, greywackes and siltstone metamorphosed from upper greenschist to epidote-amphibolite facies.  These units observed have been deposited upon Churchill Province gneisses in Aphebian to Paleohelikian time and have been folded, faulted in a very complex manner.

The geology of Elbo Lake consists of granulite metasedimentary rocks, a megacrystic granite unit and a medium grained granite gneiss unit.  Mylonite zones are common in the area and show up as strong topographic lineaments.  The thin section mineralogy suggests granulite Facies metamorphism with later retrogression to amphibolite Facies.  Owing to the lack of good structural data a precise determination of the deformation sequence was difficult to determine.  However stereograms of the foliation measurements indicate a dome or half dome structure in the north-eastern portion of the thesis area.

Sheared, steeply dipping volcanic rocks of the Triassic Nicola Group are found on the west side of the Thompson River.  Mapping of the 11 square kilometer Silica claim group located southwest of the town of Ashcroft, B.C., has revealed a sequence of intermediate and porphyritic felsic rocks.  This assemblage has been intruded by quartz diorite stocks, thought to be associated with the Guichon Creek batholith.  Petrographic and limited geochemical work has been done in order to better describe the observed rock units.  These studies imply that most of the siliceous, pyritic, quartz-feldspar porphyritic rocks have the magmatic characteristics of rhyolite flows, and may not be "silicified greenstones" or crystal tuffs as previously described.  Associated minor copper mineralization is seen both as co-precipitated chalcopyrite in pyrite hosted in small podiform masses of chlorite schist, and as malchite in quartz veins.  Despite the presence of the Guichon Creek batholith, the sulfide occurrences do not appear to be of porphyry-type mineralization; these may be indicative of volcanogenic sulfide concentrations located down dip or along strike of the sheared strata.

The area is underlain by Archean volcanic and sedimentary rocks of the Superior structural province and forms part of the Shebandowan-Wawa volcanic-plutonic belt.

In the study area, a volcanic succession with intercalated sedimentary rocks is exposed.  Volcanism is of the bimodal, basalt-rhyolite type.  Pyroclastic rocks from part of the volcanic pile and occur together with rudaceous sedimentary strata.  One complete and two incomplete cycles of mafic to felsic volcanism, followed by sedimentation, are observed in the area.  A sulfide (pyrite-chert) and an oxide (banded magnetite-jasper) facies iron formation outcrops within the area.

At least one deformational event is recorded by the steeply dipping bedding planes of sedimentary units.  A variably developed cleavage is present in most rocks.  Cleavage-bedding relationship and local younging data suggest a synclincal axis to the north of the area.  The rocks have been metamorphosed to greenschist and lower epidote-amphibilite facies conditions.

A small hornblende gabbro intrusive is situated near the centre of the area.

The Coldwell Complex, a group of Neohelikian alkaline rocks cutting the Archean Schreiber-White River Greenstone Belt, is the result of three westward migrating centres of intrusion.  The Little Pic River Breccia Zone is located two to three kilometers from the western margin.  Centre III syenites, xenolith compositions and dike structures are the major topics of discussion in this thesis.

Field mapping and detailed petrographic studies allowed an intrusional history to be derived for the local area.

The Little Pick River Breccia Zone is determined to be an intrusive breccia with post-intrusive block faulting altering the structure to the west.  Different structural levels are interpreted to be present in the Coldwell Complex (Mitchell and Platt, 1982).  Considering the high volume of country-roick metavolcanic xenoliths, it is surmised that the Little Pic River Breccia Zone is a "near to roof" assemblage which was downfaulted.

Textural variants of the early Centre III syenites described as coarse-grained, contaminated-porphyroblastic and fine-grained, are present.  Several colour variations of later Centre III quartz syenites also show widely variable textural relationships, grading from medium-grained to pegmatitic. 

Metavolcanics and Centre II xenoliths show varying degrees of metasomatism, resulting in porphyroblast growth and/or complete alteration to secondary mineral assemblages.

Microsyenite dikes are an important structural feature, locally defining a regional stress pattern.  Compositons vary widely in this group, hence no particular dike phase can be correlated to a specific joint set.

The Island Belt Silver Region lies within a northeast-trending fracture zone in Proterozoic sedimentary and igneous rocks of the Southern Province of the Canadian Shield.  It comprises a number of vein occurrences on offshore islands in northwestern Lake Superior and along its shoreline south and east of the City of Thunder Bay, Ontario.  The belt-like spatial association of these occurrences and their similar vein attitudes is due to structural localization in linear fracture zones related to regional rifting and subsidence of the Lake Superior Basin in the late Proterozoic time.  Not all of these veins are argentiferous, and some contain only trace amounts of silver.  Ore and gangue mineralogies vary widely between sites from simple quartz-calcite ± barite veins with galena, pyrite and sphalerite to complex "five-element" (Ag-Bi-Ni-Co-As) assemblages such as that at Silver Islet; the latter is unique in its complexity.  Vein systems may be simple, composite or fill brecciated shear zones.  The predominant primary textures are those related to open-space filling.  These include rhythmic crustification, euhedral and multi-stage crystal growth, zonation and hydrothermal brecciation.  Secondary textures, resulting from weathering, oxidation-reduction and supergene processes, are related to near surface alteration while deformation textures are probably due to ongoing fault movement and post-crystallization tectonism.  The more complexly mineralized veins crosscut igneous intrusive bodies at high angles approaching 90° and are usually associated with gabbroic rocks, while veins associated with diabase are relatively mineralogically simple.

The Mainland Belt Silver Region is found in a fracture zone that parallels that of the Island Belt and was formed during the same tectonic event.  The respective mineralogies of the veins of the two Belts are superficially similar.  The major differences are related to the homogeneity of the Mainland Belt deposits and the relative heterogeneity of those in the Island Belt, whose occurrences are associated with later diabasic and gabbroic intrusives.  The mafic rocks of both Belts are petrogenetically related.

The Island Belt occurrences may be related, but variances arising from an episodic vein-filling history imply a complex regional metallogeny.  The source of the vein metals is perhaps a combination of the distillation of metals from Rove sedimentary rocks and input of metals such as Ni, Co and Ag from an associated mafic intrusion, which is the heat source for both metal mobilization and hydrothermal circulation.