The Archean mafic metavolcanics of the map area represent the northwestern extremity of the southern sedimentary-dominated belt of the Beardmore-Geraldton Region.  As such these rocks occupy a part of the Wabigoon Volcanic-Plutonic Supracrustal Belt of the Superior Province, Canadian Shield.  The rocks display many interesting primary megascopic features including: pillows; amygdules; and brecciation.  Such features were used to define map units.  The highly fractionated basalts of the map area are significant for both structural and petrologic studies.

These rocks have been weakly deformed.  This was determined by measurements of:  pillow, amygdule, and phenocryst shape; and pillow selvage thickness.  The individual contributions of synvolcanic and regional tectonic deformation processes cannot be evaluated.  However, it is evident that both have played a part in producing the strain now observed in these rocks.

Petrology, including petrography and geochemistry, of study area samples can be used to ascertain the tectonic regime of the Beardmore-Geraldton Region.  Several factors tend to disguise this effort.  Spilitization, low grade regional metamorphism, and subsequent hydrothermal alteration must be considered.  However, these effects can be stripped off by the use of relatively immobile elements for classification discriminations.  With these facts in mind, the rocks appear to be ocean floor basalts extruded in an inter-arc basin.  This determination is proof that Archean volcanic rocks can be studied fully with only a few minor diagnostic restrictions.  To this end thoughts on modern and classical plate tectonic theory as applied to greenstone belt genesis are presented; this despite the fact that neither have been conclusively confirmed nor disproved for the Archean.

A baritic horizon occurring within the Arechean supracrustal rocks of the Hemlo area, northern Ontario, exhibits characteristics that suggest a syngenetic origin is likely.  The baritic unit outcrops in five locations situated five to thirteen kilometers east of the town of Marathon, and appears to parallel the regional stratigraphy.  It occurs between pyroclastic plus pillowed mafic metavolcanics to the south and siliceous metasediments plus intermediate to felsic pyroclastic metavolcanics to the north.  The barite is massive, thinly laminated to wispy laminated and is generally interlaminated with recrystallized quartz, albite, pyrite and carbonaceous material, forming a unit one to three meters thick.  The contacts with adjacent rock layers appear conformable.  Rock lithologies associated with the baritic unit include pyritiferous graphitic schists and DE turbiditic argillaceous siltstones (starved basin-type sediments), argillaceous siltstones with green mica (rip-up?) clasts, green mica schists, biotite-hornblende schists, sericite-carbonate schists, mafic metavolcanic fragmentals and flows, a very thin tuffaceous unit and quartz-feldspar porphyry sills.  Although these rock units have likely been structurally transposed relative to one another, their presence at all the barite occurrences suggest that they were formed in special association with the barite.

In comparing the characteristics of the Hemlo baritic horizon with those of other documented modern to Archean syngenetic and epigenetic barite occurrences throughout the world, it becomes evident that the Hemlo occurrences more closely resemble syngenetic than epigenetic deposits.  Characteristics in common with other syngenetic occurrences include: regional and local conformity of the baritic unit with associated lithologies; lateral continuity of the barite horizon (possibly eight kilometers); associated deep water/starved basin-type sedimentary units; the thinly laminated to wispy laminated character of the barite.

Skarn deposits in southern Yukon, southwestern Mackenzie and northern British Columbia are host to a variety of ore elements including tungsten, copper, zinc, lead, silver, molybdenum, and tin.  A study of five of these skarn occurrences in light of recently proposed descriptive classification schemes based on the major ore element assemblages defines each skarn occurrence as a distinct skarn type.

Studies by Dawson and Dick (1978) and Dick (1979) have shown that skarns in this area may be divided into four main groups based on the major ore element assemblages that they contain.  These are:  1) W-Cu,  2) W-Mo,  3) Zn-Pb, and 4) W-Cu-Sn.  Minor ore elements associated within these groups vary from deposit to deposit.

A more recent study by Einaudi et al, (1981) suggests that skarn deposits are best classified on the basis of the dominant economic metal and suggest six major subclasses, consisting of Fe, W, Cu, Zn-Pb, Mo and Sn.

Three scheelite-bearing skarn occurrences on the McDame Prospect in northern British Columbia are defined as tungsten skarns and reflect major ore element assemblages of W-Cu and W-Mo.

Two zinc-lead skarn occurrences on the Norquest Prospect in southern Yukon Territory are defined as zinc-lead/zinc skarns and reflect a dominantly Zn-Pb-(Ag) ore element assemblage.

The Schreiber-Marathon archean greenstone belt forms a part of the Shebandowan-Wawa Subprovince of the Superior structural Province of the Canadian shield.  This thesis focuses on the eastern portion of the Schreiber-Marathon greenstone belt.

Bedrock in this area can be broadly divided into rocks of the Playter Harbour and Heron Bay supracrustal Groups.  The Playter Harbour Group is composed predominantly of high-iron tholeiitic basalts and metasedimentary rocks primarily of volcanogenic origin.  The Heron Bay Group includes calc-alkalic pyroclastic rocks of variable composition, high-iron tholeiitic basalts, and metasedimentary rocks of diverse origin.

The supracrustal rocks of both groups form east-west trending sequences which are intruded by a number of archean plutons and proterozoic sills and dykes.  Regionally, the supracrustal rocks appear to conform closely to the contacts of extensive gneissic complexes of archean age.

Metamorphic grade is typically greenschist facies, however, amphibolite facies assemblages occur locally.

The regional structure of the rocks is complex and with the data available at present, open to a variety of interpretations.  Evidence of widespread, large scale brittle and ductile deformation can be seen throughout the belt.  In outcrop, the structures are highly diverse, often complex, and in many cases deformation is of such a magnitude as to obscure the original nature of the rocks.

A reconnaissance of five silver-bearing veins between Schreiber, Ontario and Marathon, Ontario indicate that the Pb-Zn-Ag veins in this area are genetically related.  The three veins of this type that were studied (the Deadhorse Creek North, Deadhorse Creek South, and Morley High Grade veins) have very similar mineralogies with freibergite as the Ag-bearing phase.   A general paragenetic sequence was noted, from early massive sphalerite ± pyrite to later massive galena + sphalerite ± chalcopyrite ± freibergite.

Fluid inclusion studies on these three veins indicate low to moderate temperatures of formation (approximately 160-355 degrees Celsius), low salinites, and some form of NaCl-KCl-MgCl₂-H₂O fluid compositions.

The veins are not, as previously suggested, related to intrusion of the Coldwell Alkaline Complex since one vein cuts the thermal aureole of the Complex and another is over 60 km away from it.  The veins may, however, be rift related with much of the data presented here lending support to this hypothesis.

The other two veins studied are of indeterminate origin.  They are not directly genetically to the Pb-Zn-Ag veins since they have much different mineralogies.  The Mogatherium vein contains a complex Cu-Pb-Bi-Te-Ag-S ore mineral assemblage, while only pyrite was found in the Gold Range samples analyzed.

Fluid inclusion analysis yielded poor results for these veins and thus their mode of formation is still a point of conjecture.  They may be related to the intrusion of the Terrace Bay Batholith, with which the veins are spatially associated.

The diagenetic history of a Carboniferous limestone sheet (Ardness Formation) present in the Cumberland Basin, Nova Scotia, was studied.

The diagenetic environments that altered the limestones of the study area were:  1) Near-Surface Processes  2) Vadose Processes, which only affected Knoydart Brook oolitic shoals  3) Freshwater Phreatic Processes  4) Deep Burial Processes  5) Hydrothermal Processes.

Petrographic evidence suggested the following sequence of diagenetic events:  1) bioturbation as a form of biological diagenesis in Knoydart Brook but not in Northumberland Shore,  2) microboring and the consequent micritization of bioclasts forming micrite envelopes,  3) early compaction,  4) very early freshwater-phreatic cements around echinoderm plates in the form of syntaxial overgrowth cement, and around ooids in the form of drusy cement,  5) grain-to-grain pressure solution,  6) blocky cement as well as void filling calcite cement.

Other processes which were pervasive throughout the sections are  7) neomorphism,  8) stylolite formation,  9) pyrite and hydrocarbon overprints.

The cements in the study area were mostly Mn-enriched and are likely to have precipitated from Mn-rich fluids that were related to hydrothermal vein systems.  Mn content in some ooids is higher than nearby cement indicating that the ooids were formed from Mn-rich seawater.  The hydrothermal processes were most affective near the basin margin of the shallow Windsorian area, a continental setting similar to the present day Persian Gulf.  In this case a hydrothermal vein system was operative near the continental transform faults of the Cumberland Basin during an early stage of block movement.  Hydrothermal fluids which were generated by convection within the basin rose along the permeable zones and fractures of the basin margin faults and carried Mn and other base metals towards the surface.

Ductility contrasts between individual clasts and matrix and the affects of a single, non-coaxial, pure shear deformation has resulted in the heterogeneous and non-passive strain features observed on a two dimensional outcrop surface of the Seine Conglomerate in northwestern Ontario.

Two strain analysis techniques yielded different stain values for each clast lithology thus reflecting the relative competencies.

The bulk strain of the conglomerate outcrop is partitioned between the ductile matrix and a rigid framework of the more competent clasts.  The finite strain ratios of metavolcanic clast may represent the state of strain of the matrix due to the passive manner in which the two components have deformed.  The bulk strain of 72.5% shortening is intermediate between the value calculated for the metavolcanic clasts and the granitoid clasts.

Values of strain calculated for the porphyritic igneous clasts are close to the estimated bulk strain ratio for the entire outcrop.  Thus the popphyritic clasts are a small scale analogy of the conglomerate: porphyritic clasts have a rigid phenocryst versus ductile groundmass phase similarily, the conglomerate has a rigid clast versus a ductile matrix phase.

A previously unidentified Cu-Pb-Bi-S mineral was found to be aikinite, a member of the aikinite-bismuthinite homologous series of sulphosalts, through the use of x-ray diffraction and precession analysis.  A noted compositional disparity from that of ideal aikinite was discerned.  Previous workers have attributed such compositional deviations to either limited solid solution or to disordered intergrowth of end members of the series.  An examination of % metals vs % sulphur has shown that both solid solution and disordered intergrowth mechanisms occur in the sample under study.

Three samples of Ag-Hg bearing material were analysed through the use of X-ray diffraction and elemental analysis in order to discern any structural variation from the face-centered cubic silver structure that might arise due to the mercury content.  The small size of the Big Harry vein specimen precluded any work being done on it.  The other two samples from Chile and British Columbia, previously identified as arquerite, were determined to be native lead and mercurian silver respectively.

The Quetico subprovince; which consists of metasedimentary rocks, gneisses, and migmatites, is a east-to-west trending linear belt in the Superior Province of the Canadian Shield.  This subprovince has been subjected to extensive periods of metamorphism and deformation throughout its evolution.  Hosted within this subprovince are a number of igneous intrusions that are granitic to quartz monzonitic in composition, and show little evidence of a complex geological history.  Emplacement of these plutons have resulted in the development of contact metamorphic aureoles in the regionally metamorphosed host country rock.  The objective of this study was to find evidence of such an aureole in the host rock, and to describe the mineralogical and textural features that are commonly developed in this type of aureole.

The study area under consideration is located northwest of Thunder Bay, Ontario.  In this area, a late-stage pluton, the Barnum Lake pluton is hosted in metagreywackes.  A series of samples were taken and studied for evidence of contact metamorphic overprinting.  These studies revealed features characteristic of contact metamorphic aureoles, such as the presence of hornfelsic texture and the growth of second generations of minerals such as biotite.  Mineral assemblages found in the host rock, were consistent with those described in the literature as typical of contact metamorphic aureoles.

Oriented samples were also taken directly from the Barnum Lake pluton, and were the object of anisotropy of magnetic susceptibility studies.  AMS studies revealed that the pluton was emplaced, and that the emplacement of the pluton was responsible for the contact metamorphic features observable in the host rocks of the Quetico subprovince.

No abstract provided.