<p> Sulfide-poor platinum-group element (PGE) mineralization occurs within the Archean Boston Creek Flow ferropicrite, Abitibi greenstone belt, Canada. The PGE mineralization (∑PGE+Au = up to 1000 ppb) is manifest as metre-scale platinum-group mineral-bearing pods of disseminated chalcopyrite and pyrite (< 1 modal%) within titaniferous magnetite-rich gabbroic rock at the base of its central gabbroic layer. This mineralization is distinct in character from well known PGE mineralization associated with massive Fe-Ni-Cu sulfides at the base of komatiite flows at Kambalda, Western Australia and elsewhere. Exploration strategies presently used to search for PGE in mafic and ultramafic volcanic rock terrains are based on the geological and geophysical characteristics of sulfide-rich PGE mineralization. Consequently, refinements in exploration strategies are required if economic concentrations of sulfide-poor PGE mineralization are to be discovered in volcanic terrains.</p> <p> To begin development of such exploration criteria, ground-based magnetic and VLF surveys were conducted over the PGE mineralization along a single cross-section through the BCF. Drill core samples were collected along this transect to characterize the volume magnetic susceptibility and natural remanent magnetization (NRM) of the mineralization. Magnetic highs ranging in intensity from 64000 to 65000 nT were recorded for the base of the gabbroic layer, including mineralized outcrops. Susceptibilities of up to 9700 cgs and high remanence values with variable directions were determined. VLF, as expected, was not useful in identifying the mineralized horizons. The peridotite at the base of the flow appears to be the only conductive rock in the BCF.</p> <p> The magnetic highs associated with the base of the gabbroic layer define a positive anomaly that appears to be podiform in outline and up to ten metres in maximum dimension. This result suggests that the titaniferous magnetite-rich rock is itself podiform, like the enclosed PGE mineralization. This magnetic anomaly is not extensive enough to be evident on a regional scale aeromagnetic map as a separate anomaly within the BCF, and is not evident through VLF techniques. The rocks hosting the PGE mineralization is defined by the paleomagnetic results but this is not a practical field method.</p> <p> The geophysical characterization of the PGE mineralization host rocks, and of the BCF in general, demonstrates the potential of detailed magnetic and susceptibility mapping, together with petrographic and petrologic studies, in the search for economic PGE concentrations of sulfide-poor PGE mineralization in other volcanic and possibly plutonic rocks as well. Specifically, the results suggest that podiform magnetic anomalies within titaniferous magnetite-rich pyroxenites and gabbroic rocks may have potential use in the exploration for economic sulfide-poor PGE mineralization. Although the paleomagnetic methods used in this study are probably not of direct use in exploration, they were able to distinguish the different lithologies in the BCF. This substantiates the results of the susceptibility measurements in characterizing PGE mineralized, titaniferous magnetite-bearing rocks. The results of the paleomagnetic study also show that the NRM of the Ghost Range intrusive complex is not primary and therefore the Archean apparent polar wander path as it is currently defined is incorrect.</p> / Thesis / Bachelor of Science (BSc)

Den övergripande tanken med projektet är att ta reda på vad som hände på Västra Gräddmanhällan,utanför Kalix kust, för 2 miljarder år sedan. Det görs genom att ta reda på vad det är för bergarter ochstrukturer som hittats på området och hur de korrelerar till varandra. De två huvudsakliga delarna somprojektet fokuserar på är de stromatolitiska strukturerna som finns i de sedimentära bergarterna på VästraGräddmanhällan och de magmatiska intrusionerna som går genom de sedimentära bergarterna. De skaidentifieras med hjälp av tre olika metoder som ska komplettera varandra. Alla tre metoder kräver attprover från platsen hämtas till Uppsala Universitet där de kan slipas ned till tunnslip. Det kommer finnastotalt åtta prover tagna från olika stromatolitiska strukturer, både från land och Västra Gräddmanhällanoch två stycken tunnslip från de magmatiska intrusioner som tidigare antagits vara antingen kimberliteller lamprofyr. Alla tunnslip kommer att studeras i ett optiskt mikroskop och då kommer vissa tunnslipväljas ut för att undersökas i SEM och sedan Elektronmikrosond. Det finns vissa egenskaper i de olikabergarterna som är avgörande för resultatet. I de stromatolitiska strukturerna är spår av paleobiologiviktigt. De saker som kommer att kunna ge en indikation på tidigare liv i en stromatolit är bland annatorganiskt kol och pyrit. Fynd av antingen opaka mineral, organiskt kol eller andra intressanta struktureri det optiska mikroskopet kommer därför påverka projektets gång. För de magmatiska intrusionerna blirdet istället mineralsammansättning och eventuella karbonater som blir viktiga för hur synen på Sverigesgeologiska historia kommer se ut i fortsättningen. / The overall idea of the project is to find out what happened on the Western Gräddmanhällan, off thecoast of Kalix, two billion years ago. This is done by finding out what rocks and structures that are foundin the area and how they correlate to each other. The two parts that this project focuses on is thestromatolitic structures found of the Western Gräddmanhällan and the igneous intrusions that passthrough the sedimentary rocks. They must be identified using three different methods that willcomplement each other. All three methods require samples from the site to be brought to Uppsalauniversity and then be ground down to thinsections. There will be a total of eight thin sections takenfrom different stromatolitic structures, both from the coast and the western Gräddmanhällan and twopieces of thin sections from the magmatic intrusions that are already assumed to be either kimberlite orlamprophyre. All thin sections will be studied in an optic microscope and then certain thin sections willbe selected to be examined in SEM and then Electron Microprobe. There are certain properties in thedifferent rock types that are decisive for the result. In the stromatolitic structures, traces of paleobiologyare important. The things that will be able to give an indication of past life in a stromatolite includeorganic coal and pyrite. Findings of either opaque mineral, organic carbon or other interesting structuresin the optical microscope will therefore affect the progress of the project. For the magmatic intrusions,it will instead be the mineral composition and possible carbonates that will be important for how theview of Sweden's geological history will look in the future.

The Alta-Kvænangen Tectonic Window is part of a regional greenstone belt that formed around 2.3 Ga – 2.0 Ga. The Bergmark anticline in the area has gone through greenschist to amphibolite facies metamorphism and hosts Cu, Co and Au mineralizations in hydrothermal veins, albite felsite and chemical traps. The area was mined during the late 19th century mostly in trenches but it has still got exploration potential. This project will classify carbonate veins that are hosted within two gabbro units, compare orientations between the barren and mineralized veins as well as discuss the origin of the veins.  The study area has been affected by multiple extensional and compressional events during the Svecokarelian orogeny (1.9 – 1.8 Ga) and regional hydrothermal alterations including an influx of Na + Ca ± K ± Fe. Major shear zones were activated and used for transporting fluids which are thought to have controlled the formation of mineralization in second- or even third-order structures. The veins were studied using field work, detailed mapping, optical microscopy as well as scanning electron microscopy (SEM) and structural analysis. Results gave three different types of hydrothermal veins: 1) Fe oxide veins, 2) calcite veins and 3) dolomite-plagioclase-quartz veins. All of them show strong signs of deformation and recrystallization all while the chalcopyrite mineralization is heterogeneously distributed and commonly more or less bornite-altered. The veins pinch and swell over short distances and are sinuous but with a general orientation. Albite haloes are common for the veins but far from all veins have haloes. There are at least two generations of veins as some were found to have offset others. Brecciation, tension gashes and faults are also found in the area apart from veins. From the field measurements, two groups of orientations could be determined: one with a SW-NE direction and the other in NW-SE direction, both with relatively steep dips. Considering all downhole measurements, no conclusive results could be revealed, however, the optical televiewer results showed that the area has gone through a N-S compression giving a fold axis towards the west. In the end the orientations of the larger veins were found to either run parallel to the gabbro units or are connected to the NW-SE directed main brittle faulting in the Fennoscandian Shield. Smaller, surrounding veins having more diverse orientations. There are multiple signs of deformation and recrystallization in the mafic host rock but no fabric development can be seen. Its appearance varies locally depending on which alterations are dominating. It exhibits sodic-calcic, potassic and leucoxene alteration as well as albitization and carbonatization. The grain size varies from fine-grained to medium-grained which is more typical with a dolerite or basalt, even though it has been previously mapped as a gabbro. No pyroxene was found in the host rock and the plagioclase was Na-rich instead of the expected Ca-rich.  The Bergmark anticline has multiple similarities with the Gällivare-Kiruna area in Sweden which include 1) high-temperature, low-pressure metamorphism resulting in regional alterations such as albitization, carbonatization, amphibole and magnetite alteration. 2) The mineralization consists of Cu, Co, Au, Fe and minor P. 3) The mineralization can be found disseminated in albite felsite, in chemical traps and in first to third order structures (e.g., faults or hydrothermal veins) in brittle, deformed rocks. 4) The mineralization is structurally controlled to the vicinity of major fault zones. 5) In both places, greenstone belts are important for the formation of mineralization. 6) Reactivation of brittle structures, similar to those in the Kiruna area during the second phase of subduction during the Svecokarelian orogeny (D2), is likely the cause for the veining in the Bergmark anticline. 7) A younger N-S compression is recorded in the area. Differences between the Bergmark anticline and the Gällivare-Kiruna area include the lack of intrusions in the vicinity to the Bergmark anticline.

The Archean (~3.0 Ga) Buhwa Greenstone Belt, and surrounding granite-gneiss terrane, is the least understood major greenstone belt in the Archean Zimbabwe Craton, despite occupying a critical position between an early Archean continental nucleus and the Limpopo Belt. The cover succession in the Buhwa Greenstone Belt, which was probably deposited on the margin of this nucleus, is divisible into shelfal and basinal facies associations separated by a transitional facies association. The shelfal association consists mostly of quartzarenite and shale, but also contains a thick succession of iron-formation. Geochemical characteristics of the shales indicate that the source terrane consisted of several lithologies including tonalite, mafic-ultramafic volcanic rocks, and granite that underwent intense chemical weathering. Basinal deposits consist dominantly of greenstones, with less abundant chert and ironformation. The cover succession, which was deposited on a stable shelf transitional to deep water, has no stratigraphic equivalents elsewhere on the Archean Zimbabwe Craton. However, time and lithologic correlatives in the central zone of the Limpopo The Archean (-3.0 Ga) Buhwa Greenstone Belt, and surrounding granite-gneiss terrane, is the least understood major greenstone belt in the Archean Zimbabwe Craton, despite occupying a critical position between an early Archean continental nucleus and the Limpopo Belt. The cover succession in the Buhwa Greenstone Belt, which was probably deposited on the margin of this nucleus, is divisible into shelfal and basinal facies associations separated by a transitional facies association. The shelfal association consists mostly of quartzarenite and shale, but also contains a thick succession of iron-formation. Geochemical characteristics of the shales indicate that the source terrane consisted of several lithologies including tonalite, mafic-ultramafic volcanic rocks, and granite that underwent intense chemical weathering. Basinal deposits consist dominantly of greenstones, with less abundant chert and ironformation. The cover succession, which was deposited on a stable shelf transitional to deep water, has no stratigraphic equivalents elsewhere on the Archean Zimbabwe Craton. However, time and lithologic correlatives in the central zone of the Limpopo ~2.9 Ga in southern Africa. At ~2.9 Ga, the northern margin of the greenstone belt experienced kilometerscale, oblique-slip dextral shearing. This shear zone and the surrounding margins of the greenstone belt were later intruded by the ~2.9 Ga Chipinda batholith, which ranges from granitic to tonalitic in composition. A number of events occurred during the time period spanning 2.9-2.5 Ga and current geochronology cannot separate their order; some are known to be coeval. Crustal shortening to the northwest, which resulted in map-scale folding of the cover succession (and surrounding batholith) and greenschist-facies metamorphism, occurred along a set of discrete high-angle reverse-sense shear zones in response to uplift the Northern Marginal Zone of the Limpopo Belt over the Zimbabwe Craton. Two suites of potassic granites were intruded into the area near the end of reverse shearing. Analysis of a conjugate fault pair that is developed within one of the potassic granite suites, yields a principal compressive stress consistent with continued northwest-directed crustal shortening. The region was stabilized by ~2.5 Ga, with intrusion of the Great Dyke of Zimbabwe. It is possible that the last events to affect the area, which include sinistral shearing, transecting cleavage development, and northwest-striking open folding, took place during the 2.9-2.5 Ga time intervaL These structures post-date regional folding and metamorphism, but because of limited magnitude and extent, do not show obvious cross-cutting relationships with other rocks or structures. A tenable alternative is that these late structures formed at ~2.0 Ga. an age that is proving to be of great significance in the evolution of the Limpopo Belt and along parts of the southern margin of the Zimbabwe Craton. / Ph. D.

Thesis (MSc)--Stellenbosch University, 2014 / ENGLISH ABSTRACT: The compositions of tonalite-trondhjemite-granodiorite (TTG)-series rocks from the Barberton Granite-Greenstone Terrain (BGGT) of Southern Africa vary in terms of major element concentrations (leuco-trondhjemites to tonalites), trace elements (e.g. Sr, Rb, REE) and degree of HREE depletion [(La/Yb)N ~ 0.50 - 121]. These geochemical parameters have been interpreted to have significance for the geodynamic processes that produced TTG magmas, particularly the depth of the source. In the Nelshoogte pluton, trondhjemite emplacement occurred prior to and during (D2)-tectonism, and hornblende-bearing tonalites/granodiorites occur as intrusive plugs within the trondhjemite. The geochemical range portrayed by the ca. 3230 Ma Nelshoogte pluton covers almost the whole range portrayed by all the TTG rocks of the BGGT, formed in the time interval 3550 to 3230 Ma. U-Pb zircon dating reveals no significant differences in apparent ages between the trondhjemites and tonalites of the Nelshoogte pluton; all lie between ca. 3240 and 3220 Ma. A/CNK- and Ti-maficity correlations within the Nelshoogte pluton show behaviour typical of I-type granitic rocks, confirming the metamafic character of the source and the involvement of a peritectic garnet and clinopyroxene component in the magmas. The REE and traceelement patterns resemble those of both ca. 3450 Ma TTG plutons and other ~ 3230 Ma TTG plutons in the BGGT. This suggests that these different generations of TTG magmas were generated from similar sources and by similar processes. The geochemical details are consistent with a metamafic source which underwent melting at high pressure. This TTG source was fundamentally different from the more potassic source/s that produced the younger 3100 Ma granites. Additionally, high Zr/Sm and low Nb/Ta ratios in the Barberton TTG rocks suggest that the Nelshoogte pluton originated as a group of chemically distinct magmas, in a similar way to other ~ 3200 Ma TTGs. The protoliths of ~ 3450 Ma plutons and ~ 3200 Ma plutons might typically be rutile-bearing eclogite and/or 10 to 30 % garnet bearing amphibolite. The geochemical features of the Barberton TTGs suggest similar source compositions, but different pressures of partial melting. For the ca. 3230 Ma plutons, the rocks of the Badplaas pluton and the Nelshoogte trondhjemites/tonalites correspond to the high-pressure magmas, as reflected by high Sr content, as well as high Sr/Y and (La/Yb)N ratios. In contrast, the Kaap Valley TTGs and Nelshoogte granodiorites reflect the melting of a similar source at moderate pressure. Furthermore, the Hf isotope data; Hft (+ 0.1 to + 1.9) and TDM model ages (3330 - 3230 Ma), suggest that the source rocks are ~ 20 to 100 Myr older than the pluton. / AFRIKAANSE OPSOMMING: Die samestellings van tonaliet-trondhjemiet-granodioriet (TTG)-reeks gesteentes vanaf die Baberton Graniet-Groensteen terrien (BGGT) van Suiderlike Afrika verskil in terme van hoofelement konsentrasies (leuko-trondhjemiete tot tonaliete), spoorelemente (bv. Sr, Rb en seldsameaarde-elemente(SAE)) en ook van swaar seldsameaarde-element (SSAE) uitputting [(La/Yb)N ~ 0.50 - 121]. Deur interpritasie is daar vasgestel dat hierdie geochemiese beperkings betekenis dra vir die geodinamiese prosesse wat TTG magmas produseer het, en veral vir die diepte van die bron. In die Nelshoogte pluton het trondhjemiet inplasing voor en gedurende (D2)-tektonisme voorgekom en horingblende-draende tonaliet/granodioriet kom voor as intrusiewe proppe binne-in die trondhjemiet. Die geochemiese reeks wat uitgebeeld is deur die ~ 3230 Ma Nelshoogte pluton ondersteun byna die hele reeks wat uitgebeeld is deur al die TTG gesteentes van die BBGT wat gevorm het gedurende die tydsinterval 3550 tot 3230 Ma. U-Pb sirkoon datering openbaar geen merkwaardige verskille in ouderdomme tussen die trondhjemiete en tonaliete van die Nelshoogte pluton nie. Al die ouderdomme lê tussen 3240 en 3220 Ma. A/CNK- en Ti-mafisiteit korrelasies binne die Nelshoogte pluton toon die tipiese gedrag van I-tipe granitiese gesteentes, en bevestig sodoende die metamafiese karakter van die bron, asook die betrokkenheid van ‘n peritektiese granaat en klinopirokseen component in die magmas. Die seldsameaarde-element en spoorelement patroone lyk soos dié van albei ~ 3450 Ma plutons en ander ~ 3230 Ma TTG plutons in die BGGT. Dit stel voor dat hierdie verskillende generasies van TTG magmas genereer was vanaf soortgelyke bronne en ook deur soortgelyke prosesse. Die geochemiese besonderhede stem ooreen met ‘n metamafiese bron wat smelting teen hoë druk ondergaan het. Hierdie TTG bron het fondamenteel verskil van die meer kalium-ryke bron/ne wat die jonger 3100 Ma graniete prodiseer het. In ‘n eenderse manier as ander ~ 3200 Ma TTG gesteentes, stel hoë Zr/Sm en lae Nb/Ta verhoudings in die Baberton TTG gesteentes verder voor dat die Nelshoogte pluton ontstaan het as ‘n groep chemies verskillende magmas. Die protoliete van ~ 3450 Ma plutons en ~ 3200 Ma plutons mag dalk tipies rutiel-draende eklogiet en/of 10 tot 30% granaat draende amfiboliet wees. Die geochemiese aspekte van die Baberton TTGs stel eenderse bron komposisies, maar verskillende drukke van gedeeltelike smelting voor. Vir die ~ 3230 Ma plutons stem die gesteentes van die Badplaas pluton en die Nelshoogte trondhjemiete/tonaliete ooreen met die hoë druk magmas, soos weerspieël deur hoe Sr inhoud, sowel as hoe Sr/Y en (La/Yb)N verhoudinge. In kontras weerspiel die Kaap Valley TTGs en Nelshoogte granodioriet die smelting van ‘n eenderse bron teen matige druk. Verder stel die Hf isotoop data; Hft (+ 0.1 to + 1.9) en TDM model ouderdomme (3330 - 3230 Ma) voor dat die bron gesteentes ~ 20 to 100 Mjr ouer is as die pluton.

Cette thèse correspond à une étude comparative détaillée de trois gisements aurifères birimiens (~ 2 Ga) du craton ouest africain (Syama, Tabakoroni et Tellem), situés sur la ceinture de Bagoé au Mali. La minéralisation se concentre dans les roches où les structures de déformation fragile sont les plus développées (basaltes et métasédiments bréchifiés, microgranite à Tellem) et se développe préférentiellement en bordure des veines. Les sulfures majeurs (pyrite à Syama et pyrite + arsénopyrite à Tabakoroni et Tellem) sont zonés avec : i) un cœur arsénifère riche en inclusions d'albite, d'ankérite et de rutile (accessoirement pyrrhotite); ii) une bordure limpide, globalement moins arsénifère que le coeur mais présentant une fine zonation avec des alternances de zones riches en As et de zones pauvres en As. L'or se présente sous forme d'or invisible inclus dans le réseau cristallin des sulfures, de petits grains individualisés en inclusion dans les sulfures, souvent accompagnés de sulfoantimoniures, notamment la tétraédrite et la chalcostibite, et d'or libre associé au quartz. Les pyrites arsénifères et les arsénopyrites des gisements de la ceinture de Bagoé sont parmi les plus riches en or invisible de tous les gisements d'or de l'Afrique de l'Ouest et tout à fait comparables à ceux de la ceinture d'Ashanti au Ghana. / This thesis presents a comparative study of the Syama, Tabakoroni and Tellem gold deposits, located in the N-S trending Bagoé greenstone belt of Mali. Mineralization is found preferentially along the edges of millimetre- to centimetre-sized quartz, quartz-albite, quartz-ankerite, dolomite-quartz veins developed in tension gaps that formed during brittle deformation. Gold mineralization is mostly associated with pyrite in the three deposits, and also with arsenopyrite at Tabakoroni and Tellem. These sulphides are zoned with (i) an arsenic-rich core containing several albite, ankerite and rutile inclusions (less commonly, pyrrhotite) and (ii) a clear border of finely alternating As-rich and As-poor bands. Gold occurs in the form of i) invisible gold included in their crystal lattices, ii) small individual grains bound to these sulphides, frequently accompanied by sulphoantimonides, mainly tetrahedrite and chalcostibite and iii) free gold associated with quartz. The arseniferous pyrites and arsenopyrites of the Bagoé belt deposits are among the richest in invisible gold in all gold deposits in West Africa and are quite comparable to those of the Ashanti Belt in Ghana.

The mapped area, measuring about 400m2, is situated along the southern margin of the Archaean Kaapvaal Craton south of Melmoth in KwaZulu-Natal and comprises greenstones and metasediments forming a narrow, linear E-W trending and dominantly northerly inclined belt flanked to the north and south by various granitoids and granitoid gneisses which have been differentiated for the first time in this study. This belt is here referred to as the ILANGWE GREENSTONE BELT. The lIangwe Belt rocks are grouped into the Umhlathuze Subgroup (a lower metavolcanic suite) and the Nkandla Subgroup (an upper metasedimentary suite). The former consists of: (a) the Sabiza Formation: a lower amphibolite association occurring along the southern margin of the greenstone belt; (b) the Matshansundu Formation: an eastern amphibolite-BIF association; (c) the Olwenjini Formation: an upper or northern amphibolite-banded chert-BIF association. whereas the latter is sub-divided into: (a) the Entembeni Formation: a distinctive phyllite-banded chert-BIF association occurring in the central and the eastern parts of the belt; (b) the Simbagwezi Formation: a phyllite-banded chert-amphibolite association occurring in the western part of the belt, south-east of Nkandla; (c) the Nomangci Formation: a dominantly quartzite and quartz schist formation occurring in the western part of the belt, south-east of Nkandla. The contacts between the six major tectonostratigraphic formations are tectonic. In the eastern sector of the lIangwe Belt, the lowermost metasedimentary formation, the Entembeni Formation, cuts across both the Sabiza and Matshansundu Formations (the lower formations of the Umhlathuze Subgroup) in a major deformed angular unconformity referred to as the Ndloziyana angular unconformity. In the central parts of the belt, the Entembeni Formation structurally overlies the Olwenjini Formation in what seems to be a major local unconformity (disconformity). In the western sector of the belt, the Simbagwezi Formation occurs as a structural wedge between the lower and upper formations of the Umhlathuze Subgroup. That is, it structurally overlies the Sabiza Formation and structurally underlies the Olwenjini Formation. The uppermost metasedimentary unit, the Nomangci Formation occurs as a complex series of finger-like wedges cutting and extending into the Simbagwezi Formation and in each case showing that the Nomangci Formation structurally underlies the Simbagwezi Formation. This structural repetition of lithological units is suggestive of normal dip-slip duplex structures. Palimpsest volcanic features, such as pillow structures and minor ocelli, indicate that many of the amphibolitic rocks represent metavolcanics, possibly transformed oceanic crust. This is also supported by limited major element geochemistry which suggests that the original rocks were ocean tholeiites. Evidence suggests that the talc-tremolite schists and the serpentinitic talc schists represent altered komatiites. The nature of the metasediments (represented by banded metacherts, quartzites and banded iron formations) and their similarity to those of the Barberton, Pietersburg and Nondweni greenstone complexes suggests that they were formed in relatively shallow water environments. The lIangwe magmatism is represented by different types of granitoids and granitoid gneisses and basic-ultrabasic intrusive bodies. Based on similar geochemical and mineralogical characteristics and on regional distribution, mutual associations and contact relationships, these granitoids and granitoid gneisses can be divided into three broad associations, viz: (a) The Amazula Gneiss - Nkwa/ini Mylonitic Gneiss - Nkwalini Quartzofeldspathic Flaser Gneiss Association: a migmatitic paragneiss and mylonitic to flaser gneiss association of older gneisses of Nondweni age occurring in several widely separated areas and intruded by younger granitoids. (b) The early post-Nondweni Granitoids comprising the Nkwalinye Tonalitic Gneiss (a distinctive grey gneiss intrusive into the greenstones and older gneisses) and the Nsengeni Granitoid Suite (an association of three granitoid units of batholithic proportions flanking the greenstone belt and intrusive into the greenstones, older gneisses and Nkwalinye Tonalitic Gneiss). (c) The late post-Nondweni Granitoids comprising the Impisi-Umgabhi Granitoid Suite, a batholithic microcrystic to megacrystic association of five granitoid phases/units occurring to the north and south of the greenstone belt and intrusive into the greenstones, older gneisses and early post-Nondweni granitoids. Limited major element geochemistry suggests that the granitoids and granitoid gneisses are of calc-alkaline origin and are of tonalitic, granodioritic, adamellitic and granitic composition. An igneous derivation from material located possibly at the lower crust or upper mantle is suggested. At least three major episodes of deformation (01, O2 and 03) have been recognized in the greenstones. During 01, a strong penetrative S1 tectonic foliation developed parallel to the So primary layering and bedding. This period was characterized by intense transpositional layering, recumbent and isoclinal intrafolial folding with associated shearing,thrusting and structural repetition of greenstone lithologies. These processes took place in an essentially horizontal, high strain tectonic regime. The first phase of deformation (OG1) in the migmatitic and mylonitic gneisses was also characterized by recumbent and isoclinal intrafolial folding and is remarkably similar to the 01deformational phase in the lIangwe greenstones. Structural features of the first phase of deformation suggest that it was dominated by formation of fold nappes and thrusts and was accompanied by prograde M1 medium-grade middle to upper amphibolite facies metamorphism. During D2 deformation, the subhorizontal D1 structures were refolded by new structures with steeply inclined axial planes. This resulted in the formation of superimposed Type 3 interference folding in the amphibolitic rocks and large-scale, E-W trending, doublyplunging periclinal folds in the metasediments. These periclinal folds have steeply inclined and overturned limbs and are characterized by narrow, closed elliptical outcrop patterns well-defined by extensive banded ironstones and metacherts. The second phase of deformation in the granitoids (DG 2) was characterized by steeply plunging and steeply inclined small-scale tight to isoclinal similar folds. Large-scale folds are not present in the granitoids. Evidence suggests that the second phase of deformation was a major compressional event which resulted in the large-scale upright, flattened flexural folds. It was accompanied by widespread regional greenschist metamorphism and the intrusion of the early postNondweni granitoids. The third phase of deformation produced steeply plunging small-scale folds on the limbs and axial planes of the pre-existing large-scale F2 folds and upright open folds in the granitoid terrain. This episode was characterized by the emplacement of the late postNondweni granitoids (along the D2 greenstone boundary faults) and is associated with two significant events of prograde M3 upper greenschist facies metamorphism and retrograde M3 lower greenschist facies metamorphism. Post-D3 deformation is characterized by late cross-cutting faults and the emplacement of younger basic - ultrabasic bodies. / Thesis (Ph.D.)-University of Natal, 1997.

The Beattie syenite is composed of a series of lenticular bodies of syenitic rocks, situated immediately north of the Porcupine-Destor fault zone in the town of Duparquet, approximately 32 km north of Rouyn-Noranda in the Abitibi Subprovince. The principal body is 3.3 km long and 470 m in width and is flanked by a series of smaller lenses to the south and northeast. The intrusion has been zircon dated at 2682±1Ma and 2682.9±1.1 Ma and hosted the major part of the Au-mineralization of the now defunct Beattie mine, which was an important producer of gold in the area from 1933 to 1956 (9.66 Mt at 4.88 g/t Au). A total of 5 petrographic units are defined here, on the basis of field relationships, macroscopic textures, petrology and mineralogy: 1- The porphyritic Beattie syenite unit is composed of 2% to 10% of tabular sub- to anhedral feldspar phenocrysts about 2 mm to 10 mm in size, set in a red feldspathic and aphanitic matrix. This unit can be strongly cataclastic with abundant hydrothermal minerals. 2- The equigranular magnetite-bearing syenite unit includes few feldspar phenocrysts, about 2 mm to 10 mm in a fine-grained matrix. It is characterized by unaltered titanite, epidote, hornblende porphyroblasts and is the only unit with actinolite replacing clinopyroxene. 3- The porphyritic Central Duparquet syenite unit contains between 2% - 25% of coarse equant euhedral feldspar phenocrysts, about 5 mm to 16 mm in size, in a red or sometimes grey aphanitic matrix. 4- The megaporphyritic syenite unit is composed of very coarse alkali feldspar phenocrysts, typically 1 cm to 6 cm across, in a red aphanitic matrix. The phenocrysts often form a glomeroporphyritic texture. 5- The lath syenite unit occurs as numerous ~m-width thin dykes, which cross-cut all other petrographic units. These dykes display a characteristic trachytic texture, as defined by the preferential alignment of alkali feldspar laths, which are typically 1 cm to 3 cm in a grey or red aphanitic matrix. Petrology and geochemistry investigations revealed that the syenite intruded into the older 2720-2718 Ma volcanic Deguisier Formation and the <2687±2 Ma sediments of the Porcupine Group. Detailed geochemical analysis revealed that the Deguisier Formation is composed of three units, forming a complete tholeiitic suite. The Deguisier Formation is proposed here to have been produced in a volcanic arc setting. Detailed petrological, mineralogical and geochemical studies indicate that, the syenite is part of the alkaline series and is metaluminous to peraluminous. The syenite intruded at shallow depths through a sequence of injections, yielding the five comagmatic units. The syenite and country rocks were then subjected to a series of hydrothermal alterations and brittle deformation events, combined with metamorphism to the greenschist facies. The Au-mineralization in this region is attributed to the hydrothermal alteration with brittle deformation.

Thèse (D.R.Min.) -- Université du Québec à Chicoutimi, 1992. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Sc.T.)-- Université du Québec à Chicoutimi, 1992. / Bibliogr.: f. 68-73. Document électronique également accessible en format PDF. CaQCU