Dissertations / Theses: 'Precambrien'

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DOBEREINER, PALERMO NELY. "Le gisement aurifere precambrien de posse (goias, bresil) dans son cadre geologique." Paris, ENMP, 1996. http://www.theses.fr/1996ENMP0627.

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L'or du gisement de posse est a grain tres fin (2 a 20m), etroitement associe a des tellurures, et en relation avec une mineralisation disseminee sulfuree (pyrite, chalcopyrite, pyrrhotite) et oxydee (magnetite). Les reserves sont estimees a 1,7 mt a 2,24 g/t au. La roche porteuse de la mineralisation est un orthogneiss a microcline interprete comme une roche granitique a tendance alcaline (type a), mise en place dans la sequence volcano-sedimentaire mara rosa (mr), composee principalement d'amphibolites et de metagrauwackes. L'orthogneiss a subi, comme toute la sequence mr, des plissements dont les deux principaux sont la phase 1, accompagnee d'un metamorphisme de degre amphibolite moyen, et la phase 2 responsable de la structuration de la sequence mr en trois ceintures interpretees comme des synclinaux. Les roches originelles des amphibolites de la sequence mr sont pour l'essentiel des roches volcaniques basiques de type calco-alcalin et tholeiitique, correspondant a un magmatisme de zone mobile. La mineralisation se localise au toit du corps granitique gneissifie. La zone mineralisee se caracterise par la superposition de deux evenements hydrothermaux principaux: 1) lessivage pre-metamorphisme et deformations principales, donnant des roches a kyanite-sillimanite et/ou muscovite, et depot de pyrite allongee dans la foliation, chalcopyrite et pyrrhotite ; 2) alterations post-metamorphisme, a scapolite, actinote, biotite verte, carbonate, quartz, albite, sericite, muscovite, plus intenses dans le gisement et associees a la mineralisation epigenetique a au-te et sulfures-magnetite. Dans la ceinture orientale, la sequence mr renferme de nombreux indices a au-cu, qui jalonnent notamment la zone alteree precocement au toit du magmatisme acide et se trouvent donc dans un contexte comparable a celui de posse

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Grégoire, Vincent. "CARACTERISATION PETROSTRUCTURALE DU SOCLE PRECAMBRIEN DE MADAGASCAR (PAYS BETSILEO, PROVINCE DE FIANARANTSOA) : METHODOLOGIE ET IMPLICATIONS GEODYNAMIQUES." Phd thesis, Université Paul Sabatier - Toulouse III, 1999. http://tel.archives-ouvertes.fr/tel-00367741.

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Madagascar est situé dans la zone de collision entre Est- et Ouest-Gondwana. Ce travail est consacré à la caractérisation pétrostructurale de la partie centre sud (Pays Betsileo, Province de Fianarantsoa). La première partie du travail développe les aspects méthodologiques. L'Anisotropie de Susceptibilité Magnétique (ASM) des granites de Madagascar est contrôlée par la magnétite. Des grains de magnétite rapprochés développent des interactions susceptibles de modifier l'ASM (Grégoire et al., 1995). L'étude par traitement d'images des grains de magnétite montre que c'est l'anisotropie de forme de grains allongés qui est principalement responsable de l'ASM (Grégoire et al., 1998). Les deux autres outils employés sont l'analyse d'image et la thermobarométrie. Deux signatures structurales distinctes sont reconnues dans la région des granites andringitréens. (D1) se caractérise par des foliations moyennement pentées vers l'ouest et des linéations à faible plongement OSO; elle est contemporaine de la mise en place de ces granites de type stratoïde qui s'accompagne d'un métamorphisme HT-BP dans l'encaissant. (D2) se caractérise par des foliations fortement pentées et des linéations NS subhorizontales dans des bandes de cisaillement anastomosées d'échelle kilométrique. Plus au nord, une série supracrustale schisto-quartzo-carbonatée (SQC) est conservée sur le socle granitique qui présente la structure D1, alors que la SQC montre une structure différente associée à des fabriques d'axes c de quartz indiquant un déversement vers l'est. La structure D1 est semblable à celle qui a été décrite par Nédélec et al. (1994), au nord d'Antanarivo. Il s'agirait de la phase d'extension post-collision datée à 630 Ma par Paquette & Nédélec (1998). La structure D2 résulterait d'un épisode de convergence tardi-panafricain vers 550 Ma. Seule la SQC aurait gardé les traces d'un épaississement crustal antérieur à 650Ma et qui pourrait correspondre au début de la collision panafricaine.

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Ennih, Nasser. "Le magmatisme precambrien du nord de la boutonniere de zenaga (anti-atlas marocain) : etude petrologique et structurale." Toulouse 3, 1987. http://www.theses.fr/1987TOU30129.

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Description des formations metamorphiques constituant le segment de chaine eburneenne dans lequel se developpe le plutonisme. L'etude mineralogique et geochimique du pluton d'azguemerzi met en evidence une zonation avec des tonalites et des granites entourant un corps principal de monzongranite porphyroide. L'analyse structurale indique une mise en place suivant un diapir allonge. L'etude des granites d'assersa, d'ait daoui et surtout de tazenakht met en evidence des caracteres hyperalumineux. Une foliation intense est tres developpee dans le dernier granite. Etude des roches basiques associees aux granites precedents ainsi que des nappes ignimbritiques scellent le cycle precambrien. Les principaux types de roches montrent la complexite des processus mgamatiques

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DA, MATHA SANT'ANNA MARCEL ANTON. "Etudes biogeographiques et activites humaines d'un secteur du socle precambrien au benin (zou-nord). Une approche morphodynamique." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR10019.

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Etude biocenotique basee sur la morphodynamique d'un secteur de roches cristallines et cristallophyliennes au benin pour evaluer les problemes de sante et de production rencontres par les habitants. Une premiere solution : localiser et exploiter les infero-flux par des puits pratiques et peu couteux completes par les citernes. . . Moyens efficaces pour lutter contre les maladies liees a l'eau de consommation telle la dracunculose. Une deuxieme solution : le developpement de la complementarite entre l'elevage et la production agricole accroitra la production agricole avec l'incitation a la culture attelee. Une troisieme solution : sensibilisation des paysans a cultiver et a consommer davantage fruits et legumes varies pour eviter les maladies liees a la sousnutrition Biocenotic morphodynamic research in benin on one part of precambrian socle for walue people health and production problems. As solutions : - locate and manage underflows, sinking wells and building water tanks for contest water diseases as dracunculosis ; - promote agriculture and breedins complementary with plough tilling ; - incite inhabitants to grow and consume also more somme fruit and vegetables for themselves against bad nutrition damages. On the whole, this proves the area prospected has important development potentia- lities. Human interventions musn't deteriorate them, particulary its paleo-soils

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Mayaga-Mikolo, Francis. "Chronologie des evenements sedimentaires, magmatiques et tectono-metamorphiques du precambrien d'afrique centrale occidentale (gabon) : tectogenese ogooue et heritage archeen." Clermont-Ferrand 2, 1996. http://www.theses.fr/1996CLF21824.

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Le precambrien du gabon est compose de terrains archeens des massifs du nord-gabon et du chaillu, des formations reputees d'age paleoproterozoique de l'ogooue, des sediments paleoproterozoiques du francevillien, des plutons d'age eburneen du mayombe (ou chaine ouest-congolienne). Des datations radiometriques (pb-pb, u-pb, rb-sr et sm-nd, ar-ar) ont ete utilisees afin de contraindre l'age des evenements sedimentaires, magmatiques, tectoniques et metamorphiques qui ont affecte ces differentes entites. L'etude geochronologique montre que l'accretion des terrains paleoproterozoiques se fait autour des noyaux archeens dont les plus vieux temoins, d'age anterieur a 3100 ma, seraient presents dans les monts de cristal au nord-gabon. L'histoire archeenne se deroulerait ensuite de la facon suivante: entre 3100-3000 ma: premier metamorphisme de haut grade ; 3000-2950 ma: mise en place diachrone des greenstone belts. Durant la meme periode et jusqu'a 2850 ma des intrusions granitiques a tonalitiques se mettent en place. Elles provoquent dans l'encaissant, soit des recristallisations dans des conditions granulitiques, soit des retromorphoses. L'evolution archeenne s'acheve entre 2800 et 2500 ma, avec la mise en place des ultrabasiques de kinguele, des leucogranites, des pegmatites, des monzonites et des granites. Ces processus diapiriques fini-archeens de grande ampleur associes a une tectonique verticale vont favoriser l'apparition, a partir de 2500 ma, des premiers bassins sedimentaires tels que l'ogooue. Ce dernier sera ensuite engage dans un orogene paleoproterozoique qui s'accompagne d'une remobilisation de materiel archeen. Les trois phases tectono-metamorphiques d1, d2 et d3 responsables de sa structuration en domaine orogenique collisionnel sont respectivement posterieure a 2440 ma, syn-2120 ma et syn-a post 2040-2000 ma. Parallelement les metabasites de l'ogooue, reputees pre-orogeniques s'avereraient etre d'age archeen. Les contraintes ar-ar sur l'age des mineralisations d'eteke associees a l'evolution tectono-metamorphique du domaine de l'ogooue n'ont revele que des ages de refroidissement autour de 1850-1870 ma. Les sediments fluvio-deltaiques du francevillien moyen a superieur (2050-1780 ma) s'individualisent a la fin de cette evolution tectonique collisionnelle, en position d'avant-pays. Parallelement, les investigations rb-sr dans la faille syn-d3 de l'ikoye-ikobe ont revele un rejeu panafricain de celle-ci vers 530 ma. Enfin, la comparaison de l'histoire geologique de la partie occidentale du craton du congo avec le craton de sao francisco (bresil), montre qu'en ce qui concerne les blocs archeens, les plus vieux temoins de l'histoire archeenne precoce ne sont nettement reconnus qu'au bresil (3200-3400 ma), en revanche au paleoproterozoique, de part et d'autre de l'atlantique, les processus geodynamiques et orogeniques sont similaires

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EL, ABBASS TIHAMA. "Comparaison de methodes d'interpolation de donnees geophysiques. Apport de la gravimetrie a l'etude d'un bassin precambrien superieur : bassin du gourma (mali)." Paris 6, 1993. http://www.theses.fr/1993PA066743.

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L'objet principal de ce travail est l'etude de la structure profonde du bassin precambrien du gourma au mali, a partir des donnees gravimetriques. Il s'integre dans l'etude plus globale du couloir lineamentaire guineo-nubien qui traverse l'ensemble du craton ouest africain d'est en ouest. Les resultats, de l'analyse spectrale des profils de l'anomalie de bouguer puis des modelisations, suggerent un amincissement crustal et lithospherique, compatibles avec l'hypothese de la naissance d'un rift. Cette interpretation est confortee par des manifestations d'une activite tectonique recente dans cette zone qui connait des mouvements de reactivation depuis le tertiaire. Cependant, la gravimetrie seule ne permet pas d'eliminer une seconde hypothese, celle d'une flexion de la lithosphere sous l'effet d'une surcharge due a l'intrusion de roches denses et au remplissage sedimentaire. Il faudrait faire appel a des mesures de flux de chaleur et a la sismologie pour trancher entre les deux hypotheses. Une anomalie gravimetrique locale, celle du lac faguibine, situee dans le prolongement ouest de l'anomalie du gourma a egalement ete interpretee. Les resultats s'integrent bien dans l'ensemble des donnees geologiques et geophysiques existantes et tendent a favoriser l'hypothese d'une activite recente. Ces resultats importants du point de vue geodynamique, sont precedes d'une etude methodologique sur le traitement et l'interpretation des donnees gravimetriques. En particulier le probleme de l'interpolation de donnees irregulierement reparties dans l'espace est traite, par la comparaison de cinq techniques differentes. La technique proposee par inoue (1986) basee sur l'approximation par elements finis de la deformation d'une plaque sous tension, s'est averee la plus performante. Elle a ete retenue pour l'etude des donnees qui font l'objet de ce memoire

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Boukeke, D. B. "Structures crustales d'afrique centrale deduites des anomalies gravimetriques et magnetiques : le domaine precambrien de la republique centrafricaine et du sud cameroun." Paris 11, 1994. http://www.theses.fr/1994PA112185.

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Cette etude se propose d'interpreter les anomalies gravimetriques magnetiques du domaine precambrien de la republique centrafricaine et du sud cameroun. La reduction au pole des donnees magnetiques de la r. C. A. Montre que l'anomalie magnetique de bangui est l'addition de deux anomalies majeures qui recouvrent respectivement une unite archeenne et la chaine proterozoique inferieure de bogoin-ouham. La carte reduite a l'equateur suggere l'existence des sources ayant un allongement ew notable et des aimantations essentiellement induites. Les anomalies magnetiques se superposent a deux importantes signatures gravimetriques. Les zones de contacts entre le craton du congo et les zones mobiles panafricaines du sud cameroun et de l'est de la r. C. A. Montrent deux signatures gravimetriques inversees, caracterisees par un gradient majeur qui separe une anomalie positive, d'une anomalie negative de grandes longueurs d'ondes. L'interpretation quantitative montre que: le domaine archeen est traverse par une faille intracrustale ew a pendage nord qui recoupe en profondeur un large corps dense et magnetique. Ces deux structures sont integrees dans une evolution de type granite-greenstone belts. Dans la region de bogoin-ouham, le bloc crustal reactive au proterozoique inferieur, d'orientation submeridienne, se deverse vers l'est le long d'une discontinuite assimilee a une suture de collision. En profondeur, un corps dense et magnetique s'allonge parallelement aux unites de la chaine. La chaine de bogoin-ouham est interpretee comme une chaine de collision de type rift-intracratonique. Au sud cameroun et dans l'est de la r. C. A. , le craton plonge sous le domaine reactive au panafricain le long d'une discontinuite intracrustale. Les structures crustales modelisees presentent des caracteristiques deja reconnues ailleurs, notamment en afrique de l'ouest, qui permettent de les interpreter comme des structures issues d'une compression et d'une collision continentale

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Placet, Jack. "Kolwezi et le Katanguien : observations et synthèses structurales." Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPL050N.

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Ce mémoire concerne une succession de faits géologiques propres au site précambrien cupro-cobaltifères de Kolwezi, province du Shaba, zaïre. Il décrit le roan dolomitique qui affleure sous forme d'une méga-brèche avec de grands écaillages entourés de diverses brèches. Une ultime brèche conglomératique évaporitique est en enveloppe externe. L'ensemble est en position anormale au milieu dukundelungu détritique, plus jeune et peu dérangé. Ces méga-brèches ont pu être mises en place par diapirisme. La cinétique est essentiellement verticale (excepte pour les masses atteignant la surface) et indépendante de contraintes de l'encaissant régional. Les mouvements ont commencé par différents décollements et se sont terminés par l'affleurement de plusieurs piles de sédiments du roan. En surface, les structures tectoniques zonaires apparaissent superposées aux allures sédimentologiques d'origine. La province du katanguien est présentée comme étant une plateforme installée sur un socle fracture. Pendant la période du roan, cette plateforme se comporte comme une vaste région épicontinentale avec de petits bassins de hauts-fonds contrôlés par des linéaments en relation avec le socle zambien. Cette région évolue comme un vaste sillon organise en quelques couloirs subsidents dont les organisations en rifts peuvent se croiser. Cette évolution guide les minéralisations précoces installées sur les quelques sites evaporitiques volcanoclastiques à proximité des fracturations du socle. Des décollements des niveaux lacunaires sont déclenchés par la tectonique de socle. Leurs déplacements, aidés par les caractéristiques sédimentologiques et mécaniques du roan, sont d'autant plus favorises qu'il existe un épais recouvrement de kundelungu. Des allures extrusives se manifestent en surface, répétées régionalement, et de plus en plus exacerbés vers l'ouest. Les modifications supergenes, altérations et remobilisations font partie de la même lignée de phénomènes. Écoulements de brèches, minéralogies complexes et lithologies irrégulières s'apparentent aux évolutions de caprocks de diapirs

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HALLALOUCHE, DJAMEL. "Etude de l'alteration du socle precambrien a la peripherie du bassin de tin-seririne (hoggard-sud, algerie) et mineralisations uraniferes et thoriferes associees." Rennes 1, 1995. http://www.theses.fr/1995REN10003.

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Dans le hoggar central, le socle constitue essentiellement de granites pan-africains (600-500 ma) et de roches metamorphiques (2100 ma) est recouvert par des terrains paleozoiques (les tassilis). La surface infratassilienne qui separe le socle de la couverture sedimentaire est une surface d'erosion tres remarquable par sa planeite et sa superficie. Le socle est affecte d'une alteration irreguliere allant de quelques centimetres a quelques metres d'epaisseur. Une etude petrographique et mineralogique a ete effectuee en bordure du bassin de tin-seririne et une etude geochimique a ete realisee sur 9 profils. Cette etude montre l'importance du degre d'alteration caracterisee par la formation exclusive de kaolinite et la destruction quasi totale des mineraux de la roche mere mis a part le quartz et quelques reliques de micas. Les oxydes et les hydroxydes se presentent soit a l'etat de taches plus ou moins importantes soit sous forme de cuirasses. Des silicifications secondaires se manifestent sous forme d'aureoles d'accroissement autour des grains de quartz ou sous forme de silcretes. Cette alteration a probablement debute a la fin du precambrien mais elle s'est poursuivie bien apres le depot de la serie sedimentaire: en effet en l'absence de vegetation, le climat chaud et humide a provoque une intense desagregation granulaire du socle aboutissant a une pediplaine. Mais les caracteres mineralogiques et petrographiques (kaolinite, oxydes de fer, silifications) observes dans les conglomerats et gres de la couverture sedimentaire et qui sont identiques a ceux du socle altere sous-jacent, montrent que la plupart des transformations se seraient produites sous la couverture sedimentaire permeable qui a permit la circulation de nappes d'eau. Les granites affleurant en majorite en bordure du bassin, sont des granites metalumineux a faiblement peralumineux et sont consideres comme des granites fertiles en uranium et seraient une source potentielle pour les mineralisations uraniferes et thoriferes trouvees dans le socle granitique altere et le conglomerat de base

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Poidevin, Jean-Louis. "Les ceintures de roches vertes de la republique centrafricaine (bandas, boufoyo, bogoin, mbomou). Contribution a la connaissance du precambrien du nord du craton du congo." Clermont-Ferrand 2, 1991. http://www.theses.fr/1991CLF2E423.

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Apres un rappel critique des grandes lignes de la geologie centrafricaine, sont decrits trois ceintures de roches vertes et le complexe du mbomou. Le greenstone des bandas est riche en quartzites ferrugineux rubanes (qfr) et montrent des tholeiites appauvries et enrichies en lree, ainsi que de rares komatiites serpentinisees (a la base de la serie) et des laves calco-alcalines (au sommet). Le metamorphisme principal (p=5 kb, t=550c est date a 2,930. 09 ga. Les trondhjemites se sont mises en place a 2,90,2 ga et les granites calco-alcalins a 2,70,1 ga. Le greenstone de boufoyo montre des tholeiites enrichies en lree a affinites de basaltes d'arc ou de t-morb. Il est recoupe par des trondhjemites datees a 2,630,15 ga. Le greenstone de bogoin est riche en ultrabasites. L'unite de base comporte des al-depleted komatiites et des tholeiites enrichies. L'unite intermediaire presente des grauwackes provenant de la destruction de rhyolites calco-alcalines. L'unite superieure montre des al-normal komatiites et des boninites. Le tout est recouvert par des q. F. R. Les deux unites a ultra-basites sont datees a 2,40,3 ga et 2,20,2 ga. Le complexe ancien du mbomou (tholeiites, orthogneiss trondhjemitiques ou granitiques et paragneiss) a subi un metamorphisme granulitique vers 3,2 ga et une retromorphose a 2,980,01 ga. Ces donnees permettent de definir un domaine archeen (centre de la r. C. A. ) et un fosse proterozoique inferieur (w du pays). Un schema lithostratigraphique de l'archeen du nord du craton du congo est propose. Un contexte de rifts intra-continentaux est propose pour les greenstones archeens

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Marin, Carbonne Johanna. "Composition isotopique de l'oxygène et du silicium des cherts Précambriens : implications Paléo-environnementales." Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL086N/document.

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Les cherts, roches siliceuses, sont souvent considérés comme des marqueurs des conditions environnementales de la Terre primitive. Ces roches sont constituées de quartz sous différentes formes dont le quartz microcristallin ou microquartz est la forme majoritaire. Le but de cette thèse est d'étudier à l'échelle micrométrique les compositions isotopiques de l'oxygène et du silicium des différentes formes de silice dans des cherts d'âges variés, allant de 3,5 à 1,9 Ga afin de mieux comprendre l'origine et le mode de formation de ces roches et d'essayer d'améliorer les reconstructions des températures océaniques du Précambrien. Les mesures isotopiques, réalisées à la sonde ionique ims 1270, ont une précision meilleure que 0,2 ‰ pour le [delta]18O et de l'ordre de 0,3 ‰ pour le [delta]30Si. Ces analyses isotopiques ont été combinées avec l'analyse des éléments traces (B, Na, Mg, Al, K, Ca, Ti, Fe) avec la sonde ionique 3f, avec une étude pétrographique détaillée du microquartz et avec l'analyse des inclusions fluides des veines de quartz. Le résultat principal est la mise en évidence de grandes gammes de variation du [delta]18O (entre 1 ‰ et 14?‰) et du [delta]30Si (entre 2 ‰ et 5 ‰) à l'échelle micrométrique dans le microquartz. La gamme de variation du [delta]18O a pu être interprétée dans les échantillons datés de 1,9 Ga comme témoignant de l'histoire diagenètique de ces roches. Cette gamme permet, en corrigeant de l'effet de la diagenèse, de reconstruire des températures océaniques à 1,9 Ga entre 37 et 52°C, ce qui laisse suggérer un océan assez chaud au Précambrien si ces échantillons sont représentatifs de conditions globales. Dans le cas des échantillons datés à 3,5 Ga, les variations de [delta]30Si et de concentrations en éléments traces apportent des informations sur les origines variées des cherts. Enfin, l'effet des circulations fluides sur les compositions isotopiques du microquartz a été caractérisé par l'analyse isotopique du [delta]18O et du [delta]30Si et par l'étude des inclusions fluides. Il est démontré que dans certains cas le [delta]18O du microquartz peut être entièrement rééquilibré avec les fluides hydrothermaux ou métamorphiques. L'approche développée dans cette thèse devra dans le futur être appliquée systématiquement à l'étude des cherts aux fins de reconstructions paléo-environnemantales Cherts, which are siliceous rocks, are considered as possible proxies of paleo-environmental conditions of the Early Earth. These rocks contain various forms of quartz, microquartz being the predominant one. The study of oxygen and silicon isotopic composition in the various forms of silica in cherts of different ages, from 3,5 Ga to 1,9 Ga, allowed to better understand the origin and the formation of these rocks and allowed to try to reconstruct paleo-temperatures for Precambrian seawater. Isotopic measurements were obtained with the ims 1270 multicollector ion microprobe with a precision better than 0,2 ‰ for [delta]18O and of ˜ 0,3 ‰ for [delta]30Si. These analyses were combined with the measurement of traces elements concentrations (B, Na, Mg, Al, K, Ca, Ti, Fe) with the ims 3f ion microprobe, with a petrographical study of microquartz and with the study of fluid inclusions in quartz veins. The major result is the existence at a micrometer scale of a large range of variations for [delta]18O (between 1 ‰ to 14?‰) and [delta]30Si (between 2‰ to 5‰). In the Gunflint cherts, the range of [delta]18O variation has been interpreted as due to diagenesis and has been used to reconstruct oceanic paleo-temperatures. The calculated temperatures range from +37°C to +52°C, suggesting an hot ocean during the Precambrian era if Gunflint cherts are representative of global environmental conditions. The [delta]30Si variations associated with that of trace elements concentrations allow to constrain the various origins of these cherts. The effect of fluid circulations on the isotopic compositions has been characterized by [delta]18O and [delta]30Si analyses and by fluid inclusions study. It is shown that in some cases the [delta]18O value of microquartz can be totally re-equilibrated with the hydrothermal or metamorphic fluids. The approach developed in this thesis will be decisive in future studies of Archean cherts for paleotemperature reconstructions

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Dodd, Matthew S. "Biosignatures in Precambrian sedimentary rocks." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10055383/.

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The overarching goal of this work was to trace the origins of organic matter as a possible biosignature for early life on Earth. This work documented the petrological, structural, isotopic, elemental and molecular properties of organic matter, in a suite of sediments ranging from the Eoarchean to the Phanerozoic. Particular attention was paid to iron formations which form a major part of the Precambrian sedimentological record. Optical and micro-Raman spectroscopy were used to document the petrological occurrences of organic matter and its associated diagenetic features. Focused ion beam and transmission electron microscopy were used to detail the nanoscale structures of the organic matter. Mass spectroscopic techniques were utilised to measure the isotopic, elemental and molecular properties of organic matter and its petrographically associated carbonate. The timing and possible mechanisms of organic matter formation were investigated and evaluated, against the observed attributes of the organic matter. This work has documented organic matter forming key mineral associations with apatite and carbonate, which point to the diagenetic recycling of biogenic carbon. The diagenetic cycling of organic matter is proposed, to fuel the formation of granules during organic matter, iron and sulphur cycling. This cycling is hypothesised to lead to heterogeneity in organic matter structure and preservation in sediments. Additionally, this work has demonstrated that fluid deposited graphite in metamorphosed sediments may represent redistributed, syngenetic organic matter, shedding light on the controversial origins of graphite biosignatures in Earths oldest rocks. Finally, a detailed study of microfossil structures and their associations with organic matter and biominerals in iron formations was conducted to provide evidence for the preservation of Proterozoic microfossils, and the earliest signs of life on Earth.

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13

Latham, Andrew James. "The Precambrian/Cambrian transition in Morocco." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316342.

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14

Williams, Elsie Joy Carleton University Dissertation Geology. "Precambrian plate tectonics; a geodynamic approach." Ottawa, 1986.

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15

Hira, Hethendra Gangaram. "The Precambrian metallogeny of Kwazulu-Natal." Thesis, Rhodes University, 1998. http://hdl.handle.net/10962/d1005605.

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The Precambrian rocks of KwaZulu-Natal comprise the Archaean granite-greenstone remnants of . the Kaapvaal craton and Late Archaean volcanics and sediments of the supracratonic Pongola Supergroup. These Archaean rocks have been intruded by numerous mafic/ultramafic complexes and voluminous granitoid intrusives of various ages. To the south, the basement rocks are represented by the Mid- to Late-Proterozoic Natal Metamorphic Province (NMP). The NMP comprises three discontinuity-bound tectonostratigraphic terranes. These are, from north to south, the Tugela, Mzumbe and Margate Terranes. The Tugela Terrane has been interpreted as an ophiolite suite that was thrust northwards onto the stable Archaean craton as four nappe structures. Continued thrusting resulted in the two southern terranes being thrust northwards over each other, resulting in numerous sinistral transcurrent shear zones and mylonite belts. The greenschist facies Tugela terrane has been intruded by mafic-ultramafic complexes, alpine serpentinites, plagiogranites and a number of alkaline to peralkaline granitoids. The Mzumbe and Margate Terranes comprise arc-related, felsic to mafic supracrustal gneisses and metasediments that were intruded by syn-, late- and post-tectonic granitoids. Mineralisation in the granite-greenstones consists of structurally-hosted lode-gold deposits. These deposits have many characteristics in common with lode-gold deposits found in other granitegreenstone terranes throughout the world. The Nondweni greenstones also contain volcanogenicrelated massive sulphide deposits. The Pongola Supergroup is host to lode-gold mineralisation and placer gold mineralisation. These placer deposits have been correlated with deposits found in the similarly-aged Witwatersrand Basin in an adjacent part of the craton. The metallogeny of the NMP can be described in relation to the various stages in the tectonic evolution of the belt. The initial, rifting and extension-related stage was characterised by arcrelated magmatism and volcanic arc activity. Alkali basalt magmatism due to hot-spot activity in the oceanic basin in which the Tugela Terrane initially accumulated, produced magmatic segregation deposits, while volcanic-arc activity is responsible for the submarine-exhalative massive sulphide mineralisation. All the mineralisation within the NMP is structurally-related. These thrusts and shear zones were developed during obduction and thrusting during the NMP event, and created the paths necessary for the migration of mineralising fluids. Alpine-type ophiolite deposits were also emplaced along these zones. Epigenetic, shear zone-hosted gold mineralisation occurs in the Tugela and Mzumbe Terranes. Mineralisation occurs within quartz veins and is also disseminated within the sheared host-rocks. The Mzumbe Terrane also contains small showings of massive sulphide deposits that were related to volcanogenic exhalative processes during the formation of this terrane. Potential for finding further mineralisation of this type appears to be good. The massive sulphide deposits formed early in the evolution of the belt, and were deformed and metamorphosed during the later accretionary processes. The southernmost Margate Terrane is characterised by a lack of metalliferous mineralisation, but hosts the extensive, and economically important, limestone deposits of the Marble Delta. The recently discovered spodumene-rich pegmatite deposits of this terrane may also be considered for exploitation. Post-collisional magmatism and metamorphism resulted in extensive rapakivi-type granite/charnockite plutons

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Latiff, Richard Samuel Abdul. "Structural and tectonic evolution of the Marampa Group Fold Thrust Belt, northwestern Sierra Leone, West Africa." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239966.

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17

Adetunji, Ademola Quadri. "Resistivity structure of the Precambrian Grenville Province, Canada." Tectonophysics, 2014. http://hdl.handle.net/1993/23450.

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As part of the southern Ontario POLARIS project, this thesis uses magnetotelluric methods to investigate the lithospheric architecture of the Proterozoic Grenville Province and its margin with the Archean Superior Province. The first multi-dimensional crustal and lithospheric resistivity images for this region are presented. The resistivity structure of the Phanerozoic sedimentary rocks in the lower Great Lakes region was determined using 1-D methods. The responses are strongly affected by a 20-23 S conductive layer within the sedimentary rocks, interpreted to be associated with Upper Ordovician shale units. This layer excludes resolution of resistivity structure of underlying crust. The resistivity structure of the Precambrian crust and lithosphere was determined using 2-D methods. Different strike azimuths were determined for the crust, the upper lithospheric mantle and the deeper mantle layer. The crustal resistivity model for a profile from 50oN79oW to 43oN76oW images resistive Laurentian margin rocks dipping southeast to the base of the crust, bounded by the Grenville Front and the Central Metasedimentary Belt Boundary Zone. In a 2-D model of the mantle lithosphere for the same profile, a conductor at 70-150 km depth, located along-strike from the Mesozoic Kirkland Lake and Cobalt kimberlite fields, is interpreted to be due to mantle re-fertilization. Results from multiple MT profiles indicate conductive (<10 Ω.m) lithospheric mantle beneath the Central Metasedimentary Belt and show that the northwestern Grenville Province is characterized by large-scale, resistive lithosphere (>10,000 Ω.m) extending for about 300 km beneath the Grenville Province and 800 km along strike. Lithospheric thickness is interpreted to be 280 km; local decreases in this depth are attributed to refertilization of the lower mantle lithosphere by fluids associated with Cretaceous kimberlite magmatism. Anisotropic 2-D modeling reveals minimal electrical anisotropy (<10%) at mantle depths in contrast to the factor of 15 anisotropy determined in earlier 1-D studies. This result suggests that observed MT response anisotropy is caused by large-scale structures. Strike direction in the upper lithospheric mantle is interpreted to be related to the Archean fabric of the Superior craton and in the deeper, conductive, mantle it is interpreted to have been established in the Cretaceous.

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18

Hird, Kevin. "Petrography and geochemistry of some Carboniferous and Precambrian dolomites." Thesis, Durham University, 1985. http://etheses.dur.ac.uk/1674/.

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Hyslop, Ewan Kennedy. "Strain-induced metamorphism and pegmatite development in the Moine rocks of Scotland." Thesis, University of Hull, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341013.

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20

Maurice, Charles. "The Precambrian mafic magmatism of the Northeastern Superior Province, Canada." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66736.

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Major, trace and rare earth elements (REE), along with Nd isotopes and U-Pb ages, were determined for Archean greenstone belts (2.88-2.72 Ga) and Paleoproterozoic mafic dyke swarms (2.51-2.00 Ga) of the Northeastern Superior Province (NESP) of Canada in order to gain insights on the nature of mafic magmas across the Precambrian. Geographically separate, but coeval (2.78 Ga), greenstone assemblages with distinctive Fe-tholeiites occur across a large surface area of the NESP. This geographic separation, along with the numerous inheritance ages of greenstone lithologies that replicate those of older volcanic-plutonic assemblages, are consistent with these belts being the remnants of an extensive autochthonous mafic volcanic cover sequence. An increase of Th/Nb ratios in light REE-enriched basalts reflects a change in the nature of coeval crustal contaminants, from tonalite-trondhjemite prior to 2.75 Ga, to granite-granodiorite afterwards. The isotopically-enriched character of these magmas after 2.75 Ga implies more extensive contamination by a felsic crust affected by regional partial melting, succeeding the amalgamation of the Hudson Bay (TDM 4.3-3.1 Ga) and Rivière Arnaud (TDM < 3.1 Ga) terranes. Paleoproterozoic mafic dyke swarms follow the stabilization of the Archean crust. The magmas of most dykes are sourced in fertile lherzolite at ~1.5 GPa, but others are either sourced from deep (~5 GPa) lherzolite or pyroxenite, Fe-rich mantle, or harzburgite. The presence of all dyke types within the older Hudson Bay Terrane reflects the heterogeneous nature of its lithospheric mantle. All contain a crustal component in the form of an increase in La/Yb with Zr/Nb ratios, and negative eNd values. In contrast, voluminous 2.2 Ga dykes of the Rivière Arnaud Terrane display an increase in La/Yb with a decrease in Zr/Nb ratios, and positive eNd values indicative of an alkaline mantle component similar to that of Pa Les éléments majeurs, traces et du groupe des terres rares (ÉTR), ainsi que les isotopes du Nd et des âges U-Pb, ont été déterminés pour les ceintures de roches vertes archéennes (2.88-2.72 Ga) et pour les essaims de dykes mafiques paléoprotérozoïques (2.51-2.00 Ga) du nord-est de la Province du Supérieur (NEPS) du Canada, afin de définir la nature des magmas mafiques au Précambrien. Dans les ceintures de roches vertes archéennes, des assemblages géographiquement séparés, mais contemporains (2.78 Ga) et contenant des tholéiites ferrifères distinctives, sont reconnus sur une large portion du NEPS. Cette séparation géographique, ainsi que les nombreux âges hérités qui répliquent ceux des assemblages volcano-plutoniques anciens, suggèrent que ces ceintures représentent les lambeaux d'une séquence volcanique mafique autochtone ayant couvert une grande surface. Une augmentation des rapports Th/Nb des basaltes enrichis en ÉTR légers reflète un changement de la nature de leurs contaminants crustaux, de tonalite-trondhjémite avant 2.75 Ga, à granite-granodiorite ensuite. L'enrichissement isotopique de ces magmas après 2.75 Ga implique une contamination plus importante par une croûte felsique affectée par une fusion partielle régionale, résultant de la collision des terranes de la Baie d'Hudson (TDM 4.3-3.1 Ga) et de la Rivière Arnaud (TDM < 3.1 Ga).Les essaims de dykes mafiques paléoprotérozoïques succèdent à la stabilisation de la croûte archéenne. Les magmas de la plupart de ces dykes prennent leur source dans un manteau lherzolitique à ~1.5 GPa, mais d'autres proviennent soit d'un manteau lherzolitique ou pyroxenitique plus profond (~5 GPa), d'un manteau riche en Fe, ou d'un manteau harzburgitique. La présence de tous ces dykes dans le Terrane de la Baie d'Hudson reflète la nature hétérogène du manteau lithosphérique. Tous contiennent un composant crustal

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21

Beard, Linda Sue. "Precambrian Geology of the Cottonwood Cliffs Area, Mohave County, Arizona." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/244095.

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A belt of Early Proterozoic rocks crops out in the Cottonwood Cliffs area, northwest Arizona. The belt contains an eastern and a western assemblage separated by the Slate Mountain fault. The western assemblage consists of mafic to felsic metavolcanic rocks, metapelites, and metaconglomerates. The eastern assemblage consists of phyllites, felsic to intermediate metavolcanic rocks, metagraywackes, and metagabbro bodies. The belt is bounded to the east by foliated granodiorite. The Valentine granite intruded the belt on the west and north. Steeply-plunging lineations and fold axes, and northeast-trending vertical foliation dominate the structural fabric. The regional elongation direction is near-vertical, as indicated by mineral and pebble lineations, and is parallel to fold axes. Although only one deformational event is evident, the intensity of that event may have obliterated evidence of any earlier deformation. Tertiary basalts and the Peach Springs Tuff locally overly the metamorphic rocks. Cenozoic normal faults in the area are mostly of minor displacement.

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Beard, Linda Susan 1951. "Precambrian geology of the Cottonwood Cliffs area, Mohave County, Arizona." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/558037.

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23

Cardenas, S. Fidel A. "The geochemistry of a late Precambrian weathering profile, northwest Scotland." Thesis, University of Strathclyde, 1986. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21485.

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In an attempt to understand the environment of the Precambrian weathering at Rispond, and compare it with weathering processes taking place at the present time, samples weathered to different degrees have been taken at various distances immediately below the Cambrian Unconformity. These samples have been subjected to chemical analysis by X-ray fluorescence spectometry and wet analysis, and to mineralogical analysis by X-ray diffraction and polarised light microscopy. Interpretation of these results indicate that the samples represent a weathering profile (although not necessarily an unchanged one as these rocks have been subjected to a maximum temperature of 250°C during burial subsequent to the deposition of the Cambrian strata). This is inferred from the minerals present in the soil, the nature of the chemical changes observed, the similarities of the data on the Kronberg weathering diagram to those of present-day weathering, and the position of the profile immediately below the unconformity. Further interpretation of the results in terms of the thermodynamic properties of the minerals present in the profile, the chemical reactions believed to have taken place, the geological evidence and a survey of the chemical composition of present-day surface waters leads to the conclusion that the rocks below the Cambrian Unconformity at Rispond represent a fossil soil profile. These rocks contain pyrophyllite, considered to have been formed by low-grade metamorphism rather than by weathering. Three possible modes of origin have been considered, and that involving the weathering of potassium feldspar to kaolinite alone in an acid environment rejected. The two mechanisms involving the weathering of the feldspar to illite in an arid alkaline environment with restricted drainage are considered to be more likely. The illite produced in these mechanisms was further weathered to produce, in the one case, kaolinite, and in the other one, potassium beidellite as a mixed layer mineral with illite. These two mechanisms can be mixed in any proportion, the exact amount of potasium beidellite present depending upon the relative thermodynamic stabilities of kaolinite and beidellite. As the latter is unknown, further accuracy cannot be achieved at present. The presence of abundant potassium feldspar in the Fucoid Beds, and the existence of trace fossil planolites in such rocks as well as the temperature to which they have been heated (about 250°C) suggested the possible existence of an ammonium feldspar in the area. Therefore, a method to measure the amount of ammonia content in these rocks has been designed. The results of twenty-two samples from the Cambro-Ordovician succession of N.W. Scotland analysed by this method show that the ammonia content is very low. If all the ammonia is present as an ammonium feldspar (buddingtonite), it represents about 0.3% of the mineral in the shales and even less in other rock types.

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24

Hemmingsson, Christoffer. "Estimating soluble arsenic and phosphorus concentrations under Precambrian oceanic conditions." Thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107374.

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Original estimates of phosphorus (P) concentrations in the Precambrian oceans before 1.9 Ga gave a budget of ~10-25% of modern day levels. This budget was challenged by accounting for high silica (Si) concentrations that were believed to have outcompeted P for binding sites on precipitating iron oxide-hydroxide particles during the chemical oxidation and burial of iron (Fe). Such iron oxide-hydroxide particles are considered as proxies of ancient iron-rich sedimentary rocks, such as banded iron formations, which are often used to infer the dissolved chemistry of trace elements in the ancient oceans. This study raises the question of wether arsenic (As) had an effect of the binding of P to precipitating iron minerals, during the co-precipitation of Iron oxide- hydroxide in elevated Fe and Si concentrations characteristic of the early oceans. This hypothesis is based on the chemical similarities seen between P and As. Results show a more pH dependent competition between P and AsIII, whereby P outcompetes AsIII at a pH <7. The effect decreases as the pH rises until pH ~8 at which the effect cancels out and AsIII becomes somewhat predominant over P. AsV on the other hand, an analogue to P, is outcompeted by P throughout pH 5-10. Distribution coefficients (Kd) of P on iron oxide-hydroxide particles were not affected by the concentration of Si in solution. Average Kd and standard error between concentrations of Si, across the sample pH of 5-10 revealed an average Kd of 0.072 (±0.01) μM-1. This is strikingly similar to another experimental Kd at 0.075 (±0.003) μM-1, when the effects of Si are excluded. The average Kd in this study is also consistent with the average Kd of 0.06 μM-1 from a range of As-rich hydrothermal systems reported in a previous study, supporting the original idea of Precambrian P levels being low. The average Kd between concentrations of Fe revealed a Kd of 0.12 (±0.03) μM-1 although this was not statistically significant from the average Kd between groups of Si. In addition to low levels of P, the Precambrian oceans likely also contained high levels of As, due to the high hydrothermal activity. This scavenging of P from oceanic waters would have become increasingly important as surface oceans became more oxygenated and the presence of AsV would have been greater. Because the availability of Si does not show any great effect on the uptake of P by precipitating iron oxide-hydroxides, Si concentration is likely not a proxy for oceanic P concentrations. It is proposed that low dissolved P levels are consistent with early oceans that w!ere a lot more hydrothermally influenced than the oceans of today. Prekambriska fosfor (P) nivåer var ursprungligen estimerade till ca 10-25% utav koncentrationen funnen i dagens havsvatten. Denna budget blev motsagd i och med att kisel (Si) sades kunna ersätta bundet fosfor på järn oxid-hydroxid partiklar som precipiterade genom kemisk oxidation och sedimentering av järn (Fe). Dessa järn oxid-hydroxid partiklar anses användbara som proxy för formationen av uråldriga järn-rika sedimentära bergarter såsom banded iron formation (BIF), vilka används idag för att bestämma mängden spårämnen i de uråldriga haven. Denna studie ställer frågan huruvida arsenik (As) påverkar mängden P som binder till precipiterande järn mineral under procession av co-precipitering av järn oxid-hydroxid i lösning med förhöjda koncentrationer av Fe och Si, karakteristiska för the uråldriga haven. Denna hypotes är baserad på de kemiska likheter som finns mellan P och As. Resultaten påvisar en pH beroende konkurrens mellan P och AsIII där P utkonkurrerar AsIII vid låg pH. Effekten av denna konkurrans minskar med ökande pH tills effekten blir omvänd omkring pH 8 och P blir istället till viss del utkonkurrerad av AsIII. AsV å andra sedan, en verklig kemisk analog till P, är kontinuerligt utkonkurrerad av P genom alla utförda pH, pH 5-10. Distribueringskoefficienter (Kd) för P på järn oxid-hydroxid partiklar visade ingen påverkan av mängden Si tillgängligt. Medelvärdet av Kd och standard error mellan data av alls pH, grupperat av Si, gav ett värde av 0.072 (±0.01) μM-1. Detta är påfallande nära ett experimentellt framtaget Kd värde av 0.075 (±0.03) μM-1 då effekten av Si är borttagen. Medelvärdet i denna studie är också sammanfallande med det Kd medelvärde man finner idag från olika hydrotemala system av 0.063 (±0.01) μM-1. Detta ger support till den originala idén att de prekambriska haven troligen hade låga halter P tillgängligt. Medelvärdet av Kd mellan koncentrationer av Fe gav ett värde av 0.12 (±0.03) μM-1, dock var detta värde ej statistiskt significant från det Kd utifrån koncentrationer av Si. Förutom de låga nivåer av P i de Prekambriska haven så var det troligen även höga halter av As på grund av utbredd hydrotermal aktivitet. Detta uppfångande av P i de tidiga haven var troligen en alltmer viktigare process då ytvatten blev syrerikare och den oxiderade formen av As, det vill säga AsV hade varit mer vanligt förekommande. Framför allt då den konkurrerande effekten av Si kan bortses när P såväl som As inte påverkas av dess närvaro till den grad man hade trott. Detta gör även att mängden Si troligen inte är en tillförlitlig proxy för att estimera P nivåer i de uråldriga haven. Därmed föreslås det att de prekambriska haven var k!arakteriserade av låga P nivåer, jämfört med idag.

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25

Thomas, Katherine S. S. M. Massachusetts Institute of Technology. "Organic geochemistry and stable isotope constraints on Precambrian biogeochemical processes." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69474.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2011. Cataloged from PDF version of thesis. Includes bibliographical references (p. 91-101). Details of the biogeochemical cycles and the dominant mechanisms present in Precambrian remain heavily debated topics. The events of the Late Proterozoic onset to glaciations and what types of early life existed in the Archean are two of the many provoking topics within the Precambrian. We set out to improve the understanding of these geologic intervals by examining stable isotopic signatures and molecular fossils (biomarkers) in Late Proterozoic and Mesoarchean ages sedimentary rocks in Northwestern Territories, Canada and Pilbara, Western Australia, respectively. This thesis presents sulfur, carbon, oxygen and nitrogen stable isotopic data along with distribution of steranes and hopanes biomarkers. Geochemical data is analyzed in the context of elucidating the key biological and environmental factors involved in the Mesoarchean marine biosphere and the Late Proterozoic onset of glaciations. Stable isotopic analysis of the Gorge Creek Group in Pilbara, Western Australia reveals organisms capable of microbial sulfur disproportionation were likely the dominant biological players in Mesoarchean deep-ocean sulfur cycling. Biomarker and isotopic proxies of the Coppercap Formation reveal diverse biological activity directly prior to the Sturtian Glaciation with communities of green and purple sulfur bacteria as well as methanotrophs and cyanobacteria. Possible environmental implications of these communities co-existing are explained in context of changes in ocean chemistry and the diversification of eukaryotic life. by Katherine S. Thomas. S.M.

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26

Downey, Matthew. "The Structural Geology, Kinematics and Timing of Deformation at the Superior craton margin, Gull Rapids, Manitoba." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/1258.

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The Gull Rapids area, Manitoba, lies on the Superior craton margin and forms part of the Superior Boundary Zone (SBZ), a major collisional zone between the Archean Superior craton and the adjacent Paleoproterozoic Trans-Hudson Orogen. There are two main rock assemblages at Gull Rapids: orthogneisses (of possible Split Lake Block origin) and supracrustal rocks (metavolcanic and metasedimentary). Late, crosscutting felsic and mafic intrusive bodies (mostly dykes and sills) are used to constrain the relative and absolute timing of deformation and metamorphism. The Gull Rapids area records a complex tectonic history. The area experienced four generations of Neoarchean ductile and brittle deformation (G1 ? G4) and one of Paleoproterozoic ductile-brittle deformation (G5). G1 deformation produced the main foliation in the map area, as well as local isoclinal folding which may be related to an early shearing event. M1a prograde mid-amphibolite facies metamorphism is contemporaneous with the early stages of G1. Widespread, tight to isoclinal sheath folding during G2 was recorded in the supracrustal assemblage, and is the result of southwest-side-up, dextral shearing during the early shearing event. A ca. 2. 68 Ga widespread phase of granitoid intrusion was emplaced late-G1 to early-G2, and is rich in metamorphic minerals that record conditions of M1b upper-amphibolite facies peak metamorphism. M1b metamorphism, late-G1 to early-G2 deformation, and intrusion of this felsic phase are contemporaneous. M2 retrograde metamorphism to mid-amphibolite facies was recorded sometime after M1b. G1 and G2 structures were re-folded during G3, which was then followed by G4 southwest-side-up, dextral and sinistral shearing, contemporaneous with late pegmatite intrusion at ca. 2. 61 Ga. This was followed by mafic dyke emplacement at ca. 2. 10 Ga, and then by G5 sinistral and dextral shearing and M3 greenschist facies metamorphism or hydrothermal alteration at ca. 1. 80 Ga. Deformation and metamorphism at Gull Rapids post-dates emplacement and deposition of gneissic and supracrustal rocks, respectively. This deformation and metamorphism, except for G5 and M3, is Neoarchean (ca. 2. 68?2. 61 Ga), and represents a significant movement of crustal blocks: km-scale shearing of the supracrustal assemblage and consequent uplift of the Split Lake Block. Late deformation and metamorphism (G5, M3) may be related to the Paleoproterozoic Trans-Hudson orogeny. The Neoarchean and Paleoproterozoic zircon populations in the geochronological data suggest that the Gull Rapids area largely experienced Neoarchean deformation and metamorphism with a weak Paleoproterozoic overprint. All of the evidence presented above suggests that the Gull Rapids area lies in a part of the Superior Boundary Zone, yet does not lie at the exact margin of the Superior craton, and therefore does not mark the Archean-Proterozoic boundary proper in northeastern Manitoba.

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27

Sun, Weiguo. "Contributions to palaeontology and stratigraphic correlation of the late precambrian in China and Australia /." Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09phs957.pdf.

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28

Peters, D. "A geochemical and geochronological assessment of the Great Glen Fault as a terrane boundary." Thesis, Keele University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.344063.

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The Great Glen Fault (GGF) is a major northeast to southwest trending structure and has been interpreted as a terrane boundary separating the Precambrian Moine terrane to the northwest from the Precambrian Dalradian terrane to the southeast (e. g. Bluck & Dempster 1991). If the GGF is a terrane boundary no `Moine' rocks could be found southeast of the GGF and no `Dalradian' rocks could be found to the northwest of the GGF and each crustal block would have distinct tectonometamorphic, provenance and igneous intrusive characteristics. To assess this, carefully selected orthoamphibolite and metasediment samples were collected from both the Northern and Central Highlands, and were analysed by a combination of petrography, geochemistry and geochronology. Geochemical analysis suggests that a Neoproterozoic metagabbro and metadolerite suite was emplaced during crustal extension across the Northern and Central Highlands at approximately the same time, and that this suite represents an earlier intrusive event to that represented by amphibolites in the Dalradian Appin Group. Geochemistry also suggests that the Upper Morar Psammite Formation of the Moine Supergroup in the Northern Highlands is unlikely to correlate with the pebbly psammite formations in the Central Highlands and shows that the Upper Shiaba Psammite Formation metasediments on the Isle of Mull are geochemically distinct from the Upper Morar Psammite Formation metasediments on the mainland. The Glen Urquhart Complex in the Northern Highlands cannot be correlated with the Ord Ban Subgroup or Grantown Formation in the Central Highlands. However, despite these differences U-Pb detrital geochronology shows that the Upper Morar Psammite and Central Highland pebbly psammite formations are dominantly derived from similar Mesoproterozoic and Palaeoproterozoic sources, with a small amount of material of Archaean derivation. This, together with the matching amphibolite suites, means that the Great Glen Fault is very unlikely to be a terrane boundary.

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29

Munn, Barbara J. "Metamorphism in the Northern Front Range, Colorado." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29154.

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Thermobarometry, detailed petrography, electron microprobe analysis, and fluid inclusion microthermometry were used to quantify the history of a high grade Proterozoic terrane exposed within the northeastern Colorado Front Range. Pressure-temperature calculations identified two blocks from different crustal levels exposed adjacent to one another within the Poudre Canyon west of Fort Collins. They are the eastern, higher pressure, block (HPB; 734 degree C, 7.1 kbar) and the western, lower pressure, block (LPB; 655 degree C, 5.2 kbar). The blocks followed a clockwise uplift path and were juxtaposed by ductile shear near the end of the decompressive stage of uplift. Final assembly of the separate blocks to the same crustal level was constrained by mineralogic and textural considerations and by the isochores of identical low density carbon dioxide inclusions trapped by both blocks. Both blocks experienced peak metamorphism within the sillimanite-K-feldspar zone accompanied by partial melting, are characterized by stromatic migmatites, and show textural evidence for localized reactions related to decompression and cooling. Differences between the blocks include the type of melt-generating reactions and the pronounced late muscovite in the LPB. Gibbs' Method calculations indicate that local (outcrop scale) textural and mineralogical differences between HPB Mg-enriched pelites are caused by small differences in bulk composition and locally variable H2O content. The quartzo-feldspathic biotite gneisses in the LPB generated migmatites by wet melting, whereas the pelitic schists and gneisses in the HPB generated migmatites by dehydration melting of muscovite and biotite. Biotite dehydration melting enriched the leucosomes in HPB pelitic migmatites in K-feldspar and garnet. The minor presence of late muscovite in the HPB relative to the LPB was controlled by the different positions of their uplift paths relative to the muscovite breakdown reaction. Ph. D.

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Gangopadhyay, Amitava. "A petrologic, geochemical and osmium isotopic study of selected Precambrian komatiites." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/2011.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2004. Thesis research directed by: Geology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Simmons-Ferguson, Heather Elizabeth. "Total and organic mercury in periphyton from a Precambrian shield lake." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq21700.pdf.

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Steck, Christian D. "Correlation of gravity anomalies with Precambrian crystalline basement, Bellefontaine Outlier, Ohio /." Connect to resource, 1997. http://hdl.handle.net/1811/24797.

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Mattsson, Håkan Johannes. "Magnetic anisotropy and paleomagnetism of precambrian rocks in the Fennoscandian shield /." Luleå, 2001. http://epubl.luth.se/1402-1544/2001/32/index.html.

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Anderson, Phillip. "THE PROTEROZOIC TECTONIC EVOLUTION OF ARIZONA (PRECAMBRIAN, PLATE TECTONICS, VOLCANIC, STRATIGRAPHY)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183853.

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Archean tectonics are irreconcilable with modern plate tectonics without clearly understanding Proterozoic tectonic accretionary prosesses. Arizona best displays a convergent margin where Proterozoic accretion to an Archean craton generated a new Proterozoic crust from 1800 to 160 Ma. This 12 year study independently formulated a definitive understanding of Arizona's Proterozoic tectonic evolution with new lithologic, petrologic, geochemical, structural and relative age data, and extensive new mapping. The Northwest Gneiss Belt contains an early Proterozoic arkosic clastic wedge at the Wyoming Archean edge, but only intraoceanic elements--Antler-Valentine and Bagdad volcanic belts--on Proterozoic oceanic crust south of the wedge. The Central Volcanic Belt evolved diachronously on oceanic crust: 1800-1750 Ma formative volcanism (Bradshaw Mountain, Mayer, Ash Creek and Black Canyon Creek Groups) stepped SE to form the Prescott-Jerome island arc above a SE-dipping subduction zone; a 1740 Ma NW subduction flip accreted the arc to the Archean craton, evolved I-type plutons of NW alkali-enrichment opposit to arc tholeiites, and formed calc-alkaline Union Hills Group volcanics at the southeast arc front. Except for hiatal Alder Group deposition in structural troughs, the central magmatic arc emerged as the trench stepped southeastward across SE Arizona with flattening of subduction, growth of the Pinal Schist fore-arc basin, 1700 Ma accretion of the Dos Cabenzas arc to the margin, eruption of felsic ignimbrite fans across the central arc front, and Mazatzal Group shallow marine sedimentation across the emergent arc. Proterozoic plate tectonics were subtly different from modern plate tectonics, producing oceanic crust, island arcs and other features very different in detail from modern and Archean analogs. The Proterozoic Plate Tectonic Style warrants clear distinction from those of other eras. This study establishes for Arizona an extensive, accurate and new Proterozoic data base, for central Arizona a detailed relative chronology surpassing isotopic resolution, and a new formal stratigraphic framework to be the foundation for future studies. This dissertation is superceded by a new book on Arizona's Proterozoic Tectonic Evolution, published by the Precambrian Research Institute, 810 Owens Lane, Payson, Arizona, 85541.

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DuBois, Mark A. "Laramide Deformation in Precambrian Granitic Rocks, Northeastern Wind River Range, Wyoming." DigitalCommons@USU, 1990. https://digitalcommons.usu.edu/etd/6596.

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Fractures and faults in the Jakey's Fork area, northeastern Wind River Range, Wyoming, caused by brittle Laramide deformation in the Precambrian granitic basement have been studied in detail at airphoto, outcrop, and thin-section scales. The study area is bounded on the south by the approximately east-west and vertical Jakey's Fork Fault and on the east by the approximately northwest-southeast and vertical Ross Lakes Fault. Both were active during Laramide deformation. Four distinct structural domains, defined by fracture pat terns and proximity to the two major faults nave emerged in this study. The areas are: 1) Along Ross Lakes Fault granite cores a fold defined by shallowly and steeply east dipping Cambrian Flathead Sandstone. Laramide movement on Ross Lakes Fault appears to have post-dated, Jakey ' s Fork Fault movement and was discordant with Precambrian zones. Fractures at all scales studied strike approximately northeast-southwest, consistent with the inferred maximum Laramide principal stress. 2) Along east-west striking Jakey's Fork Fault, Laramide movement appears to have reactivated Precambrian mylonite zones as evidenced by the chlorite-rich, foliated cataclasite along its trace. Fractures at all scales have an approximate east-west orientation. 3) Near the intersection of the two faults, deformation was intense, as shown by mylonitic, breccia, and veined clasts. Discrete airphoto fractures were not recognized due to intense deformation in this interaction zone. 4) In the central area, away from the two faults, airphoto and outcrop fracture orientations have a north to northeast strike. Fracture orientations at the thin-section scale are more variable and do not agree with macroscopic orientations; they strike west to northwest. The central area is a 'block', possibly divided into 'sub-blocks' , bounded by zones along which much of the deformation occurred. Thus, these zones had an insulating effect at thin-section scale. The Paleozoic rocks were at least partially decoupled from the basement during deformation, suggested by gouge along the contact and different fracture orientations on opposite sides of the contact. At least two fluid systems are represented in the study area. Relatively wide-spread, pre-Laramide chlorite development occurred at temperatures and pressures higher than those present during Laramide deformation. A Laramide (or post-Laramie ) pervasive fluid system (especially near Ross Lakes Fault) is reflected by abundant fracture porosity, advanced feldspar alteration, and kaolinite development.

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de, Oliveira Elson Paiva. "Petrogenesis of mafic-ultramafic rocks from the Precambrian Curaca terrane, Brazil." Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/35079.

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The Caraiba copper-rich hypersthenite-norite complex in the Early Proterozoic Curaca terrane of northern Bahia, Brazil, is not a tholeiitic layered sill as has been previously suggested. It is re-interpreted as a series of multiple dyke-like intrusions, possibly derived through partial melting of an incompatible element enriched harzburgitic to orthopyroxenitic lithospheric mantle source region. It contains peridotitic and gabbroic xenoliths. Copper-rich gabbroic xenoliths may represent volcanic rocks taken to upper mantle depths by a process of subduction. The chemistry of some of the regional mafic rocks and of three granitoid generations suggest for the Curaca terrane a tectonic evolution similar to Phanerozoic continent-continent collision belts, which was possibly initiated at an Andean-type margin. A Middle Proterozoic mafic dyke swarm that post-dates the main period of crustal growth is interpreted as having originated from a heterogeneous garnet-bearing source in the asthenospheric mantle, and is likely to be related to a mantle plume or hotspot during the development of the coeval Espinhaco aulacogen. The parental magma of these dykes is thought to have resided in small zoned magma chambers. Comparison with other mafic dykes from the Brazilian shield suggests derivation of the Early Proterozoic dykes from more depleted, more refractory, lithospheric mantle sources than those of the younger dykes, which are believed to have had a significant asthenospheric contribution in their petrogenesis. The chemistry of these dykes reflects the evolution of the sub-continental mantle with time.

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Magaia, Luis. "Processing Techniques of Aeromagnetic Data. Case Studies from the Precambrian of Mozambique." Thesis, Uppsala universitet, Geofysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183714.

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During 2002-2006 geological field work were carried out in Mozambique. The purpose was to check the preliminary geological interpretations and also to resolve the problems that arose during the compilation of preliminary geological maps and collect samples for laboratory studies. In parallel, airborne geophysical data were collected in many parts of the country to support the geological interpretation and compilation of geophysical maps. In the present work the aeromagnetic data collected in 2004 and 2005 in two small areas northwest of Niassa province and another one in eastern part of Tete province is analysed using GeosoftTM. The processing of aeromagnetic data began with the removal of diurnal variations and corrections for IGRF model of the Earth in the data set. The study of the effect of height variations on recorded magnetic field, levelling and interpolation techniques were also studied. La Porte interpolation showed to be a good tool for interpolation of aeromagnetic data using measured horizontal gradient. Depth estimation techniques are also used to obtain semi-quantitative interpretation of geological bodies. It was showed that many features in the study areas are located at shallow depth (less than 500 m) and few geological features are located at depths greater than 1000 m. This interpretation could be used to draw conclusions about the geology or be incorporated into further investigations in these areas.

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Panahi, Alireza. "Geochemistry of Precambrian paleosols and Huronian sedimentary rocks, Ontario and Québec, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0021/NQ58156.pdf.

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Muir, Roderick John. "The precambrian basement and related rocks of the southern Inner Hebrides, Scotland." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339724.

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Würsten, Felix. "The Precambrian crystalline basement of Salalah (Dhofar area, Sultantate [sic] of Oman) /." [S.l.] : [s.n.], 1994. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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Corvino, Adrian F. "Precambrian geology of the North Mawson Escarpment area, Prince Charles Mountains, Antarctica /." Connect to thesis, 2009. http://repository.unimelb.edu.au/10187/4879.

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Petrescu, Laura. "Precambrian lithospheric structure and evolution : evidence from broadband seismology in Eastern Canada." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/52450.

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The thick and seismically fast Precambrian continental remnants (cratons) provide fundamental clues about the tectonic processes that operated on the early Earth. Eastern Canada is a natural laboratory to study such processes: its geological record spans more than 3 Ga of Earth history, including the assembly of the largest Archean craton in the world, the Superior craton, which is surrounded by global scale Proterozoic and Phanerozoic orogenic belts. To investigate the crustal and lithospheric structure of eastern Canada, earthquake data recorded at a new broadband seismic network were analysed, in conjunction with other permanent and temporary networks. The QM-III (Quebec-Maine Across Three Sutures) network was deployed across the main tectonic boundaries in eastern Canada, extending from Hudson Bay to the Atlantic Ocean. Using Hk stacking and probabilistic inversion of receiver functions, bulk crustal composition (Vp/Vs ratio), crustal thickness and shear wavespeed (Vs) were estimated beneath seismic stations. Post- Archean crust is thicker ( ~40 km), faster (dVs ~ 0.2 km/s), more heterogenous and more ma c (Vp/Vs ~1.76), suggesting increased crustal growth efficiency, possibly stimulated by mafic underplating. Lack of correlation between Moho topography, elevation and gravity anomalies in Proterozoic terranes indicate isostatic imbalance, best explained by strong mantle buoyant support. An anisotropic seismic model of the Precambrian lithosphere was constructed using fundamental mode Rayleigh waves. Phase velocity heterogeneity and azimuthal anisotropy patterns reveal multiple lithospheric layers within the Superior craton, with distinct tectonic origins. The upper lithosphere is seismically fast ( ~2%) and preserves Archean fossil anisotropy ( ~1%), implying that plate-scale deformation occured during the Archean. This layer partially extends beneath the adjacent Proterozoic belt and survived subsequent metasomatism. The lower lithosphere is fast ( ~2%), more homogenous and weakly anisotropic ( < 0.5%), documenting post assembly lithospheric growth in a slow convection regime. Cratonization processes may be episodic and are not exclusively an Archean phenomenon.

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Winhusen, Eric. "PRECAMBRIAN SEAWATER TEMPERATURE ANALYSIS USING OXYGEN ISOTOPES FROM HAMERSLEY CARBONATES, WESTERN AUSTRALIA." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin992268720.

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Peterman, David Joseph. "Seismic Reflection Profiling near Middletown, Ohio and Interpretation of Precambrian Deformational Settings." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1463936515.

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Mattos, Gabriela Libertad Vargas. "Estudo petrográfico e geoquímico do embasamento e dos granitóides San Ignácio e Sunsás da região San Ramon, Concepción, SW do cráton amazônico da Bolívia." Universidade do Estado do Rio de Janeiro, 2006. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=158.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior O presente trabalho teve por objetivo a caracterização petrográfica e geoquímica das rochas graníticas formadas durante o evento Sunsás e de seu embasamento no SW do Craton Amazônico na Bolívia. As unidades estudadas compreendem, além dos granitóides da Orogenia Sunsás (1,30 Ga-950 Ma), o embasamento (> 1400 Ma) representado por gnaisses La Chiquitania, enderbitos e gnaisses Lomas Maneches e granitóides San Ignácio (1400-1300 Ma). A área de estudo encontra-se no extremo leste da Bolívia envolvendo os estados de Santa Cruz de La Sierra e Beni. A justificativa para este estudo é a ausência de trabalhos desde a década dos oitenta, quando foi mapeado o pré- Cambriano boliviano pelo Serviço Geológico da Bolívia com o Serviço Geológico Britânico. Para o embasamento, a unidade La Chiquitania apresenta rochas como ortognaisses de composição granítica além de litotipos granadíferos. A unidade Lomas Maneches apresenta enderbitos e rochas graníticas metaluminosas a debilmente peraluminosas. O ambiente tectônico no qual foi formada varia desde pré-colisional a tardi-orogênico com rochas preferencialmente graníticas e os ETR sugerem um processo de fracionamento magmático para a geração das rochas. Os granitóides San Ignácio incluem as intrusões graníticas San Andrés, El Refugio e San Ramón. Segundo a química, estas rochas variam de metaluminosa a debilmente peraluminosa. Os diagramas tectônicos indicam ambientes que variam de pré-colisionais a post-orogênicos e os padrões de ETR sugerem a existência de dois grupos provavelmente originados de fontes diferentes ou a partir de processos de fracionamento diferentes. Os granitóides Sunsas incluem as intrusões Talcoso, Cachuela, Naranjito, Taperas e Primavera. Os estudos petrográficos dos primeiros 3 granitóides permitem classificá-los como granitos, sendo que os últimos dois foram classificados como granodioritos. Os resultados geoquímicos dos ETR permitem sugerir que estes granitóides apresentam um comportamento metaluminoso, com afinidade pós-orogênica. Neste sentido, os granitos Naranjito, Primavera e Talcoso são produto de uma cristalização fracionada. O granito Cachuela é o representante mais primitivo e o granito Taperas tem posição intermédia no processo de fracionamento magmático. A partir dos resultados apresentados e com os dados da literatura pode-se sugerir que os gnaisses La Chiquitania e do Lomas Maneches foram resultado de um importante evento acrecionário na região (Orogênese Lomas Maneches). Ocorrido por volta de 1680-1660 Ma. Seguindo o tempo geológico foi registrado o evento San Ignácio, de idade entre 1,34 Ga e 1,33 Ga, cujo ambiente tectônico mais provável foi um arco magmático continental. Para o evento Sunsas, os corpos graníticos são classificados como granitos tipo I, resultando do estabelecimento de um arco magmático continental por volta de 1,07 Ga. Os elementos terras-raras permitem sugerir que estes granitóides foram gerados em um processo de fracionamento magmático, provavelmente de origem mantélica, durante o processo de subducção que terminou na colisão Greenviliana que, conforme a literatura, resultou na aglomeração do supercontinente Rodínia. Palavras-chave: Pré-cambriano; Bolívia The main objectives of this work were the petrographic characterization and geochemistry studies of the Sunsas granitic intrusions and their country rocks in the Bolivian sector of the SW Amazonian craton. The studied units comprise the Sunsas Orogeny granitoids (1,30 Ga-950 Ma), the basement (>1400 Ma) including La Chiquitania gneiss, enderbitic and granitic gneiss of the Lomas Maneches unit and San Ignacio granitoids (1400-1300 Ma). The studied area is located in the west sector of Bolivia and involves the Santa Cruz de La Sierra and Beni states. The justificative for this study is the absence of investigation focusing the area since the 1980 decade, when the Bolivian Geological Survey with the Geological British Survey mapped the Bolivian pre-Cambrian. The Lomas Maneches unit comprises enderbitic and granitic gneiss from metaluminous to peraluminous composition. The tectonic setting indicated by the tectonic diagrams suggest late-orogenic to post-tectonic origin and the REE patterns suggest fractional crystallization processes for the rocks formation. The La Chiquitania unit presents two types of rocks (granitic gneiss and the garnet gneiss) here interpreted as similar to the Lomas Maneches rocks. The San Ignácio granitoids include San Andrés, El Refugio and San Ramon granites. According to the geochemistry results the rocks are characterized as metaluminous and peraluminous and the tectonic setting where the rocks were formed vary from pre-collision to post-orogenic and the REE patterns suggest the existence of two groups of rocks originated in different sources or as result of different processes of magma fractionation.The Sunsas granitoids here studied included the Talcoso, Cachuela, Naranjito, Taperas and Primavera intrusions. The petrography study allowed to classificate the first three granitoids as granites and the other two as granodiorite. The geochemical study of all the granites indicates metaluminous trend and according to the REE patterns, the Naranjito, Primavera and Talcoso granites are product of the fractional crystallization processes; the Cachuela granite represents the more primitive, and the Taperas granite with intermediate position in the magmatic fractional processes.The present study and previously works suggest that the La Chiquitania paragneiss were formed as result of erosion and sedimentation from sources dating at 1,76 Ga. At about 1680-1660 occurred an important accretionary event in this region (here defined as Lomas Maneches Orogeny). Following the geological time, the San Ignácio event was recorded by granitogenesis ca. 1,34 Ga and 1,33 Ga, whose tectonic environment probably is related to a continental magmatic arc. The Sunsas event granitoids may be classificated as I-type granites, resulted of the continental magmatic arc setting at 1,07 Ga. The REE patterns allow to suggest these granites were generate from a magmatic fractionating processes, with mantelic source during which subduction finished with the Grenvillian collision, according to the literature, responsible for the Rodinia supercontinent assembly.

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Ibanez-Mejia, Mauricio. "Timing and Rates of Precambrian Crustal Genesis and Deformation in Northern South America." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/337364.

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The Amazon Craton is one of the largest Precambrian landmasses on Earth, yet its crustal growth history and evolution are relatively poorly constrained. This dissertation addresses the timing and modes of continental growth and deformation of a sizable portion of the central and western Guyana Shield, mostly using a combination of texturally-resolved U-Pb, Lu-Hf and δ¹⁸O analysis of zircon. These results provide a wealth of new information that have major implications for the role of Amazonia in Precambrian supercontinent models, its significance in the global record of crustal generation and the possible tectonic processes that were involved in its construction. It is argued that, contrary to the previously accepted Proterozoic accretionary model for the growth of northwestern Amazonia, the new data suggest that sizable portions of the shield formed during an episodic extraction event in the Neorchean. This hypothesis challenges the current tectonic model for the evolution of Amazonia, and provides evidence for the continued importance that mechanisms inducing episodic crustal generation had after subduction-driven plate tectonics had been established on Earth. During the last decade, the study of crustal growth processes by means of U-Pb-Hf-O analysis of zircon has considerably improved our understanding of the mechanisms that drive planetary differentiation. However, zircon has a significant limitation, and is that basic and ultrabasic rocks have very low fertility to form this mineral owing to their low SiO₂ composition. Therefore, the global zircon U-Pb-Hf repository is biased towards the felsic portion of the crust, leaving the mafic archive mostly unconstrained. Undersaturated rocks can form baddeleyite, a phase with high affinity for Hf and U, low affinity for Yb, Lu and Pb, and slow diffusion rates with respect to all these chemical species. Consequently, baddeleyite is an extremely robust carrier of geochronological (by using the U-Pb system) and tracer (by using the Lu-Hf system) information for the origin of mafic rocks. This dissertation provides a method for the fast, accurate and precise analysis of U-Pb-Hf isotopes in baddeleyite, a tool that in the future may prove crucial for studying the timing and processes associated with the formation of mafic crust on Earth.

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Tomlinson, Kirsty Y. "The geochemistry and tectonic setting of early Precambrian greenstone belts, Northern Ontario, Canada." Thesis, University of Portsmouth, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388557.

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Ahmed, Ashraf Ismaïl Embaby. "Groundwater properties and potentialities in the Precambrian rocks, Hafafit area, Southeastern Desert, Egypt." Thesis, Poitiers, 2015. http://www.theses.fr/2015POIT2313.

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Cette thèse s’inscrit dans le cadre des travaux de recherche de nouvelles ressources en eau en Egypte orientale. Elle est plus spécifiquement axée sur la région du désert Sud-Oriental de l'Egypte. Le présent travail porte sur les propriétés et les potentialités en eau souterraine du système aquifère précambrien dans la région de Hafafit. Les eaux souterraines représentent la ressource la plus importante pour la boisson et les autres usages (domestiques, industriels, agricoles) dans cette région.La répartition spatiale des roches réservoirs, ainsi que leur structure ont d’abord été déterminées afin de comprendre la distribution des aquifères associés et les écoulements préférentiels des eaux souterraines. La méthodologie utilisée est le couplage du travail de terrain pour identifier les roches à l'affleurement et le traitement des images Landsat en utilisant les techniques de télédétection. Cette approche a permis une cartographie géologique détaillée de la région de Hafafit et aussi de dessiner la carte de densité des linéaments et leur orientation. Les résultats ont permis d’identifier les zones potentiellement aquifères.La deuxième étape a consisté à mener une étude pétrographique afin de déterminer la minéralogie et par conséquent, les éléments chimiques qui peuvent être impliqués dans les interactions eaux-roches. L’objectif est de comprendre les processus physico-chimiques à l’origine de la minéralisation des eaux souterraines dans les rochers précambriennesEnfin, avec toutes les données climatiques, géologiques, hydrologiques, hydrogéologiques et chimiques, nous avons tenté d’élaborer un modèle conceptuel du système aquifère du Précambrien de la zone de Hafafit, expliquant ses propriétés physico-chimiques et ses potentialités.Le désert Sud-Oriental de l'Égypte est limité par les longitudes 33° 50' 00" - 35° 45' 00" E et les latitudes 24° 00' 00"- 25° 15' 00" N et couvre une superficie d'environ 17,290 km². Ainsi, il forme une longue bande d'environ 150-200 km de large, bordée à l'Ouest par le Nil et à l'Est par la Mer Rouge. La zone étudiée est située dans la partie sud de cette bande et peut être définie par un quadrilatère dont les sommets sont, au Nord, les villes de Idfu et El Qusier et ceux d'Assouan et Ras Banas au Sud.Pour la zone étudiée, des histogrammes des variations saisonnières de température et de précipitation ont été établis sur les cinq dernières décennies en utilisant les relevés météorologiques historiques (disponibles sur Tutiempo International DataBase) de deux stations situées respectivement à l'Ouest (Assouan sur le Nil) et au Nord (El Qusier sur la Mer Rouge). Les données d'une nouvelle station implantée à l’Est (Marsa Alam sur la Mer Rouge) ont été utilisées, mais sur 6 ans uniquement. Malheureusement aucune station n’a été implantée dans la partie montagneuse de la région étudiée.Ces histogrammes montrent que, dans la région de Hafafit, la température varie de 22 à 36 °C avec une moyenne de 28 °C. L'effet de la température est renforcé par l’ensoleillement relatif annuel moyen, compris entre 80% et 106% entre les deux saisons. L'humidité relative annuelle varie entre 32% et 60% de l'hiver à l'été. Les précipitations annuelles varient de 0 à 117 mm/an dans l'Ouest (Assouan) et de 0 à 195 mm/an dans le Nord (El Qusier) avec une moyenne générale de 50 mm/an pour toute la région. Cependant de longues périodes de sécheresse peuvent succéder à certains événements pluviométriques intenses (souvent 60 mm.h-1). Un autre critère important du climat local est le vent qui souffle régulièrement avec une vitesse moyenne élevée à près de 20 km/h. Par conséquent, l'évaporation potentielle peut atteindre 10 mm/jour. Toutes ces conditions témoignent du degré élevé de l'aridité de la région de Hafafit et du faible potentiel de recharge des aquifères par les apports pluviométriques Groundwater is the main water resource for drinking, domestic, irrigation and industrial purposes in the study area as a result of limited natural fresh water. The water scarcity and shortage in Egypt due to population growth, agriculture expansion, industry development, climatic changes and water pollution lead to search about new water resources to overcome the depletion of annual individual share of water such as evaluation of groundwater in Precambrian aquifer, Southeastern Desert, Egypt. Egypt is under water scarcity due to difference between water demand and available water resources, so, we need to search and explore new water resources in Egypt, especially in Southeastern Desert of Egypt. The importance of Southeastern Desert of Egypt represents one of the famous regions for mining such as gold (El-Sukkari gold mine), ilmenite (Abu Ghuson) and other economic ores, therefore the area crowded with touristic villages and resorts parallel to the red sea coast with industrial, commercial and agricultural expansion in the area. The previous factors lead to necessity of qualitative and quantitative evaluation of groundwater resources to reduce the gap between the available water resources and water demand. Applications of remote sensing and Geographic information system techniques have been utilized to investigate the hydro-geological framework and hydrochemistry of fractured Precambrian and coastal aquifers system in Southeastern Desert of Egypt. The aim of the work is evaluation and exploration for new water resources in Southeastern Desert of Egypt dealing with groundwater properties and potentially in the Precambrian aquifer, Hafafit area, Southeastern Desert of Egypt. The groundwater potentialities of Precambrian and coastal aquifers have been studied using remote sensing, geomorphology, hydrology, hydrogeology and geophysics techniques. The groundwater properties of Precambrian and coastal aquifers have been studied using remote sensing, petrography and mineralogy and hydrochemistry techniques.The area is limited by longitudes 330 50/ - 350 45/ 00// E and latitudes 240 00/ - 250 15/ N and covering an area about 17290 Km2. The study area lies within arid desert conditions based on degree of aridity with air temperature and rainfall are variable from summer to winter. The temperature ranges from 22-36 Co with average 28 Co, The average annual rainfall ranges from 3 to 50 mm/year, some intense rainfall events (often 60mm.h-1). The average annual wind velocity is 18.7 km/hour. The intensity of evaporation is 10.1 mm/day. The mean annual relative sunshine ranges between (80-106 %) from season to another, the annual relative humidity varies between (32 % -60%) from winter to summer. In regard to geological setting of the area compose mainly of sedimentary rocks in the coastal line and Precambrian rocks to the west from the coast. The coastal plain sediments include tertiary and quaternary sediments, which classifie into paleogene sediments appear as Abu Ghuson Formation is belong to Oligocene age and Neogene sedimentsare belong to Miocene and Pliocene age include [Ranga Formation, Um Mahara Formation, Abu Dabbab Formation, Sabakha Formation, Um Gheig Formation, Samah Formation, Gabir Formation, Shagra Formation and Samady Formation]. The Precambrian rocks range from the oldest to youngest as [paragneisses and migmatites, geosynclinals metasediments, cataclastic rocks, metavolcanics, serpentinites, metagabbro-diorite complex, older granitoids, Dokhan volcanics, Hammamat group, younger gabbro, younger granitoids, dykes and plugs and alkaline ring complexes].The petrological studies include the mineralogical compositions of rock-bearing minerals that help to understand chemistry of groundwater and hydro-chemical processes such as water-rock interaction, leaching and dissolution of these minerals in groundwater

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Osterhout, Jeffrey T. "Diversity of Microfossils and Preservation of Thermally Altered Stromatolites from Anomalous Precambrian Paleoenvironments." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470753351.

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50

Moore, John Michael. "A comparative study of metamorphosed supracrustal rocks from the western Namaqualand metamorphic complex." Doctoral thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/22585.

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Abstract:

Bibliography: pages 346-370. A regional study of highly metamorphosed supracrustal rocks was undertaken in the western portions of the Namaqualand Metamorphic Complex. The study area was essentially restricted to a north-south section some 50 kilometres wide and 220 kilometres long. Eight east-west-trending belts of supracrustal rocks were examined, together with several smaller paragneiss remnants, in an area dominated by quartzo-feldspathic gneisses of granitic composition. The supracrustal rocks were classified into seven major lithological groups: quartzitic rocks, metapelitic and metapsammitic rocks, quartzo feldspathic rocks, metabasites, metacarbonate rocks, magnesium-rich cordierite rocks and iron formations. Further subdivision, based on variations in mineral constituents within each group, also occurred, as well as the presence of lithologies with compositions transitional between certain groups. The various supracrustal sequences were subdivided into formations containing minor distinctive members on an informal lithostratigraphic basis. Correlation between the major supracrustal belts was then undertaken. Four subgroups were identified across the study area, comprising a quartzo feldspathic gneiss subgroup and an overlying feldspathic quartzite/garnetcordierite gneiss subgroup that both predominate in the southern and central part of the area, a glassy quartzite/mica- sillimanite schist subgroup that predominates in the northern part, and a cordierite gneiss/metacarbonate subgroup that is restricted to the Geselskapbank synform. The supracrustal rocks appear to have been emplaced on a basement of augen gneisses. This relationship is, however, complicated by the intrusion of granit i c rocks within the contact zone.

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