O Bloco São Gabriel, localizado na zona central do embasamento cristalino do Rio Grande Sul, apresenta extensos registros do Neoproterozóico do Ciclo Brasiliano, contidos em complexos ígneos e metamórficos. Esses complexos também guardam registros sedimentares, com sequências carbonáticas metamorfisadas, cuja evolução tectônica é pouco conhecida. Essas sequências são observadas na Formação Passo Feio (Caçapava do Sul), no Complexo Cambaí (Vila Nova do Sul) e no Complexo Metavulcano-sedimentar Coxilha do Batovi (São Gabriel). As rochas carbonáticas da Formação Passo Feio compreendem dolomita mármores impuros. As amostras do Complexo Cambaí são classificadas como calcita mármores impuros. Os mármores do Complexo Coxilha do Batovi compreendem litotipos calcíticos e cálcio-silicáticos, cuja assembleia mineral é composta predominantemente por calcita em alguns exemplares e por grafita em outros, com percentuais de até 10% de quartzo, demonstrando contribuição siliciclástica no protólito. Idades de zircões de rochas associadas com os mármores, de trabalhos anteriores, indicam um intervalo entre 770 – 700 Ma para a deposição dos carbonatos do Bloco São Gabriel. Os carbonatos da Formação Passo Feio sofreram dolomitização durante ou logo após a deposição, enquanto os carbonatos do Complexo Cambaí não foram afetados pela dolomitização. A geoquímica dos elementos traços e terras raras indica que os mármores analisados preservaram as assinaturas originais do protólito nos diferentes graus metamórficos: Coxiha do Batovi (grau baixo), Formação Passo Feio e Complexo Cambaí (grau médio). A análise integrada dos isotópicos de Sr, 13C e 18O da Formação Passo Feio e do Complexo Cambaí revelou a preservação de assinaturas isotópicas primárias. Na Formação Passo Feio essas assinaturas são: 0,7074 (Sr87/Sr86), -0,26‰ e 2,44‰ (δ13CPDB) e -5,68‰ (δ18OPDB). Quando comparadas com a variação desses isótopos na água do mar ao longo do Neoproterozóico, verifica-se que os mármores da Formação Passo Feio e do Complexo Cambaí estão situados no intervalo entre 740 e 730 Ma. O período sugerido para a deposição das rochas carbonáticas da Formação Passo Feio é de 770 a 730 Ma, e entre 740-730 para o Complexo Cambaí. / The São Gabriel Block, located in the central zone of the crystalline basement of Rio Grande do Sul has extensive Neoproterozoic records of the Brasiliano Cycle, contained in igneous and metamorphic complexes. These complexes also keep sedimentary records with metamorphosed carbonate sequences whose tectonic evolution is poorly understood. These sequences are found in Passo Feio Formation, located in Caçapava do Sul region, in Complex Cambaí, at Vila Nova do Sul region and in Coxilha do Batovi metavolcanosedimentary Complex, in the São Gabriel region. The Passo Feio Formation carbonate rocks consist of impure dolomite marbles. The Cambaí Complex samples are classified as impure calcite marbles. Coxilha do Batovi Complex samples include calcite and calc-silicate marbles whose mineral assemblage are composed predominantly of calcite in some samples and graphite in others, with quartz rates up to 10% showing the siliciclastic contribution to the protolith. Zircon ages of associated rocks from previous works indicate an interval between 770-700 Ma for carbonate deposition in S. Gabriel Block. The carbonates from Passo Feio Formation were affected by dolomitization process during or early after its deposition, while the carbonates from Cambaí Complex were not affected by dolomitization. Trace elements and REE geochemistry of marbles indicate preservation of original signature of carbonate protoliths along different metamorphic grades; Coxilha do Batovi (low grade), Passo Feio Formation and Cambaí Complex (medium grade). The integrated analysis of Sr isotope, 13C and 18O from Passo Feio Formation and Cambaí Complex revealed the preservation of primary isotopic signatures. The Passo Feio Formation signatures are: 0,7074 (Sr87/Sr86), -0,26‰ and 2,44‰ (δ13CPDB) and -5,68 (δ18OPDB). In Cambaí Complex, the primary signatures are: 0,7069 (Sr87/Sr86), 5,75 (δ13CPDB) and -11,64 (δ18OPDB). When compared with the variation of these isotopes in seawater along the Neoproterozoic it appears that Passo Feio Formation and Cambaí Complex are situated in the range between 740 and 730 Ma. Based on these data it is suggested that the São Gabriel Block depositional event occurred between 770-700 Ma. The period suggested for the carbonate rocks depositional event of Passo Feio Formation is between 770-730 Ma, and specifically between 740-730 for Cambaí Complex.

No presente trabalho buscou-se compor um quadro geológico-estrutural da Faixa Paraguai meridional e compreender as relações estratigráficas entre os litotipos da Formação Puga e grupos Cuiabá e Corumbá. Foram realizados trabalhos de reconhecimento geológico e perfis geológico-estruturais de detalhe, com análise estrutural e petrográfica, em conjunto com a integração de dados e mapas existentes, análise de imagens de satélite, fotos aéreas e modelos digitais de terreno. A Faixa Paraguai meridional evoluiu como um típico fold-andthrust belt. A evolução geológica do cinturão principia por processos de rifteamento, provavelmente no final do Criogeniano, evoluindo para mar restrito e margem passiva até o final do Ediacarano. A fase rifte é caracterizada pelas formações Puga e Cerradinho. A fase margem passiva está representada pelas formações Bocaina, Tamengo e Guaicurus. Propõe-se que o Grupo Cuiabá na área estudada seja constituído por depósitos marinhos profundos, turbidíticos distais depositados comitantemente aos sedimentos do Grupo Corumbá. O processo colisional responsável pela inversão da bacia com a deformação e metamorfismo associados ocorreu durante o Cambriano, com magmatismo pós-colisional no Cambriano Superior. O estilo estrutural torna-se progressivamente mais complexo de oeste para leste. São observadas até três fases de dobramento coaxiais sobrepostas com eixos subhorizontais de direção N-S. Associam-se a sistemas de falhas de empurrão com deslocamento da capa para oeste. As lineações de estiramento e indicadores cinemáticos observados sugerem que a convergência colisional em direção ao bloco Rio Apa que deu origem à faixa móvel não foi completamente frontal, existindo algum grau de obliquidade, com vetores de convergência em torno de WNWENE. Os micaxistos do Grupo Cuiabá mostram o estilo estrutural mais complexo, com três fases de dobramentos coaxiais e foliações tectônicas mais intensas. Haveria correlação temporal entre S3 gerada nos micaxistos, comumente referidos como Grupo Cuiabá, a leste com a foliação S2 gerada na porção central e a clivagem S1 gerada no limite da área cratônica a oeste, padrão que pode ser explicado pela migração do front deformacional de leste para oeste. É sugestivo que as principais falhas de empurrão coincidam com limites bacinais importantes, onde ocorrem variações de espessura e representatividades das formações basais. No processo de inversão da bacia provavelmente os empurrões reativaram as antigas falhas lístricas principais do estágio rifte. / This work aims to characterize the geological and structural context of the Southern Paraguay Folded Belt, and to understand the stratigraphic relationships between the Puga Formation, Corumbá and Cuiabá groups. Regional geological reconnaissance work and detailed geological-structural field sections were carried out, with petrographic and structural analysis, together with integration of existing data and maps and analysis of satellite images, aerial photos and digital terrain models. The southern Paraguay Belt is a typical fold-andthrust belt. Its geological evolution began with rifting (Puga and Cerradinho formations), probably at the end of Criogenian, and evolved to restricted sea and passive margin (Bocaina, Tamengo and Guaicurus formations) in the late Ediacaran. It is proposed that the Cuiabá Group in the study area consists of distal marine deposits coeval with the Corumbá Group. The collisional process responsible for basin inversion and associated deformation and metamorphism occurred in the Cambrian, with post-collisional magmatism in the Upper Cambrian. The structural style becomes increasingly complex from west to east. Up to three overprinted coaxial folding phases are observed with north / south upright axial planes dipping to east and axes plunging gently to North or South. A system of thrust faults is associated with displacement of the hangwall to the west. Down-dip to oblique and strike-slip stretching lineations are also observed, with kinematic indicators showing movement varying from inverse to sinistral. This suggests that the collisional convergence toward the Rio Apa block which generated the mobile belt was not strictly frontal, but had some degree of obliquity, with convergence vectors around SSW - ENE. The Cuiabá Group mica-schists show the most complex structural style with three superimposed coaxial fold phases and more intense tectonic foliations. It is proposed that there would be time correlation between the S3 foliation in the mica-schists in the easternmost area, with the S2 foliation in the central area and the S1 cleavage at the limit of the cratonic area to the west. This pattern can be explained by the westward migration of the deformational front. It is suggestive that the main thrusts coincide with major basin boundaries, where greater variations in thickness and expression of the basal formations occur. During the basin inversion the thrusts probably reactivated the former main listric faults of the rift stage.

Ao sul da cidade de Corumbá, MS, ocorrem imponentes elevações topográficas constituídas por depósitos sedimentares neoproterozóicos do Grupo Jacadigo. Nessas montanhas, cujo conjunto é referido como Maciço do Urucum, assentam-se discordantemente sobre o embasamento rochas siliciclásticas da Formação Urucum com espessuras máximas da ordem de 200 a 300m. A seção continua com depósitos mistos de componentes siliciclásticos e GIFs (granular iron formations), por aproximadamente 100m, e com mais 300m de predomínio de BIFs (banded iron formations). Na periferia do Maciço do Urucum ocorrem rochas carbonáticas do Grupo Corumbá, principalmente das formações Bocaina e Tamengo. Foi esse o conjunto de rochas abordado no presente trabalho por estudos sedimentológicos e estratigráficos em escala de detalhe. A análise integrada de fácies e paleocorrentes permitiu interpretar os mecanismos tectônicos geradores de espaço de acomodação, a orientação da bacia sedimentar, a estruturação de seu preenchimento, implicações geotectônicas regionais e para modelos de deposição de formações ferríferas. Para o preenchimento da bacia, definida na presente dissertação como Bacia Jacadigo, foram interpretados 6 sistemas deposicionais: (I) sistemas de leques aluviais; (II) sistema lacustre; (III) sistema fluvial entrelaçado; (IV) sistema de corpo dágua principal; (V) sistema de fluxos gravitacionais subaquáticos; e (VI) sistema de plataforma carbonática. Esses sistemas foram classificados em 3 tratos tectônicos, sendo os 3 primeiros sistemas deposicionais, essencialmente siliciclásticos e continentais, referentes ao trato de iniciação do rift; os sistemas de corpo dágua principal e de fluxos gravitacionais associados correspondentes ao clímax do rift; e a plataforma carbonática referente ao pós-rift. Esse último caracterizado pela transição entre as formações Urucum e Bocaina, de modo que a classificação em tratos tectônicos reflete os significados geodinâmicos dos grupos Jacadigo e Corumbá. A distribuição espacial dos sistemas deposicionais e dos padrões de paleocorrentes levou à interpretação de uma orientação WNW-ESE para a zona de falhas mestras da Bacia Jacadigo. Essa interpretação implica na correlação do Grupo Jacadigo com a Faixa Chiquitos-Tucavaca e não com a Faixa Paraguai como proposto anteriormente. A distribuição das unidades neoproterozóicas no contexto geotectônico das faixas Chiquitos-Tucavaca e Paraguai levou a corroboração de um posicionamento adjacente da Bacia Jacadigo a uma junção tríplice supostamente soerguida por plumas mantélicas. Toda a sucessão do Grupo Jacadigo mais a sucessão do Morro do Puga, usualmente interpretadas como produtos de processos sedimentares sob influência glacial, foram interpretadas como resposta da sedimentação à tectônica na Bacia Jacadigo, sem necessariamente associação com processos glaciais. Foram distinguidos elementos estruturais da tectônica deformadora daqueles relativos à tectônica formadora do Grupo Jacadigo e sugerida uma conformação braquianticlinal das rochas aflorantes na área urbana de Corumbá, no Maciço do Urucum e nas áreas adjacentes. / At the south of Corumbá, Mato Grosso do Sul state, there are huge topographic elevations made of Jacadigo Groups neoproterozoic sedimentary deposits. Those mountains are known as Maciço do Urucum. The basal unit named Urucum Formation is composed by siliciclastic rocks with maximum thickness of 200 to 300m. The sucession continues with mixed GIF (granular iron formation) and siliciclastic deposits for approximately 100m, and more 300m of almost only BIFs (banded iron formations). In the surroundings of Maciço do Urucum there are carbonatic rocks from the Corumbá Group, mainly from Bocaina and Tamengo formations. This research presents detailed information about sedimentology and stratigraphy of the Maciço do Urucum area and surrounding rocks. The integrated facies and paleocurrents analysis produced the following interpretations: tectonic mechanisms responsible for accommodation spaces, sedimentary basin orientation, filling styles, regional geotectonic implication and iron formation depositional models. About the filling style, six depositional systems of the here named Jacadigo Basin were interpreted: (I) alluvial fan system; (II) lacustrine system; (III) fluvial braided system; (IV) main water body system; (V) subaquatic gravitational flow system; and (VI) carbonate platform system. Those systems were classified in three tectonic system tracts. The first three depositional systems are made of continental siliciclastics and refer to the rift initiation; the main water body and associated gravitational flow systems corresponds to the rift climax; and the carbonate platform to the post rift. The post rift is characterized by the transition between Urucum and Bocaina formations. This transition reflects the geodynamic significance of Jacadigo and Corumbá groups. The spatial distribution of the depositional systems and associated paleocurrent patterns indicated a WNW-ESE orientation to the master fault zone of Jacadigo Basin. This interpretation implies the correlation of Jacadigo Group and Chiquitos-Tucavaca Belt instead of Paraguai Belt, as proposed before. The neoproterozoic units distribution at the geotectonic context of Chiquitos-Tucavaca and Paraguai belts corroborated the adjacent position of Jacadigo Basin to a triple junction supposedly a plume generated uplift. Rocks of Jacadigo Group and Morro do Puga, usually interpreted as glacial deposits, are interpreted here as sedimentation response to tectonics with no necessary relation to glacial processes. Deformation and formation tectonic structural elements were distinguished and a braquianticlinal structure is suggested for the units in the Corumbá and Maciço do Urucum area.

There exist various glacial units in the Neoproterozoic strata of southern Namibia (Kalahari Craton). They were recognised and discussed in the scientific literature for at nearly 100 years (e.g. Coleman, 1926; Gevers, 1931; Schwellnuss, 1941; Martin, 1965). The Snowball Earth theory (Hoffman et al., 1998) had an huge impact on Neoproterozoic geosciences and especially outcrops of the Otavi Group in northern Namibia helped to strengthen and support this idea. Nevertheless, the Neoproterozoic glacial horizons in southern Namibia were difficult to interpret and even more difficult to correlate, due to their tectonic overprint and their scarce outcrops. In order to correlate and differentiate the various Neoproterozoic glacial units of southern Namibia (western rim of Kalahari Craton) a multi‐method approach based on isotopic analyses on zircon grains, whole rock geochemistry, grain size measurements combined with extensive field work, mapping and sampling was applied. In total, ten sections were mapped and measured from which 33 samples were chosen for further analyses. Two of these samples represent local basement rocks, 19 the siliciclastic Neoproterozoic sedimentary cover including glacial diamictites, and twelve carbonate samples. 3474 single zircon grains were picked and measured for their dimensions (width and length). Of those, 2404 zircons were analysed with LA‐ICP‐MS techniques for their U‐Pb and Th‐U ratios in order to calculate detrital zircon ages and to obtain information about the source magma. 1535 of those gave concordant ages (90‐110 % of concordance). Further, selected zircon grains (in total 346) with concordant U‐Pb ages were analyses for their εHf(t) values. To gather more information and to be able to provide absolute ages for the Neoproterozoic glacial units the new technique of LAICP‐MS U‐Pb dating on carbonate samples was tested and gave reliable results for ten out of twelve samples (representing seven different sample locations). Field work revealed two sections containing the Sturtian as well as the Marinoan glacial diamictites in relatively undisturbed succession that qualified as reference profiles for Neoproterozoic strata in southern Namibia: the Dreigratberg and the Namuskluft section in the Gariep Belt close to the Orange River. All analysed samples contain a very similar detrital zircon isotopic record and the whole rock geochemical analyses confirm this interpretation. All siliciclastic samples show a general felsic provenance, with zircon ages mainly divided into two age groups (Mesoproterozoic 1.0 – 105 Ga and Palaeoproterozoic 1.7 – 2.1 Ga), reflecting four different growth and recycling events of Mesoproterozoic to Archaean crustal units. The samples have a geochemical signature of continental island arc and the zircon grain dimensions (width vs. length) are also very similar for all samples. Direct age dating of the samples based on detrital zircons was not possible caused by the lack of ages reflecting deposition times. Nevertheless, the most important differences between the various glacial horizons were found in petrographic features (diamictite pebble contents) and the age peak shift of detrital zircon U‐Pb ages (P/M ratio). Based on these and the two reference profiles correlations to other sections were achievable and the differentiation of four distinct Neoproterozoic glacial horizons for southern Namibia was possible. Furthermore, these new results provide new insights into the Neoproterozoic Gariep Belt formation comprising Tonian rifting events, Cryogenian formation of the Arachania Terrane and final Ediacaran collision of the Rio de la Plata and Kalahari cratons. The combination of all results reflects a continuous sedimentary recycling on the western Kalahari Craton. Comparison and statistical similarity tests based on zircon age data bases for possible source areas defined the Namaqua Natal and Gariep belts as the most likely sedimentary source areas, providing the rock material that got recycled for at least 200 Ma from Kaigas glaciation at ca. 750 Ma to Vingerbreek glaciation at ca. 550 Ma. In addition, the lack of exotic detrital zircon ages within the two Snowball Earth events of this study suggests the interpretation of none or only very minor glacial movement confirming the idea of a completely ice‐covered Earth. The assumed Sturtian and Marinoan ages of Numees Fm and Namaskluft Mbr diamictites were confirmed by the results of U‐Pb cap carbonate dating. Based on these, a minimum duration of ca. 8 Ma for the Sturtian and of ca. 14 Ma for the Marinoan glaciation can be assumed.:Abstract Kurzfassung Contents List of Figures List of Tables List of abbreviations Scientific question and thesis structure 1 Introduction 1.1 The Neoproterozoic era: Supercontinent dispersal and global glaciations 1.1.1 Rodinia supercontinent: Formation, dispersal, and location of Kalahari Craton 1.1.2 Glacial events during the Neoproterozoic era 1.1.2.1 A brief history on the discovery of Snowball Earth events 1.1.2.2 Formation and termination of a Snowball Earth event: The Snowball Earth flow chart 1.1.2.3 Hypotheses for cap carbonate formation 1.1.2.4 Survival of life during a Snowball Earth event 1.2 The Kalahari Craton 1.2.1 Evolution of the Kalahari Craton 1.3 Overview over the Geology of Namibia under special consideration of southern Namibia (Kalahari Craton) 2 Characteristics of southern Namibian Neoproterozoic glacial samples and sides 3 The problematic correlations of Neoproterozoic glacial deposits of the Kalahari Craton (southern Namibia) 4 Methods 4.1 Field work 4.2 Whole Rock geochemical analyses 4.3 Heavy mineral separation and SEM analyses on zircon grains of siliciclastic samples 4.4 Zircon grain size analyses 4.5 LA‐ICP‐MS analyses on zircon grains 4.5.1 U‐Pb analyses with LA‐SF‐ICP‐MS 4.5.2 Th‐U ratio determination on zircon grains 4.5.3 Hf‐isotope measurements with LA‐MS‐ICP‐MS 4.6 LA‐ICP‐MS U‐Pb dating on carbonates 4.7 Provenance interpretations and likeness tests based on zircon U‐Pb age data bases 5 Study I: “The Namuskluft and Dreigratberg sections in southern Namibia (Kalahari Craton, Gariep Belt): a geological history of Neoproterozoic rifting and recycling of cratonic crust during the dispersal of Rodinia until the amalgamation of Gondwana” 5.1 Introduction and geological setting 5.2 Samples and methods 5.3 Results 5.4 Discussion and interpretation 5.5 Summary 6 Study II: “The four Neoproterozoic glaciations of southern Namibia and their detrital zircon record: The fingerprints of four crustal growth events during two supercontinent cycles” 6.1 Introduction 6.2 The samples 6.3 Methods 6.4 Results 6.5 Interpretation and discussion 6.6 Conclusion/Summary 7 Study III: “Correlation of Neoproterozoic diamictites in southern Namibia” 7.1 Introduction 7.2 Sample sites 7.2.1. The Kaigas and Sturtian Numees diamictites at the Orange River section 2.1.1. Outcrops of the Kaigas Fm diamictites 7.2.1.2 Outcrop of the Numees Fm diamictites (Sturtian) 7.2.2 The Sturtian diamcitite of the Blaubeker Fm (Witvlei Grp) at the farmgrounds Blaubeker and Tahiti 7.2.2.1 The Blaubeker diamictite at Blaubeker Farm (type locality) 7.2.2.2 The Blaubeker diamictite at Tahiti Farm (Gobabis‐syncline) 7.2.2.3 Correlation of Blaubeker diamictite at Blaubeker and Tahiti farms 7.2.3 The Sturtian diamictite at the Trekpoort Farm section 7.2.4 The Sturtian and Marinoan diamictites at Namuskluft section (reference profile) 7.2.5 The Sturtian and Marinoan diamictites at Dreigratberg section 7.2.6 Sturtian diamictite and Marinoan‐type cap carbonate at Dreigratberg North section 7.2.7 The Marinoan diamictite at the Witputs Farm section 7.2.8 The post‐Gaskiers Vingerbreek diamictite 7.2.8.1 The Vingerbreek diamictite along the Orange River 7.2.8.2 The Vingerbreek diamictite at Tierkloof Farm (Klein Karas Mountains) 7.3 Methods 7.4 Data and Results 7.4.1 Results of the U‐Pb detrital zircon data 7.4.2 Results of the U‐Pb carbonate dating 7.4.3 Results of zircon grain width and length measurements 7.4.4 Results of the Th‐U zircon ratios 7.4.5 Results of Lu‐Hf isotopic measurements 7.4.6 Geochemical results of the siliciclastic and basement samples 7.4.7 Geochemical results of the carbonate samples 7.5 Discussion and Conclusion 8 Sediment provenance and Snowball Earth ice dynamics 9 Implications on the evolution of the Gariep Belt 10 Conclusions and outlook 11 References Supplementary Material / Die neoproterozoischen Einheiten des südlichen Namibias (Kalahari Kraton) umfassen verschiedene glaziale Einheiten, die schon seit fast 100 Jahren bekannt sind und wissenschaftlich beschrieben wurden (z.B. Coleman, 1926; Gevers, 1931; Schwellnuss, 1941; Martin, 1965). Die Schneeball Erde Theorie (Hoffman et al., 1998) hatte einen enormen Einfluss auf die geologischen Studien des Neoproterozoikums, wobei besonders Aufschlüsse der Otavi Gruppe Nordnamibias die Theorie stärken und bestätigen. Im Gegensatz dazu sind neoproterozoische glaziale Horizonte Südnamibias aufgrund ihrer tektonischen Überprägung und der wenigen Aufschlüsse schwer zu interpretieren und zu korrelieren. Mit dem Ziel, die neoproterozoischen glazialen Einheiten Südnamibias zu unterscheiden und zu korrelieren, wurde ein Multimethodenansatz basierend auf Isotopenanalysen an Zirkonmineralen, Gesamtgesteinsgeochemie, Mineralkorngrößenmessungen und intensiver Feldarbeit angewandt. Insgesamt wurden zehn Profile kartiert und vermessen, von denen 33 Proben zur weiteren Analyse ausgewählt wurden. Zwei dieser Proben stammen vom lokalen Grundgebirge, 19 aus den sedimentären Einheiten darüber (inklusive der glazialen Ablagerungen) und zwölf repräsentieren Karbonatgesteinsproben. 3474 Einzelzirkone wurden hinsichtlich ihrer Breite und Länge vermessen, wovon 2404 Minerale mittels LA‐ICP‐MS nach ihren U‐Pb und Th‐U‐Gehalten analysiert wurden. 1535 dieser Minerale ergaben konkordante Alter (90 – 110% Konkordanz). Darüber hinaus wurden von 346 ausgewählten konkordanten Zirkonen die εHf(t) Werte bestimmt. Um das Datenset zu vervollständigen wurden LA‐ICP‐MS U‐Pb Analysen an Karbonatgesteinen an zehn von zwölf Proben erfolgreich getestet. Im Zuge der Feldarbeiten kristallisierten sich zwei Profile nahe des Oranje heraus, welche die Sturtian und die Marinoan Vereisung in nahezu ungestörter Lagerung enthalten und sich deshalb als Referenzprofile qualifizieren. Alle analysierten Proben zeichnen sich durch sehr ähnliche Zirkonisotopenwerte aus, was durch die Gesamtgesteinsgeochemieanalysen weiterhin bestätigt wird. Alle siliziklastischen Proben zeigen eine generelle felsische Provenienz mit Zirkonaltern welche sich hauptsächlich in zwei Altersgruppen unterteilen lassen (mesoproterozoisch 1.0 – 1.5 Mrd Jahre, paläoproterozoisch 1.7 – 2.1 Mrd Jahre). Diese reflektieren vier verschiedene krustale Entwicklungsstadien vom Mesoproterozoikum bis Archaikum. Die geochemische Signatur aller Proben deutet auf einen kontinentalen Inselbogen hin und auch die Zirkonmineralgrößen sind für alle Proben ähnlich. Eine direkte Altersdatierung auf Grundlage der detritischen Zirkone war aufgrund fehlender junger Alter nicht möglich. Dennoch ist eine Unterscheidung der glazialen Schichten Südnamibias basierend auf den petrographischen Eigenschaften und dem sich verschiebenden Alterstrend der detritischen Zirkone möglich (P/M Verhältnis). In Kombination mit den zwei Referenzprofilen ist eine umfassende Korrelation aller untersuchten Profile möglich und die Unterscheidung von vier Neoproterozoischen glazialen Schichten in Namibia gelungen. Die Ergebnisse geben weitere Einblicke in die neoproterozoische Entwicklung des Gariep Gürtels, welcher durch Riftvorgänge im Tonium, die Bildung des Arachania Terranes während des Cryogeniums und die ediakarische finale Kollision zwischen den Rio de la Plata und Kalahari Kratonen geprägt ist. Die Kombination aller Ergebnisse zeigt ein kontinuierliches Sedimentrecycling auf dem westlichen Kalahari Kraton. Vergleiche und statistische Ähnlichkeitsanalysen basierend auf U‐Pb Zirkonalterdatenbanken ergaben, dass der Namaqua Natal und der Gariep Gürtel die wahrscheinlichsten Liefergebiete sind. Das Recycling fand für mindestens 200 Millionen Jahre zwischen der Kaigas Vereisung (etwa vor 750 Millionen Jahren) und der Vingerbreek Vereisung (etwa vor 550 Millionen Jahren) statt. Darüber hinaus zeigt das Fehlen fremder Zirkonalter für die Schneeball Erde Proben, dass sich die Eispanzer kaum oder nur sehr wenig bewegt haben können, was die Theorie einer komplett zugefrorenen Erde unterstützt. Die Ergebnisse der U‐Pb Karbonatgesteinsdatierungen bestätigen des angenommene Sturtian und Marinoan Alter der Numees Fm und des Namaskluft Mbr. Basierend auf diesen Analysen kann eine Mindestlänge von etwa 8 Millionen Jahren für das Sturtian und etwa 14 Millionen Jahren für das Marinoan Schneeball Erde Ereignis angenommen werden.:Abstract Kurzfassung Contents List of Figures List of Tables List of abbreviations Scientific question and thesis structure 1 Introduction 1.1 The Neoproterozoic era: Supercontinent dispersal and global glaciations 1.1.1 Rodinia supercontinent: Formation, dispersal, and location of Kalahari Craton 1.1.2 Glacial events during the Neoproterozoic era 1.1.2.1 A brief history on the discovery of Snowball Earth events 1.1.2.2 Formation and termination of a Snowball Earth event: The Snowball Earth flow chart 1.1.2.3 Hypotheses for cap carbonate formation 1.1.2.4 Survival of life during a Snowball Earth event 1.2 The Kalahari Craton 1.2.1 Evolution of the Kalahari Craton 1.3 Overview over the Geology of Namibia under special consideration of southern Namibia (Kalahari Craton) 2 Characteristics of southern Namibian Neoproterozoic glacial samples and sides 3 The problematic correlations of Neoproterozoic glacial deposits of the Kalahari Craton (southern Namibia) 4 Methods 4.1 Field work 4.2 Whole Rock geochemical analyses 4.3 Heavy mineral separation and SEM analyses on zircon grains of siliciclastic samples 4.4 Zircon grain size analyses 4.5 LA‐ICP‐MS analyses on zircon grains 4.5.1 U‐Pb analyses with LA‐SF‐ICP‐MS 4.5.2 Th‐U ratio determination on zircon grains 4.5.3 Hf‐isotope measurements with LA‐MS‐ICP‐MS 4.6 LA‐ICP‐MS U‐Pb dating on carbonates 4.7 Provenance interpretations and likeness tests based on zircon U‐Pb age data bases 5 Study I: “The Namuskluft and Dreigratberg sections in southern Namibia (Kalahari Craton, Gariep Belt): a geological history of Neoproterozoic rifting and recycling of cratonic crust during the dispersal of Rodinia until the amalgamation of Gondwana” 5.1 Introduction and geological setting 5.2 Samples and methods 5.3 Results 5.4 Discussion and interpretation 5.5 Summary 6 Study II: “The four Neoproterozoic glaciations of southern Namibia and their detrital zircon record: The fingerprints of four crustal growth events during two supercontinent cycles” 6.1 Introduction 6.2 The samples 6.3 Methods 6.4 Results 6.5 Interpretation and discussion 6.6 Conclusion/Summary 7 Study III: “Correlation of Neoproterozoic diamictites in southern Namibia” 7.1 Introduction 7.2 Sample sites 7.2.1. The Kaigas and Sturtian Numees diamictites at the Orange River section 2.1.1. Outcrops of the Kaigas Fm diamictites 7.2.1.2 Outcrop of the Numees Fm diamictites (Sturtian) 7.2.2 The Sturtian diamcitite of the Blaubeker Fm (Witvlei Grp) at the farmgrounds Blaubeker and Tahiti 7.2.2.1 The Blaubeker diamictite at Blaubeker Farm (type locality) 7.2.2.2 The Blaubeker diamictite at Tahiti Farm (Gobabis‐syncline) 7.2.2.3 Correlation of Blaubeker diamictite at Blaubeker and Tahiti farms 7.2.3 The Sturtian diamictite at the Trekpoort Farm section 7.2.4 The Sturtian and Marinoan diamictites at Namuskluft section (reference profile) 7.2.5 The Sturtian and Marinoan diamictites at Dreigratberg section 7.2.6 Sturtian diamictite and Marinoan‐type cap carbonate at Dreigratberg North section 7.2.7 The Marinoan diamictite at the Witputs Farm section 7.2.8 The post‐Gaskiers Vingerbreek diamictite 7.2.8.1 The Vingerbreek diamictite along the Orange River 7.2.8.2 The Vingerbreek diamictite at Tierkloof Farm (Klein Karas Mountains) 7.3 Methods 7.4 Data and Results 7.4.1 Results of the U‐Pb detrital zircon data 7.4.2 Results of the U‐Pb carbonate dating 7.4.3 Results of zircon grain width and length measurements 7.4.4 Results of the Th‐U zircon ratios 7.4.5 Results of Lu‐Hf isotopic measurements 7.4.6 Geochemical results of the siliciclastic and basement samples 7.4.7 Geochemical results of the carbonate samples 7.5 Discussion and Conclusion 8 Sediment provenance and Snowball Earth ice dynamics 9 Implications on the evolution of the Gariep Belt 10 Conclusions and outlook 11 References Supplementary Material

Cette thèse de doctorat se focalise sur la fin du Précambrien, le Néoprotérozoïque, une période charnière dans lhistoire de la Terre, par létude dunités ophiolitiques datées entre 800 et 700 Ma. Les travaux présentés ici portent sur létude pétrographique, géochimique et magnétique des serpentinites de ces ophiolites. Associées à des sutures panafricaines en bordure des cratons ouest africain et amazonien, ces ophiolites sont les témoins des subductions et de la lithosphère océanique associées à la dislocation du supercontinent Rodinia. Létude de ces ophiolites permet de proposer des contextes de formation pour ces sections de lithosphère océanique. Une autre question à lorigine de ce travail était : Létude de la serpentinisation et de lhydrothermalisme associé permet-elle dapporter des contraintes sur le paléoenvironnement océanique ? Les travaux sur les serpentinites et les roches mafiques associées des unités ophiolitiques de lAraguaia belt (757 ± 49 Ma1, Brésil) constituent la première étude géochimique réalisée sur ces unités. La chimie des spinelles couplée à des travaux de modélisation géochimique, portant essentiellement sur les concentrations en REE, attestent dun protolithe hautement réfractaire, ayant enduré entre 14 et 24 % de fusion partielle. Ces travaux témoignent aussi de laffinité abyssale de ces serpentinites, confirmée par les signatures N-MORB et E-MORB des basaltes associés. Il apparait que la serpentinisation de ces unités sest probablement opérée en deux temps, en domaine océanique, puis par interaction avec des fluides dérivés des sédiments encaissants, aboutissant à de forts enrichissements en LILE, en B et en Li dans ces serpentinites. Finalement, nous proposons que ces sections de lithosphère océanique, ainsi que les métasédiments les abritant (Tocantins group), soient les reliques dune transition océan-continent (TOC) en bordure est du craton amazonien. Les études de terrain, pétrographiques et géochimiques sur les sections ophiolitiques de Khzama (762 ± 2 Ma2) et dAït Ahmane (Anti-Atlas, Maroc) ont dans un premier temps permis de confirmer le lien supposé entre ces deux ophiolites. Les spinelles des serpentinites de ces unités sont caractérisés par des Cr# très élevés et des Mg# bas témoignant dun protolithe ayant enduré des taux de fusion supérieurs à 25 %, confirmant leur affinité avec la zone de subduction anti-atlasique. Ceci est corroboré par de très faibles concentrations en éléments incompatibles comme Al, Ti, HREE et HFSE. Le contexte le plus probable concernant la genèse de ces sections de lithosphère est ainsi un même centre daccrétion arrière-arc intra-océanique, à la marge du supercontinent Rodinia. Létude comparative des serpentinites de ces ophiolites a aussi permis de mettre en évidence en évidence lintérêt des mesures magnétiques pour tracer le degré daltération des spinelles chromifères dans les serpentinites, approche pouvant être étendue à dautres types de roches. Notamment, nous montrons que la Cr-magnétite et la ferritchromite peuvent être identifiées à laide des mesures de susceptibilité magnétique en chauffe. Enfin, lassociation des méthodes magnétiques, pétrographiques et géochimiques nous permet de proposer un modèle concernant la formation des veines de magnétite massives de lunité dAït Ahmane Nord. Nous montrons que le triptyque : serpentinites et spinelles altérés et veines de magnétite centimétriques, constitue un système hydrothermal abyssal fossile, de type fumeur noir. Dans ce contexte, les compositions isotopiques en oxygène des veines de magnétite permettent de proposer une valeur du 18O des océans néoprotérozoïques profonds de -1.33 ± 0.98 (VSMOW), soit une valeur très similaire à lactuel (entre -1 et +1 VSMOW). Elle tranche aussi le débat sur lévolution du 18O des océans au cours des temps géologiques en attestant dune constance de celui-ci, au moins depuis le Néoprotérozoïque. / This Doctoral thesis focus on the end of the Precambrian, the Neoproterozoic, a pivotal period in the Earth history, by the study of ophiolitic units dated between 800 and 700 Ma. This work essentially deals with the petrography, geochemistry and magnetism of serpentinites from these ophiolites. They are associated with Panafrican orogenic belts along the West African and the Amazonian cratons and witnesses the subductions and the oceanic lithosphere associated to the break-up of the supercontinent Rodinia. The study of these neoproterozoic ophiolites allowed us to propose the formation settings for these sections of oceanic lithosphere. Another question behind this work is: Does the study of serpentinization and associated hydrothermalism allows one to provide constraints on the oceanic paleoenvironment? Work on the serpentinites and associated mafic rocks from the Araguaia belt ophiolitic units (757 ± 49 Ma1, Brazil) constitute the first geochemical study realized on these units. The Cr-spinel chemistry coupled with geochemical modeling, concerning essentially the REE concentrations, attest to a highly refractory protolith that endured between 14 and 24% of partial melting. This work also indicate an abyssal affinity (i.e. MOR rather than SSZ) of these serpentinites, which is confirmed by the N-MORB and E-MORB geochemical signature of the associated basalts. It appears that the serpentinization of these units probably took place in two steps, first in oceanic domain and then by interaction with fluids derived from the surrounding sediments after obduction, leading to strong LILE, B and Li enrichments in the serpentinites. Finally, we propose two potential settings concerning the origin of the sections of oceanic lithosphere presently found in the Araguaia belt: (1) an ocean-continent transition or (2) slices of a more mature lithosphere trapped into an accretionary wedge. Fieldwork, petrography and geochemical analysis on serpentinites from the Khzama (762± 2 Ma²) and Aït Ahmane ophiolitic sections (Anti-Atlas, Morocco) firstly allowed to confirm the supposed link between these two ophiolites. Cr-spinels in serpentinites from these units are characterized by very high Cr# and low Mg# testifying of a protolith having endured partial melting greater the 25%, confirming their affinity with the anti-atlasic subduction zone. This is corroborated by very low incompatible element concentrations such as Al, Ti, HREE and HFSE. Thus, the most likely setting for the genesis of these sections of lithosphere is a same intra-oceanic back-arc spreading center at the margin of the Rodinia supercontinent. The comparative study of all studied serpentinites from Neoproterozoic ophiolites in different settings also demonstrates the ability of magnetic measurements in monitoring the Cr-spinel alteration degree, a method which can be extended to other types of rocks. In particular, we show that Cr-magnetite and ferritchromite can be identified using thermomagnetic curves. Finally, the association of magnetic, petrographic and geochemical methods allows us to propose a model concerning the formation of the massive magnetite veins of the North Aït Ahmane unit. We show that the triptych consisting in: altered serpentinites, spinels and centimetric magnetite veins, results from a fossil, black smoker type, abyssal hydrothermal system. In this context, the oxygen isotopic compositions of the magnetite veins provide a 18O value of the deep Neoproterozoic oceans of -1.33 ± 0.98 (VSMOW), a value that is very similar to the current one (between -1 and +1 VSMOW). It also settles the debate on the evolution of the 18O of the oceans during geological time, attesting of its consistency, at least since the Neoproterozoic.

A Formação Sete Lagoas, base do Grupo Bambuí, tem sido alvo de constantes discussões sobre o contexto temporal e ambiental sob a qual esta unidade foi depositada. Sua idade tem sido atribuída a dois momentos distintos do Neoproterozoico, e ambas têm implicações evolutivas significativas. A primeira proposta, baseadas em dados geoquímicos e litoestratigráficos,relaciona a deposição da Formação Sete Lagoas após o fim da glaciação Marinoana (do modelo paleoclimático Snowball Earth), há cerca de 635 Ma, quando mudanças paleogeográficas e geoquímicas levaram a mudanças climáticas de escala global, o quepode ter impactado significativamente na bioprodutividade do Edicarano. O segundo modelo deposicional baseia-se na ocorrência de Cloudina sp., um fóssil-guia do Ediacarano final, em níveis estratigráficos próximos à base da Formação Sete Lagoas, apontando, portanto, para uma idade mais nova que a primeira hipótese. No entanto, ambos os modelos preveem um cenário de mudanças, ocorridas no Neoproterozoico tardio, enquanto a Formação Sete Lagoas estava sendo depositada. Tais mudanças foram de natureza climática, paleogeográfica e geoquímica, que influenciaram a composição da atmosfera e da hidrosfera, e culminaram em profundas mudanças na biosfera. Propôs-se aqui uma análise pormenorizada de microbialitos e microfósseis da Formação Sete Lagoas, visando compreender como os produtores, base dos ecossistemas, teriam respondido a tantas transformações ambientais e ecológicas, além de estabelecer a abrangência estratigráfica dos microbialitos e microfósseis desta unidade. Foram analisadas tramas de microbialitos carbonáticos e precocemente silicificados, amostras de mão para comparação e dados de afloramentos. Uma avaliação de materiais reportados em meados e na segunda metade do século passado também foi necessária, tendo em vista os avanços recentes no campo da Paleobiologia do Pré-Cambriano. Os dados demonstraram que a Formação Sete Lagoas conta com uma riqueza treze formasmicrobialíticas, sendo onze detalhadas neste trabalho e encontradas ao longo de toda a formação, tanto sobre o Cráton do São Francisco, quanto sobre a Faixa Brasília, porém em baixa quantidade. Estas formas são compostas por onze tipos de tramas, cujo conteúdo biogênico em última análise, remete, mesmo que de forma reliquiar, à formas cianobacterianas recentes reconhecidas como formadoras de estromatólitos. Por outro lado, microfósseis silicificados não são comuns, e foram observados apenas em três localidades, onde já tinham sido reportados. Porém, a re-análise deste material permitiu refinar os dados e identificar cinco táxons, quatro cianobacterianos - os gêneros Siphonophycus, Oscillatoriopsis e Eosynechococcus- e um Incertae sedis - o gêneroArchaeotrichion. A baixa diversidade de microfósseis, ou seja, baixa riqueza e baixa abundância, somada à baixa abundância e densidade de microbialitos nos afloramentos analisados foi interpretada como resultados de eventos diagenéticos e tectônicos que resultaram na perda de material. Outra vertente do  presente trabalho foi a re-avaliação de estruturas reportadas como fósseis há cerca de 50 anos, cuja interpretação à luz dos conhecimentos atuais, permitiram a identificação de alguns como pseudofósseis, a reclassificação deuma espécie de acritarco esferomórfico (Leiosphaeridia jacutica[Timofeev 1966]) e de outro espécime como provável Nemiana simplexPalij 1976. De um modo geral, pode-se perceber que, embora poucos espécimes tenham sido preservados, o registro fóssil da Formação Sete Lagoas é variado e inclui microbialitos, microfósseisbentônicos e planctônicos, identificados neste trabalho, além de icnofósseis, biomarcadores e metazoários reportados em trabalhos anteriores, mas que ainda demandam novas considerações. A ocorrência vertical de microbialitos ao longo de toda a unidade e a diversidade de tramas que os compõem demonstram que a bioprodutividade não sofreu declínio com as mudanças paleoambientais, seja por conta de mudanças climáticas, se considerarmos a Formação Sete Lagoas como capa carbonática, seja pelo estabelecimento de metazoários nos ecossistemas, se a considerarmos uma unidade depositada a partir do Ediacarano tardio. / The Sete Lagoas Formation, base of BambuíGroup, has been under constant discussion about the temporal and environmental context under it was deposited. Its age has been attributed to two different moments ofNeoproterozoic, each one comprising significative evolutionay changes. The first one, based on geochemical and lithostratigraphic data, related the deposition of Sete Lagoas Formation to the end of Marinoan glacial episode (the Snowball Earthpaleoclimatic model), ca. 635 Ma, when pelogeographic and geochemical changes resulted in global climatic changes, that could result in significative impacts over the Ediacaran bioprodutivity. The second age model is based on the occurrence of Cloudinasp., an index fossil of Terminal Neoproterozoic, in stratigraphic levels near the base ofthe formation, pointing for a younger age that previously proposed. However, both modelspredict a scenario of environmental changes, occurred during the Late Ediacaran, while the Sete Lagoas Formation deposited. Such changes include climatic, paleogeographic and geochemical, that influenced the composition of atmosphere and hydrosphere, what resulted in profound changes in the biosphere. Here it was proposed a detailed study of microbialites and silicified microfossils of Sete Lagoas Formation, aiming to understand the responses of producers, the framework of any ecosystem, would reacted to suchpaleoenvironmental and ecological changes, as well also establish the stratigraphic occurrence of Sete Lagoas Formatiom microbialites and microfossils. Fabrics of carbonate and early silicified microbialites were analyzed, aswell hand samples for comparison and data acquired in the outcrops. Previous reported material, collect in the past half century was also re-evaluated due to new knowledge concerning the Paleobiology of Precambrian. The data showed that the Sete Lagoas Formation has a richness of thirteen microbialite forms, which eleven were detailed in this paper and found throughout the unit, on the São Francisco Craton, as well on the Brasília Fold Belt, but in low abundance. These forms are composed of eleven types of fabrics, which biogenic content ultimately refers, even if reliquiar preservation, to Recent cyanobacteria recognized as mat formers. Moreover, silicified microfossils are not common, and were only observed in three localities, where they had already been reported. However, re-analysis of this material allowed to refine the data and identify five taxa, four cyanobacteria - Siphonophycus, Oscillatoriopsis, Eosynechococcus- and one Incertae sedis - Archaeotrichion. The low diversity of microfossils, including low richness and low abundance, coupled with the low abundance and density of microbialites in outcrops were interpreted as a result of diagenetic and tectonic events that resulted in the loss of material. Another aspect of this work was the re-evaluation of structures reported as fossils for about 50 years, whose interpretation in the light of updated knowledge, allowed the identification of some pseudofossils as the reclassification ofa species of sphaeromorphic acritarch (Leiosphaeridia jacutica [Timofeev 1966]) and putative Nemiana simplexPalij 1976. In general, it can be seen that, although a few specimens have been preserved, the fossil record of the Sete Lagoas Formation is varied and includes microbialites, benthic and planktonic microfossils, identified in this work, as well as trace fossils, biomarkers and metazoan reported in previous works, which require new considerations. The vertical occurrence of microbialites throughout the unit and the variety of frames that make up demonstrate that bioproductivity did not declined due to paleoenvironmental changes, either due to climate change, considering the formation Sete Lagoas Formation as cap carbonate, or by establishment ofmetazoan ecosystems, if we consider a unit deposited during the Late Ediacaran.

Cette thèse de doctorat se focalise sur la fin du Précambrien, le Néoprotérozoïque, une période charnière dans l'histoire de la Terre, par l'étude d'unités ophiolitiques datées entre 800 et 700 Ma. Les travaux présentés ici portent sur l'étude pétrographique, géochimique et magnétique des serpentinites de ces ophiolites. Associées à des sutures panafricaines en bordure des cratons ouest africain et amazonien, ces ophiolites sont des vestiges des subductions et de la lithosphère océanique associées à la dislocation du supercontinent Rodinia. L'étude de ces ophiolites permet de proposer des contextes de formation pour ces sections de lithosphère océanique. Une autre question à l'origine de ce travail était : L'étude de la serpentinisation et de l'hydrothermalisme associé permet-elle d'apporter des contraintes sur le paléoenvironnement océanique ? / This Doctoral thesis focus on the end of the Precambrian, the Neoproterozoic, a pivotal period in the Earth history, by the study of ophiolitic units dated between 800 and 700 Ma. This work essentially deals with the petrography, geochemistry and magnetism of serpentinites from these ophiolites. They are associated with Panafrican orogenic belts along the West African and the Amazonian cratons and witnesses the subductions and the oceanic lithosphere associated to the break-up of the supercontinent Rodinia. The study of these neoproterozoic ophiolites allowed us to propose the formation settings for these sections of oceanic lithosphere. Another question behind this work is: Does the study of serpentinization and associated hydrothermalism allows one to provide constraints on the oceanic paleoenvironment?

Ever since the first plate-tectonic model for the Appalachians was proposed, the Laurentian margin has been interpreted as having experienced a collision-related dynamo-thermal event during the Middle Ordovician Taconic orogeny. In the western Newfoundland Appalachians, evidence for this collision is well-preserved in the Dashwoods subzone. Nevertheless, rocks of the neighbouring Corner Brook Lake block (CBLB), which is located in the heart of the Laurentian realm, did not show evidence for such an event. Instead, it was affected by Early Silurian Salinic deformation and associated peak metamorphism. Even though this difference in Early Palaeozoic tectonic history between the Dashwoods and the CBLB is widely known, it has not been satisfactorily explained. To better understand the Early Palaeozoic history of the region, in particular to test and better explain the lack of a Taconic dynamo-thermal event in the CBLB, field mapping, microscopic work, and U-Pb and 40Ar/39Ar geochronological studies were undertaken in the western and northern part of the Dashwoods subzone, and in the southern part of the CBLB. In addition, the kinematic history of the Baie Verte-Brompton Line - Cabot Fault Zone (BCZ), the tectonic zone that separates the two unique tectonic fragments, was studied. The western and northern parts of the Dashwoods subzone contain variably foliated igneous units of Middle Ordovician age (ca. 460 Ma) that are associated with the regionally voluminous Notre Dame continental arc. A ca. 455 Ma conjugate set of late syn-tectonic pegmatite dykes in the BCZ demonstrates a dextral sense of shear along the BCZ (DBCZ-1) during the Late Ordovician to earliest Silurian, and constrains the minimum age of the main phase of ductile deformation in the Dashwoods subzone. The fault-bounded CBLB has been affected by a single west-vergent deformational event, constrained between ca. 434 and ca. 427 Ma. More importantly, no evidence – neither petrographic nor geochronological – is present that would indicate that the CBLB was affected by a significant Taconic dynamo-thermal event. Hence, the CBLB and Dashwoods could not have been juxtaposed until after the late Early Silurian. Furthermore, the basement to the CBLB is devoid of any Grenville (sensu lato; ca. 1.0-1.3 Ga) U-Pb ages, which is in sharp contrast with crystalline basement elsewhere in the region, such as the Long Range Inlier. Therefore, it is highly unlikely that the CBLB represents the para-autochthonous leading edge of the Laurentian craton in the Newfoundland Appalachians, as commonly accepted. The CBLB is interpreted as a suspect terrane that has moved over 500 km parallel to the strike of the orogen. Docking to the external Humber Zone is likely to have occurred during the Early Silurian. Final juxtaposition with the Dashwoods took place after the late Early Silurian (post-Salinic) as a result of protracted dextral movement along the BCZ (DBCZ-2 and DBCZ-5). Current tectonic models for the Newfoundland Appalachians mainly focus on well-documented Early Palaeozoic orthogonal convergence of various terranes with the Laurentian margin, but large-scale orogen-parallel movements have rarely been considered. The possibility of large-scale strike-slip tectonics documented here, in addition to the convergent motions, may have significant implications for the tectonic interpretation of the Early Palaeozoic evolution of the Newfoundland Appalachians.

Ever since the first plate-tectonic model for the Appalachians was proposed, the Laurentian margin has been interpreted as having experienced a collision-related dynamo-thermal event during the Middle Ordovician Taconic orogeny. In the western Newfoundland Appalachians, evidence for this collision is well-preserved in the Dashwoods subzone. Nevertheless, rocks of the neighbouring Corner Brook Lake block (CBLB), which is located in the heart of the Laurentian realm, did not show evidence for such an event. Instead, it was affected by Early Silurian Salinic deformation and associated peak metamorphism. Even though this difference in Early Palaeozoic tectonic history between the Dashwoods and the CBLB is widely known, it has not been satisfactorily explained. To better understand the Early Palaeozoic history of the region, in particular to test and better explain the lack of a Taconic dynamo-thermal event in the CBLB, field mapping, microscopic work, and U-Pb and 40Ar/39Ar geochronological studies were undertaken in the western and northern part of the Dashwoods subzone, and in the southern part of the CBLB. In addition, the kinematic history of the Baie Verte-Brompton Line - Cabot Fault Zone (BCZ), the tectonic zone that separates the two unique tectonic fragments, was studied. The western and northern parts of the Dashwoods subzone contain variably foliated igneous units of Middle Ordovician age (ca. 460 Ma) that are associated with the regionally voluminous Notre Dame continental arc. A ca. 455 Ma conjugate set of late syn-tectonic pegmatite dykes in the BCZ demonstrates a dextral sense of shear along the BCZ (DBCZ-1) during the Late Ordovician to earliest Silurian, and constrains the minimum age of the main phase of ductile deformation in the Dashwoods subzone. The fault-bounded CBLB has been affected by a single west-vergent deformational event, constrained between ca. 434 and ca. 427 Ma. More importantly, no evidence – neither petrographic nor geochronological – is present that would indicate that the CBLB was affected by a significant Taconic dynamo-thermal event. Hence, the CBLB and Dashwoods could not have been juxtaposed until after the late Early Silurian. Furthermore, the basement to the CBLB is devoid of any Grenville (sensu lato; ca. 1.0-1.3 Ga) U-Pb ages, which is in sharp contrast with crystalline basement elsewhere in the region, such as the Long Range Inlier. Therefore, it is highly unlikely that the CBLB represents the para-autochthonous leading edge of the Laurentian craton in the Newfoundland Appalachians, as commonly accepted. The CBLB is interpreted as a suspect terrane that has moved over 500 km parallel to the strike of the orogen. Docking to the external Humber Zone is likely to have occurred during the Early Silurian. Final juxtaposition with the Dashwoods took place after the late Early Silurian (post-Salinic) as a result of protracted dextral movement along the BCZ (DBCZ-2 and DBCZ-5). Current tectonic models for the Newfoundland Appalachians mainly focus on well-documented Early Palaeozoic orthogonal convergence of various terranes with the Laurentian margin, but large-scale orogen-parallel movements have rarely been considered. The possibility of large-scale strike-slip tectonics documented here, in addition to the convergent motions, may have significant implications for the tectonic interpretation of the Early Palaeozoic evolution of the Newfoundland Appalachians.

O estágio pós-colisional Neoproterozoico no sul do Brasil é marcado por intenso magmatismo granítico controlado por zonas de cisalhamento transcorrentes, relacionadas ao Cinturão de Cisalhamento Sul-brasileiro (CCSb). O CCSb controlou a ascensão e o posicionamento de magmas crustais e mantélicos. Neste contexto, O Granito Corre-mar (GCM) representa uma pequena intrusão posicionado em uma zona de baixa deformação localizada entre dois importantes segmentos do CCSb: as Zonas de Cisalhamento Major Gercino e Itajaí- Perimbó. O GCM possui um diagnóstico par de foliações subevetical que forma um par S-C sinistral, presente em todas as intrusões, independentemente do tamanho, e foi posicionado em um sistema conjugado, onde um cisalhamento sinistral de direção NNE, e uma extensão na direção NW-SE, gerando espaço ao longo da direção NE. Deformação de estado sólido associada ao cisalhamento NNE é atestado por microestruturas como recristalização de feldspatos e caudas de recristalização assimétricas. A abertura é atribuída à dinâmica regional destral transcorrente das zonas de cisalhamento Major Gercino e Itajaí-Perimbó, sendo que o posicionamento foi controlado essencialmente pela componente de estensão NW-SE. A idade de cristalização em zircão U-Pb LAMC- ICP-MS do GCM de 615 ± 4 Ma, muito próxima a outros granitos regionais, como as idades de 611 Ma do Granito Serra dos Macacos (GSM) e de 620 Ma do Granito Rio Pequeno (GRP) sugere que esses três corpos graníticos são sincrônicos. As fortes feições de deformação presents no GCM, diferentemente dos granitos Neoproterozoicos próximos, demonstra que o espaço, mais do que o tempo, pode explicar a diferença dos padrões estruturais identificados no GCM. Assinaturas geoquímicas e de isótopos de Sr-Nd, como caráter levemente peraluminoso, altos conteúdos de K, altas razões de ETRL/ETRP, moderados conteúdos de Rb, Nb, Zr e ETR em relação à SiO2, juntamente com baixas razões de 86Sr/87Sri e valores de εNdt fortemente negativos, indicam que o GCM é derivado de fontes crustais antigas, possivelmente relacionadas à rochas quartzofeldspáticas ortognáissicas Paleoproterozoicas do Complexo Camboriú. A relaçãodas das idades das heranças Arqueanas a Paleoproterozoicas do GCM com as idades dos eventos de migmatização identificados no Complexo Camboriú, além da relação das idades de cristalização de ~615-611 Ma dos granitos crustais da área com o último evento de migmatização em 640-610, reforça a conexão genética entre eles. As idades TDM paleoproterozoicas, as assinaturas geoquímicas e isotópicas, a cristalização e as idades de heranças do GCM e do GSM atestam que eles representam pulsos graníticos contemporâneos e comagmáticos, com uma conexão genética com o evento de migmatização Neoproterozoico do Complexo Camboriú. / The Neoproterozoic post-collisional stage in south Brazil is marked by intense granitic magmatism controlled by transcurrent shear zones all related to the Southern Brazilian Shear Belt (SBSB). The SBSB controls the ascent and emplacement of crustal and mantle magmas. In such scenario, the Corre-mar Granite (CMG), represent a small intrusion emplaced in a low strain zone located between two important segments of the SBSB: the Major Gercino and Itajaí-Perimbó Shear Zones. The CMG have a diagnostic subvertical foliation pair that form a sinistral S-C pair, present in all intrusions regardless of their size, and was emplaced within a conjugate system, where sinistral NNE shearing and NW-SE extension were both active, generating space along the NE direction. Solid state deformation associated to the NNE shearing is attested by microstructures as feldspar recrystallization and asymmetric recrystallization tails. The opening is attributed to the regional dextral transcurrent dynamics of the Major Gercino and Itajaí-Perimbó shear zones and magma emplacement was essentially conditioned by the NW extension component. The zircon U-Pb LA-MC-ICP-MS crystallization age of CMG at 615 ± 4 Ma, very close to other regional granites, as the 611 Ma Serra dos Macacos (SMG) and 620 Ma Rio Pequeno Granite (RPG) points these three granitic bodies as quite synchronous. The strong deformation features present in the CMG, as opposed to the other nearby Neoproterozoic granites (RPG and SMG) demonstrate that space, rather than time, must be called upon to explain the difference in the structural patterns identified in the CMG. Geochemical and Sr-Nd isotopic signatures, as slight peraluminous character, high-K contents, high LREE/HREE ratios, moderate Rb, Nb, Zr, and REE contents to regular SiO2, together with low 86Sr/87Sri and the strongly negative εNdt values indicate that the CMG is derived from old crustal sources possibly related to the Paleoproterozoic Camboriú Complex quartz-feldspatic orto-gneissic rocks. The match of the Archean to Paleoproterozoic inheritance ages of the CMG with the migmatization event ages identified in the Camboriú Complex and moreover the match of the crystallization ages of ~615-611 Ma of the crustalderived granites with the last migmatization event at 640-610 Ma reinforces the genetic link between them. The Paleoproterozoic TDM ages, the geochemical and isotopic signatures, the crystallization and inheritance ages resemblance of the CMG and the SMG attest that they represent comagmatic and contemporaneous granitic pulses with a genetic connection with the Neoproterozoic migmatization event in the Camboriu Complex.