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Region surrounding the Central Bohemian Plutonic Complex represents one of the most important gold bearing zones in the Czech Republic. Several types of gold deposits dominated by hydrothermal quartz gangue were explored here and distinguished: the Intrusion related gold deposits ("Petráčkova hora" and "Mokrsko") and the orogenic gold deposits ("Jílové u Prahy" and "Kasejovice" ). Deposits "Libčice u Nového Knína" and "Roudný u Vlašimi" are partially similar to the orogenic gold type, but are different from other orogenic type deposits in the region. All together 38 samples from these five deposits were analyzed with laser ablation technique (LA- ICP-MS) to produce 228 measurements. Selected samples were selected to represent both main quartz gangue carrying the Au ore and latter weakly mineralized quartz gangue. Samples representing hydrothermal quartz gangue with no direct relation to Au-ore deposits were also collected in order to compare chemical composition of both quartz types originating from the same area. Main concern of this work was in-situ analysis of chemical composition of different generations of quartz gangue and statistical comparison of differences within individual deposits as well as comparing the examined deposits themselves. Total 65 isotopes were measured, trace element...

The primary objective of this thesis was to date the age of gold mineralization in the Jiaodong and Liaodong Peninsulas, China. Based on SHRIMP U-Pb zircon ages of dykes and host rocks at 13 gold deposits in the two peninsulas and the 40(subscript)Ar-39(subscript)Ar dating of sericite at the Cangshang deposit in the Jiaodong Peninsula, a single gold mineralization event at ca. 122 - 119 Ma has been identified.Ten gold deposits in the Jiaodong Peninsula and three gold deposits in the Liaodong Peninsula were examined. Gold mineralization can be divided into the disseminated-and-veinlet type (Jiaojla-style) and vein type (Linglong-style) and all these deposits are strongly controlled by faults. The most common host rocks are granitoids, with a SHRIMP 206(subscript)Pb/238(subscript)U age of 150 - 165 Ma. The youngest host rocks in the Jiaodong Peninsula are granodiorite, with an age of ca. 128 Ma. The oldest dated host rock in the Jiaodong Peninsula is amphibolite with a metamorphic zircon age of 1852 plus or minus 37 Ma; in the Liaodong Peninsula, the oldest host rock is metasandstone with the youngest detrital zircon giving an age of 1886 plus or minus16 Ma. The Jiaodong and Liaodong Peninsulas are underlain by Precambrian basement with components up to ca. 3.7 Ga old and these are reflected in the zircon population. There are three main peaks of inherited zircons, which yield Late Archaean (ca. 2500 Ma), Palaeoproterozoic (1800-2200 Ma) and Early Mesozoic (ca. 200-250 Ma) ages.The close spatial and temporal relationships between dykes and gold mineralization has only recently been recognized in China. Based on the cross-cutting relationship between dykes and gold lodes (and the alteration style of dykes), three types of dykes are recognized: pre-, syn- and post-mineralization dykes. Premineralization dykes yield an age of ca. 124 Ma; syn-mineralization dykes give an ++ / age of ca. 122-119 Ma, which can also be interpreted as the time of gold mineralization; further work is needed to date post-mineralization dykes, since no suitable samples were identified during this study.40(subscript)Ar-39(subscript)Ar dating of sericite has been used to determine the timing of gold mineralization at the Cangshang Gold Deposit. It gives a well-defined 40(subscript)Ar-39(subscript)Ar age of 121.3 plus or minus 0.2 Ma.The second objective of this thesis was to understand why the tectonic setting of the Jiaodong and Liaodong Peninsulas is favourable for gold formation and what is a sound genetic model for these gold deposits. Based on this study, it is interpreted that multiple orogenic events created a favourable tectonic environment for the Jiaodong and Liaodong gold deposits. It is suggested that delamination related to orogenic events occurred beneath the Jiaodong and Liaodong Peninsulas. The substantial heat and fluid transfer caused by delamination allowed mantle-derived magma and auriferous fluids to be channelled along deep faults to favourable structures within the crust. This probably explains why the dykes and gold lodes are closely associated in both time and space.

Ore deposits of the Krásná Hora ore district are the main representative of the Sb-Au mineralization in the Czech Republic. It can be classified genetically as epizonal subtype of orogenic gold deposits. Spatially and partly temporally are associated with the intrusion of the Central Bohemian Pluton. The ore bodies are related to quartz veins that follow the course of E-W striking lamprophyre dykes, which are usually heavily crushed and altered. Ore shoots with massive stibnite are located mainly at the intersections of these E-W trending veins with the NW-SE striking tectonic fault zones. Au-Sb ores at Krásná Hora ore district formed in an area of repeatedly activated fault zones. Three generations of hydrothermal quartz were identified on microscopic scale. Earliest quartz (Qtz1), which was considered in the literature auriferous originated from low-salinity H2O - CO2 fluids at ~350 řC and at a depth of about 5 km. The younger quartz (Qtz2) originated at lower temperatures of about 260 řC and lower depth of about 3-4 km from low/saline aqueous fluids. Both older (Qtz1) and younger quartz (Qtz2) are not auriferous. The gold is associated with younger paragenetic formation (Anti + Au + Cc + Qtz3) that fills in intergranular spaces and fractures in Qtz1 and Qtz2 . Due to the partial exhumation of the...

The Goldstrike property is located in northern Nevada and contains one of the largest and highest-grade Carlin-type gold deposits. The majority of the Eocene Au mineralization (e.g., Ore I) is hosted in intensely altered Paleozoic lower-plate impure carbonate rocks, and is characterized by strong to moderate silicification, higher calculated pyrite and ore-related element concentrations (e.g., As, Cu, Hg, Ni, Tl, Sb, W, and Zn) than Ore II, which is weakly altered. However, both ore types contain similar Au concentration in whole rock and pyrite chemistry analyses. Lithogeochemical and microprobe data suggest that the Paleozoic sedimentary rocks may have been a major source of Cd, Mo, Ni, U, V, and Zn and minor As, Cu, Hg, and Se. The Jurassic lamprophyre dikes might have been a significant source of Ba, Co, and Se, and minor Au, and some of the Jurassic and Eocene intrusive rocks may have provided some Fe. Moreover, the Eocene magmas are interpreted to be the main source of auriferous mineralizing fluids and ore-related elements. Trace element abundances and ratios of the Jurassic intrusive rocks suggest that they are shoshonitic and formed from a metasomatized mantle-derived magma, crystal fractionation, and crustal contamination. The Eocene dikes, also shoshonitic, are considerably more evolved and contaminated than the studied Jurassic rocks. Furthermore, Ar-Ar results show that the Jurassic intrusive rocks were negligibly affected by the Eocene thermal event, and that temperature of mineralizing fluids were below the closure temperature of biotite (> 3500C). A magmatic-related model is proposed to explain the formation of the Carlin-type gold deposits at the studied area. In this model, Au and the ore-related elements were exsolved along with volatiles by degassing of a deep and large plutonic complex during its early stage of crystallization. As these magmatic-hydrothermal fluids moved upward along major conduits (e.g., NNW-striking faults), they may have interacted with a Fe-rich fluid, pervasively altering the Paleozoic impure carbonate rocks (e.g., carbonate dissolution, silicification, pyritization) and forming Ore I. Subsequently, these fluids moved laterally further away from the major conduits, became cooler, less acidic, and depleted in ore-related elements and interacted with the Fe-bearing host rocks (e.g., sulfidation), favoring the precipitation of Ore II. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2009-09-25 21:37:33.76

abstract: Geoscience educators commonly teach geology by projecting a photograph in front of the class. Geologic photographs often contain animals, people, and inanimate objects that help convey the scale of features in the photograph. Although scale items seem innocuous to instructors and other experts, the presence of such items is distracting and has a profound effect on student learning behavior. To evaluate how students visually interact with distracting scale items in photographs and to determine if cueing or signaling is an effective means to direct students to pertinent information, students were eye tracked while looking at geologically-rich photographs. Eye-tracking data revealed that learners primarily looked at the center of an image, focused on faces of both humans and animals if they were present, and repeatedly returned to looking at the scale item (distractor) for the duration an image was displayed. The presence of a distractor caused learners to look at less of an image than when a distractor was not present. Learners who received signaling tended to look at the distractor less, look at the geology more, and surveyed more of the photograph than learners who did not receive signaling. The San Antonio area in the southern part of the Baja California Peninsula is host to hydrothermal gold deposits. A field study, including drill-core analysis and detailed geologic mapping, was conducted to determine the types of mineralization present, the types of structures present, and the relationship between the two. This investigation revealed that two phases of mineralization have occurred in the area; the first is hydrothermal deposition of gold associated with sulfide deposits and the second is oxidation of sulfides to hematite, goethite, and jarosite. Mineralization varies as a function of depth, whereas sulfides occurring at depth, while minerals indicative of oxidation are limited to shallow depths. A structural analysis revealed that the oldest structures in the study area include low-grade to medium-grade metamorphic foliation and ductile mylonitic shear zones overprinted by brittle-ductile mylonitic fabrics, which were later overprinted by brittle deformation. Both primary and secondary mineralization in the area is restricted to the later brittle features. Alteration-bearing structures have an average NNW strike consistent with northeast-southwest-directed extension, whereas unaltered structures have an average NNE strike consistent with more recent northwest-southeast-directed extension. / Dissertation/Thesis / Ph.D. Geological Sciences 2011

<p> The Larder Lake Break (LLB) is one of the structures controlling the location of gold deposits in the Kirland Lake camp. This intensly carbonated and often strongly foliated zone is part of the Larder Lake Group as defined by Downs (1980). Protoliths at the LLB are problematical. Misema River is a well exposed occurrence of the LLB, showing chlorite schist, pervasively fuchsite quartz carbonate and syenite dyke material. It is divided into three sections. Section I samples indicate an ultramafic protolith as suggested by Jensen Cation plots, and the section is interpreted as komatiitic flow(s). Section II is well foliated and shows both ultramafic and calc-alkalic components which decrease and increase in intensity respectively away from the section I-section II contact. Section II is interpreted as a polymodal sediment. Section III is similar chemically and texturally to section I, and is therefore a komatiitic flow(s). The intrusion of syenite dykes into section I occurred after initial carbonatization and defonnation of the flows and associated sediments. Radiochemical neutron activation analysis shows all but one of the syenite dyke samples to contain greater than 10 ppb gold whereas the other rock types averages approximately 2 ppb. A peak content of 64 ppb occurred at a dyke contact. The high gold contents clearly originate from the syenite dykes, which also provide a heat source for a second period of carbonatization. </p> / Thesis / Bachelor of Science (BSc)

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Numerous quartz-vein hosted gold prospects in the Karibib district in central Namibia testify to the presence of a large hydrothermal system during Pan-African times in rocks of the Damara Belt and centred around the Navachab Gold Mine. This study presents the results of the regional and detailed mapping of the Navachab synform, a NE-SW trending, regional-scale structure hosting a number of these gold prospects, locally referred to as the “zoo prospects”, in the direct vicinity of the main Navachab Gold Mine. The zoo prospects are located in the marble-dominated, up to 800 m thick Karibib Formation, which forms the core of the Navachab synform. Regional mapping of the synform identified six main lithological units comprising massive and banded dolomitic and calcareous marbles, intraformational breccias and interlayered calc-silicate felses. Despite characteristic thickness variations, the six units can be correlated throughout the synform, allowing for a lithostratigraphic correlation of units in the otherwise monotonous marble sequence. All of the prospects are spatially closely associated with and adjacent to unit 5, an up to 100 m thick, competent dolomitic marble unit. This suggests a strong lithological control of the mineralisation. The first-order Navachab synform formed during the regional D2 phase of deformation. The strongly non-cylindrical, doubly-plunging fold shows open- to close interlimb angles and a pronounced NW vergence in the SW, but is tight- to isoclinal and upright in the NE. Higher fabric intensities and detachment folding are confined to the subvertical limbs of the synform in the north. Here, structures record a subhorizontal, NW-SE directed co-axial shortening strain interpreted to have developed in response to the geometric hardening and layer-normal shortening following the rotation of the fold limbs to subvertical attitudes during progressive D2 shortening. The mineralisation of the zoo prospects is located where D2 high-strain zones intersect unit 5. This suggests an additional structural control of the mineralisation. The detailed mapping of the zoo prospects identified five distinct quartz-vein sets. The geometry, orientation and progressive deformation of the vein sets indicate that veining occurred during the late stages of the D2 event and during NW-SE directed, subhorizontal shortening. Areas of increased veining and mineralisation occur preferentially in areas of strain incompatibilities, where the combined effects of D2 strains and prominent lithological contacts created zones of localized dilatancy. This includes most prominently dilational jog geometries developed between anastomosing D2 shear zones, where hydrothermal fluid flow has produced pervasive quartz-vein stockworks. This also includes areas of detachment folding, where deformation of the rheological stiffer dolomitic marbles and less competent calcareous marbles has led to detachment surfaces and, locally, dilatancy. Zones of increased permeability are also created where two or more vein sets intersect, which is particularly common within and adjacent to boudin interpartitions of competent dolomite units and along rheologically prominent contacts. The zoo prospects illustrate the interplay of (1) prominent rheological contrasts between adjacent lithologies, (2) the presence of high-strain zones, and (3) the geometry of host structures for the formation of auriferous quartz veins in the Karibib district. / AFRIKAANSE OPSOMMING: Talle goud vooruitsigte, wat kwarts-aar geherberg is, in die Karibib-distrik in Sentraal-Namibië getuig van die teenwoordigheid van 'n groot hidrotermale stelsel tydens die Pan-Afrika-tye in die rotse van die Damara-Belt en is gesentreer rondom die Navachab goudmyn. Hierdie studie stel die resultate van die streeks- en gedetailleerde kartering van die Navachab sinform, 'n NW-SO neiging, streeks-skaal struktuur wat ʼn aantal van hierdie goud prospekteerplek herberg, plaaslik bekend as die "zoo prospects", in die direkte omgewing van die hoof Navachab goudmyn. Die “zoo prospects” is geleë in die marmer-gedomineerde, tot 800 m dik Karibib formasie, wat deel vorm van die kern van die Navachab sinform. Streeks kartering van die sinform het ses belangrike litologiese eenhede geidentifiseer wat uit massiewe en gestreepte dolomitiese kalk marmer, intraformasie breksie en tussengelaagdheid kalksilikaat felses bestaan. Ten spyte van die kenmerkende dikte variasies, kan die ses eenhede gekorreleer word oor die hele sinform, wat toelaat vir 'n litostratigrafiese korrelasie van eenhede in die andersins eentonige marmer opeenvolging. Al die vooruitsigte is ruimtelik verbind met en aangrensend aan Eenheid 5, 'n tot 100 m dik, bevoegde dolomitiese marmer-eenheid. Dit dui op 'n sterk litologiese beheer van die mineralisasie. Die eerste-orde Navachab sinform het gevorm tydens die plaaslike D2 fase van deformasie. Die sterk nie-silindriese, dubbelduikende plooi wys oop- tot noue tussenflankhoeke en 'n uitgespreek NW-vergensie in die SW, maar is styf- tot isoclinaal en regop in die NO. Hoër maaksel sterkte en losmaking plooie is beperk tot die subvertikale flank van die sinform in die noorde. Hierdie strukture is 'n aanduiding van 'n subhorisontale, NW-SO gerigte ko-aksiale verkorting wat geïnterpreteer is as vervorming wat ontwikkel het in reaksie op die geometriese verharding en die laag-normaal verkorting as gevolg van die rotasie van die plooi flanke tot subvertikale houdings tydens die progressiewe D2 verkorting. Die mineralisasie van die “zoo prospects” is geleë waar D2 hoë-spanning sones Eenheid 5 sny. Dit dui op 'n addisionele strukturele beheer van die mineralisasie. Die gedetailleerde kartering van die “zoo prospects” het vyf verskillende kwarts-aar stelle geïdentifiseer. Die geometrie, argitektuur en progressiewe vervorming van die aar-stelle dui daarop dat aar-vorming plaasgevind het gedurende die laat stadium van die D2 gebeurtenis en tydens die NW-SO gerugte, subhorisontale verkorting. Gebiede van verhoogde aar-vorming en mineralisasie kom verkieslik voor in die gebiede van vervorming verskille, waar die gekombineerde effek van die D2 vervorming en prominente litologiese kontakte sones van gelokaliseerde dilatansie. Dit sluit die mees prominente uitsettings uitwyking geometrie wat ontwikkel tussen anastomoserend D2 skuifskeursones, waar hidrotermale vloeistof stroming deurdringende kwarts-aar stokwerke geproduseer. Dit sluit ook die gebiede van losmaking plooie, waar die vervorming van die reologiese stywer dolomitiese marmer en minder bevoegde kalk marmer losmaking oppervlaktes gelei het, en plaaslik, dilatansie. Sones van 'n verhoogde deurlaatbaarheid is ook geskep waar twee of meer aar stelle sny, wat is veral algemeen binne en aangrensende boudin tussendeelpartisies van bevoegde dolomiet-eenhede en langs reologiese prominente kontakte. Die “zoo prospects” illustreer die wisselwerking tussen (1) prominente reologiese kontraste tussen aangrensende litologie, (2) die teenwoordigheid van hoë-spanning sones, en (3) die geometrie van die geherbergte strukture vir die vorming van goudhoudende kwarts are in die Karibib-distrik.

[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] The formation of world-class Archean orogenic gold deposits in the Eastern Goldfields Province of Western Australia was the result of a critical combination of physical and chemical processes that modified a single and widespread ore-fluid along fluid pathways and at the sites of gold deposition. Increased gold endowment in these deposits is associated with efficient regional-scale fluid focusing mechanisms and the influence of multiple ore-depositional processes at the deposit-scale. Measurement of the complexity of geologic features, as displayed in high-quality geologic maps of uniform data density, can be used to highlight areas that influence regional-scale hydrothermal fluid flow. Useful measurements of geological complexity include fractal dimensions of map patterns, density and orientation of faults and lithologic contacts, and proportions of rock types. Fractal dimensions of map patterns of lithologic contacts and faults highlight complexity gradients. Steep complexity gradients, between domains of high and low fractal dimensions within a greenstone belt, correspond to district-scale regions that have the potential to focus the flow of large volumes of hydrothermal fluid, which is critical for the formation of significant orogenic gold mineralization. Steep complexity gradients commonly occur in greenstone belts where thick sedimentary units overly more complex patterns of lithologic contacts, associated with mafic intrusive and mafic volcanic units. The sedimentary units in these areas potentially acted as seals to the hydrothermal Mineral Systems, which resulted in fluid-pressure gradients and increased fluid flow. The largest gold deposits in the Kalgoorlie Terrane and the Laverton Tectonic Zone occur at steep complexity gradients adjacent to thick sedimentary units, indicating the significance of these structural settings to gold endowment. Complexity gradients, as displayed in surface map patterns, are an indication of three-dimensional connectivity along fluid pathways, between fluid source areas and deposit locations. Systematic changes in the orientation of crustal-scale shear zones are also significant and measurable map features. The largest gold deposits along the Bardoc Tectonic Zone and Boulder-Lefroy Shear Zone, in the Eastern Goldfields Province, occur where there are counter-clockwise changes in shear zone orientation, compared to the average orientation of the shear zone along its entire length. Sinistral movement along these shear zones resulted in the formation of district-scale dilational jogs and focused hydrothermal fluid-flow at the Golden Mile, New Celebration and Victory-Defiance deposits. Faults and lithologic contacts are the dominant fluid pathways in orogenic gold Mineral Systems, and measurements of the density of faults and contacts are also a method of quantifying the complexity of geologic map patterns on high-quality maps. Significantly higher densities of pathways in areas surrounding larger gold deposits are measurable within 20- and 5-kilometer search radii around them. Large variations in the sulfur isotopic composition of ore-related pyrites in orogenic gold deposits in the Eastern Goldfields Province are the result of different golddepositional mechanisms and the in-situ oxidation of a primary ore fluid in specific structural settings. Phase separation and wall-rock carbonation are potentially the most common mechanisms of ore-fluid oxidation and gold precipitation. The influence of multiple gold-depositional mechanisms increases the potential for significant ore-fluid oxidation, and more importantly, provides an effective means of increasing gold endowment. This explains the occurrence of negative δ34S values in ore-related pyrites in some world-class orogenic gold deposits. Sulfur isotopic compositions alone cannot uniquely define potential gold endowment. However, in combination with structural, hydrothermal alteration and fluid inclusion studies that also seek to identify multiple ore-forming processes, they can be a useful indicator. The structural setting of a deposit is also a potentially important factor controlling ore-fluid oxidation and the distribution of δ34S values in ore-related pyrites. At Victory-Defiance, the occurrence of negative δ34S(py) values in gently-dipping dilational structures, compared to more positive δ34S(py) values in steeply-dipping compressional structures, is potentially associated with different gold-depositional mechanisms that developed as a result of fluid-pressure fluctuations during different stages of the fault-valve cycle. During the pre-failure stage, when fluids are discharging from faults, fluid-rock interaction is the dominant gold-depositional mechanism. Phase separation and back-mixing of modified ore-fluid components are dominant during and immediately after faulting. Under appropriate conditions, any, or all, of these three mechanisms can oxidize orogenic gold fluids and cause gold deposition. The influence of multiple gold-depositional mechanisms during fault-valve cycles at dilational jogs, where fluid pressure fluctuations are interpreted to be most severe, can potentially explain both the large gold endowment of the giant to world-class Golden Mile, New Celebration and Victory-Defiance deposits along the Boulder-Lefroy Shear Zone, and the presence of gold-related pyrites with negative δ34S values in these deposits. This study highlights the interplay that exists between physical and chemical processes in orogenic gold Mineral Systems, during the transport of ore fluids in pathways from original fluid reservoirs to deposit sites. Potentially, a single and widespread orogenic ore-fluid could become oxidized, and lead to the formation of ore-related sulfides with variable sulfur isotopic compositions, depending on the nature and orientation of major fluid pathways, the nature of wall-rocks through which it circulates, and the precise ore-depositional processes that develop during fault-valve cycles.

Orientadores: Roberto Perez Xavier, Carlos Roberto de Souza Filho, Lena Virginia Soares Monteiro / Tese (doutorado) -Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-12T19:03:21Z (GMT). No. of bitstreams: 1 Carvalho_EmersondeResende_D.pdf: 11938678 bytes, checksum: fdc3794a3948e2508d41b33690dcf01d (MD5) Previous issue date: 2009 / Resumo: O depósito de óxido de ferro-cobre-ouro de Sossego na Província Mineral de Carajás (PMC), região norte do Brasil, consiste de três corpos de minério principais, denominados Sossego-Curral, Sequeirinho-Baiano e Pista, envolvidos por zonas de alteração hidrotermal sódica, sódico-cálcica, potássica, clorítica e hidrolítica. Essas zonas de alteração hidrotermal mostram diferentes graus de desenvolvimento em cada corpo de minério. Os estágios iniciais de alteração foram controlados pelo fluxo de fluido em zonas de cisalhamento regionais, enquanto a mineralização cupro-aurífera corresponde a uma fase tardia e se formou em um ambiente estrutural rúptil. Salmouras hipersalinas, quentes (> 500 oC) e compostas essencialmente por NaCl-CaCl2-H2O podem estar associadas com o desenvolvimento inicial do sistema hidrotermal Sossego. As brechas sulfetadas Sequeirinho e Sossego mostram um enriquecimento em Cu-Fe-Au-(Ag)- Ni-Co-Se-Y-V-P-La-Ce e baixo conteúdo de Ti, semelhante a outros depósitos de óxido de Fe-Cu-Au em Carajás e em termos mundiais. O alto conteúdo de Ni, Co, Se, V e Pd, especialmente no corpo Sequeirinho, possivelmente é decorrente da lixiviação de metais a partir de fontes como o gabro, que tem relação espacial com os corpos de magnetitito e as zonas mineralizadas, e lente de rochas metaultramáficas do Supergrupo Itacaiúnas. Os processos de interação fluido-rocha devem ter resultado em significativa lixiviação de metais da seqüência de rochas hospedeiras, que foi acentuado por fluidos hidrotermais inicialmente de alta temperatura (>500 oC) e alto conteúdo de cloreto no sistema hidrotermal Sossego, movido pelo calor dos vários episódios de intrusões registrados na PMC. As inclusões fluidas de amostras dos estágios finais da evolução do sistema hidrotermal Sossego, indicam a participação de (1) salmouras hipersalinas; (2) salmouras salinas, de baixa temperatura (~150 oC) e ricos em CaCl2; e (3) fluidos de baixa salinidade e baixa temperatura (< 250 oC) e compostos por NaCl-H2O, representativos, respectivamente dos estágios inicial, principal e final da mineralização de Cu-Au. As salmouras salinas ricas em CaCl2 poderiam refletir uma evolução contínua a partir de um fluido hipersalino magmático ou envolver fluidos bacinais de baixa temperatura, incluindo um componente derivado de evaporitos. Os fluidos portadores de NaCl e de baixa salinidade predominam nos estágios finais do evento mineralizante e podem representar o influxo de fluidos meteóricos. A transição para um regime estrutural dominantemente rúptil e o resfriamento do sistema favorecem o influxo desses fluidos meteóricos oxidados. A mistura de fluidos pode ter sido o mecanismo principal que desencadeou a precipitação da maior parte do Cu e Au nos diferentes corpos de minério do depósito de Sossego. / Abstract: The Sossego iron oxide-copper-gold deposit in the Carajás Mineral Province (CMP), northern Brazil, consists of three main orebodies, named Sossego-Curral, Sequeirinho-Baiano and Pista, enveloped by sodic, sodic-calcic, potassic, chloritic, and hydrolithic hydrothermal alteration zones. These alteration zones display different degrees of development in these orebodies. The early alteration stages were controlled by fluid-flow in large-scale regional shear zones, whereas bulk copper-gold mineralization was late and formed in a brittle structural environment. Hypersaline NaCl-CaCl2-H2O hot (>500 oC) brines could be associated with the initial development of the hydrothermal system. Sequeirinho and Sossego sulfide ore breccias are marked by enrichment in Cu-Fe-Au-(Ag)-Ni-Co-Se-Y-V-P-La-Ce and low contents of Ti, which also occur in other IOCG deposits of CMP and worldwide IOCG deposits. The high contents of Ni, Co, Se, V and Pd, particularly in Sequeirinho orebody, possibly were originated by metal leaching from sources such as intrusive gabbro, which have spatial relationship with massive magnetite bodies and mineralized zones, and metaultramafic lenses of Itacaiúnas Supergroup. Fluid-rock interaction process might have resulted in significant metal leaching from host sequences, enhanced by early high temperature (>500 oC) and high chloride concentrations of hydrothermal fluids in the extensive Sossego hydrothermal system driven by heat from several intrusive episodes recorded in the CMP. Fluid inclusions of the samples from the final stages of evolution of the Sossego hydrothermal system in brittle conditions, indicated participation of hot hypersaline brines, low temperature (~150 oC) CaCl2-rich saline brines and low-temperature (<250 oC) low salinity NaCl-H2O fluids in early, main and late mineralization stages. The CaCl2-rich saline brines could reflect continuum evolution from magmatic hypersaline fluids or involve low temperature basinal, including evaporite-derived fluids. Low salinity, NaCl-bearing fluids, predominates in late stages and reflect channelized influx of meteoric fluids. The transition to a dominantly brittle structural regime and cooling of the system favors the influx of these oxidized meteoric-derived fluids. Fluid mixing could have represented a major influence on ore precipitation in different orebodies from the Sossego IOCG deposit and could have had fundamental importance to trigger the bulk of copper deposition. / Doutorado / Metalogenese / Doutor em Ciências