Dissertations / Theses on the topic 'Placer deposits'

This review summarises the factors which control the formation and distribution of surficial gold placer deposits. Regional tectonic and climatic conditions as well as gold source are considered. The characteristics of eluvial, alluvial, marine, glacial and fluvioglacial gold placer deposits are described. Particular attention is paid to the gold grains within these placers. These gold grains have a distinctive morphology and chemical composition which reflect the manner in which they were transported, deposited and concentrated within the placers. The knowledge of the processes which lead to the formation and location of surficial gold placers is then used to guide exploration and target potential deposits, which can then be evaluated.

The Witwatersrand basin is unique in terms of its mineral wealth. The gold in the Witwatersrand basin is mainly concentrated in the placers and two types of unconformities are associated with the placer formation. This paper attempts to quantitatively describe the origin and depositional process of placers within the context of basin analysis, geohistory and sequences stratigraphic framework. Several tectonic models have been proposed for the evolution of the Witwater~rand basin and it seems as if a cratonic foreland basin accounts for many of the observed features observed the Central Rand Group basin. The tectonic subsidence curve generated for the Witwatersrand Basin clearly implies foreland basin response which was superimposed an older, deep seated extensional basin. These compressive tectonics can be superimposed on extensional basins, where the shift from extensional to compressional tectonics lead to inversion processes. The critical issues about the Witwatersrand basin which were addresed in this review, is the validity of basin wide correlation of placer unconformuties and whether sequence stratigraphy is applicable to fluvial systems of the Witwatersrand sequence. It is believed that the Central Rand Group was deposited as alluvial - fan deltas by fluvially dominated, braidplain systems with minor marine interaction which had a considerable impact on the preservation of economically viable placers. Most important to the exploration geologist is the recognition of stacking patterns of the fluvial strata to determine change in the rate at which accommodation was created. Identifying sequence boundaries and other relevant surfaces important for identifying these stacking patterns of the sequences, depends entirely on the recognition of a hierarchy of stratal units including beds, bedsets, parasequences, parasequence sets and the surfaces bounding sequences. Placers are closely associated with the development of disconformities and therefore become important to recognise in fluvial strata. If these placers are to become economic, the duration of subaerial exposure of the unconformities that allowed the placers to become reworked and concentrated must be determined. In order to preserve the placer, a sudden marine transgression is necessary to allow for minimal shoreline reworking and to cap the placer to prevent it from being dispersed. The placers in the Witwatersrand basin occur in four major gold-bearing placer zones in the Central Rand Group. Accordingly they can be assigned to four supercycles, which are cyclical and therefore predictive. It is the predictive nature of these rocks and the ability of sequence stratigraphy to enhance this aspect, which is a pre-requisite for an effective exploration tool in the search for new ore bodies or their extension in the Witwatersrand basin.

ENGLISH ABSTRACT: The farm Geelwal Karoo is situated some 16km north of the Olifants River mouth on the West Coast of South Africa and hosts fluvial, marine and aeolian deposits of post-Gondwana age. The oldest basal fluvial succession, unconformably overlies Proterozoic and Palaeozoic basement rocks and is in turn capped by aeolianite and littoral packages representing two transgressive cycles. The fluvial channel clay succession is deposited in shallow bedrock-incised channels, has a wedge-shape and is deposited parallel to the present coastline. The flow direction is along the coast and the northwardtapering, angular, poorly sorted basal vein-quartz lag indicates a northward palaeo-flow direction. Less than 1% total heavy minerals (THM) is found in the matrix of these gravel units and the heavy mineral suite is distinguished by zircon, pseudorutile and kyanite. The channel clay unit is dominated by an upper, mediumgrained quartzose sand and kaolin clay facies, which shows advanced post-depositional weathering. The fluvial unit is correlated with the channel clay unit of Hondeklip Bay and a Cretaceous age is proposed for the initial channel incision. The two shallow marine successions have been correlated with the Late Miocene, Early Pleistocene, +30m and +50m packages respectively. These marine sediments were first described by John Pether (1994) in the Hondeklip Bay area and were named according to their transgressive maxima. They are transgressive successions arranged en echelon down the coastal bedrock gradient, from oldest and highest to youngest. The offshore environment of the +50m package consists of fine silty sand, which is moderately sorted. The mineral assemblage is dominated by quartz and the average THM is 18%. The inshore environment is distinguished by a single poorly sorted basal cobble lag which shows an overall fining upward succession. The beachface environment is composed of medium to fine-grained sand, which is moderate to well-sorted. Mineral diversity is greatest in the inshore and beachface environments and the average THM for these two units is greater than 35%. The +30m package has been extensively eroded due to its lower erosion and outcrops were sporadic along the coast. The +30m offshore sediments are recognised by fine sediments with high concentrations of glauconite and organic matter. The inshore environment is distinguished by numerous poorly sorted pebble lags with fining upward successions. Both the inshore and beachface units have higher feldspar concentrations than the corresponding +50m units. The average THM for these two units is less than 3%. The aeolianite unit, which comprises several distinct units, extends over the entire length of the study area and is characterized by calcrete and red bed horizons. Colour variations in the otherwise homogeneous unit are due to heavy mineral enrichment and/or different degrees of in situ weathering and cementation. The unit is composed exclusively of fine- to medium-grained sand and the THM concentration averages 9%. This unit is composed of more than one generation of aeolian sand and forms part of an aeolian transport corridor which transported sand from the beach to the interior. The oldest unit has been equated with the Upper Miocene Prospect Hill Formation, whereas the more recent yellow dune sand is equated with the Pleistocene Springfontyn Formation. At Geelwal Karoo, only the heavy sand placer in the +50m package was deemed to be of any economic significance. The average THM of this placer was calculated to be 40% and some 150 thousand tons of Tibearing material can be expected from this succession. This relatively small volume of heavy minerals and extensive cementation however, make this placer a less attractive prospect than the neighbouring Namakwa Sands operation.
AFRIKAANSE OPSOMMING: Die plaas Geelwal Karoo is ongeveer 16km noord van die Olifantsriviermond aan die Weskus van Suid- Afrika geleë en het voorkomste van fluviale, marine en eoliese afsettings van post-Gondwana ouderdom. Die oudste eenheid, ‘n basale fluviale eenheid, oorlê Proterosoiëse en Paleosoiëse plaaslike vloer gesteentes wat op hulle beurt weer bedek word deur eoliese en littorale eenhede verteenwoordigene ven twee transgressiewe siklusse. Die fluviale kanaalklei-opeenvolging, afgeset in vlak ingesnyde rotsbedding-kanale, is wigvormig en is afgeset parallel aan die huidige kuslyn in ‘n alluviale waaier-afsetting. Die vloeirigting was langs die kus en die noorwaards toespitsende, hoekige, swak gesorteerde basale aar-kwarts bodemgruis dui op ‘n noordwaards palaeo-vloeirigting. Minder as 1% totale swaarminerale (TSM) is gevind in die tussenmassa van hierdie gruis-eenhede en die swaarmineraal reeks word onderskei deur sirkoon, pseudo-rutiel en kianiet. Die kanaalklei eenheid word oorheers deur ‘n boonste, medium-korrelrige kwarts-bevattende sand en kaolien kleifasies was dui op gevorderde verwering na afsetting. Die fluviale eenheid word gekorreleer met die kleikanaal en ‘n Kryt-ouderdom word voorgestel vir die aanvanklike insnyding van die kanaal. Die twee vlak marine opeenvolgings word gekorreleer met die Laat Mioseen, vroeg Pleistoseen, naamlik die +30m en +50m eenhede onderskeidelik. Die aflandige omgewing van die +50m eenhied bestaan uit matiggesorteerde, fyn slikkerige sand. Die mineraalversameling word oorheers deur kwarts en die gemiddelde TSM is 18%. Die subgetysone word onderskei deur ‘n enkele swak-gesorteerde gruislaag en is oorwegende opwaarts fynerwordend. Die strandomgewing is goed verteenwordige en bestaan uit matig tot goedgesorteerde medium- tot fynkorrelrige sand. Die grootste mineraal-diversiteit kom voor in die subgety- en strandomgewings en die gemiddelde TSM vir hierdie eenhede is hoër as 35%. As gevolg van algemene erosie kom die +30m eenheid sporadies voor. Die aflandige omgeving is herken deur fyn kleierige of slikkerige sedimente met hoe konsentrasies gloukoniet en organiese materiaal. Die subgetysone omgewing is gekenmerk deur verskeie gruislae wat almal opwaarts fynwordend is. Altwee die subgety- en strandomgewings het hoer feldspar konsentrasies as die +50m eenhede. Die gemiddelde THM vir hierdie enhede is minder as 3%. Die eolitiese eenheid, bestaan uit verskeie duidelik-onderskeibare eenhede, beslaan die totale lengte van die studiegebied en word kenmerk deur uitgebreide kalkreet en rooi-laag horisonne. Kleurverskille in die andersins homogene eenheid kan verklaar word in terme van lae swaarmineraal konsentrasies en/of as gevolg wan verskillende grade van in situ verwering en sementering. Die eenheid bestaan uitsluitlik uit fyntot medium-korrelrige sand en het ‘n gemiddelde TSM konsentrasie van 9%. Die eenheid bestaan uit meer as een generasie eoliese sand en maak deel uit van ‘n eoliese vervoersisteem wat sand vanaf die strand na die binneland vervoer het. Die oudste sande in hierdie eenheid is gekorreleer met die Laat Mioseen Prospect Hill Formasie terwyl die meer onlangse geelduin sand vergelyk word met die Pleistoseen Springbokfontein Formasie. By Geelwal Karoo is slegs die +50m eenhede beskou as economies van belang. Die gemiddelde TSM van hierdie swaarmineraal-ertsligaam is bereken op 40% met ‘n verwagte 150 duisend ton Ti-draende material van die opeenvolging. Die relatiewe klein volume swaarminerale en uitgebreide sementering het tot gevolg dat dit ‘n minder aanloklike proposisie is as die aanliggende Namakwa Sands aanleg.

This study focusses on the marine diamond placers within Exclusive Prospecting Licence 1950 and Mining Licence 103a, located northwest of the north-facing Hottentot Bay which is 60 km north of Lüderitz, along the central Namibian coastline. The thesis follows the natural geological evolution of the marine placer deposit from primary source, through alluvial and/or glacial transportation, concentration along the coastline by wave, aeolian and alluvial/sheet-wash processes and finally marine diamond placer preservation. All of these processes are reviewed as they are important in understanding of the evolution marine placer deposits. The poly-cyclic role of coastal aeolian, alluvial, and marine processes, in marine placer enrichment is shown to be particularly important in considered target identification and prioritisation. A detailed bathymetric, sonographic and seismic interpretation, is an integral part of diamond placer exploration, and was used to examine and describe surficial and sub-bottom characteristics within the study area. Marine placers are formed along palaeo-strandlines during periods of marine transgression and regression and are therefore fundamental in marine placer exploration. A detailed bathymetry map, compiled for this study, of the area between Lüderitz Bay and Clara Hill, provides the foundation for a detailed terrace level investigation. Regionally, twelve well-developed stillstand levels are identified, nine of which fall into the study area. These interpretations are compared with global eustatic as well as terrace and resource/reserve levels in the Lüderitz area and are found to correlate well. Sediment dynamic studies involve the use of accredited application software for wave refraction modelling, to determine the wave angle and orbital wave velocity at the seabed. Bedload velocities, required to move diamonds of specific sizes, can be empirically determined and therefore areas of diamond entrainment and deposition can be modelled and target features delineated and prioritised. These detailed interpretations provide a sound platform for evaluating diamond placer process models in the study area. By integrating both previously published and newly formulated ideas, a revised, holistic model for the formation of marine diamond placer deposits in central Namibian is postulated. The proposed model is tested by comparing it to the lateral distribution of presently defined resource/reserve areas in the Lüderitz area and shows a close correlation with most of these enriched deposits. Based on this model, a matrix for the delineation and prioritisation of marine placer deposits is developed and the best target features within the study area are identified.
KMBT_363
Adobe Acrobat 9.54 Paper Capture Plug-in

[Partial abstract]: This study presents the first detailed geochemical and morphological characterisation of gold grains from the southern Seward Peninsula, Alaska, a region with significant historical and on-going placer gold mining. Quantitative Au, Ag, Hg, and Cu data are presented for gold grains from eleven sites. Additionally, quantitative Te, W, As, and Sb trace element data are presented for gold grains from ten of the eleven sites. Although it is acknowledged that quantitative trace element analysis of gold grains is a relatively new endeavour, the limited trace element data obtained in this study suggest that trace element analysis could be useful for characterising gold sources on the southern Seward Peninsula. Major and minor element geochemical profiling is sufficient at differentiating between sites from regional provenance systems but insufficient at differentiating between sites within a single system. Differentiating among sites within a single system will likely require microchemical analysis of mineral inclusions and analysis of trace element signatures.

Placed deposits have received increasing attention over the past 30 years, particularly in prehistoric British archaeology. Although disagreement still exists over the definition, identification, and interpretation of placed deposits, significant advances have been made in theoretical and methodological approaches to placed deposits, as researchers have gradually moved away from relatively crude ‘ritual’ interpretations toward more nuanced considerations of how placed deposits may have related to daily lives, social networks, and settlement structure, as well as worldview. With the exception of comments on specific deposits and a recent preliminary survey, however, Anglo-Saxon placed deposits have remained largely unstudied. This thesis represents the first systematic attempt to identify, characterize, analyse and interpret placed deposits in early to middle Anglo-Saxon settlements (5th–9th centuries). It begins by disentangling the various definitions of ‘placed’, ‘structured’, and ‘special’ deposits and their associated assumptions. Using formation process theory as a basis, it develops a definition of placed deposits as material that has been specially selected, treated, and/or arranged, in contrast with material from similar or surrounding contexts. This definition was applied to develop contextually specific criteria for identifying placed deposits in Anglo-Saxon settlements. Examination of 141 settlements identified a total of 151 placed deposits from 67 settlements. These placed deposits were characterized and analysed for patterns in terms of material composition, context type, location within the settlement, and timing of deposition relative to the use-life of their contexts. Broader geographical and chronological trends have also been considered. In discussing these patterns, anthropological theories of action, agency, practice, and ritualization have been employed in order to begin to understand the roles placed deposits may have had in structuring space and time and expressing social identities in Anglo-Saxon settlements, and to consider how placed deposition may have articulated with Anglo-Saxon worldview and belief systems.

The Old Hickory is the largest of a series of Pliocene (?) age heavy mineral sand deposits in Virginia and North Carolina. The high density of heavy minerals allows for selective concentration during transport and deposition. Under the right conditions, placers of considerable size can be formed. The elliptically shaped ore body of the Old Hickory Deposit extends in a North - South direction and is approximately 13 km (8 miles) long and up to 2.5 km (1.5 miles) wide, with an average thickness of 6.5 m (20 feet). The deposit lies along the Fall Zone, where a thin wedge of Cenozoic Coastal Plain sediments unconformably overlies the older rocks of the Piedmont. The principal minerals of economic interest found in the heavy mineral sands at the site are ilmenite (FeTiO₃), leucoxene (Fe_2-xTi_3+xO_9+x/2) where x is less than or equal to 2, rutile (TiO₂), and zircon (ZrSiO₄). An important focus of this study is the alteration of ilmenite by leaching away of iron, which results in enrichment in titanium. Titanium metal is highly valued for its light weight and high strength. In terms of total economic value, however, the use of titanium dioxide pigments for paint, coated paper, and other products is far more important. As the value of the ore is heavily dependent on the titanium content, the weathering process is a matter of considerable interest to the mineral industry. Analysis of ilmenite grains using reflected light microscopy revealed a wide range of alteration textures. Quantitative analysis and mapping of trace elements showed altered areas with enrichment in Ti and depletion in Fe, Mn, Mg, and Cr. It is believed that the weathering process took place in a reducing environment prior to final deposition according to the reaction:

Fe²⁺TiO₃ + 2H⁺ --> Fe²⁺ (aq) + TiO₂ + H₂O

Reducing environments are found in water-logged soils such as floodplains and other low-lying areas. Repeated cycles of burial and exhumation during transport would have created conditions ideal for the removal of iron from the ilmenite.
Master of Science

Orientadores: Alvaro Penteado Crosta, Carlos Roberto Souza Filho
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias
Made available in DSpace on 2018-07-23T16:51:13Z (GMT). No. of bitstreams: 1 Pedroso_EnricoCampos_M.pdf: 16933120 bytes, checksum: 7918ebfdabea7851e56024cfbc779447 (MD5) Previous issue date: 1998
Resumo: Nas regiões tropicais onde há freqüente cobertura de nuvens ou condições atmosféricas adversas, a aquisição de produtos de sensoriamento remoto no espectro ótico é muitas vezes dificultada. Por outro lado, os sistemas de radar são sensores ativos capazes de penetrar através de nuvens que fornecem informações relacionadas à rugosidade de superfície, topografia, condições de umidade e vegetação.Este trabalho apresenta os resultados do mapeamento geológico automático da distribuição espacial das principais unidades litológicas da área de estudo e dos depósitos secundários do tipo placer. Foram utilizadas imagens de radar JERS-I / SAR, imagens multiespectrais (LANDSAT-5 / TM), mapa geológico na escala de 1:250.000 e métodos geoestatísticos de classificação textural por variogramas e por matrizes de co-ocorrência. A análise comparativa dos resultados do processamento dos dados digitais foi realizada mediante técnicas de superposição e integração com dados de verdade terrestre, representados pelo mapa geológico, a fim de avaliar o grau de eficiência dos métodos propostos. A classificação textural por variogramas provou ser uma ferramenta importante na caracterização espacial de domínios texturais em imagens de radar. Entretanto, as etapas de préprocessamento e segmentação destes dados revelaram-se indispensáveis para os processos de análise textural supracitados. A integração entre dados SAR e TM consiste em uma técnica poderosa se aplicada ao mapeamento geológico e exploração mineral, onde as componentes espectrais e texturais são reunidas em um único produto temático, que retrata o padrão de variabilidade espacial das feições investigadas
Abstract: This work presents the results of semi-automated approaches for the geological mapping of a significant metallogenic province of Brazil, the Tapajós gold province. The geology of the Tapajós region comprises Archaean to Phanerozoic rock assemblages. The main gold accumulations occur as placer deposits associated with Quaternary alluvium sediments. The Tapajós Province is located in the Brazilian Arnazon, in an area covered by a dense tropical rain forest. As optical remote sensing data is severely constrained by almost permanent cloud coverage, we have selected JERS-I SAR data, together with a 1:250,000 scale geological map as the basis for this work. ln tropical regions such as the Amazon, radar imagery is an important source of textural information. The main goal of this research was therefore to evaluate image processing techniques that allow to recognise textural domains that could be correlated to the underlying geology. Geostatistic-based semivariogram textural classifiers and the grey-level co-occurrence matrices methods were employed for the semi-automated textural recognition task. Both are based on the spatial distribution of pixel values within an image. A set of textural channels is produced by either method that can be displayed as a pseudocolor image. The technique based on the semivariogram analysis yielded the best results. This technique first calculates the value of the semivariogram function for given training areas of different textural features. After a detailed interpretation of the curves, the best lags are selected interactively by the user, i. e. the lags that best distinguish the textural units. Next in the process, a bayesian unsupervised classification is performed in the entire image, using a moving window of predefined dimensions, based on the function values previously established. A comparison of the results derived from the textural classifiers, additional information extracted by digital image processing of Landsat TM data and ground truth data showed a good correlation in the spatial distribution of the main geologic units. Furthermore, it allowed distinguishing the alluvium that host gold-mineralized placers, based on their distinctive geomorphic texture. The semivariogram classifier is a powerful mapping technique that can be successfully applied for regional geologic mapping and mineral exploration in tropical regions and in particular to the vast geologically unknown terranes of the Amazon. The integration of SAR and optical data such as JERSI /SAR and Landsat TM imagery is a very useful procedure to enhance textural and spectral information provided by these sensors
Mestrado
Metalogenese
Mestre em Geociências

L’archéologie funéraire s’attèle à comprendre la place qu’occupent les morts dans les sociétés anciennes. Elle passe par la compréhension des rituels entourant le défunt. Ces usages se reflètent dans les modes de traitement du défunt, dans la structuration de la sépulture et dans le dépôt de mobiliers funéraire. Les rituels, fondés sur la religion romaine, sont en usage dans toutes les provinces de l’Empire et sont adoptés par l’ensemble des peuples sous domination romaine. Les rituels funéraires modèlent ainsi des assemblages de mobiliers, des assemblages de vaisselle, issus de contextes clos et bien datés. Les séries de récipients ainsi constituées permettent de travailler sur la représentation numérique des différents vaisseliers en céramique, en verre ou en métal, sur la fonction des objets et sur l’évolution typochronologique des récipients. Les ensembles funéraires abondants découverts ces dernières années dans le nord de la France ont laissé qu’il existait un lien entre évolution des pratiques funéraires et évolution des types de récipients. C’est pourquoi nous avons choisi de travailler sur une aire géographique, définie par les limites administratives actuelles, regroupe quatre cités de tradition gauloise, situées au carrefour entre la Gaule Belgique, la Gaule Lyonnaise et la Bretagne. Cette région riche en découvertes et archéologiquement dynamique, était propice à l’élaboration d’un corpus de vases important, suffisant et bien documenté. Les données proviennent des fouilles conduites sur un nombre important de nécropoles tardives (fouilles anciennes et fouilles récentes), des études faites sur les pratiques funéraires et des travaux menés sur l’organisation administrative de la région. Afin de retracer les différentes étapes d’évolution du verre dans les tombes, nous avons choisi de travailler sur un cadre chronologique large afin de retracer les différentes étapes du verre funéraire à la période gallo-romaine et mérovingienne, soit entre le Ier et le VIIe s. ap. J.-C. Ainsi, le séquençage chronologique des verres nous a permis de cerner l’évolution progressive de la place du verre dans la tombe : d’abord discret au début du Ier s. ap. J.-C, le verre est ensuite de plus en plus présent dans les tombes du IIe s. ap. J.-C. jusqu’à devenir un mobilier indispensable. Son apogée intervient, entre la fin du IVe s. ap. J.-C. et le début du VIe s. ap. J.-C., car il devient représentatif non plus d’un rite, mais du défunt lui-même. Nous avons remarqué que derrière l’évolution rituelle et symbolique, existe une réalité économique et commerciale. La constitution des groupes de formes privilégiées et la cartographie de leurs aires de diffusion ont permis de distinguer les productions importées des productions à caractère régional et de caractériser différentes aires d’influence commerciale : entre Rome, Gaule Belgique, Gaule Aquitaine et Rhénanie
The organisation of the burials and the social way the deceased are treated are the point of the funeral archaeology. The rituals are visible in the organisation of the graves and in the way the artefacts are placed around the body – they are common to the roman area. The combination of the sets in the grave makes a good way to représent the evolution of the ceramic, metal or glass vessels. The large number of discoveries in north France these last ten years, sets a good material up for this studies. We registered the funeral structures located in the south of Gallia Belgica, dated from the Ist Century Bc to the VIIth Century Ad. This large chronological scale allows us to identify the way the glass is put down the graves and the way it makes part of the rituals : discreet at the beginning of the Ier Century, the glass is essential in the funerary set of the VIth century. More than a symbol, the glass vessel is also a commercial good. The cartography of the vessel types shows different areas of diffusion, that means some of them are imported and some are locally produced. The commercial roads are also well defined : to the north of Gallia Belgica, to Rhenania and to the south of Gallia Aquitania

India, gifted with a coastline of over 6000 km, hosts some of the largest and richest shoreline placers. The beach and dune sands in India contain heavy minerals like ilmenite, rutile, garnet, zircon, monazite and sillimanite. A combination of favorable factors like network of drainage, aided by wind and coastal processes like waves and currents, have influenced the formation of the beach and adjoining dune sands. Ilmenite-rich major beach and dune sand deposits occur in the coastal stretches of Kerala (Chavara), Tamil Nadu (Manavala kurichi, Midalam, Vayakallur), Andhra Pradesh, Orissa and Maharashtra. The Indian ilmenite commonly contains 50-60% TiO2 and is suitable for various process technologies. Zircon, monazite and Sillimanite are ubiquitous in both the beach and inland red Teri sands, and constitute potential co-products. The Indian resources of placer minerals are: 348 Million tons (Mt) of Ilmenite, 107 Mt of garnet, 21 Mt of zircon, 18 Mt of monazite and 130 Mt of Sillimanite. Indian resources constitute about 35% of world resources of Ilmenite, 10% of Rutile, 14% of Zircon and 71.4% of Monazite. India meets about 10% of the world requirement of garnet. This unique status is largely due to the exploratory efforts of the Atomic Minerals Directorate for Exploration and Research (AMD) of the Department of Atomic Energy, Government of India since 1950s.

Heavy mineral deposits along the east coast of South Africa represent the world's largest demonstrated resource of beach placer ilmenite. This mineral occurs as homogeneous, subrounded grains, with chemical compositions close to pure FeTi03• Concentrates contain between 48 and 52 per cent Ti02, with minor impurities of MnO, MgO, and Cr203. Most coastal ilmenites are unaltered or display only incipient alteration, but the entire spectrum of alteration products from ilmenite to rutile or anatase, is observed. Transmission electron microscopy of weathered ilmenites reveals that ilmenite commonly alters to pseudorutile and then to rutile or anatase, as described by Teufer and Temple (1966) and Grey and Reid (1975). Ilmenite may also alter directly to rutile (or anatase) in a single-stage process. In addition, ilmenite altered by high temperature oxidation and hydrothermal processes is found in the deposits. There is good mineralogical evidence that the alteration of ilmenites found in the coastal sediments is best described by a multi stage model, in which some ilmenite grains were altered prior to final deposition. Other common iron-titanium oxides in the deposits include magnetite, rutile and hematite, which may occur as discrete grains or as composite grains of two or more oxides. Ilmenite and magnetite in the coastal sediments are derived from rocks of both the Karoo Igneous Province and the Natal Basement, while rutile is derived solely from the latter. Ilmenites from certain rock groups may be distinguished on the basis of their chemical composition. However, magnetite chemistry is a better indicator of provenance, and magnetites from the above two sources can be clearly distinguished. The petrography of the iron-titanium oxides may be used as a provenance indicator, but may be misleading, as the proportions of the oxide intergrowths change with transport and weathering. Variations in the proportions and chemical compositions of iron-titanium oxides and other heavy minerals within the coastal sediments are caused by provenance, selective sorting during deposition, age of the deposit, weathering, and the recent geological history of the area. A model is proposed in this study which describes the formation of the heavy mineral deposits in relationship to the above influences.
Thesis (Ph.D.)-University of Natal, Durban, 1993.

Zircon from the zircon concentrate of Richards Bay Minerals was investigated with a view to understanding the morphology and provenance. The obsevations were applied to the reduction of uranium, thorium and other trace elements in the heavy mineral placer deposits. It is evident from differences in morphology, optical characteristics, cathodoluminescence, inclusion types and trace element analyses that the zircon is derived from numerous parent rocks. Rare earth element modelling reveals several possible parent rocks including rhyolites, granites, syenites, pegmatites and carbonatites. Fission track U mapping of individual zircons indicated an enrichment of U in the rims and grain terminations. The U maps were used to devise and test several methods, including abrasion and partial dissolution, to reduce the combined U and Th concentration from 450-563ppm to below 400ppm. The effect of magnetic cleaning, density separation and size classification of the zircon concentrate on the U +Th concentration was found to be negligible. Air abrasion and HF acid dissolution successfully reduced the U +Th concentrations to between 332 and 383ppm. The contribution of trace elements from inclusions, surface pit fillings and coatings, and foreign minerals within the zircon concentrate were evaluated by by scanning electron microscope identification.
Thesis (M.Sc.)-University of Natal, Durban, 1992.

Wyczerpywanie się światowych zasobów lądowych złóż kopalin jako źródeł surowców mineralnych stwarza potrzebę nowych poszukiwań surowców na obszarach morskich. Perspektywicznym obszarem o wysokim potencjale złożowym jest Azja Południowo – Wschodnia oraz Oceania, w tym Nowa Gwinea. W regionie prowadzone są szerokie badania, w tym z udziałem polskich geologów (Szamałek et al. 2013, 2015a, 2015b). W 2009 roku rozpoczęto projekt prospekcyjno – eksploracyjny na obszarze północnego wybrzeża Nowej Gwinei – w regionie Jayapura. Prace poszukiwawczo – prospekcyjne miały na celu: określenie i wytypowanie obszarów o potencjalnym znaczeniu złożowym, obszarów alimentacji, wstępnej oceny przydatności kopaliny oraz oceny ekonomicznej. W czasie trwania projektu prospekcyjnego „Jayapura” dokonano eksploracji osadów płytkomorskich (do głębokości 60 m p.p.m.). Z powierzchni dna oceanu wydobyto 59 próbek osadów okruchowych. Dokonano analiz mineralogiczno – petrograficznych badanej kopaliny. Przy użyciu mikroskopii optycznej oraz skaningowej (BSE) określono obecność spektrum minerałów ciężkich: płonnych oraz kruszcowych. Głównym minerałem złożowym jest chromit. Dokonano mappingu oraz punktowych analiz geochemicznych ziaren chromitów, oliwinów oraz piroksenów przy użyciu mikrosondy Cameca SXFiveFe, w celu ustalenia występowania metali grupy platyny (PGE). Przy użyciu metod analitycznych AAS oraz ICP – OES wykonano analizy geochemiczne osadów okruchowych. Badania wskazują na podwyższone wartości Pt, Cr, Co oraz Ni, we wschodniej oraz zachodniej części wybrzeża. Na podstawie uzyskanych wyników wyznaczono subprowincje mineralno – geochemiczne. Wyniki analiz mineralogiczno – geochemicznych umożliwiły wydzielenie dwóch bloków prospekcyjnych o potencjalnym znaczeniu złożowym. Projekt „Jayapura” wymaga dalszych systematycznych badań mających na celu szczegółowe rozpoznanie potencjału złożowego osadów okruchowych północnego wybrzeża Jayapury. Badaniami powinny być objęte wydzielone perspektywiczne bloki, które charakteryzują się wysoką koncentracją minerałów kruszcowych oraz podwyższonym tłem geochemicznym pierwiastków Pt – Cr – Co oraz Ni.
The depletion of the world’s land-base mineral deposits as the source of mineral resources creates a need of new raw materials research in marine areas. The perspective area of high reserve potential is South – East Asia and Oceania, including New Guinea. Extensive research with participation of Polish geologists is carried out in this area (Szamałek et al. 2013, 2015a, 2015b). In 2009, the project of geological exploration in the northern costal of New Guinea area – a region Jayapura was started. The main purpose of prospecting works was to: identify and determine potential reserve sites, alimentations areas, initial assessment of the usefulness of minerals and economic assessment. During of the prospecting „Jayapura” project exploration of the shallow marine deposits (to a depth of 60 m below sea level) was made. Fifty – nine samples of clastic sediments were extracted from the ocean’s surface. Mineralogical – petrographic study of minerals has been made there. Using an optical microscopy and scanning electron microscopy (BSE) the presence of the spectrum of heavy minerals was identified: gangue and ore. The main mineral reserve is chromite. Mapping and point geochemical analyzes of chromites grains have been made, olivine and pyroxene - using a microprobe CAMEC SXFiveFe, in order to determine the occurrence of platinum group elements (PGE). Using analytical methods: AAS and ICP – OES geochemical clastic sediments analyzes were performed. The research shows an increased value of Pt, Cr, Co, and Ni, in the eastern and western coast. Based on the research results mineralogical – geochemical subprovinces were marked. The results of the mineralogical - geochemical analyzes allowed to separate the two prospecting blocks of potential reserve sites. The „Jayapura” project requires further systematic studies for detailed identification of the reservoir clastic sediments potential of the northern coast of Jayapura. The study should cover a separate prospective blocks, which are characterized by high concentration of ore minerals and increased geochemical background elements Pt - Cr - Co and Ni.

Tese de doutoramento em Arqueologia (área de especialização em Arqueologia da Paisagem e do Povoamento)
Esta tese tem como principal objetivo aumentar o conhecimento sobre a Idade do Bronze da bacia do rio Ave, no Noroeste de Portugal. Através da articulação sincrónica e diacrónica dos dados nos seus contextos físico e cultural e à luz de novas premissas teóricas estudou-se este período de uma forma holística. Tal visa interpretar o modo como as comunidades se estruturaram no meio onde estavam imersas ou incorporadas e como interagiram com ele. Privilegiando a contextualização dos dados, nomeadamente os diferentes lugares construídos e frequentados pelas populações da Idade do Bronze, o estudo foi direcionado segundo três eixos temáticas, a saber: o povoamento, os contextos e as práticas funerárias e a metalurgia e as deposições metálicas. Foram, também, interpretados certos lugares “naturais”, cujas materialidades arqueológicas denunciavam ampla diacronia de frequência, traduzindo a sua importância na estruturação e na perceção do espaço por parte das populações da Idade do Bronze. No que respeita ao povoamento, apesar da ausência de dados para o Bronze Inicial, o Bronze Médio pauta-se pela ocupação multivariada do espaço. Prevalecem os sítios abrigados, de baixa altitude, com acesso a vales de eventual potencialidade agrícola e a corredores naturais de circulação, alguns deles relativos a ocupações frustres, enquanto outros são de maior dimensão, correspondendo, talvez, a ocupações mais duradouras. Nas regiões montanhosas os povoados sobre áreas abrigadas de planaltos estão perto de cursos de água e em locais de fácil circulação, sendo rara a ocupação do topo de montes. Para o Bronze Final, a par da variada ocupação do terreno, acentua-se o povoamento em altitude, com boas condições de visualização sobre zonas agro-pastoris de montanha mais próximas, sobre terras férteis no fundo dos vales e sobre as principais vias naturais de circulação, quer de cumeada quer de vale – pontos estratégicos de encruzilhada entre diferentes bacias ou rios. Embora a ocupação dos vales facilitasse a circulação, o povoamento em altura materializaria o domínio real e simbólico do território e dos seus recursos e permitiria consolidar e estabelecer fronteiras simbólicas entre diferentes territórios, nos quais atuariam diferentes influências. Nota-se que alguns destes povoados ocuparam montes já simbolicamente ativos desde o Neo-Calcolítico e materializados por gravuras rupestres, o que poderá ter sido importante na escolha do lugar de residência. Em termos de lógica de povoamento também se crê que certos povoados ocuparam intencionalmente locais com visibilidade para determinadas orografias de grande significação coletiva. No conjunto, as múltiplas opções de povoamento transparecem desempenhos e sentidos distintos, no âmbito de uma rede de lugares e de significados interconectados em regime de complementaridade. Em relação aos contextos e práticas funerárias desconhecem-se dados para o Bronze Final. Durante o Bronze Inicial, a presença de objetos metálicos e de alguns túmulos de grande investimento construtivo, nas áreas de vale, permite pensar que existiram personagens extremamente significantes para as comunidades, os quais seriam recordados e celebrados. Nas áreas montanhosas o facto de os monumentos sob tumuli serem, neste período, de maior envergadura do que nos seguintes, indicia, ainda, a importância do papel social da morte visível e da preservação da memória dos antepassados. No Bronze Médio os diferentes tipos de arquiteturas funerárias conectadas, respetivamente, com áreas de montanha ou de vale, parecem corresponder a populações com modos de vida e conceções distintas da morte. Para as comunidades serranas a morte, como marco no espaço, e o culto aos antepassados, ainda parece importante. Nos vales predomina a morte invisível e a perda da importância do cadáver como referência coletiva e referência espacial. Há variedade no tratamento dos cadáveres, com indícios de inumação e de cremação em urna ou in situ. As oferendas tornam-se mais simples e à base de determinadas formas cerâmicas, quando não estão ausentes de todo, tendo desaparecido os objetos metálicos, os quais parecem ser agora canalizados para outros cenários. Não raramente, as práticas funerárias implementaram-se em lugares liminares ou de passagem, entre o vale e o topo do monte ou nas imediações ou nas linhas de cumeada, entre a terra e o céu, o que se pensa ser propositado e relacionar-se com a morte percecionada como um momento de passagem entre dois estádios. Em relação a algumas estruturas funerárias, como as sepulturas planas, observam-se hipotéticas relações com a orientação das águas ou os ciclos solares ou lunares, como que associando a morte a um ciclo ou a uma viajem. Há, ainda, lugares onde a convergência de práticas mortuárias e de outras ações de difícil interpretação, denunciando larga diacronia de frequência cíclica, pelo menos desde o Bronze Inicial ao Final, revelam biografias sem paralelo. Parecem ser lugares de memória e de grande significado coletivo associados a ancestrais ciclicamente celebrados, quer através de outros enterramentos quer de deposições várias. Na bacia do Ave os indícios irrefutáveis de metalurgia. A par dos objetos associados à produção, os parcos objetos metálicos encontrados nos locais de produção, nos denominados povoados, apontam para a sua manipulação noutros contextos. A significativa quantidade destes objetos, avulsos, ou em depósitos, associada a informações contextuais, deixam transparecer a sua amortização em associação com certas caraterísticas “naturais” (como montes, vales e bacias de receção, além de poderem associar-se a afloramentos, a nascentes e ao subsolo). Tais factos, pela frequência de ocorrência, não terão sido aleatórios, notando-se padrões normativas de foro cultural. É neste cenário que ganham especial destaque, enquanto elementos estruturantes da paisagem da Idade do Bronze, o Monte da Saia (em Barcelos) e o Monte da Penha (em Guimarães). A sua excecionalidade manifesta-se pela frequência cíclica que denotam, conforme atestado pela concentração anómala de diferentes materialidades metálicas, no primeiro caso, e cerâmicas e metálicas no segundo. Essas materialidades corroboram a ampla diacronia biográfica destes lugares que, entre diversas manifestações, a partir do Bronze Médio mas, em especial, do Bronze Final, é reforçada pela deposição de objetos metálicos. Perceber o Monta da Saia e o Monte da Penha como sítios habitacionais da Idade do Bronze é redutor e, até à data, facto não comprovado. Em contrapartida, ambos integrariam uma rede de lugares da Idade do Bronze na qual as populações viveram e se movimentaram, materializando uma paisagem eivada de diferentes sentidos, significados e memórias. Saliente-se, contudo, que durante o Bronze Final há outras orografias que parecem ter sido significantes, como o Monte do Sino, o Monte de S. Romão, o Alto do Livramento ou o Monte S. Miguel o Anjo, com os quais se associam objetos metálicos. O mesmo se pode dizer dos vales do rio Este e do ribeiro da Abelheira, ótimos corredores de circulação onde depósitos de “utensílios” monotipológicos, sempre no subsolo, todos diferentes e efetuados em diversos moldes, levam a equacionar a hipótese de terem sido amortizados como atos celebrativos comunais visando a concretização de pactos ou acordos entre membros de diferentes comunidades, que usufruíam de pontos de confluência e de passagem comuns conhecidos, muito provavelmente, desde longa data.
This thesis aims to increase the knowledge about the Bronze Age of the river Ave’s basin, in the Portuguese Northwest. Through the data’s synchronic and diachronic articulation with its physical and cultural contexts, and using new theoretical approaches, that chronological period was studied in a holistic manner. This seeks to interpret the way how communities were structured in the environment where they were immersed or incorporated, and how they interacted with it. Emphasizing the data’s contextualization, namely the different places constructed and used by the Bronze Age populations, this study was carried out according to three main topics: settlement, funerary contexts and practices and metallurgy and metallic depositions. It also were interpreted certain “natural places”, whose archaeological materialities denounce large frequency diachronies, revealing its importance to space’s structuration and perception for the Bronze Age societies. In regard to settlement there is no data to the Early Bronze Age. The Middle Bronze Age shows a multivariate space occupation. The most common are sheltered sites, in lower altitudes, with easy accesses to eventual agricultural valleys and natural circulation corridors. Some of this sites are sparing occupations, although other show larger dimensions, probably corresponding to long lasting dwellings. In mountainous regions the settlements occupy well irrigated plateaus, near water courses easily accessed. The top of mountains occupation is rare. During the Late Bronze Age the varied occupation continued, but the settlement in higher altitude becomes more usual. These places have good visual contact over the surrounding nearest shepherding zones, the fertile soils in the valleys and the main circulation pathways from the valley or the ridge, strategic intersection points between different rivers or basins. Although the valleys’ occupation favored the circulation, the high altitude settlement materialized the real and symbolic domination over the territory, where different influences acted. Note that some of these settlements occupied Neo-Chalcolithic symbolic mounts, activated from previous times by rock art engravings. This probably was important to the choice of those loci. With respect to settlement’s logic we also believe that some settlements were intentionally located in sites with good visibility to some kind of hills, probably with collective significance. As a hole, the multiple options may show distinct significances and assignments, in the scope of a network of places and meanings interconnected by complementary relations. Concerning to the funerary contexts and practices there is no data to the Late Bronze Age. During the Early Bronze Age the metallic objects are common in graves, some of which showing great constructive investment. These structures, connected with the valley, allow us to thing that extremely important characters to the communities existed, which would be remembered and celebrated. During this period in the mountainous areas some monuments under tumuli are larger than the subsequent, presumably indicating that the social role of death still remained visible, so as the ancestors’ memory preservation. In the Middle Bronze Age the different types of funerary architectures are connected with higher altitudes and valley, and may correspond to populations with distinct lifestyles and conceptions of death. To the mountainous communities death is a way to mark the space, where still remains the ancestors’ worship. In the valleys proliferates an invisible death and the loss of the body as spatial collective reference. There are varieties on the corpse’s treatment, showing uses of inhumation and cremation in urn or in situ. The offerings are simpler and restricted to some kind of ceramic pots. Sometimes there are no offerings at all and metallic objects are absent, probably channeled to other scenarios. More often, funerary practices were implemented in laminar or passage places, between the valley and the top of the mountains or near the ridges, between the sky and the earth, which we think that has to do with the manner how death was seen, probably percept and conceived as a passage moment between two stages. In relation to some funerary structures, like flat graves, we observe hypothetic links with the water courses and the solar or lunar cycles, as associating death to a cycle or a journey. There are also places where mortuary practices and other actions converged. Although difficult to interpret, they denounce large cyclical frequencies, at least since between the Early and Late Bronze Age. Revealing uncommon biographies and probably working as memorial places of great collective significance, the associations with the ancestors and their cyclical celebration, either by burials or by some kind of depositions, seems to be practiced. Irrefutable evidences of metallurgy are also known in the Ave’s basin, as the presence of objects associated with the production show. However, the scarce objects found in the production sites, in the so called settlements, points out to their manipulation in other contexts. The significant quantity of those objects, discovered either alone or in deposition sets, show high links with some “natural” features (such as mounts, valleys and water basins, beyond their usual connection with outcrops, water sources and the subsoil). These facts, often registered, cannot be seen as random, since some cultural and normative patterns are noticed. In this scenario some structurating elements on the Bronze Age’s landscape stand out, such as Mount Saia (Barcelos) and Mount Penha (Guimarães). Their exceptionality is manifested by the cyclical frequency exhibited, as one can see by the anomalous concentration of different metallic materialites in the first case, and ceramic and metallic in the latter. Those materialities corroborate the unique and wide diachony of both places which by the mean of various manifestations, from the Middle Bronze Age but specially during the Late Bronze Age, was reinforced by the amortization of metallic objects. To understand Mount Saia and Mount Penha as simple sites for Bronze Age settlements is quite reducer, besides the lack of confirmation that exists. By the contrary, both were part of the Bronze Age network of places where people lived, acted and moved, materializing a landscape crowded with different senses, meanings and memories. However, let us stress that during the Bronze Age there are other orographies that show some significance, like Mount Sino, Mount S. Romão or Mount S. Miguel-o-Anjo, where metallic objects were also recovered. The same can be said in relation to the valleys of rivers Este and Abelheira, good circulation corridors where the deposition of monotypological sets of tools took place under the subsoil. As a working hypothesis, the amortization of these sets could be the result of communal celebration acts to concretize pacts or agreements established between members of different communities, which benefit from the same confluence points of passage known, very likely, since ancient times.
Fundação para a Ciência e a Tecnologia (FCT) sob a forma de Bolsa de Doutoramento (Ref. SFRH/BD/41776/2007).
Programa Operacional Temático Factores de Competitividade (COMPETE) - ENARDAS (PTDC/HIS-ARQ/112983/2009).