Mineral Province Research Articles

Hydrothermal Fluid Processes and Evolution of the Giant Serra Norte Jaspilite-Hosted Iron Ore Deposits, Carajas Mineral Province, Brazil

Hydrothermal Fluid Processes and Evolution of the Giant Serra Norte Jaspilite-Hosted Iron Ore Deposits, Carajas Mineral Province, Brazil

Depósito de Cu-Zn Pojuca Corpo Quatro: IOCG ou VMS?

Este trabalho trata do depósito de Cu-Zn designado como Pojuca Corpo Quatro, localizado na Província Mineral de Carajás, e procura estabelecer parâmetros para definir seu modelo metalogenético. O Depósito Pojuca Corpo Quatro está hospedado em rochas metavulcanossedimentares do Grupo Igarapé Pojuca, correlacionáveis às rochas do Grupo Grão Pará, de idade arqueana. A história metalogenética do depósito é complexa. Duas formas diferentes de ocorrência caracterizam os minerais de minério do depósito: uma mineralização stratabound, coerente com o bandamento das rochas hospedeiras e considerada primária, e um minério em brechas, vênulas e disseminado, aqui descrito como minério remobilizado ou secundário. As características das diferentes tipologias de minério sugerem duas fases de mineralização: mineralização primária, stratabound, cuja paragênese é constituída de calcopirita, pirrotita e esfalerita, considerada neste trabalho como sendo do tipo VMS, e a mineralização secundária ou remobilizada, de paragênese formada por pirrotita, calcopirita e molibdenita, descrita como sendo produto de eventos hidrotermais posteriores do tipo IOCG.

Quantified spatial relationships between gold mineralisation and key ore genesis controlling factors, and predictive mineralisation mapping, St Ives Goldfield, Western Australia

Determining the spatial relationships between various geological features and mineralisation is not only important for understanding the ore genesis of mineral deposits, but can also help to guide mineral exploration by providing predictive mineral maps. In this GIS-based study, we quantify the spatial relationships between gold mineralisation and plausible controlling factors in the central part of the St Ives area, Western Australia. We weigh plausible control factors including rock types, lithological boundaries and faults, using gold occurrences in drill-cores, and then apply the weights to the geological data to generate a predictive map for the entire St Ives area. The three major findings of this study are: (1) all major gold deposits are controlled by faults, and small-scale fault systems have a stronger correlation with gold mineralisation than large faults; (2) felsic to intermediate intrusive rocks show strong correlations with gold mineralisation, whereas metamorphic mafic rocks (greenstones) possibly acted as part of the broad regional environment for the mineral province rather than as a factor controlling the exact locations of the deposits; and (3) our predictive mapping indicates that the southeast part of the St Ives goldfield has a high potential for discovering new gold mineralisation.

U/Pb age and origin of supergene uranophane-beta from the Borborema Pegmatite Mineral Province, Brazil

Uranophane-beta of supergene origin formed in the Borborema Pegmatite Mineral.Province, which is situated in the north-easternmost part of Brazil. The sampling site lies in the topmost parts of the Quintos Pegmatite, about ten kilometers north of the town of Equador. The uranyl silicate was investigated for its age and physical chemical regime of formation. Age dating yielded a U/Pb age of 6.77 ± 0.61 Ma. Uranophane has been derived together with autunite from weathering of brannerite in a tropical climate under alternating wet and dry seasons, when the pH was below 8. This canary-yellow well-crystallized uranyl silicate can be used as a physical chemical marker as well as a clock for supergene alteration.

Geology and Geochemistry of the Bianbianshan Au‐Ag‐Cu‐Pb‐Zn Deposit, Southern Da Hinggan Mountains, Northeastern China

Abstract:The Bianbianshan deposit, the unique gold‐polymetal (Au‐Ag‐Cu‐Pb‐Zn) veined deposit of the polymetal metallogenic belt of the southern segment of Da Hinggan Mountains mineral province, is located at the southern part of the Hercynian fold belt of the south segment of Da Hinggan Mountains mineral province, NE China. Ores at the Bianbianshan deposit occur within Cretaceous andesite and rhyolite in the form of gold‐bearing quartz veins and veinlet groups containing native gold, electrum, pyrite, chalcopyrite, galena and sphalerite. The deposit is hosted by structurally controlled faults associated with intense hydrothermal alteration. The typical alteration assemblage is sericite + chlorite + calcite + quartz, with an inner pyrite – sericite – quartz zone and an outer seicite – chlorite – calcite – epidote zone between orebodies and wall rocks. δ34 S values of 17 sulfides from ores changing from –1.67 to +0.49‰ with average of –0.49‰, are similar to δ34 S values of magmatic or igneous sulfide sulfur. 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb data of sulfide from ores range within 17.66–17.75, 15.50–15.60, and 37.64–38.00, respectively. These sulfur and lead isotope compositions imply that ore‐forming materials might mainly originate from deep sources. H and O isotope study of quartz from ore‐bearing veins indicate a mixed source of deep‐seated magmatic water and shallower meteoric water. The ore formations resulted from a combination of hydrothermal fluid mixing and a structural setting favoring gold‐polymetal deposition. Fluid mixing was possibly the key factor resulting in Au‐Ag‐Cu‐Pb‐Zn deposition in the deposit. The metallogenesis of the Bianbianshan deposit may have a relationship with the Cretaceous volcanic‐subvolcanic magmatic activity, and formed during the late stage of the crust thinning of North China.

Clay mineral provinces in tidal mud flats at Germany's North Sea coast with illite K–Ar ages potentially modified by biodegradation

Mineralogical studies, chemical analyses and K–Ar dating were carried out on clay fractions from tidal mud flats along the Lower Saxony coast and its bays to identify material sources and sedimentary processes at this dynamic interface between air, land and sea.From the coast into the bays, sediments are enriched in fine-grained smectite relative to the coarser grained illite, chlorite and kaolinite, due to the weakening of the tidal current energy in the bays. In addition, the study area can be divided into two provinces on the basis of the illite K/Rb ratios and Mg contents. To the west [Schiermonnikoog, Dollart, Ley Bay up to Norderney island], longshore currents carry suspensions from the Belgian and Dutch coasts; to the east [from Langeoog island, Jade Bay to the Helgoland mud area] suspensions from the Elbe and Weser rivers are mixed with submarine reworked glacial sediments, whereas the portion of longshore current suspensions from the west decreases, becoming negligible in the Helgoland mud area off the Elbe and Weser estuaries. The illite K–Ar data vary considerably and fail as source indicators due to differential settling and mixing of the clay material and probably to Ar loss from illite by biodegradation during digestive processes. Only further offshore, outside the zone of dynamic sediment dispersion, do the K–Ar data fit provenance patterns.

Dating the Itabira iron formation, Quadrilátero Ferrífero of Minas Gerais, Brazil, at 2.65 Ga: Depositional U–Pb age of zircon from a metavolcanic layer

Uranium–Pb dating of zircon from a metavolcanic layer within the Itabira iron formation, or Cauê Itabirite, Quadrilátero Ferrífero of Minas Gerais, Brazil, indicates that its deposition occurred at 2.65Ga, i.e., considerably earlier than proposed by previous geochronological studies, which suggested deposition between 2.58Ga (detrital zircon age from the underlying Moeda Formation) and 2.42Ga (Pb–Pb isochron age from dolomitic rocks of the immediately overlying Gandarela Formation). The new age has major implications for the geology of the Quadrilátero Ferrífero and connects it with the Neoarchaean iron formation of the Carajás mineral province.

Igneous Geochemistry of Mineralized Rocks of the Baguio District, Philippines: Implications for Tectonic Evolution and the Genesis of Porphyry-Style Mineralization

The Baguio district of the Philippines is one of the world’s premier mineral provinces, containing >35 million ounces (Moz) of gold and 2.7 million metric tons (Mt) of copper in epithermal, porphyry, and skarn deposits that formed in the last 3.5 m.y. Pliocene and Pleistocene magmatic rocks of the Baguio district that are spatially and temporally associated with mineralization can be broadly subdivided into an intermediate to felsic suite of mineralized low to medium K intrusions, some of which have adakitic affinities and a suite of mafic to intermediate, medium K to shoshonitic hornblende-phyric dikes. The geochemical and isotopic characteristics of the dikes are consistent with primitive mantle-derived melts that underwent minimal crustal contamination as they ascended through the arc crust. In contrast, the intermediate to felsic suite has been contaminated by young arc crust, suggesting ponding and fractionation within shallow-crustal magma chambers. The Philippine arc has formed in a complex tectonic environment and is currently sandwiched between two active subduction zones. Eastward-directed subduction of the Scarborough Ridge along the Manila trench is currently associated with flattening of the downgoing slab. The formation of the Mafic dike complex is broadly coeval with the onset of subduction of the Scarborough Ridge and slab flattening. The extinct Scarborough Ridge would have been younger than the downgoing plate and consequently more susceptible to melting. These melts can account for the isotopic recharge of the Pliocene subarc mantle as well as the generation of the primitive melts and adakitic rocks found within the Baguio district. The interaction between primitive mafic melts and the more felsic calc-alkaline rocks has

Multi-scale approach using remote sensing images to characterize the iron deposit N1 influence areas in Carajás Mineral Province (Brazilian Amazon)

Mining activities cause a wide range of changes to the environment, substantially affecting both the physical and biological environmental sectors. In the Carajas Mineral Province, located in the Amazon rainforest, environmental regulations tend to be more rigorous, due to the fragility of the environment in which large iron deposits are found. The characterization of the impact of mining on environment considers: the type and extent of the impact, the physical chemistry differences and similarities of the mineral deposits, the deposit size, the adopted mining process, and the environment (both natural and economic) in which the mining process was developed. Remote sensing technology is utilized in this study, in particular, the use of ortho-aerial photograph, and optical and radar images with distinct spatial resolution. These permit the elaboration in synoptic maps, multi-scale and dynamic, of the changes wrought upon the environment: deforestation, removal of vegetation cover, topographic surface and landscape alteration, and slope instabilities among others. In this aspect, determining the extent of influence of the mining activity is directly tied to the characterization of its impact on various natural systems at the observed scale, and not by simply defining a predetermined Euclidean distance. The results showed that remote sensing technology, optical and radar images, proved to be efficient in the study of environmental information and the areas of influence on the semi-regional and local scales in the Amazon forest.

Structural characteristics of chalcopyrite from a Cu(Au) ore deposit in the Carajás Mineral Province, Brazil

Mossbauer spectra and X-ray diffraction data show a chalcopyrite from the Cristalino Cu(Au) deposit in the Carajas Mineral Province in northern Brazil to consist of a single, tetragonal phase. This is in stark contrast to a previously described chalcopyrite from the Camaqua copper mine in southern Brazil, obviously reflecting differences in mineral (and thus ore deposit) genesis.

Modeling of Airbone Data (Magnetic and Electromagnetic) of Cristalino Cu-Au Deposit, Carajás, Pará, Brazil

The Cristalino Cu-Au deposit is located in Carajas Mineral Province. The area of the deposit was covered by an airborne survey (magnetic and time domain electromagnetic) in order to identify the most conductive areas. Six resistivity depth images were built for these data, using the software ImagEM and the magnetic data was processed and interpretation was based on the Analytical Signal. The ImagEM software is under development by the Electromagnetic Interpretation Research Group of Universidade de Brasilia. ImagEM showed very good results for the Cristalino area, where the low resistivity core has a good correlation with the deposit.

Iron and sulphur isotopes from the Carajás mining province (Pará, Brazil): Implications for the oxidation of the ocean and the atmosphere across the Archaean–Proterozoic transition

Mineralogical analyses and major and trace element geochemistry combined with iron and sulfur isotopes were applied to banded iron formations (BIFs) and pyrite-bearing sandstones from the Carajás mineral province, Brazil. The BIFs belong to the 2.7 Ga old Grão Pará Group and show a rather simple mineralogy (hematite and quartz or cryptocrystalline silica). Their REE + Y patterns suggest deposition under marine sub-oxic conditions. Fe isotopes show highly positive values (δ 57Fe IRMM-14 = 2.06 ± 0.34‰ in average) which can be explained by the partial oxidation of Fe 2+ aq in the surface ocean, subsequent to the upwelling of deep anoxic seawater. The resulting iron oxy-hydroxides likely formed in the shallow photic zone as a seasonal process and acquired highly positive iron isotope signature values consistent with a Rayleigh distillation model. The pyrite-bearing sandstones belong to the Aguas Claras Formation of (Palaeoproterozoic) younger age and were cored at the base of the giant Azul manganese deposit. Diagenetic pyrite is characterized by positive δ 57Fe IRMM-14 = 1.02 ± 0.2‰ and δ 34S VCTD (11.97 ± 0.12‰) average values, that are different from values of modern marine biogenic pyrite. Results likely indicate that dissolved sulfate was the limiting factor controlling biogenic pyrite formation at that time. Near-zero Δ 33S values (0.013 ± 0.003‰) indicate minimal mass-independent sulfur isotope fractionation (MIF-S), consistent with the 2.1 Ga age previously obtained from the Aguas Claras pyrites. This result suggests deposition at a time when the oxygen partial pressure in the atmosphere was already high enough (10 − 5 to 10 − 2 PAL- or Present Atmospheric Level-) to hinder MIF-S by photochemical reactions. Incidentally, this also confirms that the giant Mn deposit of Carajás is in the same age range (2.1 ± 0.2 Ga) as other Mn ores in Gabon and South Africa, pointing to the importance of Mn precipitation in Paleoproterozoic times.

Hydrothermal alteration, fluid inclusions and stable isotope systematics of the Alvo 118 iron oxide–copper–gold deposit, Carajás Mineral Province (Brazil): Implications for ore genesis

The Alvo 118 iron oxide–copper–gold (IOCG) deposit (170 Mt at 1.0 wt.% Cu, 0.3 g/t Au) lies in the southern sector of the Itacaunas Shear Belt, Carajas Mineral Province, along a WNW–ESE-striking, 60-km-long shear zone, close to the contact of the ~2.76-Ga metavolcano-sedimentary Itacaiunas Supergroup and the basement (~3.0 Ga Xingu Complex). The Alvo 118 deposit is hosted by mafic and felsic metavolcanic rocks and crosscutting granitoid and gabbro intrusions that have been subjected to the following hydrothermal alteration sequence towards the ore zones: (1) poorly developed sodic alteration (albite and scapolite); (2) potassic alteration (biotite or K-feldspar) accompanied by magnetite formation and silicification; (3) widespread, pervasive chlorite alteration spatially associated with quartz–carbonate–sulphide infill ore breccia and vein stockworks; and (4) local post-ore quartz–sericite alteration. The ore assemblage is dominated by chalcopyrite (~60%), bornite (~10%), hematite (~20%), magnetite (10%) and subordinate chalcocite, native gold, Au–Ag tellurides, galena, cassiterite, F-rich apatite, xenotime, monazite, britholite-(Y) and a gadolinite-group mineral. Fluid inclusion studies in quartz point to a fluid regime composed of two distinct fluid types that may have probably coexisted within the timeframe of the Cu–Au mineralizing episode: a hot (>200°C) saline (32.8‰ to 40.6 wt.% NaCl eq.) solution, represented by salt-bearing aqueous inclusions, and a lower temperature (<200°C), low to intermediate salinity (<15 wt.% NaCl eq.) aqueous fluid defined by two-phase (LH2O + VH2O) fluid inclusions. This trend is very similar to those defined for other IOCG systems of the Carajas Mineral Province. δ18OH2O values in equilibrium with calcite (−1.0‰ to 7.5‰ at 277°C to 344°C) overlap the lower range for primary magmatic waters, but the more 18O-depleted values also point to the involvement of externally derived fluids, possibly of meteoric origin. Furthermore, sulphide δ34S values (5.1‰ to 6.3‰), together with available boron isotope and Cl/Br–Na/Cl data provide evidence for a significant component of residual evaporative fluids (e.g., bittern fluids generated by seawater evaporation) in this scenario that, together with magma-derived brines, would be the main sources of the highly saline fluids involved in the formation Alvo 118 IOCG deposit. The restricted high temperature sodic alteration, the pervasive overprinting of the potassic alteration minerals by chlorite proximal to the ore zones, ore breccias with open-space filling textures in brittle structures, microthermometric and stable isotope data indicate, collectively, that the Alvo 118 IOCG system developed at structurally high levels and may be considered the shallower representative of the IOCG systems of the CMP.

Effects of hydrocarbon generation on fluid flow in the Ordos Basin and its relationship to uranium mineralization

The Ordos Basin of North China is not only an important uranium mineralization province, but also a major producer of oil, gas and coal in China. The genetic relationship between uranium mineralization and hydrocarbons has been recognized by a number of previous studies, but it has not been well understood in terms of the hydrodynamics of basin fluid flow. We have demonstrated in a previous study that the preferential localization of Cretaceous uranium mineralization in the upper part of the Ordos Jurassic section may have been related to the interface between an upward flowing, reducing fluid and a downward flowing, oxidizing fluid. This interface may have been controlled by the interplay between fluid overpressure related to disequilibrium sediment compaction and which drove the upward flow, and topographic relief, which drove the downward flow. In this study, we carried out numerical modeling for the contribution of oil and gas generation to the development of fluid overpressure, in addition to sediment compaction and heating. Our results indicate that when hydrocarbon generation is taken into account, fluid overpressure during the Cretaceous was more than doubled in comparison with the simulation when hydrocarbon generation was not considered. Furthermore, fluid overpressure dissipation at the end of sedimentation slowed down relative to the no-hydrocarbon generation case. These results suggest that hydrocarbon generation may have played an important role in uranium mineralization, not only in providing reducing agents required for the mineralization, but also in contributing to the driving force to maintain the upward flow.

Mesoarchean (3.0 and 2.86 Ga) host rocks of the iron oxide–Cu–Au Bacaba deposit, Carajás Mineral Province: U–Pb geochronology and metallogenetic implications

The Bacaba iron oxide–copper–gold deposit, situated within a WNW–ESE-striking shear zone in the Carajas Domain, Carajas Mineral Province, is hosted by the Serra Dourada Granite, the Bacaba Tonalite, and crosscutting gabbro intrusions, which were intensely affected by sodic (albite–scapolite), potassic, chloritic, and hydrolytic hydrothermal alteration. This deposit is located 7 km northeast of the world-class Sossego iron oxide–copper–gold deposit and might represent a distal and deeper portion of the same or related hydrothermal system. The U–Pb laser ablation inductively coupled plasma–mass spectrometry data for zircon from a sodically altered sample of the Serra Dourada Granite yielded a 2,860±22 Ma (MSWD=11.5) age. Three samples from the Bacaba Tonalite, including one with potassic alteration and two with Cu–Au mineralization, rendered the 3,001.2±3.6 Ma (MSWD=1.8), 2,990.9±5.8 Ma (MSWD=1.9), and 3,004.6±9 Ma (MSWD=2.2) ages, respectively. The ca. 2.86 and ca. 3.0 Ga ages are interpreted as the timing of the igneous crystallization of the Serra Dourada Granite and the Bacaba Tonalite, respectively, and represent the oldest magmatic events recognized in the Carajas Domain. The Serra Dourada Granite and the Bacaba Tonalite are interpreted to greatly predate the genesis of the Bacaba deposit. A genetic link is improbable in the light of the similarities with the Sossego deposit, which is also hosted by younger ca. 2.76 Ga metavolcano-sedimentary units of the Itacaiunas Supergroup. In this context, the iron oxide–copper–gold deposits in the southern sector of the Carajas Domain could be mainly controlled by important crustal discontinuities, such as a regional shear zone, rather than be associated with a particular rock type. These results expand the potential for occurrences of iron oxide–copper–gold deposits within the Mesoarchean basement rocks underlying the Carajas Basin, particularly those crosscut by Neoarchean shear zones.

Análise prospectiva para ouro nas regiões Ouro Roxo-Cantagalo e Chico Torres, Província Mineral do Tapajós

Spatial modeling (fuzzy logic) was used to predict key areas for gold exploration in the Tapajos Mineral Province (Brazilian Amazon), specifically in the regions here named Ouro Roxo-Cantagalo and Chico Torres. The data used were regional airborne geophysical and SAR-R99B data. The airborne geophysical data processing allowed the generation of evidence layers for modeling approaches. The best evidences in current models were anomalous potassium, F parameter, radioelement ratios, radioelement normalization, and amplitude of the analytical signal of the magnetic anomalous field. The SAR images were used in the photointerpretation stage. In the case of regions of the Ouro Roxo-Cantagalo and Chico Torres shear zones, geophysical images and interpretations (when necessary) were used to application of fuzzy logic, and the gold locations were used to evaluate the quality of the modeling results. The main contributions of this research include the observation of potential gamma-ray spectrometry signatures, the refining interpretation of the digital data, and improving the information of the current geological maps. The prospective Ouro Roxo-Cantagalo and Chico Torres modeling results using the conceptual fuzzy logic method exemplify the generation of regional exploration models for the cartography and selection of gold potential areas. This methodology can be extended to others regions of the Tapajos Mineral Province using airborne geophysical data current available by CPRM and the SAR images of the Centro Tecnico Operacional do Sistema de Protecao da Amazonia (CENSIPAM).

Ecodynamics of anthropogenic mining provinces: From degradation to rehabilitation

The unity, interrelationship, and interdependence of the processes proceeding in anthropogenic provinces caused by the activity of mining industries are considered from the viewpoint of the concept of hierarchical passivity of natural components. The processes of degradation of natural complexes under the influence of mining industries and the processes of rehabilitation of the vegetation cover when the anthropogenic pressure decreases are analyzed taking the ZAO Karabashmed’, Chelyabinsk region, and the Severonikel’ Combine, Murmansk region, as examples. The intrinsic potential of rehabilitation of natural systems (air, water, and soil) is assessed, and the most passive components are identified. A strategy of reclamation of disturbed territories is enunciated based on the information obtained taking the natural self-recovering ability of ecosystems in different climate zones into account.

A guide for mineral exploration through the regolith in the Yilgarn Craton, Western Australia

The Yilgarn Craton is one of the world's principal mineral provinces, with considerable resources of gold, nickel, bauxite and iron ore, as well as lesser amounts of a wide range of other commodities. As such, it is a major target for exploration. However, as most of the Craton has been exposed to sub-aerial conditions since at least the Late Proterozoic, it has had a long history of weathering and erosion under a wide variety of climatic conditions, resulting in a widespread and complex regolith cover. This diverse and extensive regolith poses considerable difficulties for exploration—as well as opportunities in terms of different sample media and the formation of resources within the regolith itself. The development of appropriate geochemical exploration procedures has been the subject of considerable research by government, university and industry for nearly 50 years. This guide is intended to summarise the results of this research in a single, stand-alone document to assist mineral explorers. It provides a synthesis of the characteristics and evolution of the Yilgarn landscape and advice on appropriate strategies and techniques for exploring through different types of cover, based on current knowledge and best practice. Because broadly similar deeply weathered regolith-dominated terrains occur elsewhere in Australia and, indeed, in other continents, many of the principles discussed here can be more widely applied. The guide develops exploration strategies for gold, base metals, nickel and surficial uranium deposits within the context of the evolution of the landscape and regolith of the Yilgarn Craton. The guide commences with a brief introduction to the geology and principal ore deposits of the Craton, followed by a description of the development and characteristics of the regolith, and the relationship between regolith type and landforms. The distribution, characteristics and use of the principal sample media are described. The regolith and landforms provide a framework for empirical models that describe the processes of geochemical dispersion, based on numerous case histories and other investigations, grouped according to the principal commodities. The models anticipate and summarise the surface expression of mineralisation and include recommendations on exploration procedures, such as sample selection, sampling interval and analytical approach. A comprehensive reference list provides a source for further information.

Assessment of radargrammetric DSMs from TerraSAR-X Stripmap images in a mountainous relief area of the Amazon region

The Brazilian Amazon is a vast territory with an enormous need for mapping and monitoring of renewable and non-renewable resources. Due to the adverse environmental condition (rain, cloud, dense vegetation) and difficult access, topographic information is still poor, and when available needs to be updated or re-mapped. In this paper, the feasibility of using Digital Surface Models (DSMs) extracted from TerraSAR-X Stripmap stereo-pair images for detailed topographic mapping was investigated for a mountainous area in the Carajás Mineral Province, located on the easternmost border of the Brazilian Amazon. The quality of the radargrammetric DSMs was evaluated regarding field altimetric measurements. Precise topographic field information acquired from a Global Positioning System (GPS) was used as Ground Control Points (GCPs) for the modeling of the stereoscopic DSMs and as Independent Check Points (ICPs) for the calculation of elevation accuracies. The analysis was performed following two ways: (1) the use of Root Mean Square Error (RMSE) and (2) calculations of systematic error (bias) and precision. The test for significant systematic error was based on the Student’s-t distribution and the test of precision was based on the Chi-squared distribution. The investigation has shown that the accuracy of the TerraSAR-X Stripmap DSMs met the requirements for 1:50,000 map (Class A) as requested by the Brazilian Standard for Cartographic Accuracy. Thus, the use of TerraSAR-X Stripmap images can be considered a promising alternative for detailed topographic mapping in similar environments of the Amazon region, where available topographic information is rare or presents low quality.

Geotectonic setting and metallogeny of the northern São Francisco craton, Bahia, Brazil

Abstract This paper aims at establishing a tectonic and temporal framework to characterize the metallogenic processes that contributed to the origin of the mineral provinces in the northern Sao Francisco Craton. Many Archean mineralizations (eg. massive sulfide zinc, lead, zinc and copper, besides magnesite–talc, iron–titanium–vanadium, iron, chromite and manganese) were generated before the assembly of the Craton. Deposits of chromite, nickel, gold and emerald were produced during the Paleoproterozoic orogenic cycle, when the Craton was amalgamated into the Atlantica paleocontinent. An extension event is recorded in the Neoproterozoic, during the breakup of Rodinia, associated with deposits of phosphorite and uranium. Kimberlite diamond and gold mineralization were generated during the Brasiliano orogenic cycle, coeval with the amalgamation of West Gondwana. A long-lasting and rather uniform crustal stress is recorded in the area during the Cambrian period. Resetting of the isotopic and magnetic systems that affected the Neoproterozoic sediments of the Irece Basin at about 520 Ma was attributed to the regional-scale fluid migration and mineralization in the aftermath of the Brasiliano orogenic cycle.