Belt Segment Research Articles

Trends in the Growth of Damage Extents in a Steel Conveyor Belt’s Core

The initial set of four measurements (scans) captures the failures occurring in the core of steel cable conveyor belt segments used in a lignite coal mine in Poland. These measurements utilize the DiagBelt+ magnetic system, enabling the analysis of averaged damage sizes. The scanning results allowed the analysis of complete changes in the failure sizes to a maximum of six different time intervals from 1 to 19 months. The cumulative increase in the length and width of the failure (their total extent in both directions) is a linear function of time. However, the inclination of the selected lines (growth speed) depends on the age of the belt segment at the time of its first scan. It is possible to find the best regression function of slope coefficients for the age of the belt segment. The obtained results are crucial for rational belt management, including reliable short-term forecasts of belt needs with the flow of time, indications of the best moments for belt segment replacements, and estimating the budget of the belting department.

Design of a laboratory scale Automatic Optical Inspection prototype system for scanning of conveyor belt surfaces — A case study

The design and assembly of an Automatic Optical Inspection (AOI) system is a complex process for any production scenario that considers process quality outcome and loss as an important aspect. This paper discusses the design and implementation of a laboratory-based AOI system through inspection parameter optimization for monitoring the surface condition of conveyor belt segments. The system utilizes a low-cost web camera and a line laser projection device as sensor components in a non-intrusive setup to capture color and depth images of the belt surface. A mixed-level full factorial design of experiment (DoE) approach is devised to examine how different control factors, which in this case are the inspection parameters, such as- the surface illumination, inspection speed, imaging distance, camera frame rate, and camera field of view, affect the response factor, which is the measurement error percentage of the AOI system. The error percentage is obtained by comparing the inspection results of a belt region of known dimensions with corresponding manual measurements. Comprehensive data collection runs followed by the factorial analysis revealed that all individual inspection parameters were significant except for the interaction between imaging distance and field of view. Based on the range of inspection parameter settings investigated, the optimal settings were found to be an imaging distance of 60 cm, a field of view of 75, illumination of 0 lux, an inspection speed of 9 cm/s, and a camera frame rate of 75 frames per second to achieve an inspection error of 0.26%, which is acceptable for our investigation.

Tectonics may affect closed watersheds used to monitor climate change and human activity effects

AbstractPlaya lakes developed in closed watersheds have been used as environmental impact indicators (global warming, water extractions, etc.), but they could be also sensitive to active tectonics. Our study area is located in the main watershed in the western Betics, the northern branch of the Gibraltar arc, which is within the fold‐and‐thrust belt. This area is characterized by an endorheic zone that includes some playa lakes floored by low‐permeable rocks. Our study shows the reduction or disappearance of playa‐lake flooded surfaces due to the reduction in their watershed area. This area reduction is favoured by stream catchments related to knickpoints, which seem to be generated by the quaternary activity of a dextral‐transpressive band within the Betics fold‐and‐thrust belt. χ map also shows the higher erosion power of Mediterranean streams, which will likely catch this endorheic area in tectonics quiescence.Statement of significancePlaya lakes developed in closed watersheds are commonly used to study environmental impacts such as global warming or water extractions. In this work, we analyse how these endorheic systems are sensitive to small water balance variations due to active tectonics. The endorheic area we chose to apply this new approach is located in the main Atlantic‐Mediterranean water divide of the western Betics (northern branch of the Gibraltar arc). The recent tectonics in this fold‐and‐thrust belt segment provoked the Atlantic‐Mediterranean gateway closure and the Messinian Salinity Crisis at 5.6 My. Our study of playa‐lake flooded surface and watershed modifications, together with structural and other geomorphic analyses such as the χ index, never before has it been made to detect active structures. Active tectonics likely influenced in the medium‐term evolution of the studied watersheds and this study is useful to predict both landscape and drainage network evolution in the future. In fact, the possible effect of active tectonic should be taken into account when using closed watersheds to monitor the impacts of climate change and/or local stressors such as water pumping activities.

Aegean-style extensional deformation in the contractional southern Dinarides: incipient normal fault scarps in Montenegro

Abstract. We describe two 5–7 km long normal fault scarps (NFSs) occurring atop fault-related anticlines in the coastal ranges of the Dinarides fold-and-thrust belt in southern Montenegro, a region under predominant contraction. Both NFSs show well-exposed, 6–9 m high, striated, and locally polished fault surfaces, cutting uniformly northeastward-dipping limestone beds at high angles and documenting active faulting. Sharply delimited ribbons on free rock faces show different colors, varying karstification, and lichen growth and suggest stepwise footwall exhumation, which is typical of repeated normal faulting during earthquake events. Displacements, surface rupture lengths, and geometries of the outcropping fault planes imply paleoearthquakes with Mw≈6 ± 0.5 and slip rates of ∼ 0.5–1.5 mm yr−1 since the Last Glacial Maximum. This is well in line with (more reliable, higher-resolution) slip rates based on cosmogenic 36Cl data from the scarps for which modeling suggests 1.5 ± 0.1 mm yr−1 and 6–15 cm slip every 35–100 years during the last ∼ 6 kyr. The total throw on both NFSs – although poorly constrained – is estimated to ∼ 200 m and offsets the basal thrust of a regionally important tectonic unit. The NFSs are incipient extensional structures cutting (and postdating emplacement of) the uppermost Dinaric thrust stacks down to an unknown depth. To explain their existence in a region apparently under pure contraction, we consider two possibilities: (i) syn-convergent NFS development or – less likely – (ii) a hitherto undocumented propagation of extensional tectonics from the hinterland. Interestingly, the position of the extensional features documented here agrees with geodetic data, suggesting that our study area is located broadly at the transition from NE–SW-directed shortening in the northwest to NE–SW-directed extension to the southeast. While the contraction reflects ongoing Adria–Europe convergence taken up along the frontal portions of the Dinarides, the incipient extensional structures might be induced by rollback of the Hellenic slab in the southeast, whose effects on the upper plate appear to be migrating along-strike of the Hellenides towards the northwest. In that sense, the newly found NFSs possibly provide evidence for a kinematic change of a thrust belt segment over time. However, with a significantly higher probability, they can be regarded as second-order features accommodating geometrical changes in the underlying first-order thrust faults to which they are tied genetically.

Post-collisional magmatism of 1.88–1.84 Ga in the southern Siberian Craton: An overview

The paper presents an overview of geological, geochronological, geochemical, and isotopic data on 1.88–1.84 Ga igneous rocks from the South Siberian post-collisional magmatic belt that records the final event of craton assembly. The belt consists mainly of granitoids and coeval felsic volcanics, less abundant mafic rocks, and sporadic carbonatites. In spite of the chronological and geodynamic proximity, the igneous rocks from different parts of the belt have dissimilar chemical and isotopic signatures, which are well consistent with the events that preceded the final assembly of the craton. Samples from the southwestern part of the belt show the greatest diversity, with an affinity of granitoids and felsic volcanics to different granite types (I-, S-, and A), and large εNd(T) ranges from positive to strongly negative for both felsic and mafic rocks. The compositional diversity of post-collisional igneous rocks here may be due to their origin shortly after the collisional events (1.90–1.87 Ga) during the orogen collapse. The diversity can have different explanations for felsic and mafic rocks: melting of heterogeneous sources assembled in the thickened orogen, as well as lithospheric delamination and asthenospheric upwelling, respectively. In the latter case, a source for mafic melts can be both asthenospheric material and subcontinental lithospheric mantle. The rocks of the southeastern belt segment are less diverse. Almost all granitoids and felsic volcanics have ferroan compositions, A-type granite affinity, and variable negative εNd(T) values similar to those in mafic rocks and in the Aldan shield carbonatites. The granitoids and volcanics here have compositions that commonly form in within-plate extension settings, which correlate with the 2.00–1.90 Ga age of collisional events in the area prior to the belt formation. The cessation of collisional movements in the southwestern craton part led to extension throughout its southern (and southeastern) areas. The ensuing melting of continental crust and subcontinental lithospheric mantle produced, respectively, felsic and mafic melts. The igneous rocks of the easternmost part of the South Siberian belt include also alkaline carbonatites and host diverse mineral deposits indicates that this part of the craton may have been exposed to the effect of a hot spot.

Coastal Belt Linked Classification (CBLC): A System for Characterizing the Interface between Land and Sea Based on Large Marine Ecosystems, Coastal Ecological Sequences, and Terrestrial Ecoregions

Finkl, C.W. and Makowski, C., 2020. Coastal Belt Linked Classification (CBLC): A system for characterizing the interface between land and sea based on large marine ecosystems, coastal ecological sequences, and terrestrial ecoregions. Journal of Coastal Research, 36(4), 677–693. Coconut Creek (Florida), ISSN 0749-0208.The Coastal Belt Linked Classification (CBLC) is a novel approach based on interpretation of satellite images and assimilation of collateral data to characterize coastal belt segments that function as discrete interfaces between land and sea. This method is based on the formulation of concepts derived from the Biophysical Cross-shore Classification System (BCCS), the worldwide and regional-scale Large Marine Ecosystems (LME) classification, and the global distribution of terrestrial Ecoregions (ER). The coastal belt, a zone that extends across the shore from marine environments to inland terrestrial habitats, has recently been described in terms of cross-shore catenary sequences based on biophysical attributes of geomorphology and ecology. The CBLC formulates a cross-shore coastal classification by conjoining the Dominant Catenary Sequences (DCS) and Coastal Ecological Sequences (CES) with marine (LME) and terrestrial (ER) ecological systems; thus, a linkage is now provided between marine and terrestrial areas across coastal belts that function as transitional succession zones. This study proposes to combine the traditionally separated tripartite marine, coastal, and terrestrial delineations by melding them into a single descriptive code sequence that can be ascertained from interpretation of Google Earth satellite imagery and accessing collateral data via interactive LME and ER online platforms. Development of the CBLC is facilitated by the fact that LME and ER units are codified by numerals that are easily added to the formulated CES as prefixes and suffixes. The resulting combined alphanumeric code brings together a trove of information at different levels of investigation (Levels I – IV) that was heretofore not easily assimilated. This linkage of DCS and CES catenas with marine LME and terrestrial ER units brings added advantage to the interpretation of satellite imagery of the world's coasts, as it allows coastal belts to be viewed within the context of transitional interfaces between connected marine and terrestrial parameters. Recognition of coastal belts as interfacial bridges linking terrestrial and marine ecosystems into one codified descriptor sequence allows for cross-shore transects to be defined in the form of the Coastal Belt Linked Classification (CBLC) and provides an opportunity to fully comprehend the dynamic nature of coastal zones around the world.

Electronic Energy Relaxation in a Photoexcited Fully Fused Edge-Sharing Carbon Nanobelt.

Carbon nanobelts are cylindrical molecules composed of fully fused edge-sharing arene rings. Because of their aesthetically appealing structures, they acquire unusual optoelectronic properties that are potentially suitable for a range of applications in nanoelectronics and photonics. Nevertheless, the very limited success of their synthesis has led to their photophysical properties remaining largely unknown. Compared to that of carbon nanorings (arenes linked by single bonds), the strong structural rigidity of nanobelts prevents significant deformations away from the original high-symmetry conformation and, therefore, impacts their photophysical properties. Herein, we study the photoinduced dynamics of a successfully synthesized belt segment of (6,6)CNT (carbon nanotube). Modeling this process with nonadiabatic excited state molecular dynamics simulations uncovers the critical role played by the changes in excited state wave function localization on the different types of carbon atoms. This allows a detailed description of the excited state dynamics and spatial exciton evolution throughout the nanobelt scaffold. Our results provide detailed information about the excited state electronic properties and internal conversion rates that is potentially useful for designing nanobelts for nanoelectronic and photonic applications.

East Bohemian finds of belt segments with a central knob and side plates as evidence of interregional contacts during the La Tène period

Text se zabýva východoceskými nalezy opaskových clanků se středovým vývalkem a postrannimi destickami datovanými do obdobi LT C2–D1, jejichž původ lze hledat v oblasti středniho Podunaji. Soucasti clanku je celkove zhodnoceni stavu poznani, typologie i chronologických a geografických aspektů teto problematiky. Opaskove clanky ziskane v prostoru východnich Cech jsou nahliženy v kontextu dalsich východoceských nalezů, ktere v uvedene oblasti dokladaji působeni jihovýchodnich vlivů nejpozději od stupně LT B2.

New insights into the Gondwana breakup at the Southern South America by apatite fission-track analyses

Abstract. Apatite fission-track (AFT) analyses, applied to Southern Brazil and Uruguay samples, was employed aiming to understand the low temperature history of the Dom Feliciano Belt Segment. The Dom Feliciano Belt formed during the Neoproterozoic to Early Paleozoic, linked to the Brasiliano/Pan-African Orogeny. Twenty-four samples were dated, and confined track lengths of twenty samples were measured. The spatial distribution of ages shows three domains with different evolution cut by shear zones and, or suture zones in the Dom Feliciano Belt. The Western Domain exhibits AFT ages > 250 Ma (Permian to Devonian) while the Eastern Domain shows AFT ages < 230 Ma (Paleogene to Triassic). In the Central Domain, the AFT ages range from ∼196 to 130 Ma (Jurassic to Early Cretaceous). The thermal modeling in the domains revealed a complex evolution, with cooling and reheating phases, and a denudation of ∼2600 m. The AFT ages clearly postdate the Gondwanide, Paraná-Etendeka and Rio Grande Cone exhumation history of the Dom Feliciano Belt.

Estimation of Purchase and Replacement Costs of Conveyor Belts and their Splices in an Underground Mine Based on their Durability

A cost model for the purchase and replacement of conveyor belts using the average durability of belts and splices of various types (including adhesive and vulcanized splices) was developed for a hypothetical underground mine which uses continuous belt transport. Variant cost models of belt maintenance were developed for the given belt purchase prices and costs of splicing belt segments in the loop. The investigations focused on how the total costs of belting are influenced by various factors, including: belt prices, splicing costs, durability of belts and their joints, type of splicing, time and costs of planned and emergency belt replacements. The analyzes were performed without taking into account random differences in durability, and therefore the confidence interval for total costs for the given confidence level was not presented. The calculations were based on data obtained from users. They were not preceded by any statistical analyzes of actual operating times for either belts or splices. The results are therefore of qualitative rather than quantitative nature. Nevertheless, they should accurately reflect the level of costs and the impact of the analyzed factors on its changes.

Condition-Based Conveyor Belt Replacement Strategy in Lignite Mines with Random Belt Deterioration

In Polish lignite surface mines, condition-based belt replacement strategies are applied in order to assure profitable refurbishment of worn out belts performed by external firms specializing in belt maintenance. In two of three lignite mines, staff asses belt condition subjectively during visual inspections. Only one mine applies specialized diagnostic device (HRDS) allowing objective magnetic evaluation of belt core condition in order to choose the most profitable moment for the dismantling of worn out belt segments from conveyors and sending them to the maintenance firm which provides their refurbishment. This article describes the advantages of a new diagnostic device called DiagBelt. It was developed at the Faculty of Geoengineering, Mining and Geology, Wroclaw University of Science and Technology. Economic gains from its application are calculated for the lignite mine and for the belt maintenance firm, taking into account random life (durability) of new and reconditioned belts (after the 1st and the 2nd refurbishment). Recursive calculations for following years allow the estimation of the length and costs of replaced, reconditioned and purchased belts on an annual basis, while the use of the Monte Carlo method allows the estimation of their variability caused by random deterioration of belts. Savings are obtained due to better selection of moments (times) for the replacement of belt segments and die to the possibility to qualify worn out belts for refurbishment without the need to remove their covers. In effect, increased belt durability and lowered share of waste belts (which were not qualified for reconditioning) create savings which can quickly cover expenditures on new diagnostic tools and regular belt inspections in the mine.

Accelerated Comparative Fatigue Strength Testing of Belt Adhesive Joints

Belt joints are the weakest link in the serial structure that creates an endless loop of spliced belt segments. This affects not only the lower strength of adhesive joints of textile belts in comparison to vulcanized splices, but also the replacement of traditional glues to more ecological but with other strength parameters. This is reflected in the lowered durability of adhesive joints, which in underground coal mines is nearly twice shorter than the operating time of belts. Vulcanized splices require high precision in performance, they need long time to achieve cross-linking of the friction mixture and, above all, they require specialized equipment (vulcanization press) which is not readily available and often takes much time to be delivered down, which means reduced mining output or even downtime. All this reduces the reliability and durability of adhesive joints. In addition, due to the consolidation on the Polish coal market, mines are joined into large economic units serviced by a smaller number of processing plants. The consequence is to extend the transport routes downstream and increase reliability requirements. The greater number of conveyors in the chain reduces reliability of supply and increases production losses. With high fixed costs of underground mines, the reduction in mining output is reflected in the increase in unit costs, and this at low coal prices on the market can mean substantial losses for mines. The paper describes the comparative study of fatigue strength of shortened samples of adhesive joints conducted to compare many different variants of joints (various adhesives and materials). Shortened samples were exposed to accelerated fatigue in the usually long-lasting dynamic studies, allowing more variants to be tested at the same time. High correlation between the results obtained for shortened (100 mm) and traditional full-length (3×250 mm) samples renders accelerated tests possible.

Random Deterioration Process of Conveyor Belt Evaluated by Statistical Analysis of Core Failures Detected Along Belt Axis and Elapsed Time

Magnetic diagnostic methods are used for steel cord belt condition evaluation since the beginning of 1970s. Initially they generated an analogue signal for several tens of centimetres of conveyor belts scanned sequentially with one measuring head in several cycles or the whole width of the belt at one time thanks to the installation of many measuring heads across the entire cross section. This did not allow identification of single centimetre failures, but rather an aggregate assessment of the state of quite wide waist. Modern diagnostic devices, thanks to miniaturization, allow up to 200 heads per belt width to identify damage of individual cords. Instead of analogue signals, they generate a zero-one digital signal corresponding to a change in the magnetic field sign, which can illustrate damage on 2D images. This makes it easier to identify the location and size of the damage in the belt image. Statistical analysis of digital signals summed up for consecutive sections along the belt axis allows to present both the source signal and its aggregation for band of a given width to form aggregate measures of belt damage such as the damage density per 1 meter of belt. Observation of changes in these measurements at different times allows on evaluation of its rate of change over time, which can be used to forecast future belt condition and to select the proper moment of preventive belt replacement to another one to avoid emergency downtimes (egg in underground mines) or to recondition of belts (egg. in lignite surface mines). The paper presents the results of investigations of the damage condition of a core of a single belt segment working in one of the copper ore underground mines. Scanning of the belt condition was performed few times at intervals of several months. The paper presents the results of the analysis of the changes in core condition, showing the random character of the damage process along the axis and its change over time.

Probabilistic model of divided conveyer belt to increase input performance of sorter feed systems

Maximization of input performance and throughput in sorting systems is a crucial interest of the industry. Due to self-impediment and mutual impediment at the input stage, a considerable reduction of throughput may occur. In this paper, a new design of a feeding system is discussed that addresses this deficiency, the divided conveyer belt (proposed by the author in 2003, patent DE 100 51 932 A). The new design is based on belt segments working at different, sequentially increasing speeds and takes into account ergonomic aspects to avoid worker fatigue. Based on a probabilistic model, that is the topic of this article, it will be argued that combined with sufficient spatial input variability the divided conveyer belt design substantially reduces the deficiency caused by mutual impediment and, consequently, increases input performance.

Inspección de calidad para un sistema de producción industrial basado en el procesamiento de imágenes

Este trabajo presenta el diseño y construcción de un sistema de visión artificial, basado en el pro­cesamiento digital de imágenes que permita au­tomatizar la inspección de calidad en un proceso de producción. El prototipo desarrollado fue implementado en una banda transportadora que hace parte de una cadena de ensamblaje y su función es medir el diámetro interno y externo, con una sen­sibilidad de +/- 0,1 mm y una velocidad de proce­samiento de 1400 piezas por hora, de dos tipos de piezas que simulan la geometría de una arandela y un tornillo. Lo anterior con el propósito de identificar cuáles piezas se encuentran dentro de los requerimientos de fábrica para su posterior en­samblaje. Para desarrollar el prototipo de manera oportuna se dividió el trabajo en tres etapas prin­cipales: hardware, control electrónico y software.

Research on Gun Dynamic Characteristic under Muzzle Strong Impact

Muzzle strong impact is a new test method of gun firing simulation test method. Based on the virtual prototyping technology, hydraulic simulation technology and rubber tests, gun model, power system model and material model of waveform generator were established. Finally, simulation model of gun firing simulation test machine was obtained. Simulation results indicated that the test machine can simulate the dynamic characteristic of recoil mechanism and load distribution of key components, for example, turret race, trunnion, belt segment, torsional axis and sprocket and so on..

Novel Approaches for Processing of Multi-Channels NDT Signals for Damage Detection in Conveyor Belts with Steel Cords

Belt conveyors are one of the most popular methods of material transport in many branches of industry, especially in mining. The average length of mining belt conveyor is about 1000 m. Taking into account that total length of transportation ways in averaged mine can approach several dozen of kilometers and network of several conveyors may cover large area, maintenance of such specific transportation system is very difficult. In this work we propose an automatic multi-channel system for data acquisition and processing for damage detection in belts. Belts with steel cords are considered here, they consist of top and bottom rubber covers and steel cords in between them. Due to many reasons (mainly sharpness of transported materials) covers may be damaged and it may initiate degradation process or straight damages in steel cords. Properties of steel cords are therefore crucial for overall strength of belts, if they are damaged, it may cause catastrophic failure of the whole conveyor. So, monitoring of belts conditions is a crucial issue. We proposed a monitoring system that measure and process data from array of magnetic sensors. The system allows to acquire up to 24 channels of NDT signals and uses automatic algorithms to process them in order to get information about begin of the belt loop, location of joints of particular belt segments and the final location and size of damages related to corrosion or cuts of steel cords inside belts. These techniques will be presented in the paper. Our approach has been validated in a lignite mine for several conveyor belts.

Constraints on the Devonian–Carboniferous closure of the Rheic Ocean from a multi-method geochronology study of the Staré Město Belt in the Sudetes (Poland and the Czech Republic)

This paper attempts to clarify the complex nature of how and when the Rheic Ocean closed in what is now Central Europe and, with respect to the various terranes that were involved, offer a regional chronology for the associated structural, metamorphic and igneous processes that accompanied and followed this closure. The Variscan orogen in Europe originated from the multiple collisions of Gondwana-derived terranes (the Armorican Terrane Assemblage) with Laurussia: however, many important structural details on the timing of these collision-related events remain obscure. In the Sudetes, the Staré Město Belt represents a WNW-dipping part of the Rheic suture that developed from the continental collision of the eastern terranes of the Armorican Terrane Assemblage (now in the Bohemian Massif) with the Brunovistulian Terrane (a part of Laurussia/Old Red Continent). In this study, the results of monazite Th–U–total Pb, garnet Lu–Hf and zircon U–Pb geochronology were integrated into a newly established D1–D3 tectonometamorphic sequence. A Th–U–total Pb age of ~368Ma from a monazite that grew concurrently with D2 metasedimentary garnet, as well as Lu–Hf ages of ~361Ma and ~355Ma obtained from D2 metasedimentary garnets, implies that the regional contractional deformation and progressive metamorphism of D2 took place mainly during the Famennian (Late Devonian) and extended into the Visean (Middle Mississippian of the Early Carboniferous). The ion probe U–Pb zircon ages of ~355Ma and ~359Ma obtained from leucocratic neosomes in migmatized amphibolites confirmed a lag in the peak temperature that followed crustal thickening during D1–D2. Metamorphic monazites dated at ~340Ma provide a time for the subsequent D3 dextral transpressional regime. The closure of the Staré Město Belt segment of the Rheic Ocean probably resulted from a head-on hard collision between the westerly subducting Brunovistulian promontory of Laurussia and the eastern members of the Armorican Terrane Assemblage. Thus, the Rheic Ocean closed during the Late Devonian at ~370–360Ma and preceded the collision of the Armorican Terrane Assemblage with East Avalonia at the western margin of what is now the Bohemian Massif. Following ocean closure, the Rheic slab may have broken off, resulting in the suture zone becoming dominated by lateral “tectonic escape” movements of the colliding terranes at ~340–330Ma (Visean). Syntectonic D3 intrusions of granodiorite/tonalite magma acted as a hot lubricant and stitched the suture zone together.

O Grupo Canastra em sua área-tipo, região de Tapira, sudoeste do estado de Minas Gerais

This work aimed at describing the Neoproterozoic evolution of a Southern Brasilia Fold Belt segment, in Tapira area (southwest of Minas Gerais state, Brazil), using detailed geologic mapping. This area, the Canastra Group type-area, has showed great tectonic and stratigraphic complexities unlike the simplicity suggested in previous works. From recognizing the main tectonic discontinuities, it was possible to subdivide the area into some domains. In the west domain, they were individualized in tectonic sheet I, marked by pelitic rocks and pelitic-graphite rocks with psammitic intercalations, and II, pelitic rocks with psammitic and mafic-ultramafic intercalations overlapped by gneisses. In the east domain, a group of three tectonic sheets was defined, in which, in the two lower tectonic sheets, pelitic and pelitic-graphite rocks with psammitic rock intercalations prevailed, which is different in metamorphic conditions. The lower tectonic sheet is marked by mineralogical associations with muscovite + chlorite + quartz ± graphite ± albite, without biotite; however, the superior one is with muscovite + quartz + garnet ± chlorite ± biotite ± chloritoid ± graphite ± albite. In the upper tectonic sheet, pelitic rocks with local contributions of psammitic and ultramafics rocks occur. In the south domain, psammitic rocks basically occur with contributions of pelitics and rudaceous rocks, where the preservation of textures and sedimentary structures is common. Rocks of the several domains are interpreted as part of a passive continental margin basin, located in the western margin of the Sao Francisco paleocontinent. Thus, the south domain rocks would represent the facies of proximal platform; rocks of the lower and middle tectonic sheets (east domain) and of the tectonic sheet I (west domain) are of facies distal platform; and the ones from the upper tectonic sheet (east domain) and tectonic sheet II (west domain) were acknowledged as deposited in an environment of continental shelf and/or oceanic seafloor.

Metallogenic features of Miocene porphyry Cu and porphyry-related mineral deposits in Ecuador revealed by Re-Os, 40Ar/39Ar, and U-Pb geochronology

Mineralization and alteration events at ten Miocene porphyry Cu and porphyry-related epithermal mineral deposits in southern, central, and northern Ecuador were dated by means of molybdenite Re-Os, biotite and alunite 40Ar/39Ar, and titanite U-Pb geochronology. Most of these hydrothermal events show a spatio-temporal correlation with porphyry intrusion emplacement as constrained by zircon U-Pb ages. The total age range for these events spans the 23.5–6.1 Ma period, without displaying systematic along- or across-arc age distribution trends. While epithermal deposits tend to be spatially associated with volcanic rocks of a similar age, porphyry Cu deposits in Ecuador are frequently spatially associated with deeper-seated basement units and batholith-scale precursor intrusive systems assembled over ≥5 m.y. time periods. In most cases, formation of the porphyry Cu deposits is related to the youngest magmatic (-hydrothermal) event in a given area, postdating batholith construction at a regional scale. The majority of Miocene deposits occurs in southern Ecuador where areally extensive, post-mineralization (late Miocene to recent) volcanic sequences with the potential to conceal mineralization at depth are lacking. Only few Miocene deposits occur in northern-central Ecuador, where they mainly crop out in the Western Cordillera, west of the productive present-day volcanic arc. The surface distribution of post-mineralization arc volcanism reflects along-arc variations in subducting slab geometry. Porphyry Cu and epithermal deposits in Ecuador define a Miocene metallogenic belt broadly continuous with its coeval counterpart in northern-central Peru. Although both belt segments were formed in an overall similar tectonomagmatic and metallogenic setting, their respective metal endowments differ significantly.