Large Hydrothermal System Research Articles

Pb isotope fingerprinting of mesothermal gold deposits from central Victoria, Australia: implications for ore genesis

New Pb isotope data from three major mesothermal lode gold deposits (Ballarat West, Tarnagulla, Maldon) in central Victoria support a model whereby the metals derived from a large reservoir with a long residence time in the crust below the Palaeozoic Lachlan Fold Belt. The Pb isotopic ratios of least radiogenic samples from these deposits are in close agreement with published Pb signatures for turbidite-hosted gold deposits, and for Devonian granites, elsewhere in the Lachlan Fold Belt. Despite their spatial distribution and variations in the geological setting, the Pb signatures point to the extraction and transport of metals from a crustal source area by long-lasting, large-scale hydrothermal systems, resulting in the prominent homogenisation of Pb isotopic ratios. The enduring interaction between large hydrothermal systems and an extensive crustal source reservoir were a vital pre-requisite in the formation of the Victorian gold province. In this regard, the prospectivity of Victoria is analogous to world-class ore provinces elsewhere, such as the Archaean Yilgarn Block in Western Australia.

Self‐potential and magnetic surveying of La Fournaise volcano (Réunion Island): Correlations with faulting, fluid circulation, and eruption

Self‐potential (SP) and magnetic surveys have been performed on the basaltic La Fournaise volcano (Réunion Island, Indian Ocean) between 1989 and 1992. The 1992 SP mapping of the inner caldera (Enclos Fouqué) reveals high relative positive SP anomalies. They are interpreted as related to a large hydrothermal system. A large SP anomaly of 2 V is centered on the terminal cone. A horseshoe‐shaped positive SP anomaly intersects the cone. This anomaly outlines the main arcuate fracture zone (MFZ), oriented north‐south on the cone and extending to the northeast and southeast away from the summit. The zone controls the volcano dynamism. Most of the fissure eruptions occur along this volcanotectonic axis. A second mechanical weakness axis is evidenced by a positive SP anomaly lying along a 120°N trend. Both volcanoes of the island, Piton des Neiges and later La Fournaise, have been built up along it. A large structure with reverse magnetization is found at the southeastern tip of this axis. This 120°N axis is interpreted as an old regional structure associated with a lithospheric weakness zone located beneath Réunion Island. The SP anomalies are thought to be of electrokinetic origin. In the central part of the volcano, along the MFZ, and the 120°N axis, positive SP data suggest hydrothermal upwelling caused by thermal transfer from the magma chamber and the dikes of the last eruptions. Away from the summit, SP data suggest groundwater infiltrates the massif by gravity effect. Changes of the SP with time are related to volcanic activity. The SP anomaly associated with main fracture zone has been generated by the 23 eruptions occurring between 1981 and 1992. Short‐time local SP anomalies that disappear in a few months are associated with individual eruptions.

Review of the application of isotopic studies to the genesis of Cu‐Au mineralisation at Olympic Dam and Au mineralisation at Porgera, the Tennant Creek district and Yilgarn Craton

This paper reviews the application of radiogenic isotopes to the study of four Cu‐U and Au deposits or deposit types in the Australasian region: Olympic Dam, Porgera, the Proterozoic Au deposits of the Tennant Creek district and the Archaean gold deposits of the Yilgarn Craton. In each case it has been possible to date the mineralisation and to correlate ore formation with a specific igneous event or stage in crustal evolution. In three cases it was also possible to use radiogenic isotopes to trace the source of the metal(s) or to constrain the fluid pathway. The results illustrate the power of radiogenic isotopes in ore‐genesis studies. At the Porgera gold deposit in Papua New Guinea K‐Ar and 39Ar/40Ar dating has shown that both the mineralisation, and the spatially associated Porgera Igneous Complex, have an age of ca 6 Ma. Sr and Pb isotopic tracing of the ore fluids indicate that these elements were derived from a mixed sedimentary‐igneous source, as might be expected for a large hydrothermal system developing around a hypabyssal igneous complex. SHRIMP U‐Pb dating of zircons from the Olympic Dam Cu‐U‐Au deposit in South Australia has constrained the age of mineralisation to be ca 1590 Ma, the same as the age of the Gawler Range thermal event in South Australia. Nd isotopic tracing of the ore fluid has shown that it contains a significant mantle component. The most likely source of mantle Nd is a suite of hydrothermally altered alkali ultramafic dykes that cut, but are coeval with, the Olympic Dam breccias. A possible common link between Porgera and Olympic Dam is that both were derived from oxidised alkali mafic/ultramafic bodies. It is suggested that these magmas had unusually high fo2 so that Cu and Au concentrated in these magmas as they fractionated to produce the Au‐ or Cu‐Au‐rich magmatic‐hydrothermal fluids that gave rise to the mineralisation. SHRIMP U‐Pb dating of zircons from felsic intrusives that cut, or are cut by, Au mineralisation constrain the age of most of the gold mineralisation in the Yilgarn Craton to lie between 2660 and 2630 Ma. Direct 39Ar/40Ar dating of hydrothermal minerals associated with the mineralisation gave ages of 2627 for Victory (Kambalda), 2629 for the Golden Mile (Kalgoorlie) and 2623 for Matilda M1 (Wiluna) that are consistent with the above constraint. An age of ca 2630 Ma correlates with late felsic magma‐tism in the Yilgarn Craton and with metamorphism in the lower crust. Mt Charlotte (Kalgoorlie), Wiluna East Lode and Lady Bountiful give younger ages of 2602, 2565 and 2590 respectively. The young age at Mt Charlotte is consistent with the field relationships and is believed to be the age of mineralisation but the Wiluna and Lady Bountiful dates may have been reset by later thermal events. Isotopic tracing at Mt Charlotte, using Nd in scheelites, showed that most of that element came from a komatiitic source. 39Ar/40Ar dating of the gold mineralisation in the Tennant Creek Block place the age of this event at 1825 Ma, towards the end of the felsic volcanism of the Barramundi Orogeny. Therefore the gold mineralisation in both the Yilgarn Craton and Tennant Creek Block can be related to the waning stages of a major period of felsic magmatism. This can be interpreted to mean that gold originated from late felsic magmas or that it was derived from the supracrustal rocks, buried deep in the crust, during the peak metamorphism in the lower crust.

Large Fossil Hydrothermal Systems in Variscan Granites and Pre-Variscan Gneisses of the Schwarzwald

The Schwarzwald is part of the Moldanubium core zone of the Variscan fold belt. The basement consists of orthoand paragneisses of Caledonian and of Precambrian age. S-type granites are exposed in four different regions of the Schwarzwald: north, central, southwest and southeast. The granites of each region form a granite series, the separate intrusions being chemically and temporally related within each region. According to the petrogenetic model of Emmermann (1977) the evolution of the granites commenced with the melting of plagioclaseand biotite-rich paragneisses, producing large volumes of parautochtonuous biotite granites. Later melting at deeper crustal levels formed K-rich, water-undersaturated magmas that intruded to h igher crusta l levels ( two-mica grani tes) . Extensive Rb-Sr and more limited K-Ar and U-Pb studies indicate that granite magmatism occurs between 330 and 300 Ma in the southern Schwarzwald and at about 290 Ma in the northern Schwarzwald. Mainly through the work of H.P. Taylor and coworkers it has become well established that certain igneous intrusions have interacted with meteoric groundwaters on a very large scale. The interaction and transport of large amounts of meteoric water through hot igneous rocks have now been observed in many localities. The aim of this study is to demonstrate that a very large fossil hydrothermal system occurs in the Schwarzwald, which has been already demonstrated in earlier studies by Hoefs and Emmermann, 1983; Simon, 1990; Taylor et a/.1991. In contrast to these earlier studies which have concentrated on the granites of the South Schwarzwald we present here additional data on granites from the Middle and Northem Schwarzwald and on gneisses from the Southern and Middle Schwarzwald, which support the earlier conclusions, but also indicate (1) that hydrothermal alterations do occur in a much larger area and (2) that the hydrothermal history is more complex than originally thought. Results

Sm-Nd dating of scheelite and tourmaline; implications for the genesis of Archean gold deposits, Val d'Or, Canada

Sm-Nd analyses of 19 scheelite samples from auriferous quartz-carbonate-tourmaline-scheelite-gold veins from three mines in the Val d'Or gold camp in the Abitibi greenstone belt in western Quebec (the Sigma, Pascalis-North, and Siscoe Extension mines) yield a linear array on an isochron diagram with a mean square weighted deviation (MSWD) of 3.6 corresponding to an age of 2596 + or - 33 Ma and epsilon (sub Nd 1 ) = 2.5. Eight scheelite samples from the Pascalis-North mine alone define an excellent linear array with an MSWD = 0.31, an age of 2593 + or - 18 Ma, and epsilon (sub Nd 1 ) = 2.7. These ages are interpreted to represent the age of quartz-carbonate-tourmaline-scheelite vein-hosted gold mineralization in the three mines sampled. Sm-Nd analyses of tourmaline suggest that this mineral may also be useful for Sm-Nd dating of hydrothermal mineralization. The Sm-Nd scheelite age of ca. 2600 Ma is in good agreement with U-Pb ages obtained from mineralization-related rutile and titanite in the Val d'Or area. These results indicate that the quartz-carbonate-tourmaline-scheelite vein-hosted gold mineralization was emplaced approximately 70 m.y. later than the youngest observed premineralization magmatic activity and approximately 60 m.y. later than peak regional metamorphism in the Val d'Or area. These ages do not support hypotheses for deposit formation which involve fluids derived from spatially related intrusive rocks or metamorphism, although they do not preclude an earlier stage of introduction of gold into the Val d'Or area.The scheelite Sm-Nd age and depleted mantlelike epsilon (sub Nd 1 ) , and the mineralogy and alteration of the quartz-carbonate-tourmaline veins, are consistent with the derivation of the mineralizing fluids from a relatively homogeneous external source, and introduction into the upper crust as part of a single, large hydrothermal system. The formation of the Val d'Or gold deposits also appears to be broadly synchronous with the growth of zircon in high-grade metamorphic rocks of the lower crust underlying the greenstone belt material, suggesting that these may be related processes.

Galena lead isotopic variations in a Mesozoic–Cenozoic Andean arc, Antarctic Peninsula

The Antarctic Peninsula magmatic arc was the site of Andean-type subduction from at least Silurian times to the late Cenozoic. Hydrothermal galenas from eight localities in accretionary complex, arc volcanic sequences and plutonic rocks along a strike length of 1100 km have restricted 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb compositions (18.628–18.734, 15.599–15.673 and 38.441–38.689 respectively) plotting on crustal average growth curves. The local geological setting, and comparison with Andean leads, suggest that the major source reservoir was isotopically homogeneous sedimentary rocks forming the late Palaeozoic–Triassic accretionary complex. The lead data suggest that old continental basement is absent at least as far south as 65°S. Galenas from a large (13 × 2 km) epithermal vein system on Hurd Peninsula fall in three populations: a main isotopically homogenous array (18.643, 15.647 and 38.503, 2σ = 0.020, 0.020 and 0.050, n = 33) interpreted as a large hydrothermal system that extracted homogenous leads from early Triassic turbidites. Two smaller sub-populations, with more radiogenic 206 Pb/ 204 Pb, are associated with mid- to late Cretaceous intrusive rocks, and may represent either local contributions of magmatic lead or younger hydrothermal episodes. In western Graham Land, two localities associated with mantle-derived mafic intrusions of Cenozoic age have low 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios indicating addition of some mantle-type lead.

Short term operation and power exchange planning of hydro-thermal power systems

This paper considers a unified problem of short-term operation planning and power exchange scheduling of large hydro-thermal power systems including: unit commitment, hydro power plant operation planning, pumped-storage hydro power plant operation planning and scheduling of power exchange with other power utilities. The criterion function is the total variable profit incurred by energy production, sales of energy to the users inside the power system, sales of energy to other power companies and purchase of energy from them, or from other sources. The overall problem is solved using the Lagrangian relaxation method. A decomposition technique is applied to solve the dual (mixed-integer) and primal (continuous programming) problem. Dynamic programming, feasible direction method and linear programming method are used for the solution of subproblems. The results of the application of the method to a numerical example are given. >

Hydrothermal alteration and mass exchange in the hornblende latite porphyry, Rico, Colorado

The Rico paleothermal anomaly, southwestern Colorado, records the effects of a large hydrothermal system that was active at 4 Ma. This hydrothermal system produced the deep Silver Creek stockwork Mo deposit, which formed above the anomaly's heat source, and shallower base and precious-metal vein and replacement deposits. A 65 Ma hornblende latite porphyry is present as widespread sills throughout the area and provided a homogenous material that recorded the effects of the hydrothermal system up to 8 km from the center. Hydrothermal alteration in the latite can be divided into a proximal facies which consists of two assemblages, quartz-illite-calcite and chlorite-epidote, and a distal facies which consists of a distinct propylitic assemblage. Temperatures were gradational vertically and laterally in the anomaly, and decreased away from the centra heat source. A convective hydrothermal plume, 3 km wide and at least 2 km high, was present above the stock-work molybdenum deposit and consisted of upwelling, high-temperature fluids that produced the proximal alteration facies. Distal facies alteration was produced by shallower cooler fluids. The most important shallow base and precious-metal vein deposits in the Rico district are at or close to the boundary of the thermal plume. Latite within the plume had a large loss of Na2O, large addition of CaO, and variable SiO2 exchante. Distal propylitized latite samples lost small amounts of Na2O and CaO and exchanged minor variable amounts of SiO2. The edge of the plume is marked by steep Na2O exchange gradients. Na2O exchange throughout the paleothermal anomaly was controlled by the reaction of the albite components in primary plagioclase and alkali feldspars. Initial feldspar alteration in the distal facies was dominated by reaction of the plagioclase, and the initial molar ratio of reactants (alkali feldspar albite component to plagioclase albite component) was 0.35. This ratio of the moles of plagioclase to alkali feldspar albite components that reacted evolved to 0.92 as the reaction progressed. Much of the alkali feldspar albite component in the proximal facies reacted while the, primary plagioclase was still unreacted, but the ratio for these assemblages increased to 1.51 when the plagioclase entered the reaction paragenesis. Plagioclase reaction during distal propylitic alteration resulted in pseudomorphic albite mixed with illite and a loss of Na2O. CaO is lost in the distal facies as hornblende reacts to chlorite, although some calcium may be fixed in calcite. CaO is added to the proximal facies as the quantity of chlorite replacing hornblende increases and epidote and calcite are produced.

Hydrothermal alteration in volcanic rocks, eastern part of the Lukavice Group, ?elezn� Hory Mountains, Czech Republic

Many rocks mapped as felsic metavolcanics in the eastern part of the Lukavice Group are shown to be altered mafic metavolcanics, similar to those in the Noranda and Flin Flon-Snow Lake mining districts, Canada. The relatively fresh rocks of the Lukavice Group are rhyolite, dacite-andesite, and andesite-basalt of calcalka-line character. Assuming no substantial volume change during alteration, Ti, P, La, Ce, Yb, Lu, Th (partly), Sc and V contents remained unchanged. Altered rocks are enriched in (Fe + Mg), K and Si and depleted in Na, Ca and Zr. Some elements show both increased and decreased contents in altered rocks (Mg, Ba, Sm, eu, Tb and Hf). Although hydrothermal alteration in the Lukavice Group is of large extent, it is of the proximal Kuroko style and not of regional ‘Amulet Rhyolite’ style. Implications for a large hydrothermal system within a volcanic pile are discussed in relation to the Ordovician Lukavice Group and its mineral deposits and to some other parts of the Bohemian Massif with volcanosedimentary sequences of the same age.

K/Ar dates of hydrothermal clays from core hole VC-2B, Valles caldera, New Mexico and their relation to alteration in a large hydrothermal system

Abstract Seventeen K/Ar dates were obtained on illitic clays within Valles caldera (1.13 Ma) to investigate the impact of hydrothermal alteration on Quaternary to Precambrian intracaldera and pre-caldera rocks in a large, long-lived hydrothermal system (∼ 1.0 Ma to present). Clay samples came from scientific core hole VC-2B (295°C at 1762 m) which was spudded in the Sulphur Springs thermal area and drilled into the boundary between the central resurgent dome and the western ring-fracture zone. Six illitic clays within Quaternary caldera-fill debris flow, tuffaceous sediment, and ash-flow tuff (48 to 587 m depth) yield ages from 0.35 to 1.09 Ma. Illite from Miocene pre-caldera sandstone (765 m) gives an age of 6.74 Ma. Two dates on illite from sandstones in Permian red beds (1008 and 1187 m) are 4.33 and 4.07 Ma, respectively. Surprisingly, three dates on illites from altered andesite pebbles within the red beds (1010–1014 m) are 0.95 to 1.06 Ma. Four illite dates on variably altered Precambrian quartz monzonite (1615–1762 m) range from 2.90 to 276 Ma. Post-Valles age illite is not correlated with alteration style (argillic to propylitic). Rather, post-Valles ages are uniformly obtained from illites in highly fractured, intensely altered, caldera-fill rocks and the Permian volcanic clasts. Generally, finer clay fractions from identical samples yield younger ages. Plots of 40 Ar/ 36 Ar versus 40 K/ 36 Ar and 40 Ar∗ versus 40 K for the illites in caldera-fill rocks lie close to a 1-Ma isochron. Most illite dates older than Valles caldera are difficult to interpret because they correspond to the ages of pre-Valles volcanic and hydrothermal episodes in the Jemez volcanic field (⩽ 13 Ma). In addition, older dates may be caused by co-mingling of different illites during sample preparation, or by inherited argon or lost argon in illites from rocks with potentially complex hydrothermal histories. However, the range of ages obtained from illites in Permian sands and pebbles and from Precambrian crystalline rocks indicates that Valles hydrothermal activity is overwhelming illite produced by earlier geologic events.

Geology of the Gold Quarry mine

The Gold Quarry mine has developed a large, epithermal, disseminated gold deposit hosted by Paleozoic siliciclastic sediments. The deposit consists of two, easterly tilted, stacked orebodies; an upper structural stockwork and a lower stratabound replacement. Anomalous crustal heat flow associated with Oligocene volcanic rocks appears responsible for the formation of a large hydrothermal system at Gold Quarry. Wallrock alteration and mineral concentration are spatially and temporally associated with this event. Rock alteration types include decalcification, silicification, alunitization, argillization and oxidation. Complex and repeated compressional and extensional tectonic events combined with litho-chemical characteristics of the host sediments to form sites favorable to mineral deposition. A dominant elemental association of AuAsSbHgTl is directly associated with mainstage Oligocene mineralization. A subordinate association of AgPbZnCuNi appears to represent earlier mineralizing events. A continuing deep exploration program has shown that mineralization remains open to the south.

Cenozoic stratigraphy, magmatic activity, compressive deformation, and uplift in northern Peru

Research Article| August 01, 1990 Cenozoic stratigraphy, magmatic activity, compressive deformation, and uplift in northern Peru DONALD C. NOBLE; DONALD C. NOBLE 1Mackay School of Mines, University of Nevada-Reno, Reno, Nevada 89557 Search for other works by this author on: GSW Google Scholar EDWIN H. McKEE; EDWIN H. McKEE 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar THOMAS MOURIER; THOMAS MOURIER 3Laboratoire de Géologie Historique, Université de Paris-Sud, 91405 Orsay Cedex, France Search for other works by this author on: GSW Google Scholar FRANÇOIS MÉGARD FRANÇOIS MÉGARD 4Centre National de la Recherche Scientifique, Centre Géologique et Géophysique, U.S.T.L., Place E. Bataillon, 34060 Montpellier Cedex, France Search for other works by this author on: GSW Google Scholar Author and Article Information DONALD C. NOBLE 1Mackay School of Mines, University of Nevada-Reno, Reno, Nevada 89557 EDWIN H. McKEE 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 THOMAS MOURIER 3Laboratoire de Géologie Historique, Université de Paris-Sud, 91405 Orsay Cedex, France FRANÇOIS MÉGARD 4Centre National de la Recherche Scientifique, Centre Géologique et Géophysique, U.S.T.L., Place E. Bataillon, 34060 Montpellier Cedex, France Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1990) 102 (8): 1105–1113. https://doi.org/10.1130/0016-7606(1990)102<1105:CSMACD>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation DONALD C. NOBLE, EDWIN H. McKEE, THOMAS MOURIER, FRANÇOIS MÉGARD; Cenozoic stratigraphy, magmatic activity, compressive deformation, and uplift in northern Peru. GSA Bulletin 1990;; 102 (8): 1105–1113. doi: https://doi.org/10.1130/0016-7606(1990)102<1105:CSMACD>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Integrated field study and radiometric dating in the Llama-Bambamarca area of the Western Cordillera of northern Peru have resulted in major revisions in the stratigraphic and structural relations and ages of thick sequences of Tertiary volcanic rocks and constrain the timing of compressive deformation, magmatic activity, and uplift. Rocks of the upper part of the Llama Formation yield K-Ar mineral dates of 54.8 ± 1.8 and 44.2 ± 1.2 Ma; altered volcanic rocks composing the lower part of the formation in the western part of the area may be older. Eocene K-Ar dates have been reported for several granitic plutons in the region, and other plutons of probable similar age intrude the Llama Formation and are overlain by upper Eocene strata. The pervasive alteration that affects much of the Llama Formation may be the result of large hydrothermal systems driven by a coeval, and presumably cogenetic, batholith. The Chota Formation, which is mostly volcaniclastic, has yielded ages of about 50 and 44 Ma. The Chota Formation thus does not predate the Llama Formation but rather is an eastern distal-facies equivalent of rhyolitic ash-flow sheets and dacitic volcanic rocks of the Llama Formation.The major unconformity at the base of the Llama Formation reflects deformation during Late Cretaceous (Peruvian tectonic phase) and/or Paleocene (Incaic I) time. The time of Incaic II deformation is bracketed between the 44.2 ± 1.2 Ma date on the Llama Formation and the age of about 39 Ma of a thick ash-flow sheet that comprises the lower part of the unconformably overlying Huambos Formation. Dates on rocks postdating Incaic II tectonism in central Peru suggest that deformation had ceased by about 41 Ma. Incaic II tectonism in northern and central Peru appears to have been a short but intense compressive event that peaked about 43 m.y. ago. The Incaic II event is coeval with formation of the Hawaiian-Emperor bend and with a period of rapid convergence of the Nazca and South American plates and therefore may reflect a major plate change in lithospheric plate movement patterns.A largely volcaniclastic sequence of early Miocene age shows that the early Neogene pulse of volcanic activity recognized throughout the Central Andes is represented in northern Peru. Beds of conglomerate within this sequence are probably the result of Quechua I tectonism, although the 23.2 ± 1.5 Ma date obtained on tuff from the unit appears somewhat older than the time of about 19 Ma recognized for Quechua I tectonism in central and southern Peru. Units of partly welded and unaltered ash-flow tuff that fill deeply incised paleovalleys have ages of about 8.2 and 11.4 Ma, showing that the Western Cordillera of northern Peru was uplifted before late Miocene time. This content is PDF only. Please click on the PDF icon to access. 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Mineralized and unmineralized calderas in Spain; Part II, evolution of the Rodalquilar caldera complex and associated gold-alunite deposits

The Rodalquilar caldera complex is located in the western part of the Cabo de Gata volcanic field in southeastern Spain and is the first documented example of epithermal gold-alunite mineralization within a caldera in Europe. The Rodalquilar caldera is an oval collapse structure having a maximum diameter of 8 km and formed at 11 Ma from eruption of the Cinto ash-flow tuff. The oval Lomilla caldera, with a diameter of 2 km, is nested within the central resurgent dome of the older Rodalquilar caldera. The Lomilla caldera resulted from the eruption of the Lazaras ash-flow tuff which was ponded within the moat of the Rodalquilar caldera. The last phase of volcanic activity in the caldera complex was the emplacement of hornblende andesite flows and intru- sions. This magmatic event resulted in structural doming of the caldera, opening of fractures and faults, and pro- vided the heat source for the large hydrothermal systems which deposited quartz-alunite type gold deposits and base metal vein systems. The gold-alunite deposits are enclosed in areas of intense acid sulfate alteration and localized in ring and radial faults and fractures present in the east wall of the Lomilla caldera. Like other acid-sul- fate type deposits, the Rodalquilar gold-alunite deposits are closely related in time and space to porphyritic, inter- mediate composition magma emplaced along caldera structures but unrelated to the caldera forming magmatic system.

A contribution to the midterm scheduling of large scale hydrothermal power systems

A concise mathematical model and nonlinear minimization algorithm were presented as a joint approach to set optimal midterm production targets for power systems with predominance of hydroelectric power generation. The algorithm uses the network structure of the problem and takes into account nondifferentiable points. The approach was successfully applied to the optimal midterm scheduling of a very large hydroelectric power system in southeastern Brazil. Further insight into the problem allowed the adoption of an optimization-simulation strategy which achieved a very good suboptimal solution with great savings in computer requirements. The main purpose of this research was to develop a working tool able to assist engineers in setting optimized midterm targets for the large power systems in Brazil, where more than 90% of the electric energy comes from hydraulic sources. >

An Integrated, Hierarchical Forecasting, Scheduling, Monitoring and Dispatching System for a Large Hydro-Thermal Power System

Application software tools provided to the Power System Control Supervisor by an Energy Management System (EMS) play an important role in the economic operation of power systems.This paper describes an integrated, hierarchical set of application software tools designed to assist the Control Supervisor to perform his functions in an organized and effective manner. Various operating economic principles, strategies, performance objectives and constraints are built into various application software packages. These packages are loose-coupled to provide flexibility and are used in a concerted manner by the System Control Supervisor.Significant aspects of this paper are the following:•The way in which operating economics of daily to hourly to minute-by-minute concern are accomplished in a hierarchical manner•The presentation of an overview of key operating economic principles, performance objectives, constraints and techniques in each application software package and the overall software system•The way these application packages are integrated with the Control Supervisor playing the “review, intervene if necessary, and step forward” role as power system conditions demand, or using these applications in a standalone mode, with the ultimate goal of maintaining optimal system dispatch•Our experiences so far, the current development status and future plans.

Main Design Parameters Optimization of a Large Hydro-Thermal Electric Power System

Abstract This paper presents a nonlinear programming model and a solution technique for optimizing such main design parameters of a large hydro-thermal electric power system as total storage, dead storage and installed capacity of each station. This technique uses an augmented Lagrangian algorithm with a new approach to save computer core storage. Application of this model to Yunnan Province (P.R.C.) hydro-thermal electric power system which involves five reservoirs, eleven hydropower stations and several thermal stations is summarized.

Optimal Short Term Operation Planning of a Large Hydrothermal Power System Based on a Nonlinear Network Flow Concept

Optimal Short Term Operation Planning of a Large Hydrothermal Power System Based on a Nonlinear Network Flow Concept

Optimal Short Term Operation Planning of a Large Hydrothermal Power System Based on a Nonlinear Network Flow Concept

This paper presents a procedure for solving the short term generation scheduling problem for a large hydrothermal system that includes transmission limitations. The integrated system is divided into a hydro and a thermal subsystem. A reduced gradient algorithm is employed for the solution of the hydro subproblem. This algorithm is specialized to efficiently solve nonlinear network flow problems with additional constraints of non-netwrk type. The thermal subsystem is solved using a fast unit commitment and dispatch algorithm. A case study with the Swedish system is discussed.

Reliability Assessment in Operational Planning for Large Hydro-Thermal Generation Systems

A probability based method and a computer program for reliability assessment in the operational planning of large hydro-thermal generation systems are described. The expected unsupplied energy in a given time interval divided by the annual peak load is used as the reliability index. In calculating this index, the forecast hourly loads, sales and purchases, the changes in the operating schedule and unit operating modes, and the capacity and energy constraints on hydraulic generation are considered. Applications in generation schedule reliability assessment, economy sales assessment, mid-term reserve planning, and maintenance scheduling are presented.

Reliability Assessment in Operational Planning for Large Hydro-Thermal Generation Systems

Reliability Assessment in Operational Planning for Large Hydro-Thermal Generation Systems