Geology, geochemistry and exploration implications of. Geology and geochemistry of epithermal vein systems 423 elements strongly correlated with high gold concentrations in the vein sys tem include molybdenum, tellurium, bismuth, lead, silver, copper, zinc and arsenic table 2. Geology and geochemistry of epithermal precious metal vein systems in the intraoceanic arcs of palau and yap, western pacific. In general, however, geothermal drilling ignores the upper few hundred meters of the active systems and drill sites are situated well away from natural features such as hot springs or geysers, the very features whose characteristics silica sinter, hydrothermal breccias are recognizable in a number of epithermal preciousmetal deposits see, for example, white, 1955. Epithermal deposits in north xinjiang, nw china springerlink. Introduction to geology and resources of gold, and. Mclemore new mexico bureau of geology and mineral resources, new mexico institute of mining and technology, socorro, new mexico, 87801, usa abstract.
The midas epithermal system is one of the larger lowsulfidation epithermal vein systems discovered in the western us in recent years, containing in excess of 3 moz of gold premining. Geology and geochemistry of epithermal systems edited by b. Epithermal gold deposits part ii geology and gold deposits of the oatman district, northwestern arizona by ed dewitt, jon p. Rhea 2 abstract extensive areas of jasperoid occur in paleozoic sedimentary rocks near mackay, idaho. Geology and geochemistry of epithermal systems edited by. Geology and geochemistry of jasperoid near mackay, idaho. The environmental geochemistry of mineral deposits. Geology and geochemistry of jasperoid near mackay, idaho anna b. Models and exploration methods for major gold deposit types.
Jul 14, 2011 the depositscale geology and geochemistry of epithermal systems in north xinjiang are essentially similar to those in other parts of the world. Front matter geology and geochemistry of epithermal systems. The word epithermal comes from the greek words for nearby heat referring to the fact that epithermal deposits form very close to the surface of the crust, by definition, within a thousand meters. These data are used to develop exploration vectors for use at both deposit and district scales, plus techniques have been established. Some of these zones contain elevated concentrations of au and te, and varying concentrations of. Geological survey, ms 973, box 25046, federal center, denver, co. The key geology features of the oreforming environments and the key geologic manifestations of the different deposit types form the footprints of ore systems that are targeted in exploration programs. All epithermal deposits in north xinjiang are hosted in volcanic rocks with ages ranging from devonian to triassic, with the early carboniferous volcanic sequences being the most important, followed by. He was director of the economic geology research unit and professor of economic geology at james cook university in australia from 1997 to. The geothermal framework of epithermal deposits geology. Pdf pyrite geochemistry and textures in the epithermal au. Geology and resources of gold in the united states introduction to geology and resources of gold, and geochemistry of gold the case for gold an introduction to geology and resources of gold in the united states by daniel r. Geology, geochemistry, geochronology and evolution of epithermal au mineralization system in bazman area, w of makran volcanic arc thesis pdf available june 2018 with 249 reads. The deposit is spatially and temporally related to bimodal volcanism in the northern nevada rift.
Geology and geochemistry of epithermal systems presents a synthesis of the current under standing of the processes responsible for the concentration of metals especially gold and silver in nearsurface environments, provides an overview of the systematics of the most important approaches to. Geology, geochemistry, geochronology and evolution of epithermal au mineralization system in bazman area, w of makran volcanic arc dissertation submitted in partial fulfillment of the. Based on alteration, mineralization, vein texture, ore geochemistry and fluid inclusion data results, therefore the deposit type at the study area is an intermediate epithermal sulphidation is. Geochemistry and statistical analyses of epithermal veins at the carlisle and center mines, steeple rock district, new mexico, usa virginia t.
Geochemistry and fluid inclusions analysis of vein quartz in. We now know that this association is a consequence of the hot magmas which not only produce volcanic eruptions and volcanic rocks but also are the source of the hot fluids that transport gold and other. Tantalizingly, in a number of hot springs, transitory redorange precipitates occur which are found to be ore grade in gold and silver and which carry a suite of elements as, sb, hg, tl now recognized as. Society of economic geologists, economic geology v100 pp463490 8 the pascua hse system model shows preservation of the gold poor steam heated alteration cap overlying the concealed 27 moz aueq mineralization hosted by vuggy. Geochemistry and origin of the oreforming fluids in. Observations the most basic characteristics of any ore deposit are its form, mineralogy. Porphyry and epithermal systems free download as powerpoint presentation. Geology, geochemistry, and 3d geological modelling of the.
Geochemistry and statistical analyses of epithermal veins at. Shawe abstract gold has long been a store of wealth, whether held by governments or in private hoards. Purchase geochemical and tectonic evolution of arcbackarc hydrothermal systems, volume 8 1st edition. The observation made here is that an aluniteenargite assemblage records a similar geochemical environment, whether forming an epithermal deposit or as part of the alteration. Other articles where epithermal deposit is discussed. The first involves degassing of hot, acid magmatic vapors that are responsible for intense leaching of the host rock to form the porous.
Geology and geochemistry of epithermal precious metal vein systems in the intraoceanic arcs of palau and yap, western pacific james j. Campbell summary of relevant geologic, geoenvironmental, and geophysical information deposit geology manganese oxide concentrations are present as small veins, stringers, nodular masses, brecciafillings, and coatings. The use of petrographic and epma analyses demonstrate there are distinctive textural zones within pyrite grains that vary in chemistry and appearance. Generalised model of porphyry and epithermal deposits associated with shallow subvolcanic intrusions and stratovolcano active volcanichydrothermal systems extends from degassing magma to fumaroles and acidic springs, and incorporate porphyry and or highsulfidation ore environments. Epithermal veins tend not to have great vertical continuity, but many are exceedingly rich and deserving of the term bonanza. The mineral assemblage of arsenopyritepyrrhotitetennantiteullmanitenative antimonystibnite developed at 280240 c, log f s 2 of. Clarke epithermal mineralisation research unit, geology department, universityof auckland, privatebag, auckland, new zealand abstract vein samplesfrom the exploration for epithermal mineralisation are commonly subjectedtomultielement. Some active geothermal systems are currently depositing gold, silver, and base metals, and most epithermal ore deposits formed in onceactive geoth skip to main content close. Porphyry and epithermal systems geological processes. Geology and geochemistry of epithermal precious metal vein. Smith2 abstract mines in the oatman mineralized district, near oatman in northwestern arizona, have produced more than 1.
Geology and genesis of the multistage highsulfidation epithermal pascua auagcu deposit, chile and argentina. Outcrops range from massive, graypink colored, hard and dense jasperoid. Siddeley editors, epithermal gold mineralization of the circumpacific. Geology and geochemistry of epithermal precious metal vein systems in the intraoceanic arcs of palau and yap, western pacific journal of geochemical exploration by. Temperatures at these depths are generally somewhere between 100 300 degrees celsius and pressures are much lower and deeper down so the fluids. Geology, geochemistry, and geochronology of epithermal goldsilver deposits in the seven troughs district, pershing county, nevada chapter pdf available january 2006 with 723 reads how we. Knowledge of the upper few hundred meters of active geothermal systems is scant and largely based on interpretation of hotspring chemistry. We will deliver a specific focus on application of structural geology and geochemistry to understanding epithermal systems, ideal for geologists to use and consider when looking at their own systems.
Geology, geochemistry, and geochronology of epithermal. Ore petrography, geochemistry, and geochronology data collected for some lowsulfidation epithermal precious metal deposits in the northern great basin indicate that the midmiocene deposits have consistent ore mineralogy, geochemistry that varies between two end members, and a narrow range of ages. Front matter geology and geochemistry of epithermal. Unfortunately, the tonnage of ore in epithermal veins is typically small compared with other types of lower grade gold deposits. The association of gold mineralization with volcanic and geothermal hot spring activity has long been recognized by prospectors and geologists. Characteristics of high sulphidation epithermal gold deposits. Geology and geochemistry of epithermal systems authors. Fifarek, light stableisotope systematics in the epithermal environment, geology and geochemistry of epithermal systems econ. A model has been provided for the formation of highsulphidation epithermal systems that reflects the complexities related to possible variations of gold speciation in this environment arribas et al.
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