Hydrothermal alteration institute for mining geology. Geochemistry of hydrothermal ore deposits pdf free download. Earthscience reoiews, 20 1984 1104 elsevier science publishers b. Clay minerals in hydrothermally altered rocks 195 fig. In both deposits, the goldrelated hydrothermal alteration minerals consistently replace and locally overprint metamorphic minerals indicating that hydrothermal alteration is postpeak metamorphism. The interaction of hydrothermal fluids with rocks results in the hydrothermal alteration of primary minerals. Pdf hydrothermal alteration mapping, using the crosta. In general, there is a progression from central quartzsericite. One hypothesis proposed to explain the causes of fe isotope fractionation in igneous rocks involves hydrothermal alteration. The rhyolitic tuffs, which host most of the kaolinized bodies, were deposited on top of the.
Available to purchase and download in shapefile and kmz vector formats. Hydrothermal mineralization at seafloor spreading centers. Mineral reactivity and evolution of surface properties. Maps of hydrothermal alteration in the basin and range province of the us. The dissolution and transformation of primary minerals and the precipitation of secondary minerals affect rocks in terms of mechanics, stress conditions, and induced seismicity. Hydrothermal alteration economic geology geoscienceworld. To be useful to exploration geologists and researchers, however, alteration needs to be typi. Hydrothermal alteration in orogenic gold deposits, nz.
Composition, distribution and formation conditions in a conductive geothermal environment dr. Multiplestage hydrothermal alteration in porphyry copper. The petrographical studies revealed that the alteration mineral. It is the replacement of one rock by another of different mineralogical and chemical composition. Hydrothermal alteration an overview sciencedirect topics. Sep 01, 2019 the predominance of disseminated replacement ore over faultfill and extensional quartzcarbonate vein systems suggests that the mineralized fracture networks remained relatively permeable and that fluids circulated at a nearconstant hydraulic gradient during the main phase of auriferous hydrothermal alteration. The intensity of k metasomatism, encompassing both k gains and na and ca losses, can be represented by the. Using hyspiri preparatory data for rapid classification of hydrothermal alteration and lithology. Hydrothermal alteration zones present in the lastarria sensu stricto volcano are directly related to the recent. In the hydrothermal alteration zones, the f favours partitioning into apatite under lower temperature, the f contents of hydrothermal apatite increase from the potassic zones to the propylitic zones accompanying with the decrease of temperature. Hydrothermal alteration, also referred to as wallrock alteration, is a general term that encompasses many processes by which rockforming minerals are altered due to reactions accompanying the flow. Geochemistry and mineral chemical behavior of hydrothermal. Geomechanical observations at soultz are interpreted on the basis of synthetic clay content logs, which are created from borehole logging data, and which identify clay in hydrothermally altered. Research open access the significance of hydrothermal.
Foley, zsanett pinter, in magmas under pressure, 2018. Click download or read online button to get geochemistry of hydrothermal ore deposits book now. Pdf orogenic hydrothermal systems in the south island of new zealand. Quartz, zeolites, gemstones, perovskite type oxides, ferrite, carbon allotropes, complex coordinated compounds and many more all products now being produced using hydrothermal technology. Hydrothermal alteration of the oceanic crust is widespread and locally thorough in oceanic crust scambelluri et al. The primary silicate minerals such as feldspar and amphibole are replaced by hydrothermal minerals stable at temperatures of about 400 c or less such as chlorite, epidote, muscovite and quartz. Volcano collapse promoted by hydrothermal alteration and. The minerals which compose the rocks are dissolved and new mineral formations are deposited in their place. View hydrothermal alterations ppts online, safely and virusfree. In a geothermal area, an anomaly of low magnetic susceptibility values of rocks in a homogenous litho unit characterized by high magnetic susceptibility may suggest hydrothermal alteration. Hydrothermal alteration, fumarolic deposits and fluids from. May 24, 2015 to avoid the confusion and controversy that surround the terminology for hydrothermal alteration, the organization of the atlas is based on the simplest mineralogical approach. Mineralization related hydrothermal alteration is developed as narrow zones beside of the. The patterns of distribution of tile mica and clay minerals resulting from alteration of feldspars are nmeh less regular and well defined in the porphyry copper.
Hydrothermal alteration definition, mineral exploration. Hydrothermal alteration of a 1 km section through the. Mapping hydrothermal alteration decorrelation stretch of aviris swir bands dcs bands 190. The calcic fluids formed hydrothermal cement grading from tirich andraditic to grossularitic garnet in the core of the breccia to a diopside and magnetitedominated assemblage at the margins. Some minerals, such as biotite, may be susceptible to alteration but on occasion form as an alteration product. Handbook of hydrothermal technology brings together the latest techniques in this rapidly advancing field in one exceptionally useful, longneeded volume. The present study investigates commonly observed phenomena of hydrothermal alteration and observations at the. Saponitic bentonite mined in the magan deposit toledo, spain, has been classified as a suitable clay barrier in the storage of high level radioactive waste. Hydrothermal alteration mapping, using the crosta technique. A series of hydrothermal alteration maps, which identify the potential locations of hydrothermal silicarich, propylitic, argillic, and phyllic rocks on landsat thematic mapper tm band 7 orthorectified images, and arcgis1 shape files of hydrothermal alteration units are provided in this study. Physical volcanology and hydrothermal alteration of the. Infotierra also offers existing alteration maps for most of the arid and super arid zones of south america. The significance of hydrothermal alteration zones for the.
Hydrothermal alteration is proximal to many base and precious metal deposits, and its products can provide insights into the characteristics of hydrothermal systems. Oct 16, 2014 the occurrence of hydrothermally altered zones is a commonly observed phenomenon in brittle rock. Geochemistry of hydrothermal ore deposits download ebook. Hydrothermal alteration in the reykjanes geothermal system.
Hydrothermal alteration mapping from landsat8 data, sar. Olivine is pseudomorphed by chlorite, and clinopyroxene alters to actinolite. The alteration may appear to be simply a color change or it may involve major textural, mineralogical andor chemical changes. The humboldt system is fundamentally basaltic and has compelling geological and geochemical evidence for nonmagmatic brine involvement with little if any magmatic aqueous fluid johnson. Major styles of mineralization and hydrothermal alteration. Hydrothermal alteration in the geothermal field, kyushu, japan masahiko yagi kunio kai japex research center, hamada, chiba 260 japan petrographical and geochemical studies on cores and cuttings from the fushime geothermal wells were carried out using microscopy, xrd, xrf, and epma. Volcanic influences on hydrothermal and diagenetic alteration. Geochemistry of hydrothermal alteration in volcanic rocks. Pdf hydrothermal alteration styles in ancient and modern. Using hyspiri preparatory data for rapid classification of hydrothermal alteration and lithology betsy pace.
These relationships also are in full accord with the inferred physicalchemical requirements of the corresponding facies. Facies and types of hydrothermal alteration economic. Pdf mapping hydrothermal alteration zones and lineaments. Hydrothermal alteration data based on aster satellite images. Hydrothermal alteration of a 1 km section through the upper oceanic crust, deep sea drilling project hole 504b. Maps and data showing the geographic distribution of surficial minerals likely produced by hydrothermal alteration, which may indicate areas permissive of gold and copper mineral deposits. An apparent feeding fissure is centered to the west of the main area of mineralization. Maps of hydrothermal alteration in the basin and range. Cliffs adjacent to this terrace also host abundant white hydrothermal alteration both as flanges and peridotite. Hydrothermal alteration of the oceanic crust is widespread and locally thorough in oceanic crust. The extent of the alteration may be measured in millimeters or kilometers. Hydrothermal alteration and fluid chemistry of the endako.
Phyllic alteration and argillicadvanced argillic assemblages are derived from increasing acidic hydrothermal fluids generally of lower temperature than common for potassic and propylitic assemblages. We thoroughly search for unstable regions throughout the mount. Dominant alteration minerals are quartz, adularia, sericite, chlorite, actinolite, epidote, illite, and smectite. Hydrothermal alteration and fluid chemistry data of the early cretaceous endako porphyry molybdenum deposit, british columbia, provide new information on the hydrothermal fluids associated with lowfluorine molybdenite mineralization. A case study of element mobility and reaction paths1, year.
Alteration is strongest near microfractures and veins that we interpret to be the main fluid conduits. High temperature hydrothermal alteration in active geothermal systems a case study of olkaria domes james nyandigisi and christine katana kenya electricity generating company limited, kenya, p. The reykjanes geothermal system is a seawaterrecharged hydrothermal system that appears to be analogous to seafloor hydrothermal systems in terms of host rock type and low waterrock alteration. Acknowledgments i owe a debt of gratitude to several colleagues and friends. The similarities make the reykjanes system a useful proxy for seafloor vents. Wholerock geochemical techniques for evaluating hydrothermal. Landsat 8 oli data for identification of hydrothermal alteration zone in singhbhum shear zone using successive band depth difference techniquea new image processing. Previous oxygen isotope delta18o analyses of bulkrocks, pyroxene. Geochemical changes during hydrothermal alteration of basement in the stockwork beneath the active tag hydrothermal mound 1 susan e. Hydrothermal alteration mapping from landsat8 data, sar cheshmeh copper mining district, southeastern islamic republic of iran amin beiranvand pour. Hydrothermal alteration and gold mineralization are associated with the d 2 event. These serpentinites are less a source for melts than an important source of water that triggers.
Sodic alteration is one of the most extensive alteration styles in hydrothermal iron oxide ioa and iocg deposits arancibia and clark, 1996. Lopez and williams, 1993, so alteration could be important for promoting and localizing large collapses. Tectonic elements in the northwest corner of the canadian shield. Halos of hydrothermal alteration are frequently a prelude to metallic mineralization. Diagrammatic compilation of data obtained in wairakei drillhole 71 showing stratigraphic sequence, faults, fresh rock, hydrothermal mineral distribution, temperature variations, and lithostatic and watervapour pressures. Massive sulfide ore is enclosed in a discordant alteration envelope that extends at least 60 m above ore and is known to a depth of 150 m in the footwall.
Numerous and frequentlyupdated resource results are available from this search. Using hyspiri preparatory data for rapid classification of. Pdf hydrothermal alteration is proximal to many base and precious metal deposits, and its products can provide insights into the. Reliable information about the coronavirus covid19 is available from the world health organization current situation, international travel. In most cases, the first step in describing hydrothermal alteration during field work or microscopy is the recognition of a secondary mineral. Hydrothermal alteration is a complex process involving mineralogical, chemical and textural changes, resulting from the interaction of hot aqueous fluids with the rocks through which they circulate, under evolving physicochemical conditions. Hydrothermal alteration mineralogy and geochemistry of the. During hydrothermal alteration, plagioclase is generally albitised, sometimes with the formation of epidote, and albite may be subsequently a1tered to chlorite. Hydrothermal alteration and weathering crust of the earth. Molybdenite mineralization and hydrothermal alteration occur as. Quartz is the only abundant primary mineral that commonly resists destruction by hydrothermal processes. This paper emphasizes on the specific robust, fast, simple and highlyeffective spectral transform techniques for the identification of hydrothermal alteration minerals.
In this report, we assigned various geochemical data to one of the. Major styles of mineralization and hydrothermal alteration and. Hydrothermal alteration varies widely from district to district and among individual deposits, and the literature on this topic is voluminous. The chemical composition of rocks and of hydrothermal solutions forms chemical systems of extreme complexity. The occurrence of hydrothermally altered zones is a commonly observed phenomenon in brittle rock. Hydrothermal alteration and mineralization in the faina. Essentially similar alteration aggregates may result from rocks as dissimilar as diorite and alaskite, while tremendous differences in the magnitude of the alteration halo may be noted between a porous tuff and a compact quartz monzonite even in the same district.
Hydrothermal alteration, also referred to as wallrock alteration, is a general term that encompasses many processes by which rockforming minerals are altered due to reactions accompanying the flow of heated aqueous fluids along fractures and grain boundaries. Oclcs webjunction has pulled together information and resources to assist library staff as they consider how to handle coronavirus. The second period of hydrothermal activity caused brecciation and calcic alteration in the central replacement zone. Mapping hydrothermal alteration zones and lineaments associated with orogenic gold mineralization using aster data. Generally each type of alteration characterizes a subzone of alteration that bears consistent relationships to neighboring zones and to a presumed source of heat and altering fluids. To be useful to exploration geologists and researchers, however, alteration needs to be typified and quantified. Stanford libraries official online search tool for books, media, journals, databases, government documents and more. Case study of the kibi goldfields osino concession, ghana.
Hydrothermal alteration, mineralization, and structural. Regional structural investigations by swager et al. Pdf landsat 8 oli data for identification of hydrothermal. Hydrothermal fluids chemically attack the mineral constituents of the wall rocks, which tend to re.
In this belt, the abundance of known porphyry copper deposits reflects the potential economic importance and warrants the exploration of the new prospects. The university of western australia, perth peter a. Pdf hydrothermal alteration of a saponitic bentonite. Hydrothermal alteration is proximal to many base and precious metal deposits, and its products can. Hydrothermal alteration the wallrock on both sides of each veinlet is typically altered to varying degrees. Hydrothermal alteration and mineralization of the galore. Identification of hydrothermal alteration minerals for.
Plagioclase, in association with skeletal clinopyroxene, alters to chlorite and epidote. These areas were differentiated in order to characterize and contrast the geochemical signatures of solids and waters in a variety of mineralized areas. Hydrothermal alteration is widespread throughout the deposit and is marked by silicification, chloritization, sericitization, and carbonitization as well as minor epidote and local biotite alteration. Structural and hydrothermal alteration evidence for early. The simplest means of producing these lower ph, lower temperature fluids is to interact. The hydrothermal alteration of oceanic basalts by seawater. Geochemistry of hydrothermal alteration in volcanic rocks 43 whereas in the equivocada mine, kaolinite is associated with dickite and traces of alunite without pyrophyllite marfil et al. Magnetic susceptibility of volcanic rocks in geothermal areas. Cl element is much more sensitive to the ph, pressure, and fluid composition than f element. Several hydrothermal alteration assays have been carried out in teflon. Hydrothermal alteration can lower rock shear strength watters and delahaut, 1995 over wide areas frank, 1985, 1995. Hydrothermal alteration in active geothermal fields. Honnorez4 abstract major, trace, and rare earth element ree analyses of 57 samples of altered and relatively fresh basalts from four different.
Multiplestage hydrothermal alteration in porphyry copper systems in northern turkey. Hydrothermal alteration and weathering crust of the. Movement of hydrothermal fluids through the system could result in removal of light fe isotopes, leaving a heavier fe isotope composition in the rocks. Alteration of primary plagioclase and kfeldspar to albite is a common phenomenon in the altered zones of the deposits since albite is more stable than caplagioclase bird and helgeson, 1981. Hydrothermal alteration is a very complex process involving mineralogical, chemical and textural changes, resulting from the interaction of hot aqueous fluids with the rocks through which they pass, under evolving physicochemical conditions. A reexamination of hydrothermal alteration and feti. However, the chemical changes induced by metamorphism are generally less intense than those observed within altered rocks.
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