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Relevant bibliographies by topics / Lithogeochemical alteration

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Academic literature on the topic 'Lithogeochemical alteration'

Author: Grafiati

Published: 4 June 2021

Last updated: 12 February 2022

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Journal articles on the topic "Lithogeochemical alteration"

1

Mokhtari, Ahmad Reza. "Hydrothermal alteration mapping through multivariate logistic regression analysis of lithogeochemical data." Journal of Geochemical Exploration 145 (October 2014): 207–12. http://dx.doi.org/10.1016/j.gexplo.2014.06.008.

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Byrne, Kevin, Guillaume Lesage, Sarah A. Gleeson, Stephen J. Piercey, Philip Lypaczewski, and Kurt Kyser. "Linking Mineralogy to Lithogeochemistry in the Highland Valley Copper District: Implications for Porphyry Copper Footprints." Economic Geology 115, no. 4 (June 1, 2020): 871–901. http://dx.doi.org/10.5382/econgeo.4733.

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Abstract The Highland Valley Copper porphyry deposits, hosted in the Late Triassic Guichon Creek batholith in the Canadian Cordillera, are unusual in that some of them formed at depths of at least 4 to 5 km in cogenetic host rocks. Enrichments in ore and pathfinder elements are generally limited to a few hundred meters beyond the pit areas, and the peripheral alteration is restricted to narrow (1–3 cm) halos around a low density of prehnite and/or epidote veinlets. It is, therefore, challenging to recognize the alteration footprint peripheral to the porphyry Cu systems. Here, we document a workflow to maximize the use of lithogeochemical data in measuring changes in mineralogy and material transfer related to porphyry formation by linking whole-rock analyses to observed alteration mineralogy at the hand specimen and deposit scale. Alteration facies and domains were determined from mapping, feldspar staining, and shortwave infrared imaging and include (1) K-feldspar halos (potassic alteration), (2) epidote veins with K-feldspar–destructive albite halos (sodic-calcic alteration), (3) quartz and coarse-grained muscovite veins and halos and fine-grained white-mica–chlorite veins and halos (white-mica–chlorite alteration), and two subfacies of propylitic alteration comprising (4) prehnite veinlets with white-mica–chlorite-prehnite halos, and (5) veins of epidote ± prehnite with halos of chlorite and patchy K-feldspar. Well-developed, feldspar-destructive, white-mica alteration is indicated by (2[Ca-C] + N + K)/Al values <0.85, depletion in CaO and Na2O, enrichment in K2O, and localized SiO2 addition and is spatially limited to within ~200 m of porphyry Cu mineralization. Localized K2O, Fe2O3, and depletion in Cu, and some enrichment in Na2O and CaO, occurs in sodic-calcic domains that form a large (~34 km2) nonconcentric footprint outboard of well-mineralized and proximal zones enriched in K. Water and magmatic CO2-rich propylitic and sodic-calcic–altered rocks form the largest lithogeochemical footprint to the mineralization in the Highland Valley Copper district (~60 km2). Calcite in the footprint is interpreted to have formed via phase separation of CO2 from a late-stage magmatic volatile phase. Several observations from this study are transferable to other porphyry systems and have implications for porphyry Cu exploration. Feldspar staining and shortwave infrared imaging highlight weak and cryptic alteration that did not cause sufficient material transfer to be confidently distinguished from protolith lithogeochemical compositions. Prehnite can be a key mineral phase in propylitic alteration related to porphyry genesis, and its presence can be predicted based on host-rock composition. Sodic-calcic alteration depletes the protolith in Fe (and magnetite) and, therefore, will impact petrophysical and geophysical characteristics of the system. Whole-rock loss on ignition and C and S analyses can be used to map enrichment in water and CO2 in altered rocks, and together these form a large porphyry footprint that extends beyond domains of enrichment in ore and pathfinder elements and of pronounced alkali metasomatism.

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Grunsky, E. C. "Recognition of alteration in volcanic rocks using statistical analysis of lithogeochemical data." Journal of Geochemical Exploration 25, no. 1-2 (March 1986): 157–83. http://dx.doi.org/10.1016/0375-6742(86)90012-9.

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4

Halley, Scott, John H. Dilles, and Richard M. Tosdal. "Footprints: Hydrothermal Alteration and Geochemical Dispersion Around Porphyry Copper Deposits." SEG Discovery, no. 100 (January 1, 2015): 1–17. http://dx.doi.org/10.5382/segnews.2015-100.fea.

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ABSTRACT Whole-rock lithogeochemical analyses combined with short-wave infrared (SWIR) spectroscopy provide a rapid and cost-effective method for prospecting for porphyry-type hydrothermal systems. Lithogeochemistry detects trace metals to average crustal abundance levels and allows vectoring via gradients of chalcophile and lithophile elements transported by magmatic-hydrothermal ore and external circulating fluids that are dispersed and trapped in altered rocks. Of particular use are alkalis in sericite and metals such as Mo, W, Se, Te, Bi, As, and Sb, which form stable oxides that remain in weathered rocks and soils. SWIR mapping of shifts in the 2,200-nm Al-OH absorption feature in sericite define paleofluid pH gradients useful for vectoring toward the center of the buoyant metal-bearing magmatic-hydrothermal plume.

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Barker, Shaun L. L., Shawn Hood, Rosie M. Hughes, and Shannon Richards. "The lithogeochemical signatures of hydrothermal alteration in the Waihi epithermal district, New Zealand." New Zealand Journal of Geology and Geophysics 62, no. 4 (August 26, 2019): 513–30. http://dx.doi.org/10.1080/00288306.2019.1651345.

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6

Honarpazhouh, Jamal, Ali Asghar Hassanipak, and Kumars Seifpanahi Shabani. "Integration of Stream Sediment Geochemical and Aster Data for Porphyry Copper Deposit Exploration in Khatun Abad, North West of Iran / Integracja geochemicznych danych o osadach dennych oraz danych pozyskanych z systemu aster do poszukiwań geologicznych w rejonie złóż miedzi porfirytowej w khatun abad, w północno-zachodniej części iranu." Archives of Mining Sciences 58, no. 1 (March 1, 2013): 37–54. http://dx.doi.org/10.2478/amsc-2013-0003.

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Urumieh-Dokhtar magmatic belt is the host of large porphyry copper deposits in Iran. Khatun Abad area is located in north west part of this belt, so in this study, the stream sediment geochemical survey and hydrothermal alteration zones extracted from ASTER data were used to generation new target for future lithogeochemical survey. In this study after a brief discussion on descriptive statistics, principal component analysis (PCA) and hierarchical cluster analysis were used to compress the information to a few maps and to assist in determining multi-element associations. Then C-A fractal method was used for map classification. In order to extraction hydrothermal zones ASTER data were used. ASTER SWIR bands are most useful for the identification of alteration minerals such as Alunite, Pyrophylite, Kaolinite, Sericute and Carbonates. In this paper based on spectral analysis of ASTER SWIR data six maps of alteration zones were prepared. Geochemical study and spectral analysis of ASTER data showed that mineralization and alteration are limited to E1lb and gr lithological units and have NW-SE trends from east of Khatun Abad to Ghezeljeh-Gheshlaghi.

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Murphy, D. M. K., and C. R. Stanley. "Lithogeochemical constraints on the host rock, hydrothermal alteration and weathering of the Groundrush gold deposit." Geochemistry: Exploration, Environment, Analysis 7, no. 4 (November 2007): 363–75. http://dx.doi.org/10.1144/1467-7873/07-143.

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Darabi-Golestan, F., R. Ghavami-Riabi, and H. Asadi-Harooni. "Alteration, zoning model, and mineralogical structure considering lithogeochemical investigation in Northern Dalli Cu–Au porphyry." Arabian Journal of Geosciences 6, no. 12 (October 12, 2012): 4821–31. http://dx.doi.org/10.1007/s12517-012-0689-0.

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9

Hollis, Steven P., Sabri Foury, Stefano Caruso, Sean Johnson, Vitor Barrote, and Andrew Pumphrey. "Lithogeochemical and Hyperspectral Halos to Ag-Zn-Au Mineralization at Nimbus in the Eastern Goldfields Superterrane, Western Australia." Minerals 11, no. 3 (February 28, 2021): 254. http://dx.doi.org/10.3390/min11030254.

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With new advances in rapid-acquisition geochemical and hyperspectral techniques, exploration companies are now able to detect subtle halos surrounding orebodies at minimal expense. The Nimbus Ag-Zn-(Au) deposit is unique in the Archean Yilgarn Craton of Western Australia. Due to its mineralogy, alteration assemblages, geochemical affinity, and tectonic setting, it is interpreted to represent a shallow water (~650 mbsl) and low-temperature (<250 °C) volcanogenic massive sulfide (VMS) deposit with epithermal characteristics (i.e., a hybrid bimodal felsic deposit). We present a detailed paragenetic account of the Nimbus deposit, and establish lithogeochemical and hyperspectral halos to mineralization to aid exploration. Mineralization at Nimbus is characterized by early units of barren massive pyrite that replace glassy dacitic lavas, and underlying zones of polymetallic sulfides that replace autoclastic monomict dacite breccias. The latter are dominated by pyrite-sphalerite-galena, a diverse suite of Ag-Sb ± Pb ± As ± (Cu)-bearing sulfosalts, minor pyrrhotite, arsenopyrite, and rare chalcopyrite. The main sulfosalt suite is characterized by pyrargyrite, and Ag-rich varieties of boulangerite, tetrahedrite, and bournonite. Zones of sulfide mineralization in quartz-sericite(±carbonate)-altered dacite are marked by significant mass gains in Fe, S, Zn, Pb, Sb, Ag, As, Cd, Ni, Cu, Ba, Co, Cr, Tl, Bi, and Au. Basaltic rocks show reduced mass gains in most elements, with zones of intense quartz-chlorite-carbonate±fuchsite alteration restricted to thick sequences of hyaloclastite, and near contacts with dacitic rocks. Broad zones of intense silica-sericite alteration surround mineralization in dacite, and are marked by high Alteration Index and Chlorite-Carbonate-Pyrite Index (CCPI) values, strong Na-Ca depletion, and an absence of feldspar (albite) in thermal infrared (TIR) data. White mica compositions are predominantly muscovitic in weakly altered sections of the dacitic footwall sequence. More paragonitic compositions are associated with zones of increased sericitization and high-grade polymetallic sulfide mineralization. Chlorite in dacitic rocks often occurs adjacent to zones of sulfide mineralization and is restricted to narrow intervals. Carbonate abundance is sporadic in dacite, but is most abundant outside the main zones of Na-Ca depletion. Basaltic rocks are characterized by strongly paragonitic white mica compositions, and abundant chlorite and carbonate. Shifts from Ca carbonates and Fe-rich chlorites to more Mg-rich compositions of both minerals occur in more intensely hydrothermally altered basaltic hyaloclastite, and near contacts with dacitic rocks. Hanging-wall polymict conglomerates are characterized by minor amounts of muscovitic to phengitic white mica (2205–2220 nm), and an absence of chlorite and carbonate alteration.

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Pazand, Kaveh, Ardeshir Hezarkhani, and Mohammad Ataei. "The application of lithogeochemical and alteration index for copper mineralization in the Sonajil area, NW Iran." Arabian Journal of Geosciences 6, no. 5 (November 16, 2011): 1447–56. http://dx.doi.org/10.1007/s12517-011-0453-x.

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Dissertations / Theses on the topic "Lithogeochemical alteration"

1

Madeisky, Hans Eberhard. "Quantitative analysis of hydrothermal alteration : applications in lithogeochemical exploration." Thesis, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362438.

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Fahlvik, Anton. "Hydrothermal alteration and lithogeochemical marker units at the Svärdsjö Zn-Pb-Cu deposit, Bergslagen, Sweden, and their implications for exploration." Thesis, Luleå tekniska universitet, Geovetenskap och miljöteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-71762.

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In exploration, a lithogeochemical approach can be used to aid the characterisation of rocks surrounding metamorphosed and hydrothermally altered deposits. Accurate description of the geological setting of deposits is crucial for understanding the ore forming processes and identifying targets for exploration. The Svärdsjö Zn-Pb-Cu deposit is located in the heavily mineralised and metamorphosed Bergslagen ore province of south-central Sweden. The deposit and surrounding minor occurrences were actively mined for over 500 years, producing more than 1 Mt of Zn-Pb-Cu-Ag massive sulphide ore. The combination of strongly metamorphosed and hydrothermally altered rocks in Svärdsjö makes geological interpretation challenging. Therefore, an approach combining lithogeochemical and petrographic methods is used in this study. The characterisation of the rocks and hydrothermal alteration surrounding the deposit allowed for an interpretation of ore formation and its implications for further exploration in the Svärdsjö area. The results verified that the Svärdsjö mineralisations are hosted by 2–15 m thick dolomitic marble units, commonly altered to skarn. Surrounding the deposit are subvolcanic intrusions and volcanoclastic rocks of mainly dacitic composition. The combined approach also helped identifying a strong to intense hydrothermal chlorite-sericite alteration enveloping the mineralised marble units and resulted in large mass gains of Fe and Mg whereas Na was depleted. Multiple episodes of alteration and metamorphism are evident from cross-cutting relationships with less altered dykes and overprint by metamorphic minerals such as cordierite and anthophyllite. An ore formation model involving sub-seafloor volcanic-associated replacement is suggested for the Svärdsjö deposit based on (i) the presence of a zoned hydrothermal alteration system within a volcanoclastic rock sequence and (ii) the irregular stratabound sulphide lenses hosted by thin marble units in the centre of the alteration system. Additionally, it is inferred that the stratabound nature of the deposit is caused by the neutralisation of a hot acidic fluid, resulting in precipitation of the sulphides within the marble. Finally, two geochemically distinct lithological units have been identified adjacent to the mineralised zones, providing new, larger exploration targets in the area. Mass change calculations reveal that Fe and Mg enrichment and Na depletion are useful vectors towards mineralisation, with detectable changes extending for up to 100 m from the mineralised lenses. These findings showcase the usefulness of the incorporation and careful interpretation of lithogeochemical data when exploring for metamorphosed hydrothermal ore deposits in mineralised provinces of the Fennoscandian Shield or elsewhere in the world.

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Whitbread, Michael Andrew Ian, and n/a. "Lithogeochemichal alteration aound the Century and Elura Zn-Pb-Ag deposits: detecting alteration expressions in deep and near surface environments." University of Canberra. Resource, Environmental & Heritage Sciences, 2004. http://erl.canberra.edu.au./public/adt-AUC20051129.112425.

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Exploration companies commonly rely on geochemistry to identify alteration of distinctive geochemical and mineralogical character, surrounding metal sulphide deposits that were precipitated from hydrothermal fluids. However, examination of raw analytical data is prone to error due to closure effects and the difficulty in removing the effects of background variation in unaltered rocks from the variations imposed by later hydrothermal alteration. Closure can be avoided by using ratios, or by utilising mass balance approaches based on fixing volume, mass or concentration changes between samples of parent and daughter lithologies. Using a parent-daughter approach is limiting, because only pairs of samples can be compared at any one time and because an unaltered equivalent must be produced for each sample examined in this way. Pearce Element Ratio analysis and General Element Ratio analysis (PER and GER) are not restricted in this fashion, and are more amenable to interrogation of large data sets. PER and GER are also capable of decoupling background variation from that variation due to hydrothermal alteration. Furthermore, these ratio methods are readily applied to commercially derived lithogeochemical assays. In this study, various analytical methods and interpretive techniques (including PER and GER) have been applied to identify alteration in rocks around the Century and Elura Zn-Pb-Ag deposits, and to assess whether primary ore-related alteration effects can still be identified once altered rocks have been subjected to weathering. Ratios of trace elements over a conserved element have been used to generate a suite of pathfinder elements for each deposit. Elements enriched in host rocks around both deposits include the economic metals Zn, Pb and Ag, along with Rb and Tl. Sodium is ubiquitously depleted in altered rocks. Other elements in the pathfinder suites are distinctive to each deposit type, and include a number of major and trace elements that are added or removed from the rocks around the mineralised zones. For example, Sb and As are enriched in rocks around Elura mineralisation while Ge and Cd are enriched in samples around Century deposit. Iron carbonate development accompanied by potassic alteration, the destruction of albite and the absence of chlorite are the dominant mineral alteration effects at both deposits. PER and GER diagrams have been used to quantify the intensity of this alteration and allow lithogeochemistry to be used to vector towards high intensity alteration, which is adjacent to Century and Elura mineralisation. These ratio methods are applied to both visibly and cryptically altered rocks at both deposits, and have a very high degree of success in classifying alteration in unweathered rocks. The following simple PER ratios indicate proximity to Elura mineralisation: Ca/C, K/Al for shales, K/(Al-Na) for siltstones/sandstones. The following simple PER ratios indicate proximity to Century mineralisation: Mn/Ti, Mg/Ti and Fe/Ti vs C/Ti, K/Ti vs Al/Ti, K/Ti vs (Al-Na)/Ti. Pathfinder elements can be overlain onto PER and GER diagrams to aid in ranking the prospectivity of samples, and to assess mineral hosts for individual pathfinder elements. Weathering destroys most indicators of alteration in the Elura area, while alteration signatures are better preserved in host rocks around the Century deposit.

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4

Stoynov, Hristo Simeonov. "A lithogeochemical study of hydrothermal alteration associated with Mafic Hosted and Besshi-type Massive Sulphide deposits." Thesis, 2003. http://hdl.handle.net/2429/14827.

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Pearce element ratio (PER) analysis was proposed in 1968 as a graphical method to be applied in petrology. Using major element chemical compositions of rocks, it allows for the determination of primary mineral parageneses. The application of the technique was later expanded to include studies of hydro thermal alteration associated with mineral deposits. This study tests the applicability of PER analysis and the related generalized element ratio (GER) analysis methods to the study of alteration associated with two classes of Volcanic-Hosted Massive Sulphide deposits. Presented are case studies of the Chu Chua and the Konuto Lake Mafic-Hosted Massive Sulphide deposits and the Goldstream Besshi-type deposit. Molar element ratio techniques (PER and GER) are used to identify altered samples and to differentiate between individual chemical alteration types. It is demonstrated that the technique is capable of identifying the exact alteration reaction for an individual sample or for a coherently altered group of samples. The format in which the chemical analytical data are presented allows for a convenient interpretation of the mineralogical effects of alteration. Thus, the validity of the conclusions based on major element lithogeochemistry can be independently verified by petrographic methods. The most typical chemical alteration types found in the three studied deposits are silica mobility (loss and addition), loss of Ca and Na and addition of Fe and Mg. Mineralogically, the alteration process involves the destruction of plagioclase and pyroxene, local deposition of quartz and deposition of iron sulphides. At Chu Chua, extreme Fe-Mg addition caused the characteristic talc-magnetite assemblage whereas at Goldstream Fe and Mg-rich clays were deposited in a seafloor hydrothermal vent setting. Mobilized Ca, Na and excess Si02 were exhaled on the seafloor, giving rise to exhalative chert deposits, carbonate and clay minerals. The tested technique allows the degree of alteration to be quantified in each individual sample. The geographic coordinates of altered samples are then plotted to reveal the spatial patterns of alteration. The outlined alteration anomalies coincide spatially with the known ore bodies and are significantly larger in overall dimensions. Thus, in an exploration context, they would represent intermediate targets. The study proposes exploration parameters, which can be used in similar geologic settings.

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Conference papers on the topic "Lithogeochemical alteration"

1

Onstad, Courtney, Kevin M. Ansdell, Camille Partin, and Anders Carlson. "THE LITHOGEOCHEMICAL SIGNATURES OF HYDROTHERMAL ALTERATION FRAMING PALEOPROTEROZOIC AURIFEROUS QUARTZ VEINS, FISHER PROPERTY, SEABEE GOLD OPERATION, SASKATCHEWAN, CANADA." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-357598.

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Laakso, K., J. M. Peter, B. Rivard, and R. Gloaguen. "Combined hyperspectral and lithogeochemical estimation of alteration intensities in a volcanogenic massive sulfide deposit hydrothermal system: A case study from Northern Canada." In 2016 8th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS). IEEE, 2016. http://dx.doi.org/10.1109/whispers.2016.8071707.

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Reports on the topic "Lithogeochemical alteration"

1

Schetselaar, E. M., G. Bellefleur, J. A. Craven, S. M. Ansari, and R J Enkin. Elucidating mineralizing fluid pathways from the geophysical responses to hydrothermal alteration: integrated 3D modelling of lithogeochemical, petrophysical, seismic and magnetotelluric data, Lalor volcanogenic massive sulphide deposit, Manitoba. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2018. http://dx.doi.org/10.4095/306479.

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