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Application of Spectral Angle Mapper Classification to Discriminate hydrothermal alteration in Southwest Birjand, Iran, Using Advanced Spaceborne Thermal Emission and Reflection Radiometer Image Processing

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Acta Geologica Sinica(English Edition) 2012年第5期86卷 1289-1296页

作者： Maryam ABDI Mohammd H. KARIMPOUR Department of Geology Ferdowsi University of Mashhad P.O. Box 91775-1436 Mashhad Iran Research Center for Ore Deposit of Eastern Iran Ferdowsi University of Mashhad Mashhad Iran

The purpose of this study is to evaluate the Spectral Angle Mapper （SAM） classification method for determining the optimum threshold （maximum spectral angle） to unveil the hydrothermal mineral assemblages related to mineral deposits. The study area indicates good potential for Cu-Au porphyry, epithermal gold deposits and hydrothermal alteration well developed in arid and semiarid climates, which makes this region significant for Advanced Spaceborne Thermal Emission and Reflection Radiometer （ASTER） image processing analysis. Given that achieving an acceptable mineral mapping requires knowing the alteration patterns, petrochemistry and petrogenesis of the igneous rocks while considering the effect of weathering, overprinting of supergene alteration, overprinting of hypogene alteration and host rock spectral mixing, SAM classification was implemented for argillic, sericitic, propylitic, alunitization, silicification and iron oxide zones of six previously known mineral deposits： Maherabad, a Cu-Au porphyry system; Sheikhabad, an upper part of Cu-Au porphyry system; Khoonik, an Intrusion related Au system; Barmazid, a low sulfidation epithermal system; Khopik, a Cu-Au porphyry system; and Hanish, an epithermal Au system. Thus, the investigation showed that although the whole alteration zones are affected by mixing, it is also possible to produce a favorable hydrothermal mineral map by such complementary data as petrology, petrochemistry and alteration patterns.

关键词： hydrothermal alteration Spectral Angle Mapper Advanced Spaceborne Thermal Emission and Reflection Radiometer image process Iran

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ASTER Data Processing by Discrete Wavelets Transform and Band Ratio Techniques for the Identification of Lineaments and hydrothermal alteration Zones in Poli, North Cameroon

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Journal of Geoscience and Environment Protection 2023年第9期11卷 216-232页

作者： Mohamadou Ahamadou May Nome Stella Meying Arsène School of Geology and Mining Engineering University of Ngaoundéré Ngaoundéré Cameroon Centre for Geological and Mining Research Garoua Cameroon

The aim of this study is to carry out hydrothermal alteration mapping and structural mapping using ASTER images in order to identify indices that could guide mining exploration work in the Poli area and its surroundings. To achieve this, the ASTER images were first preprocessed to correct atmospheric effects and remove vegetation influence. Secondly, a lineament mapping was conducted by applying Discrete Wavelet Transform (DWT) algorithms to the First Principal Component Analysis (PCA1) of Visible Near-Infrared (VNIR) and Shortwave Infrared (SWIR) bands. Lastly, band ratio methods were applied to the VNIR, SWIR, and Thermal Infrared (TIR) bands to determine indices of iron oxides/hydroxides (hematite and limonite), hydroxyl-bearing minerals (chlorite, epidote, and muscovite), and the quartz index. The results obtained showed that the lineaments were mainly oriented NE-SW, ENE-WSW, and E-W, with NE-SW being the most predominant direction. Concerning hydrothermal alteration, the identified indices covered almost the entire study area and showed a strong correlation with lithological data. Overlaying the obtained lineaments with the hydrothermal alteration indices revealed a significant correlation between existing mining indices and those observed in the field. Mineralized zones generally coincided with areas of high lineament density exhibiting significant hydrothermal alteration. Based on the correlation between existing mining indices and the results of hydrothermal and structural mapping, the results obtained can then be used as a reference document for any mining exploration in the study area.

关键词： Discrete Wavelets Transform Band Ratio Lineaments hydrothermal alteration

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The Activity of Major Faults and the hydrothermal alteration Zone at Tianchi Volcano of Changbaishan

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Earthquake Research Advances 2004年第3期 45-54页

作者： Liu Mingjun 1), Gu Menglin 1), Sun Zhenguo 1), Wei Haiquan 2) and Jin Bolu 3) 1) Geophysical Exploration Center, CEA, Zhengzhou 450002, China 2) Institute of Geology, CEA, Beijing 100029, China 3) The No.6 Geological Survey of Geological and Mineral Resource Administration of Jilin Province, Yanji 133001, Jilin, China

It is found by field investigation that the near horizontal top surface of the brown or brick-red hydrothermal alteration zone varies obviously in elevation at different sections of the same layer on the caldera’s inner wall of Tianchi, with that at the north section near the Tianwen Peak about 110 m higher than that at the south near the Jiangjun Peak in Korea. The top surface of the hydrothermal alteration zone can be taken as key horizon to tectonic movement. The difference indicates that the total uplift height of the NW wall of the Liudaogou-Tianchi-Jingfengshan fault, the principal fault trending NE at Tianchi, is bigger than that of the SE wall ever since the occurrence of hydrothermal alteration. This also explains why the topography in the northwest side of Tianchi is steeper and with more developed river system than in the southeast. The uplifting of the northeastern wall is bigger than that of the southwest along the principal NW-trend fault, namely, the Baishanzhen-Tianchi-Jince fault. It is observed from characters of hydrothermal alteration and the palaeoresiduum, that the recent vertical movement rate along the principal NE-trend fault is larger than that of the principal NW-trend fault. The two faults intersect at Tianchi, dividing the volcano into 4 blocks, with the uplift magnitudes decreasing successively in the order of the north, the west, the east and the south block. The biggest uplift of the north block corresponds well to the shallow magma batch in the north of Tianchi observed by DSS and telluric electromagnetic sounding, and etc. and they may be related with the causes.

关键词： Tianchi volcano Major fault Caldera’s inner wall hydrothermal alteration Different uplift

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Three-dimensional geological modelling and direction of hydrothermal alteration of Horne deposit, Blake River Group, Quebec, Canada

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Global Geology 2021年第1期24卷 15-22页

作者： TIAN Liya YU Yunliang XU Haibo College of Earth Sciences Jilin UniversityChangchun 130061China

The Horne deposit with rich Cu and Au in Noranda region of Black River Group in Quebec has high economic significance.Current researches on Horne deposit are mostly based on two-dimensional maps and statistical data.It is hard to reflect the spatial structure and characteristics of Horne orebody directly.In this paper,GIS was used to digitize the mining plan-view maps at different depths,stope maps,the boundary of the massive sulfide in drilling trajectories as well as the grade data of Au and Cu of Horne deposit.Meanwhile,the authors established the grade attribute database.Subsequently the three-dimensional(3D)geological model and grade attribute model of Horne orebody were established by Geological Object Computer Aided Design(GOCAD).Positions of two vents and directions of hydrothermal alteration in Horne deposit were inferred based on the property of the major fault,characteristics of hydrothermal alteration,the enrichment morphology and spatial distribution of high-grade Cu in the Cu attribute model.

关键词： Horne deposit massive sulfide three-dimensional geological modeling hydrothermal alteration

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Application of Airborne Geophysical and ASTER Data for hydrothermal alteration Mapping in the Sar-Kuh Porphyry Copper Area, Kerman Province, Iran

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Open Journal of Geology 2016年第10期6卷 1257-1268页

作者： Mehdi Honarmand Department of Ecology Institute of Science and High Technology and Environmental Sciences Graduate University of Advanced Technology Kerman Iran

Known deposits are appropriate sites for investigating significant exploratory keys that could be helpful in mineral exploration in corresponding regions or similar areas. This study was performed to delineate hydrothermal alteration model and some geophysical characteristics of the SarKuh porphyry copper deposit located within the southern part of the central Iranian Cenozoic magmatic belt (CICMB). Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images have been used to produce hydrothermal alteration map using a fractal-aided spectral angle mapper (SAM) method. Airborne data were used to study magnetic-radiometric properties of the deposit. Image processing of ASTER images and laboratory studies proved the presence of two types of phyllic ale ration called intense and weak phyllic based on abundance of sericite mineral. It realized that radiometric anomalies of 40K, eTh and eU are limited to boundary of phyllic zone. Radiometric ratios e.g. eTh/40K were good enough to enhance phyllic zone.

关键词： Porphyry Copper Deposit hydrothermal alteration ARTER SAM Airborne Geophysics

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hydrothermal alteration of chevkinite-(Ce) in the Shuiquangou syenitic intrusion,northern China

Hydrothermal alteration of chevkinite-(Ce) in the Shuiquango...

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中国科学院地质与地球物理研究所2006学术年会

作者： Jiang,Neng Key Laboratory for Mineral Resources Research,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China

A rare-earth iron titanosilicate mineral closely associated with amphibole was found in two altered syenite samples from the Shuiquangou syenitic complex.Based on electron microprobe analyses,the mineral is chevkinite-(Ce).The mineral is altered and mantled by a corona of allanite(?)ilmenite(?)titanite(?)epidote(?)quartz.Mass balance calculations reveal that the former chevkinite was replaced directly by an allanite and ilmenite association (allanite(?)ilmenite zone) in the inner part of the corona texture.It appears that during the replacement,Si and Ti were immobile,whereas Al,Fe,Mn,Mg and Ca were externally supplied and a proportion of REE and Th were transferred out of the former chevkinite.The released REE and Th become incorporated in allanite and titanite in the allanite(?)ilmenite(?)titanite mantle where allanite contains higher Nd,Sm and Y but lower La and Ce than that in the allanite(?)ilmenite zone,suggesting that redistribution of these elements took place and the mobility of Nd,Sm and Y is enhanced during hydrothermal alteration.

关键词： Chevkinite-（Ce） Corona system hydrothermal alteration Mobilization

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Geology and hydrothermal alteration of the Duobuza Gold-Rich Porphyry Copper District in the Bangongco Metallogenetic Belt,Northwestern Tibet

Geology and Hydrothermal Alteration of the Duobuza Gold-Rich...

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中国科学院地质与地球物理研究所2012年度（第12届）...

作者： Guangming LI Jinxiang LI Kezhang QIN Ji Duo Tianping ZHANG Bo XIAO Junxing ZHAO Key Laboratory of Mineral Resources Institute of Geology and GeophysicsCASBeijing

The Duobuza gold-rich porphyry copper district is located in the Bangongco metallogenetic belt in the Bangongco-Nujiang suture zone south of the Qiangtang terrane.Two main gold-rich porphyry copper deposits (Duobuza and Bolong) and an occurrence(135 Line) were discovered in the district The porphyry-type mineralization is associated with three Early Cretaceous ore-bearing granodiorite porphyries at Duobuza,135 Line and Bolong,and is hosted by volcanic and sedimentary rocks of the Middle Jurassic Yanshiping Formation and intermediate-acidic volcanic rocks of the Early Cretaceous Meiriqie Group.Simultaneous emplacement and isometric distribution of three ore-forming porphyries is explained as multi-centered mineralization generated from the same magma chamber.Intense hydrothermal alteration occurs in the porphyries and at the contact zone with wall rocks.Four main hypogene alteration zones are distinguished at Duobuza.Early-stage alteration is dominated by potassic alteration with extensive secondary biotite,K-feldspar and magnetite.The alteration zone includes dense magnetite and quartz-magnetite veinlets,in which Cu-Fe-bearing sulfides are present.Propylitic alteration occurs in the host basic volcanic rocks.Extensive chloritization-silicification with quartz-chalcopyrite or quartz-molybdenite veinlets superimposes on the potassic alteration.Final-stage argillic alteration overlaps on all the ear Her alteration.This alteration stage is characterized by destruction of feldspar to form illite,dickite and kaolinite,with accompanying veinlets of quartz + chalcopyrite + pyrite and quartz + pyrite assemblages. Cu coexists with Au,which indicates their simultaneous precipitation.Mass balance calculations show that ore-forming elements are strongly enriched during the above-mentioned three alteration stages.

关键词： Bangongco metallogenetic belt Duobuza porphyry copper district hydrothermal alteration mass balance mineralization northwestern Tibet

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Fe-bearing minerals and implications for gold mineralization for the Wangu deposit in Central Jiangnan Orogen

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Acta Geochimica 2023年第3期42卷 552-571页

作者： Teng Deng Longyue Zhou Zenghua Li State Key Laboratory of Nuclear Resources and Environment East China University of TechnologyNanchang 330013China School of Earth Sciences East China University of TechnologyNanchang 330013China

hydrothermal alteration with bleaching of host rocks is the most important prospecting indicator for gold deposits in the Jiangnan Orogen Belt.The alteration has been identified as pre-ore carbonate(siderite)-sericitization and the Fe of siderite in the alteration zone is derived from the host rocks rather than fluids.In addition,such alteration decreases in intensity and width with depth and gold mineralization also occur in the non-bleached rocks,casting doubt on the reliability of the prospecting indicator.Detailed petrographic work and SEM analysis on the Wangu deposit indicate that there are two types of siderites,i.e.,Sd1 and Sd2.Among them,Sd1 grains are relatively small and distributed along the planes of unaltered host rocks,while Sd2 grains,only occurring in the altered slates,are commonly larger.Both types of siderites were altered by auriferous fluids,producing porous cores and minerals such as pyrite,quartz,and ankerite.Compared with unaltered parts,the altered parts have lower Fe,but higher U,Pb,and REE.In addition,Sd1 and Sd2 are similar in Mn,Na,V,and Sr concentrations but different in Fe and Mg.The occurrence and geochemical compositions of both siderites indicate that Sd1 could be transformed into Sd2 by pre-mineralization alteration through dissolution-reprecipitation.Chlorite is another important Fe-bearing mineral in the host rocks,and EPMA analysis suggests that it is ripidolite with relatively high Fe contents.Consequently,chlorite can also provide Fe to form the pre-ore carbonate(siderite)-sericitization.Geochemical modeling demonstrates that both ripidolite and siderite can result in sulfidation and therefore gold precipitation.As a result,this study demonstrates that pre-ore alteration with characterized bleaching is not a prerequisite for gold mineralization despite of its prominent features.Due to the presence of Fe-bearing Sd1 and chlorite,gold mineralization could still occur through sulfidation in the unaltered rocks.

关键词： Jiangnan Orogen Gold precipitation Wangu deposit hydrothermal alteration Fe-bearing minerals

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Magnesium isotopes of chlorite-rich hydrothermal sediments in the Okinawa Trough and indications for Mg cycle

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Science China Earth Sciences 2023年第3期66卷 648-662页

作者： Hebin SHAO Shouye YANG Aiguo DONG Zhongya HU Key Laboratory for Polar Science of the State Oceanic Administration Polar Research Institute of ChinaShanghai 200136China State Key Laboratory of Marine Geology Tongji UniversityShanghai 200092China Institute of Earth Sciences China University of Geosciences(Beijing)Beijing 100083China

Seafloor hydrothermal systems play a significant role in the oceanic Mg cycle due to ubiquitous deposits of secondary Mg-rich clays during the strong fluid-rock reactions.However,the magnitude of net Mg enrichment and Mg isotopic fractionation,particularly within the medium-high temperature hydrothermal systems in felsic-hosted settings,are not well studied yet.Here we report elemental and isotopic compositions of Mg in hydrothermal chlorite-rich sediments,volcanic materials,and terrigenous sediments collected during the IODP Expedition 331 drilled to the thick sediment-covered and felsic-hosted middle Okinawa Trough(Iheya North Knoll) in the West Pacific.We investigate the sources of Mg in chlorite and Mg isotopic behavior at medium-high temperature hydrothermal alteration.After 1 mol/L HCl leaching,Mg isotopic compositions of chlorite-rich sediments present overall similar values in the residual fractions and bulk samples albeit with slightly higher values in the leachates.Mineralogical differentiation primarily determines the Mg isotopic compositions,showing that siliciclastic residues have slightly higher δ^(26) Mg values than the leachates dominated by carbonates and oxides/hydroxides.Significant Mg isotopic fractionation happened in the medium-high temperature(~150°C to 260°C) felsic-hosted hydrothermal system,with Δ^(26)MgChl-SW ranging from 0.15‰ to 0.71‰ and yielding a negative correlation with temperature.This observation suggests the preferential incorporation of heavy Mg isotopes by the secondary chlorite precipitation.We infer that the medium-high temperature hydrothermal systems can take up about 8–14% of riverine input of Mg in the arc and back-arc regions.Incomplete removal of aqueous Mg in porewater and vent fluids by the medium-high temperature hydrothermal alterations in the arc and back-arc basins provides constraints on the Mg budget and isotopic composition of seawater.

关键词： hydrothermal alteration Chlorite Okinawa Trough Magnesium(Mg)isotopes Integrated Ocean Drilling Program

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Resolving impact volatilization and condensation from target rock mixing and hydrothermal overprinting within the Chicxulub impact structure

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Geoscience Frontiers 2022年第5期13卷 16-31页

作者： Thomas Déhais Stepan M.Chernonozhkin Pim Kaskes Sietze J.de Graaff Vinciane Debaille Frank Vanhaecke Philippe Claeys Steven Goderis Analytical Environmental and Geo-ChemistryVrije Universiteit BrusselBrusselsBelgium Laboratoire G-Time UniversitécLibre de BruxellesBrusselsBelgium Department of Chemistry Atomic&Mass SpectrometryGhent UniversityGhentBelgium

This work presents isotopic data for the non-traditional isotope systems Fe,Cu,and Zn on a set of Chicxulub impactites and target lithologies with the aim of better documenting the dynamic processes taking place during hypervelocity impact events,as well as those affecting impact structures during the post-impact phase.The focus lies on material from the recent IODP-ICDP Expedition 364 Hole M0077A drill core obtained from the offshore Chicxulub peak ring.Two ejecta blanket samples from the UNAM 5 and 7 cores were used to compare the crater lithologies with those outside of the impact structure.The datasets of bulk Fe,Cu,and Zn isotope ratios are coupled with petrographic observations and bulk major and trace element compositions to disentangle equilibrium isotope fractionation effects from kinetic processes.The observed Fe and Cu isotopic signatures,with δ^(56/54)Fe ranging from0.95‰to 0.58‰and δ^(65/63)Cu from0.73‰to 0.14‰,mostly reflect felsic,mafic,and carbonate target lithology mixing and secondary sulfide mineral formation,the latter associated to the extensive and long-lived(>105 years)hydrothermal system within Chicxulub structure.On the other hand,the stable Zn isotope ratios provide evidence for volatility-governed isotopic fractionation.The heavier Zn isotopic compositions observed for the uppermost part of the impactite sequence and a metamorphic clast(δ^(66/64)Zn of up to 0.80‰and 0.87‰,respectively)relative to most basement lithologies and impact melt rock units indicate partial vaporization of Zn,comparable to what has been observed for Cretaceous-Paleogene boundary layer sediments around the world,as well as for tektites from various strewn fields.In contrast to previous work,our data indicate that an isotopically light Zn reservoir(δ^(66/64)Zn down to0.49‰),of which the existence has previously been suggested based on mass balance considerations,may reside within the upper impact melt rock(UIM)unit.This observation is restricted to a few UIM samples only and cannot be extended to other target o

关键词： Chicxulub impact structure Non-traditional stable isotopes Impact volatilization Impact condensation hydrothermal alteration Target lithology mixing

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