Hydrothermal Alteration Identification of Ahangaran ...

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Email: Akbari_sbu @yahoo.com ... Due to high potential zone for new exploration of the sediment-hosted Pb-Fe deposits, this .... Kcd unit is the main host rock of.
International Geoinformatics Research and Development Journal

Hydrothermal Alteration Identification of Ahangaran Deposit, West of Iran Using ASTER Spectral Analysis Akbari Z.1 *, Rasa I.1, Mohajjel M.2, Adabi M.H1, and Yarmohammadi A2. 1

Department of Geology, Faculty of Earth Science, Shahid Beheshti University, Tehran, Iran

2

Department of Geology, Faculty of Earth Science, Tarbiat Modarres University, Tehran, Iran * Email: Akbari_sbu @yahoo.com

Abstract This study investigates the application of spectral image processing methods to ASTER data for mapping hydrothermal alteration zones associated with sedimentary hosted Pb-Fe Ahangaran deposit and related host rock. The study area is located in the northwestern part of the Malayer-Esfahan Metallogenic belt (MEMB) in the west of Iran. Due to high potential zone for new exploration of the sediment-hosted Pb-Fe deposits, this area has been selected for more investigation. The set of algorithms are used to extract spectral information of VNIR_SWIR and TIR data including band-ratio, band indices, spectral Angle Mapper (SAM) and Matched-Filtering (MF). Evaluation and processing of ASTER Image of the study area, aided by results of field surveying and XRD analysis, show that alteration minerals related to mineralization include dolomitic and silicic altered rocks that contain localized areas of iron oxide minerals (gossan zone). As it is apparent, the identification of the gossan zone is important in the initial stages of ore deposit exploration as an indicator of high economic-potential. Therefore, the pattern of alteration map can be used as an exploration guide for Fe-Pb mineralization similar to giant Ahangaran and Shams abad Fe-Pb deposits in the MEMB of Iran.

Keywords: ASTER, Spectral Mapping, Alteration, Pb-Fe mineralization, Malayer-Esfahan Metallogenic belt (MEMB)

Introduction The MEMB in the SW-Iran contains an enormous accumulation of sediment-hosted Fe-Pb-Ag±Cu and barite mineralizations [40]. This belt is one of the most important metallogenic zones of Iran. The mineralization is associated with the Early Cretaceous carbonate rocks. Major ore deposits in this belt include ([38], [45]): Ahangaran (40 Mt Fe ore, 6 Mt at 6% Pb), Shams abad (60 Mt Fe ore), Irankuh (20 Mt at 2.5% Pb and 11.0% Zn), and Emarat (10 Mt at 2.2% Pb and 6.0% Zn). This study focuses on the Ahangaran mining district, which are located in the northern part of the MEMB. Remote sensing is used for exploration mineral deposits [19]. Over the years, multispectral remote sensing has been successfully used for this purpose especially with the development of remote sensing sensors that provide detailed information on the mineralogy of the different rock types comprising the Earth's surface [53]. Spectral discrimination of potential areas of mineralization (e.g. hydrothermal alteration zones and iron gossans) is a common application of remote sensing ([4], [53]). Many authors have studied the extraction of spectral information related to these targets from different satellite sensors, including Landsat TM, Landsat Enhanced Thematic Mapper Plus (ETM+) and ASTER ([19], [20], [47], and [48]).

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International Geoinformatics Research and Development Journal The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), which is aboard the Earth Observing System (EOS) TERRA platform, is a multispectral imaging system, launched in December 1999 [18]. The ASTER channels are more contiguous in the short wave infrared region than those of Landsat, yielding increased accuracy in the spectral identification of rocks and minerals [15]. ASTER data is commonly used for exploration mineral deposits. Its capability in mapping lithology and hydrothermal alteration and mineralization has been documented by a number of studies ([4], [15], [16], [33], [42], [43], and [44]). The aim of this study is to investigate ASTER image detecting of different hydrothermal alteration minerals associated with Pb-Fe mineralization in the Ahangaran mining district. This investigation is based on comparing the results of analysis of ASTER images to geological map, field observations and XRD analysis in the mining district. Along with this, we have tried to identify and discriminate the most important exploration factors such as different types of alteration minerals associated with mineralization, gossan location and properties of mineralized rocks in the area. The results of this study can be useful in prospecting similar mineralization based on alteration and gossan minerals mapping in the Lower Cretaceous sedimentary rocks in the MEMB.

Geology and mineralization Based on geologic setting, the study area is located in northern part of the MEMB (Figure1a). The MEMB contains an enormous accumulation of sediment-hosted Zn-Pb-Fe-Ag±Cu and barite mineralizations [40]. The MEMB is located in the central part of the Sanandaj - Sirjan tectonic Zone (SSZ) (Figure 1a). The development of the SSZ is related to the opening of the Neo-Tethys Ocean in the Permian and its closing due to the convergence and continental collision between the Arabian and Iran plates during Cretaceous to Tertiary time ([35], [37], [5], [21]). Recent studies show that the SSZ was formed by the accretion of several Triassic to Cretaceous units ([7], [31]). The Early Cretaceous carbonate rocks of the MEMB host numerous Zn–Pb and Fe deposits. Study area contains folded shallow marine carbonate sequence with Early Cretaceous age, unconformable overlying the Jurassic shales and sandstones (Figure 1b). The Jurassic rocks as the oldest units of the area include graygreenish shale (Jph) with interlayering of sandstone (Jms). The Early Cretaceous succession is similar to that recognized elsewhere in the MEMB [38] and may be divided into three major units: The Kc terrestrial to shallow marine sediments, including red sandstone (Kcs) and thick sandy dolomite (Kcd). Kcd unit is the main host rock of Fe-Pb-Ag±Cu mineralization in the study area. The Km unit contains thin-bedded limestone with interlayering of shale and marl. The Kl unit contains thick bedded Orbitolina limestone and upper part of kl unit includes dolomitic limestone (kld). The important mineralization in the Kcd unit in the study area is Ahangaran deposit. Pb-Fe-Ag±Cu mineralization in Ahangaran deposit is located in the southeastern of Kaleband syncline with the direction to NWSE (Figure 1b). Host rock of mineralization is the dolomite rocks (Kcd). Mineralization occurred as stratabaound and stratiform in the host rock. Lead-iron mineralazation are seen at abundant veins and veinlets in a wide zone at lower part of the stratiform orebody. Mineralogy of vein and veinlets include pyrite, galena, magnetite, barite, and minor chalcopyrite and Pyrrhotite. Stratiform ore body part is located in the upper part of the veins and veinlets zone and its mineralogy includes pyrite, galena, magnetite and barite with rarely chalcopyrite. Stratiform ore body has about 1000 m length and on average 50 m width. Pyrite and magnetite in the stratiform ore body have been replaced by iron oxide minerals in supergene process and have been formed thick gossan in the study area. Mineralogy of gossans usually consists of hematite, limonite, goethite and jarosite. This gossan is extracting for iron ore now. The most important hydrothermal alteration in the Ahangaran deposit includes widely silicification and Dolomitization which has been progressed in the center and footwall mineralization of system. Outside of mineralization district, regional dolomite developed in Kcd unit. Gossan zone and alteration minerals play an important role for identifying other similar mineralization in the area by means of processing of satellite images. Vol. 6, Issue 1, March 2015

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Figure1: a) Zonal subdivision of the Zagros orogeny [6] shows location of the MEMB within the SSZ, b) generalized geological map of study area and Ahangaran deposit (solid line). Inset: generalized lithostratigraphic column of Ahangaran deposit.

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International Geoinformatics Research and Development Journal Materials and methods The ASTER satellite, launched during December 1999, provides higher spatial, spectral, and radiometric resolutions and consists of 14 channels viz. the 3 visible near infrared (VNIR) bands (within 0.52 to 0.86 μm) that have a spatial resolution of 15 m, the 9 shortwave infrared (SWIR) bands (within 1.6 to 2.43 μm) have a spatial resolution of 30 m and the 6 thermal infrared (TIR) bands (within 8.12 to 11.65μm) have a spatial resolution of 90 m in the electromagnetic spectrum ([1], [3]). The ASTER channels are more contiguous in the short wave infrared region, yielding increased accuracy in the spectral identification of minerals, rocks and soils of the Earth surface ([15], [16]). Iron minerals and Rare earth element (REE) have characteristic absorption features in the VNIR wavelength regions [25]. Most of the diagnostic spectral absorption features in argillite (clay-rich rock) and carbonate minerals are in the SWIR region [26]. Spectra of rock forming minerals, such as Quartz, Feldspar, and carbonate, display minima emissivity in TIR ASTER [34]. In the present study, the ASTER Level 1B image data acquired on September 27, 2003 and August 29 2001 are used (Figure 2). The imagery is supplied in terms of scaled radiance at sensor data with radiometric and geometric corrections applied. It is georeferenced to the UTM projection and for the WGS-84 ellipsoid. A crosstalk algorithm and Atmospheric correction factors were applied to both ASTER data ([9], [29], and [36]). Atmospheric correction was applied by using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) algorithm on the data [52]. During the atmospheric correction, raw radiance data from imaging spectrometer is rescaled to reflectance data. The geological map is used to support the present study. Field work was carried out in the study area to the occurrence and spatial distribution of hydrothermal alteration minerals and mineralization in Ahangaran mineral district. To validate the remote sensing results through comparison with field work, X-ray diffraction (XRD) technique for bulk mineralogy of the hydrothermally altered rocks were analyzed.

b

a

Figure 2: a) Two Scenes ASTER false-color composite image (RGB: 123) of the study Area. b) ASTER false-color composite image of the study area showing the location of the Ahangaran deposit (solid line)

Remote sensing applications to hydrothermal alteration and associated minerals The use of remote sensing techniques is valuable particularly in mapping hydrothermally altered minerals that have distinct absorption features [27] ,and its capability in hydrothermal alteration and mineralization has been documented by a number of studies ([4], [15], [33], [43], and [44]). Alteration zones are formed in a wide range of geological environments such as volcano-plutonic rocks and hydrothermal mineral deposits, which can be Vol. 6, Issue 1, March 2015

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International Geoinformatics Research and Development Journal exploration targets. Many image analysis and processing techniques can be used to interpret the spectral data. The performance of false-color composite (FCC), band ratio, band indices, Minimum noise fraction (MNF) transformation [12] was evaluated for ASTER data to map of the hydrothermal alteration associated with mineralization. Spectral mapping methods such as spectral angle mapper (SAM) [32], Matched-Filtering (MF) [11] were tested to distinguish alteration zones related to mineralization using VNIR_SWIR bands of ASTER. ASTER images were processed using the ENVI (Environment for Visualizing Images) version 4.8 software package. The spectral angle mapper (SAM) and Matched-Filtering (MF) methods were used on two spatial subset ASTER scenes covering study area. This method starts with reducing abundant information and data dimensionality using the MNF transform then subsequently applying PPI mapping for the determination of the purest pixels in the image and the extraction of end members utilizing the n-Dimensional Visualizer tool. The extracted end members are compared with known spectra from the USGS Spectral Library (minerals) [13] loaded in the software to further identify and prepare for classification [32]. Many of important minerals of the area have obvious absorption features in the ASTER bands region. So using diagnostic spectral absorption features of minerals in the (8–12 μm) thermal infrared TIR and (0.52-2.43μm) VNIR- SWIR region, will cause extraction of needed information for identification and mapping alteration minerals in the study area. ASTER spectral reflectance analysis has proven effective for mapping minerals characterized by ferric-iron and ferrous-iron, Al-OH, Fe, Mg-OH, and CO3 absorption features( [24], [47]) , and some spectrally subtle differences permit discrimination of calcite from dolomite, and Fe-muscovite from K-muscovite in well-exposed areas [47]. Based on results of ASTER data processing and field work in the study area , the alteration zones such as a. Hydrothermal dolomite, b. iron oxide minerals (gossan zone), c. Siliceous altered rocks in the mineralized district and main rock units of the study area such as quartz- rich shale and sandstone and carbonate rocks were identified as given below.

Carbonate minerals Most of the diagnostic spectral absorption features in carbonate minerals are in the SWIR region. In addition to the 2.31–2.33 μm (band8) absorption features observed in carbonate-rich rocks ([26], [47]). Pixel purity index (PPI) was performed on the MNF ASTER VNIR_SWIR data to map spectral endmembers, which are pixels with the most diagnostic spectral absorption features of a specific mineral or mineral groups ([47], [48]). Although PPI was developed for hyperspectral data, ASTER SWIR data have sufficient spectral resolution for defining spectral endmembers ([11], [48]). In the study area, data set the ASTER VNIR_SWIR PPI endmember spectra exhibit CO3 absorption features characteristic of calcite and dolomite (Figure 3). Many of carbonate minerals show spectral absorption in 2.31- 2.33 μm (band 8). PPI dolomite spectral endmember has greater band 7 absorption than the calcite spectrum due to the dolomite CO3 absorption at 2.26 μm (Figure 3). Using geological map as reference and field work, the PPI dolomite spectrum corresponds to Cretaceous basal dolomite (Kcd) and also altered rocks in mining district and The PPI calcite spectrum is according to carbonate rocks (km and kl unit) (Figures 1b, 4). Thus, spectral absorption features associated with dolomite (CO3, ASTER bands 7 and 8), and calcite (CO3, ASTER band 8) are critical for identification of different types of rock units and Alteration minerals using ASTER VNIR-SWIR data. Matched Filter (MF) classification, which was used with the PPI spectral endmembers, outputs gray scale images with DN pixel score values related to endmember abundance and conformity of image spectra to endmember spectral shapes ([17], [23]). According to ASTER SWIR data and PPI method, dolomitic unit of Lower Cretaceous sequence (regional dolomite) and hydrothermal dolomite in mining district has been separated (red color, Figure 4). These areas were not mapped on preexisting geological map. The most common thickness of this dolomite is seen in Ahangaran deposit. According to field work, the maximum thickness of dolomite in the Ahangaran deposit is the hydrothermal dolomite related to mineralization, which has more intensity in the central and footwall parts of ore deposit.

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International Geoinformatics Research and Development Journal Because of the importance of (Kc) unit as the host rock of Pb-Fe mineralization in the MEMB and especially Ahangaran deposit in the study area (Figures 1b, 4), spectral properties have exactly been investigated. This rock unit is separable clearly in the ASTER false color composite (RGB: 631) image with red color (Figure 5a). This unit observes as a black to dark brown horizon at the base of Cretaceous sequence in the target area (Figure 5b). Dolomitic part of this unit (Kcd) has been identified and separated by PPI method (Figure 4). Also Iron-rich rocks in the mineralized zone of Ahangaran deposit were mapped in following section.

Figure 3: ASTER PPI end member spectra in study area

Figure 4: The classes of carbonate and dolomitic rocks overlaid on the ASTER band 1. Solid line Indicate location of Ahangaran deposit with hydrothermally dolomite alteration

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Figure5: a) ASTER false-color composite image (RGB: 631) of the study area showing Kc highlighted by yellowdotted line. b) Field photograph of the study area, View of the kc unit as a black to dark brown horizon. (Abbreviations shown in Figure (b) are stand for (Jms) Jurassic shale and sandstone, (Kc) red sandstone and dolomite, and (Km, Kl) carbonate rocks respectively).

Iron oxide minerals Using the spectral domain of the short wave infrared (SWIR), part of the electromagnetic wavelength for detection of iron oxide alteration, is one of the most important usages of remote sensing in geology (e.g. [51], [30], [50]). Iron oxide minerals zones usually consist of hematite, limonite, goethite and jarosite. The reflectance spectrum of a rock depends on the mineralogical composition of its surface, which is usually a mixture of the whole rock mineralogy and weathering minerals. The presence of ferrous iron (Fe2+) in the weathered surface produces absorptions centered at about 0.45 μm, 1.0–1.1 μm, 1.8–1.9 μm, and 2.2–2.3 μm, depending on its lattice environment. The ferric iron (Fe3+) produces absorptions at about 0.65 μm and 0.87 μm ([2], [41], and [42]). Fe 2+ is soluble so rarely if ever appears in weathered materials. Indeed the oxidizing nature of the surface environment ensures that it is converted to insoluble Fe3+ ions, in oxy-hydroxides and sulfates. The surface weathering of pyrite rocks has led to the formation of abundant goethite and limonite. Goethite has particular absorption features in the VNIR wavelength region due to electronic transitions of ferric iron ([28], [14]). Goethite displays a broad ferric iron absorption feature near 0.90 μm and two additional features near 0.50 and 0.66 μm with a peak near 0.75 μm, as shown in Figure 6 ([28], [14] and [50]). Jarosite, K (Fe3+) 3(OH) 6(SO4)2, is a common iron mineral in acidic, sulfaterich environments formed by the oxidation of sulfides, especially pyrite (FeS2) [8]. Jarosite has characteristic absorption features in the VNIR and SWIR wavelength regions [10]. This mineral has a broad ferric iron absorption feature near 0.90 μm, is more reflective overall than goethite or hematite and displays a local reflectance maximum at near 0.70 μm , also diagnostic vibrational absorption features in the SWIR wavelength region due to Fe–OH and OH stretches and bending (Figure 6) [10]. Iron oxide minerals zone or gossan in the study area consist of hematite, jarosite, goethite and limonite. Their distribution and occurrences are given in the color composite image, band ratios, and SAM analysis. Iron-rich rocks were mapped using a (5/3+1/2) band ratio [48]. The (5/3+1/2) ratio map shows iron-rich rocks and surface mining activity in Ahangaran deposit (region A in Figure 7). Based on the reference of mineral spectra, PPI spectral endmembers and considering the geological conditions of the study area, spectra of specific indicator minerals were selected from the USGS spectral library and their spectral graph was determined (Figure 6). Additionally, the spectral reflectance curves of the minerals have to be resampled Vol. 6, Issue 1, March 2015

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International Geoinformatics Research and Development Journal to the ASTER spectral bands for spectral analysis. To separate the minerals in study area, the Spectral Angle Mapper (SAM) method was used (Figure 8). The occurrence and spatial distributions of iron oxide mineral zones were verified during the field check. Iron oxide minerals or gossan related to mineralization in mining district is due to weathering of first Fe -bearing minerals such as pyrite and magnetite (Figure 9). Occurrence of iron oxide minerals such as hematite in the outside of mineralized area is due to highly weathered iron rich surface in the rocks. The difference between the mineralized and the non-mineralized rocks is the presence of abundant secondary iron minerals such as jarosite, goethite, limonite and hematite along with other alteration minerals (Figure 12).

Figure 6: a) Laboratory VNIR-SWIR reflectance spectra of jarosite, hematite and goethite from the USGS spectral library. b) The same spectra after resampling to ASTER bandpasses.

Figure7: ASTER band ratio (5/3+1/2) of the study area, Bright areas indicate iron-rich rocks. Ahangaran mining district (region A) highlighted by red-solid line.

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Figure 8: a) the classes of iron oxide minerals overlaid on the ASTER band 1, Solid line indicate location of Ahangaran deposit. b) Abundant of iron oxide minerals and gossan location in mineralized district.

Figure 9: Field photographs of the study area. a) Regional view of Ahangaran deposit. b) View of the gossan zone (high economic-potential for mineralization). c) Close-up the converting of pyrite to goethite in the gossan zone.

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International Geoinformatics Research and Development Journal Siliceous rocks ASTER TIR data are considerable for mapping lithology that lack distinguishing VNIR+ SWIR absorption features, particularly quartz and feldspars [48]. The ASTER spectral emittance data evaluated in this study using the algorithm of temperature-emissivity separation (TES) algorithm developed by [22]. Quartz rich rocks exhibiting SiO2 absorption observed in the TIR data can be mapped, whilst using the VNIR-SWIR data is impossible because quartz VNIR-SWIR spectra are featureless. Spectra of quartz displays emissivity minima in ASTER band 12 (8.7μm) due to Si-O [18]. Further point that, TIR ratio images are useful for distinguishing certain geologic mapping and identifying pixels for utilizing as reference spectra for subsequent spectral analysis and classification [49]. The 14/12 band ratio image is more effective for displaying quartz-rich rocks with SiO2 (8.7 μm) spectral absorption (Figure10) [49]. ASTER TIR data was used for identifying quartz minerals in northern Nevada, USA by [46]. A Quartz Index (QI) was implemented for geologic mapping and mineral resource investigation purposes. Index (QI) [39] is defined as follow:

Quartz Index (QI) =

In the study area, Index (QI) was implemented using the ASTER TIR. Pixels with the high (DN) value were identified as quartz-rich rocks (Figure11a). The bright areas correspond to the Jurassic quartz-rich shale and sandstone in the northern part of the study area and also silicic alteration in the mining district. ASTER TIR image spectra of silicic alteration in Ahangaran deposit are depicted in Figure (11b). Regarding to this Figure, the quartzose spectrum exhibits intense absorption in 8.7 μm (band 12) due to quartz. Silicification is one of the most important indicators of the hydrothermal mineralization processes [46]. The spatial distribution of the identified silicic alteration in the study area has been verified through situ inspection. Silicic alteration is seen in the footwall and margin of the ore deposit. It is worth pointing out that there are some disturbances of sedimentary rocks appearing such hydrothermal alteration. These rocks contain large amounts quartz.

Figure 10: ASTER TIR b14/b12 ratio image of the study area, showing high DN values (bright) caused by quartz-rich rocks. Solid line indicates location of Ahangaran deposit

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Figure11: a) Image map showing the distribution of quartz- rich rocks of the study area based on Index (QI). b) ASTER TIR image spectra of silicic alteration in Ahangaran deposit.

Results and Discussion In this contribution, the analysis of ASTER relative reflectance and emissivity spectra shows alteration minerals are gained from image processing techniques. A combination VNIR-SWIR and TIR hydrothermally alteration mineral and lithological unit map is shown in Figure (12). It determined the distribution of the dolomitic alteration, Iron oxide minerals (jarosite, goethite, and hematite) or gossan and silicic alteration; so that it allowed the construction of a preliminary alteration map in Ahangaran deposit area. The distribution of the identified hydrothermal alterations has been verified through in situ inspection. Spatial distribution of these alterations and Iron oxide minerals has good compliance with their exposure in the Ahangaran deposit (Figure12). Hydrothermal dolomite detected in the center of mineralization system and silicic alteration has developed in the footwall deposit. The jarosite mineral has been detected in the center of gossan zone while the hematite-goetite minerals are expanded in the margin of gossan zone in the Ahangaran deposit. The most important difference between the mineralized and the non-mineralized rocks is the presence of abundant secondary iron oxide minerals (gossan zone) such as jarosite, goethite, limonite, hematite and other alteration minerals in the mineralized zone. The alteration map illustrates a zoning pattern of alterations and gossan location associated with mineralization that can be used as an exploration guide for similar deposits in the MEMB of Iran. Samples for X-ray diffraction (XRD) analysis were collected from mining district (table 1). The good correlation of the image processing results with field work and XRD analysis proved the accuracy of this method. According to XRD analysis of collected rock samples, the minerals predominantly were detected in altered rocks included dolomite, siderite and quartz. The XRD analysis indicated that hematite, goethite, alunite and jarosite were identified as major minerals in gossan zone. By the use of ASTER data, main rock units of the study area are the Jurassic quartz- rich shale and sandstone unit (blue, Figure12) and Lower Cretaceous carbonate rocks (green, Figure 12) in the synclinal structure of the area. Siliceous rocks have specific absorption in the Si-O near 8.7μm (band 12) due to quartz and carbonate rocks have absorption in 2.31- 2.33 μm (band 8) due to Co3. Therefore, this study indicates that image processing techniques can map the distribution hydrothermal alteration and lithological units using ASTER bands at district scale.

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Figure 12: Combined ASTER alteration minerals and rock-type map of the study area. Background image is ASTER band 1. Ahangaran deposit highlighted by black-solid line.

Conclusion The capability of ASTER spectral bands and the image processing techniques are proved in mapping and distribution of hydrothermally alteration minerals in the Ahangaran Pb-Fe deposit and have been confirmed through field investigations and laboratory study. VNIR- SWIR relative reflectance spectral analysis has been accurate and helpful for detecting and mapping of alteration minerals such as dolomitic alteration and iron oxides minerals or gossan zones. TIR emissivity data ratio images and band indices have been also useful tools for silica mineral mapping. The alteration map illustrates a zoning pattern of alteration and gossan location associated with mineralization that can be used as an exploration guide for similar deposits in the MEMB of Iran. ASTER images prove to be a powerful tool in the initial steps of ore deposit exploration because they provide high accuracy data that can be used as a basis for mapping the surface distribution of certain minerals. In this way, they allow determination of hydrothermal alteration zones and reducing of time and cost required for field evaluation.

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International Geoinformatics Research and Development Journal Acknowledgements The authors acknowledge the support of Shahid Beheshti University in the completion of this research. The authors also would like to thanks Sormak Company for providing the necessary facilities to carry out this research.

Table1: Result of XRD analysis from 10 samples of main alterations in the Ahangaran deposit

type of Alteration

mineralogy Quartz-Goethite-Kaolinite-Hematite

Gossan zone

silicic rocks

X=315698 , Y=3784750

Goethite- Quartz-Jarosite-Hematite

X=315773, Y=3784671

Muscovite-Goethite-Quartz

X=315813, Y= 3784997

Quartz-Goethite-Muscovite-Alunite

X=315448, Y= 3784962

Dolomite- Siderite-Barite-Pyrite Dolomitic rocks

Coordinate System

X=315443, Y=3784969

Quartz-Pyrite-Siderite-Dolomite

X=315136, Y= 3784785

Dolomite-Siderite- Quartz- Goethite

X=315698 ,Y=3784750

Siderite-Quartz - Fe-Dolomite

X=315592 ,Y=3784274

Quartz- Pyrite-Orthoclase

X=315543, Y=3784407

Quartz-Barite-Galena

X=315326, Y= 3784716

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