Chapter 18B. Analysis of Imaging Spectrometer Data for the 

Bakhud Area of Interest

By Daniel H. Knepper, Jr., and Stuart A. Giles

Abstract

Computer analysis of HyMap imaging spectrometer data of the Bakhud area of interest (AOI) in 

south-central Afghanistan used spectrum-matching techniques to identify the occurrence of selected 

materials at the surface based on distinctive spectral features (absorption bands) in the HyMap data 

compared to a library of known material spectra. Carbonate minerals, especially calcite and dolomite, 

occurring in Paleozoic, Mesozoic, and Cenozoic sedimentary rocks dominate the area, and their 

distribution patterns appear to be useful for identifying new members within existing geologic map 

units. Several iron oxide and hydroxide mineral concentrations within the AOI suggest possible sites of 

mineralization, but correlations of mineral occurrences with sites of known polymetallic skarns and 

carbonate-hosted fluorite deposits are minimal. Especially conspicuous is the overall lack of any of a 

suite of minerals (buddingtonite, jarosite, alunite, kaolinite, pyrophyllite, and hydrated silica) commonly 

associated with hydrothermally altered rocks of the quartz-sericite-pyrite, argillic, and advanced argillic 

alteration suites. The general scarcity of these minerals in the HyMap data analyses suggests that 

epithermal mineral deposits are either not present in the AOI or are deeply eroded.

18B.1 Introduction

Previous U.S. Geological Survey (USGS) analyses of existing geologic data of Afghanistan 

revealed numerous areas with indications of potential mineral resources of various types (Peters and 

others, 2007). From these areas of interest, several were selected for follow-on studies using modern 

imaging spectrometer remote sensing data to further characterize surface materials. One of those areas is 

the Bakhud area of interest (AOI) in south-central Afghanistan.

The Bakhud AOI is about 380 kilometers (km) southwest of Kabul (fig. 18B–1) and is believed 

to have the potential for carbonate-hosted fluorite deposits and polymetallic skarn deposits with tin, lead, 

zinc, copper, and iron that are probably associated with Oligocene granitic rocks (Abdullah and others, 

1977). To help assess these potential resources, high-resolution imaging spectrometer data were 

analyzed to detect the presence of selected minerals that may be indicative of past mineralization 

processes. This report contains the results of the imaging spectrometer data analyses and identifies sites 

within the Bakhud AOI that deserve further investigation, especially detailed geological mapping, 

lithologic sampling, and geochemical studies.

18B.2 Imaging Spectrometer Data Collection and Processing

In 2007, imaging spectrometer remote sensing data were acquired over most of Afghanistan with

the HyMap imaging spectrometer (Cocks and others, 1998) as part of the USGS project "Oil and Gas 

Resources Assessment of the Katawaz and Helmand Basins” (Kokaly and others, 2008). These data 

provide a means for characterizing surface materials in support of assessments of resources (coal, water,

minerals, and oil and gas) and earthquake hazards in the country. HyMap measures the reflectance of 

visible and near-infrared light from the Earth’s surface in many narrow channels, producing a 

reflectance spectrum for each image pixel. These reflectance spectra can be interpreted to identify 

specific chemical transitions and molecular bonds that provide compositional information about specific

materials occurring at the surface. The imaging spectrometer sensor data can only be used to 
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1329

characterize the upper surface materials and not subsurface composition or structure. However, in 

epithermal systems, subsurface processes are commonly expressed by secondary surface-alteration 

products that can be identified using imaging spectroscopy data (Rowan and others, 1994). 

Figure 18B–1.

After undergoing a complex and rigorous data calibration process, the georeferenced and 

calibrated reflectance data were processed. The reflectance spectrum of each pixel of HyMap data was 

compared to the spectral features of reference entries in a spectral library of minerals, vegetation, water, 

and other materials (King, Kokaly, and others, 2011; Kokaly and others, 2011). The best spectral 

matches were determined, and the results were clustered into classes of materials discussed below. 

Index map of the Bakhud area of interest in south-central Afghanistan.

18B.2.1 Collection

HyMap data were acquired during the interval of August 22, 2007, to October 2, 2007. There 

were 207 north-south flight lines and 11 cross-cutting calibration lines collected over the country of 

Afghanistan for a total of 218 flight lines covering a surface area of 438,012 square kilometers (km2) 

(Kokaly and others, 2008). Each flight line was georeferenced to Landsat base imagery in UTM 

projection (Davis, 2007). 
1330 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

18B.2.2 Calibration

To ensure the utility of the imaging spectrometer dataset, a calibration process to remove 

atmospheric absorptions and residual instrument artifacts was applied. Because of the extreme 

topographic relief and restricted access to ground calibration sites, modifications to the traditional USGS 

calibration procedures were required to calibrate the 2007 Afghanistan HyMap dataset (Hoefen and 

others, 2010). First, the radiance data were converted to apparent surface reflectance using the radiative 

transfer correction program Atmospheric CORrection Now (ACORN; ImSpec LLC, Palmdale, Calif.). 

ACORN was run multiple times for each flight line using average elevations in 100-meter (m)

increments, covering the range of minimum to maximum elevation within the flight line. A single 

atmospherically corrected dataset was assembled from the ACORN results in 100-m increments. This 

was done by determining the elevation of each pixel and selecting the atmospherically corrected pixel 

from the 100-m increment closest to the elevation of the pixel. The atmospherically corrected dataset 

was further empirically adjusted using ground-based reflectance measurements from the Kandahar Air 

Field, Bagram Air Base, and Mazar-e-Sharif Airport as well as soil samples from two fallow fields. To

further improve the data quality, new calibration techniques were developed to address the atmospheric 

differences within a flight line. The lack of access to ground calibration sites and the size of the HyMap 

dataset required the acquisition of cross-cutting calibration flight lines (Kokaly and others, 2008). To 

refine the data quality of ground-calibrated flight lines, a multiplier correction was computed by crosscalibrating north-south flight lines with a flight line that passed over a ground calibration site. For each 

north-south flight line, the pixels in overlap regions between north-south and cross-cutting calibration 

lines, subject to slope, vegetation cover, and other restrictions, were used to develop these correction 

factors (Hoefen and others, 2010). The cross-calibration multiplier corrected any residual atmospheric 

contamination in the imaging spectrometer data that was not present in the spectra of the ground 

calibration site.

18B.2.3 Materials Maps and Presentation

HyMap reflectance data were processed using MICA (Material Identification and 

Characterization Algorithm), a module of the U.S. Geological Survey PRISM (Processing Routines in 

IDL for Spectroscopic Measurements) software (Kokaly and others, 2011). MICA compares the 

reflectance spectrum of each pixel of HyMap data to entries in a reference spectral library of minerals, 

vegetation, water, and other materials. The HyMap data were compared to 97 reference spectra of wellcharacterized mineral and material standards. The resulting maps of mineral and material distribution,

resampled to a 23×23-square-meter (m

2

) pixel grid, were used in the creation of thematic maps of 

surface mineral and material occurrences. HyMap data were analyzed twice. MICA was run using the 

set of minerals with absorption features in the visible and near-infrared wavelength region, producing 

the 1-micrometer (μm) map of iron-bearing minerals and other materials (King, Kokaly, and others, 

2011), and again using the minerals with absorption features in the shortwave infrared, producing the 

2-μm map of carbonates, phyllosilicates, sulfates, altered minerals, and other materials. For clarity of 

presentation, some individual classes in these two maps were bundled by combining selected specific 

mineral types (for example kaolinites, montmorillonites, and hematites) to reduce the number of mineral 

classes. The iron-bearing minerals map has 28 classes including pixels that were not mapped.

Iron-bearing minerals with different mineral compositions, but similar spectral features, are difficult to 

classify as specific mineral species. Thus, generic spectral classes, including several minerals with 

similar absorption features, such as Fe3+ type 1 and Fe3+ type 2 are depicted on the map. The carbonates, 

phyllosilicates, sulfates, and altered minerals map has 31 classes. Minerals with slightly different 

mineral compositions, but similar spectral features, are less easily discriminated; thus, some identified 

classes consist of several minerals with similar spectra, such as the chlorite or epidote class. When 
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1331

comparisons with reference spectra produced no viable match, a designation of “not classified” was 

assigned to a pixel.

18B.3 Geologic Setting

The Bakhud AOI includes portions of the Kandahar and Daykundi Provinces in south-central 

Afghanistan. The contrast-stretched natural-color Landsat Thematic Mapper image in fig. 18B–2 

provides a general overview of the Bakhud AOI terrain and is useful for understanding the general 

characteristics and distribution of surficial material including rocks and soil, unconsolidated sediments, 

vegetation, and water features.

18B.3.1 Topography

Elevations in the Bakhud AOI range between 1,073 and 2,701 m with most of the area being 

below 1,840 m (fig. 18B–3). The high areas are mostly east- to east-northeast-trending sharply defined 

mountain ranges and foothills that are commonly controlled by faults. The low areas below 1,840 m, 

largely underlain by unconsolidated Quaternary sediments and semiconsolidated Pliocene sedimentary 

rocks, are relatively flat, modern intermountain valleys. 

18B.3.2 Lithology and Structure

The oldest rocks in the Bakhud AOI are Silurian and Permian limestones and dolomites exposed 

in various fault blocks primarily in the northwestern portion of the area (fig. 18B–4). Mesozoic and 

Tertiary sedimentary rocks consisting of abundant limestone and dolomite cover much of the remaining 

area in fault blocks and isolated mountains and hills surrounded by Quaternary surficial deposits. 

Cretaceous felsic to mafic plutonic rocks intrude Mesozoic strata in the southwestern corner of the area. 

Two stages of Oligocene granitic rocks intrude the sedimentary rocks in the southern portion of the 

Bakhud AOI; a single exposure of Oligocene granitic rocks, surrounded by Quaternary surficial 

deposits, has been mapped in the northeastern portion of the area (Doebrich, and others, 2006). 

18B.3.3 Known Mineralization

Figure 18B–4 shows 17 locations where reconnaissance field geology has identified 

mineralization suggesting a potential for mineral resources may exist (Abdullah and others, 1977). The 

locations of these mineralized occurrences are also shown on the HyMap materials maps shown in 

figures 18B–5 through 18B–11 to illustrate how these known mineralized sites are reflected in the 

HyMap data analyses. The mineralogical characteristics of the mineralized locations are summarized in 

table 18B–1. These mineralization occurrences are of two primary types, polymetallic skarns and 

carbonate-hosted fluorspar and vein fluorspar deposits. Many of the noted mineral occurrences are 

relatively small and are at or below the spatial resolution of the HyMap data, but others are quite 

extensive.
1332 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 18B–2. Landsat Thematic Mapper natural-color image of the Bakhud area of interest. Geologic data from Doebrich and others (2006) and Peters 

and others (2007).
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1333

Figure 18B–3. Range of elevations in the Bakhud area of interest. 
1334 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 18B–4. Geologic map of the Bakhud area of interest (AOI) from 1:500,000-scale geologic map of Afghanistan (Doebrich and others, 2006). Sites of 

mineralization identified during reconnaissance field work in the Bakhud AOI (Abdullah and others, 1977) are indicated by deposit type.
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1335

Figure 18B–5. Map of iron-bearing minerals and other materials derived from HyMap data in the Bakhud area of interest. 
1336 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 18B–6. Map of carbonates, phyllosilicates, sulfates, altered minerals, and other materials derived from HyMap data in the Bakhud area of interest. 
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1337

Figure 18B–7. Map of distribution of carbonate minerals derived from HyMap data in the Bakhud area of interest. 
1338 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 18B–8. Map of distribution of clay and mica minerals derived from HyMap data in the Bakhud area of interest. 
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1339

Figure 18B–9. Map of distribution of iron oxides and hydroxides derived from HyMap data in the Bakhud area of interest. 
1340 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 18B–10. Map of distribution of common alteration minerals derived from HyMap data in the Bakhud area of interest. 
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1341

Figure 18B–11. Map of distribution of common secondary minerals derived from HyMap data in the Bakhud area of interest. 
1342 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Table 18B–1. Dominant ore, gangue, and alteration mineralogy of known sites of mineralization in the Bakhud area of

[Data are from Abdullah and others (1977). Cu, copper; Fe, iron; Pb, lead; Sn, tin; Zn, zinc; NA, not available] 

 interest. 

Name Deposit type Mineralogy Gangue Alteration

Gbarghey

Ziadan I

Darra-i-Nur (Dailanar,

Yakhata-Khum, Dik)

Chinar (Kanai)

Ziadan

Shin-Ghar

Outcrop no. 7757

Khwaji-Alam (Haji-Alam)

Unnamed

Surkhbed

Aumliyt

Ganighay

Bakhud

Saraw, I, II, III

Anaghey

Tirin Rurl

Chura

skarn Cu

skarn Sn

skarn ZnPb

skarn Fe

skarn Sn

skarn Sn

skarn Zn-Pb

skarn Fe

unclassified

vein 

fluorspar

skarn Fe

vein 

fluorspar

Fluorspar

vein 

fluorspar

vein 

fluorspar

skarn Fe

vein 

fluorspar

Magnetite; ludwigite; pyrite; chalcopyrite

Cassiterite; magnetite; malachite; azurite

Magnetite; chalcopyrite; cerussite; smithsonite;

bornite; malachite; limonite; pyrite; galena

Ironstone; hematite

Cassiterite; arsenopyrite; scheelite

Chalcopyrite; pyrite; sphalerite; galena; 

ludwigite; magnetite

Galena; chalcopyrite; pyrrhotite

Magnetite; copper sulfides; lead sulfides

Pyrite; chalcopyrite

Chalcopyrite; galena; azurite; malachite; 

chalcocite; fluorite; calcite

Magnetite; hematite; chalcopyrite; pyrite

Fluorite

Fluorite; sphalerite; galena; pyrite; 

chalcopyrite; tennantite; molybdenite; iron 

hydroxide; cerussite;anglesite; smithsonite; 

calamine; azurite; chrysocolla; chalcocite; 

silver native

Fluorite; barite; azurite; malachite; limonite

Fluorite

NA

Fluorite

No data

No data

Diopside; garnet; quartz

No data

Dolomite; rhodochrosite

Garnet; pyroxene; serpentine

No data

No data

No data

Fluorite; calcite

No data

Chalcedony

Calcite; quartz; barite; ankerite; 

dolomite; calcite; aragonite

Calcite

Calcite

NA

Calcite

Skarn alteration

Skarn alteration

Skarn alteration of diopside-garnet 

facies; silicification; limonitization

Skarn alteration

Skarn alteration

Skarn alteration of ludwigite facies; 

skarn alteration of magnetite facies;

overprinting serpentinization

Skarn alteration

Skarn alteration of magnetite facies

NA

Calcite-fluorite alteration

Skarn alteration

Fluoritization

Carbonatization ; fluoritization; 

silicification; chloritization; argillic 

alteration

Carbonatization; fluoritization; 

silicification

Calcite alteration; fluoritization

NA

Calcite alteration; fluoritization
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1343

The polymetallic skarns are characterized by the several sites in the Chinar district in the 

southwest corner of the Bakhud AOI. The principal mineralization is represented by tin, lead, zinc, and 

iron occurrences with subordinate copper and tungsten. Tin occurs in magnesian ludwigite and 

stannoborate skarns (Gbarghey, Chinar, and Shin-Ghar sites) and in calcareous skarns (Chinar site). 

Cassiterite is found in ferruginous-carbonate rocks (Chinar site). Tin-bearing skarns occur at the contacts 

between Upper Triassic dolomite and limestone and Oligocene granites. Lead and zinc deposits and 

occurrences are found in skarn-type copper-lead-zinc and lead-zinc rocks. Metalliferous 

pyroxene-garnet skarns were formed at the contacts between Silurian and Upper Triassic limestone and 

Oligocene granites (Abdullah and others, 1977). Economic concentrations of silver, cadmium, and 

occasionally copper are found in the skarn-type lead and zinc ores (Abdullah and others, 1977).

Carbonate-hosted fluorite deposits are represented by the Bakhud deposit (fig. 18B–4; table 

18B–1). The Bakhud fluorite deposit consists of a number of tabular zones dipping 5 to 20° and is 

located at the base of the angular unconformity between Upper Triassic dolomitic limestone of the 

Arghasu Formation and Upper Triassic to Lower Jurassic clay-marly sedimentary rocks of the Arghasu 

Formation. There are four discontinuous mineralized zones, which are 80 to 860 m long, 10 to 200 m 

wide, and 1.1 to 2.8 m thick. Alteration consists of recrystallized dolomite with silicification that is 

restricted to limestone in the underlying Alamghar Formation. Fluorite mineralization consists of 

abundant calcareous fluorite associated with lead and zinc sulfide minerals and less abundant siliceous 

fluorite (Abdullah and others, 1977).

The vein fluorite deposits are characterized by the Saraw I, II, and III sites (fig. 18B–4; table 

18B–1). The Saraw I, II, and III occurrences are contained in faulted Upper Triassic to Lower Jurassic 

limestone and in Middle to Upper Jurassic sandy limestone. The mineralized zones are nest-like, 

column-like bodies in area No. I, which is about 100 m2

, and are restricted to fault intersections in 

brecciated limestone containing fluorite, barite, and minor copper oxide minerals and limestone. The 

strongly jointed, white, greenish-gray and violet fluorite is commonly nontransparent or semitransparent. 

The No. II area is made up of conformable zones restricted to a stratigraphic contact between Upper 

Triassic to Lower Jurassic limestone and Middle to Upper Jurassic sandy limestone and consists of a 

270-m-long, 3-m-wide calcite zone containing fluorite lenses that are 2×3 m in size. The No. III area is 

hosted in Upper Triassic to Lower Jurassic dolomitized limestone and consists of a brecciated, 

mylonitized zone that is 40 to 50 m long and 3 to 5 m wide (Dovgal and others, 1971; Abdullah and 

others, 1977).

18B.4 Imaging Spectrometer Materials Maps of the Bakhud Area of Interest

Computer analysis of the HyMap imaging spectrometer data of the Bakhud AOI using spectrum 

matching techniques resulted in the identification of a wide variety of minerals exposed at the surface. 

Although the occurrence of certain minerals may suggest that mineralization processes may have once 

operated in the area, many of the minerals that were identified are also common rock-forming minerals 

or minerals that can be derived from the weathering of a wide variety of rock types. Consequently, the 

distribution patterns of the identified minerals and the geologic context in which they occur are 

extremely important in understanding the causes of mapped mineral occurrences and evaluating the 

possible potential for related mineral deposits.

Figures 18B–5 and 18B–6 depict the complete results of the computer analyses of the HyMap 

data, which show 28 possible classes of 1-μm materials and 32 classes of 2-μm materials, respectively, 

for the entire Bakhud AOI. Because of the large number of classes represented and the subtleties of the 

distribution patterns represented in these image maps, it is instructive to display these results as a series 

of image maps each depicting a selected group of minerals that are mineralogically related or commonly 

occur together in special geologic environments (figs. 18B–7 through 18B–11). Figure 18B–7 shows the 

distribution of carbonate minerals in the Bakhud AOI, whereas figure 18B–8 shows where clay minerals 

and micas occur. The distribution of iron oxide and hydroxide minerals are displayed in figure 18B–9. 
1344 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Minerals commonly found in hydrothermally altered rocks are mapped in figure 18B–10, and secondary 

minerals often associated with mineralized and/or weathered rocks are mapped in figure 18B–11. 

18B.4.1 Carbonate Minerals

Carbonate minerals, either calcite, dolomite, or iron carbonate, were mapped over a large 

majority of the Bakhud AOI (fig. 18B–7). In general, calcite appears to dominate the lowland areas, 

whereas dolomites are mostly exposed in the uplands. The variability of calcite and dolomite 

occurrences within known mapped lithologic units suggests that the HyMap data may be very useful for 

mapping subunits within the known units and generally improving the detail of existing geologic 

mapping. 

The widespread occurrence of carbonate minerals limits their usefulness for revealing potentially 

mineralized areas characterized by calcite alteration (table 18B–1; fig. 18B–4) or are formed in 

carbonate rocks. Consequently, none of the known mineralized areas are highlighted by the carbonate 

minerals map, nor are any previously unknown areas of potential mineralization identified. 

18B.4.2 Clays and Micas

With the possible exception of the Aumliyt site (table 18B–1; fig. 18B–8), none of the known 

mineralized areas are associated with a distinct concentration of clay or mica minerals. The Aumliyt site 

is within 700 m of a cluster of pixels of chlorite or epidote, and chlorite and epidote are frequently 

associated with skarns.

18B.4.3 Iron Oxides and Hydroxides

Only the Bakhud and Ganighay sites of known mineralization are located within distinct 

concentrations of iron oxide and hydroxide minerals (fig. 18B–9). The Bakhud site is surrounded by 

conspicuous northeast-trending bands of goethite intermixed with Fe-hydroxide.

The Ganighay site lies only 200 m south of a distinct, isolated concentration of goethite and 

Fe-hydroxide. Other conspicuous concentrations of iron oxide and hydroxide minerals that occur in the 

Bakhud AOI are not associated with sites of known mineralization. A very large concentration of 

goethite, Fe-hydroxide, and minor hematite occurs 13 km east-southeast of the Bakhud site. An 

east-trending band of hematite concentrations extends more than 10 km in the central part of the Bakhud 

AOI. The individual concentrations occur in several different lithologic units (Doebrich and others, 

2006, Abdullah and others 1977), but are in general associated with red-colored rocks (fig. 18B–2). A 

dense concentration of goethite, iron hydroxide, and hematite occurs in Quaternary sediments on both 

sides of the major northeast-trending drainage in the northern part of the Bakhud AOI. The surficial 

deposits in this area are distinctly reddish compared to the surrounding Quaternary sediments in the 

same lithologic unit. These three mineral concentrations will be discussed in more detail in the anomaly 

report (King, Johnson, and others, 2011). 

18B.4.4 Common Alteration Minerals

Most of the minerals in this group are commonly present in hydrothermally altered rocks 

associated with epithermal mineral deposits (fig. 18B–10). Consequently, where they occur in distinct 

clusters is of great interest in terms of potential mineral deposits. However, the pixel counts shown in 

the explanation of figure 18B–10 indicate that with the exception of the “Chlorite or epidote” class, 

which are not diagnostic of hydrothermal alteration, very few pixels of common alteration minerals were 

detected and mapped, and there are no concentrations associated with any of the known sites of 

mineralization. A concentration of kaolinite (kaolinite and muscovite, clay, or calcite) does occur with 
Chapter 18B. Analysis of Imaging Spectrometer Data for the Bakhud Area of Interest 1345

the goethite, Fe-hydroxide, and hematite concentration straddling the major northeast-trending drainage 

in the northern part of the Bakhud AOI shown in figure 18B–9.

18B.4.5 Common Secondary Minerals

Secondary minerals, especially “Serpentine,” “Serpentine or calcite and dolomite,” and 

subsidiary “Epidote” and “Chlorite or epidote” classes (fig. 18B–11) are widespread in the Bakhud AOI. 

The “Serpentine” and “Serpentine or calcite and dolomite” classes are predominantly exposed in the 

more mountainous areas of the AOI, whereas the “Epidote” and “Chlorite or epidote” classes occur 

mostly in the lower rolling hills and flatlands areas. With the exception of the “Epidote” and “Chlorite or 

epidote” concentration near the Aumliyt area of known mineralization previously mentioned in the 

discussion of clays and micas, no distinct concentrations of secondary minerals are clearly associated 

with areas of known mineralization. There are, however, several small clusters of “Epidote” and 

“Chlorite or epidote” classes of unknown origin in various parts of the Bakhud AOI.

18B.5 Summary

Carbonate rocks, both limestones and dolomites, are the predominant rock types in the Bakhud 

area of interest. Consequently, calcite and dolomite are mapped for a large percentage of the HyMap 

pixels in the area. Variations between calcite and dolomite within mapped lithologic units indicate that 

the HyMap data should be useful for adding lithologic detail to existing geologic map units and 

increasing the overall level of detail in available geologic maps.

The largely stratigraphically controlled known fluorite and polymetallic skarn deposits, which 

are both hosted by carbonate rocks, are effectively masked by the overall preponderance of carbonate 

minerals in the area. Nevertheless, iron oxide and hydroxide were mapped near the Bakhud and 

Ganighay sites. Several other iron oxide and hydroxide mineral concentrations occur in the AOI that are 

not associated with known mineralization (see section on mineral anomalies, this volume). These 

concentrations are conspicuously related to exposed red-colored rocks.

Minerals that are commonly associated with hydrothermally altered rocks and are detectable with 

HyMap imaging spectrometer data are mostly absent from the Bakhud AOI, with the exception of 

epidote. Epidote appears to be associated with the Aumliyt site of known mineralization and small 

clusters of epidote occur at various other places in the Bakhud AOI. The hydrothermal alteration 

minerals that are generally found in epithermal mineralization systems, such as porphyry copper and 

hydrothermal gold deposits, include buddingtonite, jarosite, alunite, kaolinite, pyrophyllite, and hydrated 

silica (quartz-sericite-pyrite, argillic, and advanced argillic alteration). The lack of these minerals in the 

Bakhud AOI suggests that these types of deposits are not present or, if present, are deeply eroded.

18B.6 References Cited

Abdullah, Sh., Chmyriov, V.M., Stazhilo-Alekseev, K.F., Dronov, V.I., Gannan, P.J., Rossovskiy, L.N., 

Kafarskiy, A.Kh., and Malyarov, E.P., 1977, Mineral resources of Afghanistan (2d ed.): Kabul, 

Afghanistan, Republic of Afghanistan Geological and Mineral Survey, 419 p.

Cocks, T., Jenssen, R., Stewart, A., Wilson, I., and Shields, T., 1998, The HyMap airborne hyperspectral 

sensor—The system, calibration and performance, in

Davis, P.A., 2007, Landsat ETM+ false-color image mosaics of Afghanistan: U.S. Geological Survey 

Open-File Report 2007–1029, 22 p. (Also available at 

Schaepman, M., Schlapfer, D., and Itten, K.I., 

eds., Proceedings of the 1st EARSeL Workshop on Imaging Spectroscopy, 6–8 October 1998, Zurich: 

Paris, European Association of Remote Sensing Laboratories, p. 37–43.

http://pubs.usgs.gov/of/2007/1029/

Doebrich, J.L., and Wahl, R.R., comps., with contributions by Doebrich, J.L., Wahl, R.R., Ludington, 

S.D., Chirico, P.G., Wandrey, C.J., Bohannon, R.G., Orris, G.J., Bliss, J.D., Wasy, Abdul, and 

Younusi, M.O., 2006, Geologic and mineral resource map of Afghanistan: U.S. Geological Survey 

Open File Report 2006–1038, scale 1:850,000, available at 

.)

http://pubs.usgs.gov/of/2006/1038/.
1346 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Dovgal, Yu. M., Chalyan, M.A., Nagalev, V.S., Demin, A.N., Vaulin, V.A., Belich, A.I., Sonin, I.I., 

Kononykhin, E.T., Zharikhin, K.G., Maksimov, N.P., Skvortsov, N.S., and Kharitonov, A.P., 1971, 

The geology and minerals of the south-eastern part of central Afghanistan: Kabul, Afghanistan 

Department of Geological and Mineral Survey, scale 1:200,000.

Hoefen, T.M., Kokaly, R.F., and King, T.V.V., 2010, Calibration of HyMap data covering the country 

of Afghanistan, in Proceedings of the 15th Australasian Remote Sensing and Photogrammetry 

Conference, Alice Springs, Australia, September 12–17, 2010, p. 409, available at 

http://dl.dropbox.com/u/81114/15ARSPC-Proceedings.zip/.

King, T.V.V., Kokaly, R.F., Hoefen, T.M., Dudek, K. and Livo, K.E., 2011, Surface materials map of 

Afghanistan—Iron-bearing minerals and other materials: U.S. Geological Survey Scientific 

Investigations Map 3152–B.

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