Chapter 4B. Analysis of Imaging Spectrometer Data for the 

Balkhab Copper Area of Interest

By Todd M. Hoefen and Michaela R. Johnson

Abstract

Hyperspectral remote sensing data collected over the Balkhab area of interest (AOI) in northern 

Afghanistan were analyzed with spectroscopic methods to identify the occurrence of selected materials 

at the surface. The area is believed to have the potential for volcanogenic massive sulfide, coal, and 

possible gold deposits. Absorption features in the spectra of HyMap data were compared to a reference 

library of spectra for known materials. Carbonates and vegetation cover most of the Balkhab AOI. 

Distinct patterns of muscovite, kaolinite, chlorite or epidote, and montmorillonite occur in localized 

patterns, especially along the river that crosses through the center of the AOI. Analysis of the HyMap 

data also detected small but distinct occurrences of jarosite, hydrated silica, and pyrophyllite, all of 

which may be associated with hydrothermal alteration. The Balkhab Prospect is mapped within the 

vegetation class, but the surrounding Ordovician-age rocks are mapped as illite, muscovite, chlorite or 

epidote, calcite, and Fe2+ Fe3+ Type 2 and Fe2+ Fe3+ Type 1 mineral classes.

4B.1 Introduction

Past studies of geologic data of Afghanistan revealed numerous areas with indications of 

potential mineral resources of various types (Abdullah and others, 1977; Peters and others, 2007).

Several of these areas were selected for additional studies using imaging spectroscopy to characterize 

surface materials. Imaging spectroscopy is an advanced type of remote sensing also known as 

hyperspectral remote sensing. One such area selected for imaging spectroscopy is the Balkhab area of 

interest (AOI) in northern Afghanistan, which is approximately 230 kilometers (km) northwest of Kabul 

(fig. 4B–1). The area is believed to have the potential for volcanogenic massive sulfide, coal, and 

possible gold deposits. 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 spectroscopic data analyses and 

identifies sites within the Balkhab AOI that deserve further investigation, especially detailed geologic 

mapping, lithologic sampling, and geochemical studies. 

4B.2 Data Collection and Processing

In 2007, imaging spectrometer data were acquired over most of Afghanistan as part of the 

U.S. Geological Survey (USGS) project “Oil and Gas Resources Assessment of the Katawaz and 

Helmand Basins.” These data were collected to characterize surface materials in support of assessments 

of resources (coal, water, minerals, oil, and gas) and earthquake hazards in the country (King and others, 

2010). Imaging spectrometers measure 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 absorption features that arise from specific chemical 

transitions and molecular bonds that provide compositional information about surface materials. 

Imaging spectrometer data can be used to characterize only the upper surface materials and not 

subsurface composition or structure. Subsurface processes can be indicated, however, by the distribution 

of surface materials.
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 249

Figure 4B–1. Index map of the Balkhab area of interest, northeastern Afghanistan.

4B.2.1 Collection of Imaging Spectrometer Data

The HyMap imaging spectrometer (Cocks and others, 1998) was flown over Afghanistan from 

August 22 to October 2, 2007 (Kokaly and others, 2008). HyMap has 512 cross-track pixels, and covers 

the wavelength range from 0.43 to 2.48 micrometers (μm) in 128 channels. The imaging spectrometer 

was flown on a WB-57 high-altitude aircraft at approximately 50,000 feet. There were 207 standard data 

flight lines and 11 cross-cutting calibration lines collected over Afghanistan for a total of 218 flight lines 

covering a surface area of 438,012 square kilometers (km2

) (Kokaly and others, 2008). Data were 

received in scaled radiance (calibrated to National Institute of Standards and Technology reference 

materials). Before processing, four channels that had low signal-to-noise ratios and (or) were in 

wavelength regions that overlapped between detectors were removed from the image cubes. Each flight 

line was georeferenced to Landsat base imagery in Universal Transverse Mercator (UTM) projection 

(Davis, 2007). 

4B.2.2 Calibration

HyMap data were converted from radiance to reflectance using a multi-step process. This 

calibration process removed the influence of the solar irradiance function, atmospheric absorptions and 

residual instrument artifacts, resulting in reflectance spectra that have spectral features that arise from 

the material composition of the surface. Because of the extreme topographic relief and restricted access 
250 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

to ground calibration sites, modifications to the typical USGS calibration procedures were required to 

calibrate the 2007 Afghanistan HyMap dataset (Hoefen and others, 2010).

In the first step of the calibration process, the radiance data were converted to apparent surface 

reflectance using the radiative transfer correction program Atmospheric CORrection Now (ACORN; 

ImSpec LLC, Palmdale, Calif.). The ACORN program was run multiple times for each flight line using 

average elevations in 100-meter (m) increments, covering the range of minimum to maximum elevations 

encountered within the flight line. A single atmospherically corrected image was assembled from these 

elevation-incremented ACORN results by determining the elevation of each HyMap pixel and selecting 

the atmospherically corrected pixel from the 100-m increment closest to that elevation.

Each assembled atmospherically corrected image was further empirically adjusted using groundbased reflectance measurements from a ground calibration site. Spectra of five ground calibration sites 

were collected in Afghanistan: field spectra from Kandahar Air Field, Bagram Air Base, and

Mazar-e-Sharif Airport, as well as laboratory spectra of soil samples from two fallow fields in Kabul.

These were used to calculate empirical correction factors using the pixels of atmospherically corrected 

HyMap data in the flight lines that passed over the sites. The empirical correction from the closest 

calibration site to each flight line was then applied.

To further improve the data quality, an additional calibration step was taken to address the 

atmospheric differences caused, in part, by the large distances between the calibration sites and the 

survey areas. The large distances were the result of a lack of safe access to ground calibration sites. The 

duration of the airborne survey and variation in time of day during which flight lines were acquired also 

resulted in differences in atmospheric conditions between standard flight lines and lines over ground 

calibration sites. Over the course of the data collection process, the sun angle, atmospheric water vapor, 

and atmospheric scattering differed for each flight line. To compensate for this variation, cross-cutting 

calibration flight lines over the ground calibration areas were acquired (Kokaly and others, 2008), and 

used to refine the reflectance calculation for standard data lines. A multiplier correction for each 

standard data line, typically oriented north-south, was derived using the pixels of overlap with the

well-calibrated cross-cutting line that intersected it, subject to slope, vegetation cover, and other 

restrictions on pixel selection (Hoefen and others, 2010). As a result, the localized cross-calibration 

multiplier, derived from the region of overlap, reduced residual atmospheric contamination in the 

imaging spectrometer data that may have been present after the ground calibration step.

4B.2.3 Materials Maps and Presentation

After the calibration process, the reflectance data were georeferenced and then analyzed using 

the Material Identification and Characterization Algorithm (MICA), a module of the USGS Processing 

Routines in Interactive Data Language (IDL) for Spectroscopic Measurements (PRISM) software 

(Kokaly, 2011). The MICA analysis compared 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 well-characterized mineral and material standards. The 

best spectral match to each pixel was determined, and the results were clustered into classes of materials 

discussed next. The resulting maps of material distribution, resampled to a 23 × 23-m square pixel grid, 

were mosaicked to create thematic maps of surface mineral occurrences over the full data set covering 

Afghanistan.

The MICA module was applied to HyMap data twice in order to present the distribution of two 

categories of minerals naturally separated in the wavelength regions of their primary absorption features.

MICA was applied using the subset of minerals with absorption features in (1) the visible and nearinfrared wavelength region to produce the 1-μm map of iron-bearing minerals and other materials (King, 

Kokaly, and others, 2011), and (2) the shortwave infrared region to produce the 2-μm map of 

carbonates, phyllosilicates, sulfates, altered minerals, and other materials (Kokaly and others, 2011). For 

clarity of presentation, some individual classes in these two maps were bundled by combining selected 
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 251

mineral types (for example, all montmorillonites or all kaolinites) and representing them with the same 

color in order to reduce the number of colors required to represent the mineral classes. 

The iron-bearing minerals analysis includes 28 classes. Iron-bearing minerals with different 

mineral compositions but similar broad 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 32 classes. Minerals with slightly different mineral compositions but 

comparable spectral features are less easily distinguished; therefore, some identified classes consist of 

several minerals with similar spectra, such as the “chlorite or epidote” class. When comparisons with 

reference spectra resulted in no viable match, a designation of “not classified” was assigned to a pixel.

4B.3 Geologic Setting of the Balkhab AOI

The Balkhab AOI is mainly within Sari Pul Province in northern Afghanistan, with small 

sections located in Balkh and Samangan Provinces. The Balkhab AOI is 1,858 km2, of which the 

Balkhab Prospect subarea covers 321 km2. The contrast-enhanced stretch of the natural-color composite 

of Landsat Thematic Mapper bands shown in figure 4B–2 provides a general overview of the Balkhab 

AOI terrain and is useful for understanding the general characteristics and distribution of surficial 

material, including rocks and soil, unconsolidated sediments, vegetation, and hydrologic features. 

4B.3.1 Topography

Land elevation within the Balkhab AOI ranges from 951 to 4,028 m (fig. 4B–3). The low areas 

within the Balkhab AOI follow a river that crosses the region lengthwise, flowing from the southwest 

toward the northeast. The highest areas surround the river basins throughout the AOI. The main 

population center is the district center of Balkhab in the western part of the AOI. 

4B.3.2 Lithology and Structure

Rocks in the Balkhab area range in age from Ordovician to Early Miocene (fig. 4B–4; Doebrich 

and Wahl, 2006; Abdullah and Chmyriov, 1977). The oldest rocks are Ordovician-age stratified 

formations composed of sandstone, siltstone, shale, limestone, and chert that are exposed along parts of 

the river basin. Also present along the river basin and the lower sections of' secondary streams are 

Silurian-Devonian schists and sheared metamorphic rocks. The only other intrusive type rocks are of 

Mississippian age and consist of dunite, peridotite, and serpentine, all of which occur along the southern 

border of the AOI just south of the Balkhab Prospect subarea. Two of the younger, abundant rock units 

in the Balkhab AOI are Late Cretaceous undifferentiated rocks of sandstone, siltstone, clay, limestone, 

marl, conglomerate, gypsum, and redstone, and Maestrichtian-Paleocene rocks of limestone, marl, 

dolomite, sandstone, clay, siltstone, gypsum, and conglomerate. The main sedimentary units seem to 

occur at higher elevations.
252 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–2. Contrast-enhanced Landsat Thematic Mapper natural color image of the Balkhab area of interest. 

Geology from digital geologic map of Afghanistan (Abdullah and Chmyriov, 1977; Doebrich and Wahl, 2006; Peters 

and others, 2007).

4B.3.3 Known Mineralization

Figure 4B–5 shows one location where mineralization having a potential for mineral resource 

development may exist (Abdullah and others, 1977; Peters and others, 2007). There is only one 

volcanogenic massive sulfide prospect in the Balkhab AOI. The characteristics of the mineralized 

location are summarized in table 4B–1. 

Table 4B–1. Sites of known mineralization in the Balkhab area of interest. [Data are from Peters and others (2007). Cu, copper; VMS, volcanogenic massive sulfide]

Name Deposit type Major commodity Deposit size Alteration Mineralogy Gangue

Balkhab VMS Cu Occurrence Silicification; limonitization Pyrite; malachite; galena Quartz

Copper in the Balkhab Prospect is hosted in sulfide rich rocks where pyrite, galena, and 

malachite are present. The Balkhab Prospect plus various other copper showings occur in Paleozoic 

rocks (Abdullah and others, 1977; Doebrich and Wahl, 2006; Peters and others, 2007). The largest beds 
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 253

are up to 5 km long with thicknesses from 300 to 400 m (Abdullah and others, 1977; Doebrich and 

Wahl, 2006). Smaller beds are believed to be 300 to 400 m long with thicknesses of 20 to 50 m. 

Figure 4B–3. Map showing the range of elevations in the Balkhab area of interest. 

4B.3.4 Data Limitations

Geographic registration between various datasets is not always possible because of differences in 

collection methods and resolution. The geographic accuracy and quality of each dataset is limited by the 

original source. Significant efforts were made to ensure the geographic accuracy of the HyMap data 

(Kokaly and others, 2008; Hoefen and others, 2010); however, exact registration between previously 

published known mineral occurrences, fault traces, geologic units, and structural boundaries in 

comparison to the HyMap data may not be ideal. To resolve additional details, the digital versions of 

these maps can be viewed at higher spatial resolutions than is possible for a single-page printed map. 
254 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–4. Geologic map of the Balkhab area of interest. Geology from digital geologic map of Afghanistan 

(Abdullah and Chmyriov, 1977; Doebrich and Wahl, 2006; Peters and others, 2007).
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 255

Figure 4B–5. Sites of known mineralization by deposit type (Peters and others, 2007) on the geologic map of the 

Balkhab AOI from the digital geologic map of Afghanistan (Abdullah and Chmyriov, 1977; Doebrich and Wahl, 2006; 

Peters and others, 2007).

4B.4 Mineral Maps of the Balkhab Area of Interest

Analysis of the HyMap imaging spectrometer data of the Balkhab AOI using spectroscopic 

methods resulted in the identification of a wide variety of minerals exposed at the surface. Although the 

occurrence of certain minerals 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, knowledge about 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.

Figure 4B–6 depicts the results of the MICA analyses of the HyMap data for the Balkhab AOI 

for the 2-μm materials, which include carbonates, phyllosilicates, sulfates, altered minerals, and other 

materials. The carbonate mineral groups cover most of the Balkhab AOI, as indicated by pixels mapped 

as calcite and calcite mixed with clay/mica. Pixels matching pure muscovite or illite spectra occur over 

large contiguous areas in the central and western portions of the river valley. Distinct patterns of 

kaolinite occur in spatially localized patterns, especially in the center and northwestern areas of the AOI. 

Large areas of chlorite or epidote were concentrated in the central river basin west and southwest of the 

Balkhab Prospect. Montmorillonite is present throughout the AOI in localized concentrations, usually in 

the river valleys.
256 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–7 shows the mapping results for the iron-bearing minerals. The iron-bearing materials 

map is dominated by goethite to the southwest and Fe 2+ Fe3+ Type 2 and Fe2+ Type 1 along the river 

valley. There are a few spatially distinct occurrences of hematite and epidote throughout the AOI.

Figure 4B–6. Map of carbonates, phyllosilicates, sulfates, altered minerals, and other materials derived from 

HyMap data in the Balkhab area of interest. 

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 

specific geologic environments. Figure 4B–8 shows the distribution of carbonate minerals in the 

Balkhab AOI whereas figure 4B–9 shows where clay minerals and micas occur. The distribution of iron 

oxide and hydroxide minerals are displayed in figure 4B–10. Minerals commonly found in 

hydrothermally altered rocks are shown in figure 4B–11, and secondary minerals often associated with 

mineralized and (or) weathered rocks are shown in figure 4B–12. 

4B.4.1 Carbonate Minerals

Carbonate minerals, either calcite or dolomite, were detected over a large majority of the 

Balkhab AOI (fig. 4B–8). In general, calcite and calcite + muscovite/illite group minerals are detected 

throughout the AOI and within almost every geologic unit. Calcite + montmorillonite occurs along the 

upper part of the river valley. Dolomite or dolomite mixed with calcite and (or) clay occurs in smaller 
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 257

contiguous areas that are mostly in the south-central and southwestern areas of the AOI. The known 

mineralized area is not highlighted in the carbonate minerals map. 

Figure 4B–7. Map of iron-bearing minerals and other materials derived from HyMap data in the Balkhab area of 

interest. 

4B.4.2 Clays and Micas

Abundant detections of muscovite and illite were mapped in units of Ordovician-age rocks along 

the central valley of the Balkhab AOI (fig. 4B–9). In addition, illites and muscovites were also detected 

within nearby Rhaetian and Early-Middle Jurassic stratified rock formations. Chlorite or epidote was 

detected in Ordovician-age stratified formations and Late Triassic intrusive rocks. Kaolinites were 

distributed within the Ordovician, Rhaetian, Early-Middle Jurassic, and Late Cretaceous rock formations 

in the river valley. The kaolinite occurrences start to occur 3.7 km northwest of the Balkhab Prospect 

(along a fault) and continue to map in the central to northeastern part of the AOI. South and west of this 

fault line, chlorite or epidote, muscovite, and illite dominate, whereas north and east of this fault, 

kaolinites are the dominant mineral group; this is especially true for the Ordovician rocks. A small 

occurrence of pyrophyllite (lat 35°

29'38"N., long 66°47'47"E.) was mapped approximately 9.7 km to the 

south and slightly to the east of the Balkhab Prospect. 
258 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–8. Map of distribution of carbonate minerals derived from HyMap data in the Balkhab area of interest. 

4B.4.3 Iron Oxides and Hydroxides

The Balkhab AOI contains small conspicuous areas of hematite in the western, southwestern, 

east central, and eastern portions of the area (fig. 4B–10) in Ordovician and Late Cretaceous age units. 

The description of the Late Cretaceous units includes redstone (Abdullah and Chmyriov, 1977; Doebrich 

and Wahl, 2006), which supports the HyMap mineral detections. The hematite is usually located within 

or near areas of goethite or Fe-hydroxide. Pixels mapped as goethite and Fe-hydroxide are more 

widespread across the AOI compared to hematite, and primarily occur in the western and southern parts 

of the AOI. Two spatially distinct areas of goethite and Fe-hydroxide are present in the central western 

part of the AOI (lat 35°

23'57"N., long 66°38'49"E., and lat 35°24'06"N., long. 66°31'08"E.). Jarosite is 

mapped approximately 1.9 km south of the Balkhab Prospect in both the 1-μm (fig. 4B–7) and 2-μm 

(fig. 4B–6) materials maps. Jarosite is also found in smaller concentrations throughout the western 

portion of the AOI. Spatially distinct groupings of epidote were mapped in the north-central and 

southwestern parts of the AOI along the border (fig.4B–10). 
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 259

Figure 4B–9. Map of distribution of clay and mica minerals derived from HyMap data in the Balkhab area of 

interest. 

4B.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. 4B–11). Consequently, where they occur in distinct 

clusters is of great interest in terms of potential mineral deposits. A small occurrence of pyrophyllite is 

present approximately 9.7 km to the south and slightly east of the Balkhab Prospect. Jarosite and 

hydrated silica were detected along a unit approximately 1.9 km south of the Balkhab Prospect (near lat 

35°33'32"N., long 66°45'24"E.). Because of the importance of pyrophyllite as an indicator of potential 

epithermal processes, these two occurrences should be examined in greater detail as part of subsequent 

geophysical and geologic field investigations. 

Kaolinite was detected in the river valleys in the southwestern and northeastern portions of the 

AOI. The chlorite or epidote class maps throughout the central river valley in the AOI. Carbonate 

(iron-bearing) is associated with the chlorite or epidote mineral group in the central valley (near 

lat 35°34'32"N., long 66°44'13"E.). The iron-carbonate is shown in greater detail in King, Johnson, and 

others (2011).
260 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–10. Map of distribution of iron oxide and hydroxide derived from HyMap data in the Balkhab area of 

interest. 

4B.4.5 Common Secondary Minerals

Secondary minerals, in the epidote, chlorite, and chlorite or epidote classes (fig. 4B–12) are 

primarily detected along the central river valley. In addition, there are well-defined groups of epidote 

and chlorite or epidote in the northeastern part of the Balkhab AOI. In the southern and western parts of 

the AOI, serpentine maps within the Silurian-Devonian, Late Permian, and Ordovician-age stratified 

formations and the Mississippian intrusive rocks. 

4B.4.6 Balkhab Prospect Subarea

Detailed maps of the Balkhab Prospect subarea are presented in figures 4B–13 through 4B–23. 

The Balkhab Prospect is described as a volcanogenic massive sulfide (Peters and others, 2007, Abdullah 

and Chmyriov, 1977; Doebrich and Wahl, 2006). Figures 4B–13 through 4B–16 show, respectively, the 

contrast-enhanced natural color Landsat imagery, elevation data, geology, and a known mineral 

occurrence.
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 261

Figure 4B–11. Map of distribution of common alteration minerals derived from HyMap data in the Balkhab area of 

interest. 

Figure 4B–17 depicts the results of the MICA analyses of the HyMap data for the Balkhab 

Prospect subarea for the 2-μm materials, which include clays, carbonates, sulfates, altered minerals, and 

other materials. The carbonate mineral groups cover a large percentage of the Balkhab Prospect area. 

Pixels mapped as muscovite or illite are present over large contiguous areas in the central and 

southwestern areas along the river valley. Kaolinite is detected as small distinct clusters, especially in 

the south-central and northwestern parts of the subarea. Large areas of chlorite or epidote group minerals 

were found concentrated in the central river basin west and southwest of the Balkhab Prospect (lat 

35°

34'46"N., long 66°44'01"E., and lat 35°32'13"N., long 66°41'03"E.). Montmorillonite is detected in 

localized groups commonly in the river valleys within the central part of the AOI. The close proximity 

of jarosite and hydrated silica minerals (lat 35°33'32"N., long 66°45'24"E.) and their importance as 

indicators of potential hydrothermal activity suggests the need for additional geophysical and 

geochemical investigation in the AOI.
262 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–12. Map of distribution of common secondary minerals derived from HyMap data in the Balkhab area 

of interest. 

If the known mineral occurrence location is accurate, then the Balkhab Prospect maps within the 

vegetation class, but appears to be located within Ordovician-age rocks. The Ordovician rocks in this 

area generally match the reference spectra of illite, muscovite, chlorite or epidote, and calcite. Minerals 

reported to be associated with the Balkhab Prospect include pyrite, malachite and galena (Peters and 

others, 2007; Abdullah and others, 1977). Pyrite and galena lack unique spectral features in the 

wavelength region of the HyMap data, thereby making detections of these minerals difficult. Malachite 

is not a commonly occurring mineral, and therefore, was not included in the spectral library. Future 

work could benefit from the addition of malachite to the spectral library, as this mineral could 

potentially be detected and mapped if it occurs in significant quantities that are exposed at the surface.
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 263

Figure 4B–13. Contrast-enhanced Landsat Thematic Mapper natural color image of the Balkhab Prospect 

subarea. Geologic units and faults are from Abdullah and Chmyriov (1977) and Doebrich and Wahl (2006). 

Figure 4B–18 shows the results for the iron-bearing minerals. The majority of the iron-bearing 

minerals detected in the Balkhab Prospect subarea are mapped as Fe2+ Fe3+ Type 2 and Fe2+ Type 1. 

Goethite maps in the valleys throughout the subarea, but at much lower levels then the surrounding 

areas. Again, the Balkhab Prospect is mapped within the vegetation class, but the surrounding 

Ordovician-age rocks are mapped as the Fe2+ Fe3+ Type 2 and Fe2+ Fe3+ Type 1 mineral classes.
264 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–14.

As noted earlier, the large number of classes represented and the subtleties of the distribution 

patterns represented make it useful to display the subarea 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. 4B–19 through 4B–23). Figure 4B–19 shows the distribution of 

carbonate minerals in the Balkhab Prospect subarea, mainly distributed at higher elevations. Dolomite 

and dolomite + montmorillonite/calcite group minerals were detected in small clusters in the 

southwestern portion of the subarea. Figure 4B–20 shows where clay minerals and micas occur. Chlorite 

or epidote and illite dominate the image along the river valley. A distinct boundary between the 

muscovites and illites and the kaolinite class minerals is observed in this region. The kaolinite group 

minerals start to occur 3.7 km northwest of the Balkhab Prospect along a fault and continue eastward 

into the central to northeastern area of the AOI. South and west of this fault line, chlorite or epidote, 

muscovite, and illite dominate, whereas north and east of this fault, the kaolinites are the dominant 

mineral group. The distributions of iron oxide and hydroxide minerals are displayed in figure 4B–21. 

This region lacks many iron oxide and hydroxide minerals, although small patches of goethite are 

Elevations and topography of the Balkhab area of interest. 
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 265

detected throughout the subarea. Minerals commonly found in hydrothermally altered rocks are mapped 

in figure 4B–22, and again, the chlorite or epidote and kaolinite group minerals are the major classes. A 

small occurrence of jarosite and hydrated silica is detected in the central portion of the subarea. 

Secondary minerals often associated with mineralized and (or) weathered rocks are mapped in 

figure 4B–23. The chlorite or epidote class is predominant, and serpentine minerals are mostly present in 

the southwestern part of the subarea. 

Figure 4B–15. Geologic map of the Balkhab Prospect subarea (from Abdullah and Chmyriov, 1977; Doebrich and 

Wahl, 2006; Peters and others, 2007).
266 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–16. Sites of known mineralization by deposit type (Peters and others, 2007) on the geologic map of the 

Balkhab Prospect subarea (from Abdullah and Chmyriov, 1977; Doebrich and Wahl, 2006; Peters and others, 

2007).

4B.5 Summary 

Carbonate minerals are detected throughout most of the Balkhab area of interest (AOI). 

Muscovites and illites were detected in greatest concentration in the mapped units of Ordovician and 

Silurian-Devonian age rocks in the central to southwest-central region of the Balkhab AOI, and in the 

adjacent units, suggesting that mineral distributions detected with HyMap data could be used to refine 

the locations of lithologic contacts. Epidote and chlorite were found in spatially consistent patterns 

concentrated along the central river basin west and southwest of the Balkhab Copper Prospect. 

Kaolinites were distributed within the Ordovician, Rhaetian, Early-Middle Jurassic, and Late Cretaceous

rock formations in the river valley. The largest occurrences of kaolinite in the AOI are located in the 

central and northeastern river valleys. Two areas that may be associated with hydrothermal alteration are 

an area of pyrophyllite in the southern part of the AOI (lat 35°

29'38"N., long 66°47'47"E.) and an area of 

jarosite and hydrated silica in the central part (lat 35°33'32"N., long 66°45'24"E.). These two areas 

should be studied in more detail with additional geophysical and geochemical characterization. Goethite 

and Fe2+ Fe3+ Type 2 dominate the iron-bearing materials map. Several areas of hematite are detected 

within areas of redstone, and are consistent with the geologic map. 
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 267

Figure 4B–17. Map of carbonates, phyllosilicates, sulfates, altered minerals, and other materials derived from 

HyMap data in the Balkhab Prospect subarea.
268 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–18. Map of iron-bearing minerals and other materials derived from HyMap data in the Balkhab 

Prospect subarea.
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 269

Figure 4B–19. Map of distribution of carbonate minerals derived from HyMap data in the Balkhab Prospect 

subarea.
270 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–20. Map of distribution of clay and mica minerals derived from HyMap data in the Balkhab Prospect 

subarea.
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 271

Figure 4B–21. Map of distribution of iron oxide and hydroxide derived from HyMap data in the Balkhab Prospect 

subarea.
272 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 4B–22. Map of distribution of common alteration minerals derived from HyMap data in the Balkhab 

Prospect subarea.
Chapter 4B. Analysis of Imaging Spectrometer Data for the Balkhab Copper Area of Interest 273

Figure 4B–23. Map of distribution of common secondary minerals derived from HyMap data in the Balkhab 

Prospect subarea.

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