Chapter 17B. Analysis of Imaging Spectrometer Data for the

Baghlan Area of Interest

By Todd M. Hoefen, Stuart A. Giles, and Raymond F. Kokaly

Abstract

Hyperspectral remote sensing data collected over the Baghlan area of interest (AOI) in northeast 

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

surficial material classes. Absorption features in the spectra of HyMap data were compared to a 

reference library of spectra of known materials. Carbonates and vegetation cover most of the Baghlan 

AOI. Distinct patterns of muscovite, kaolinite, chlorite or epidote, montmorillonite, serpentine, and 

dolomite + montmorillonite/calcite occur in localized patterns throughout the AOI. HyMap data were

found to be an effective tool for detecting and mapping gypsum in areas adjacent to the bedded gypsum 

prospects at Nalak and Nadr and to a lesser extent at the Kamard and Dasht-i-Safed prospects. Gypsum 

was also mapped in several other areas throughout the AOI.

17B.1 Introduction

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

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

Several of these areas were selected for follow-on studies using imaging spectroscopy to characterize 

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

hyperspectral remote sensing. One area selected for study is the Baghlan area of interest (AOI) in 

northeast central Afghanistan, which is approximately 150 km northwest of Kabul (fig. 17B–1). The 

area has the potential for clay, gypsum, copper, and bauxite deposits (Peters and others, 2007). 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 Baghlan AOI that 

warrant further investigation, especially detailed geological mapping, lithologic sampling, and 

geochemical studies.

17B.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, and 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 only be used to characterize the upper surface materials and not 

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

of surface materials.
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1285

17B.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 0.43 to 2.48 microns (μm) in 128 channels. The imaging spectrometer was flown 

on a WB-57 high-altitude aircraft at 50,000 ft. There were 207 standard data flight lines and 11 crosscutting calibration lines collected over Afghanistan for a total of 218 flight lines, covering a surface area 

of 438,012 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 and (or) were in wavelength regions that overlapped between detectors were 

removed from the HyMap data. Each flight line was georeferenced to Landsat Thematic Mapper (TM) 

base imagery in UTM projection (Davis, 2007). 

Figure 17B–1. Index map of the Baghlan area of interest (AOI), northeast Afghanistan.

17B.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 

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 
1286 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

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.).

ACORN was run multiple times for each flight line, using average elevations in 100-m increments, 

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

corrected image was assembled from these elevation-incremented ACORN results. This was done 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: Kandahar Air Field, Bagram Air Base, and Mazar-e-Sharif Airport, as 

well as 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 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 from calibration sites to where the 

HyMap data were acquired. The large distances were a result of the lack of safe access to groundcalibration 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, which were used to derive the empirical correction factors.

During the course of the data collection, the sun angle, atmospheric water vapor, and atmospheric 

scattering differed for each flight line. To compensate for this, cross-cutting calibration flight lines over 

the ground-calibration areas were acquired (Kokaly and others, 2008) and used to refine data quality of 

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 overlap region, corrected residual 

atmospheric contamination in the imaging spectrometer data that may have been present after the 

ground-calibration step. 

17B.2.3 Materials Maps and Presentation

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

calibrated reflectance data were analyzed using the Material Identification and Characterization 

Algorithm (MICA), a module of the USGS Processing Routines in IDL (Interactive Data Language) 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 below. The resulting maps 

of material distribution, resampled to a 23 x 23 meter square pixel grid, were mosaicked to create 

thematic maps of surface mineral occurrences over the full dataset covering Afghanistan.

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

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

MICA was applied using the subset of minerals with absorption features in the visible and near-infrared 

wavelength region, producing a 1-μm map of iron-bearing minerals and other materials (King, Kukaly, 

and others, 2011), and again using the subset of minerals with absorption features in the shortwave 

infrared, producing a 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 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. 
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1287

The iron-bearing minerals map has 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 carbonate, phyllosilicate, sulfates, and altered 

minerals map has 32 classes. Minerals with slightly different mineral compositions but comparable 

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 comparisons with reference spectra 

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

17B.3 Geologic Setting of the Baghlan Area Of Interest

The Baghlan AOI is within the Baghlan and Samangan Provinces in central-northeast 

Afghanistan. The main Baghlan AOI is approximately 1,800 km2

. The contrast-enhanced stretch of the 

natural-color composite of Landsat Thematic Mapper bands in figure 17B–2 provides a general 

overview of the Baghlan 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.

Figure 17B–2. Contrast-enhanced Landsat Thematic Mapper natural-color image of the Baghlan area of interest. 

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

and others, 2007).
1288 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

17B.3.1 Topography

Elevations in the Baghlan AOI range from 1,147 to 4,015 m (fig. 17B–3). The lowest areas 

within the Baghlan AOI are along the river that cuts through the southeastern region of the AOI. The 

highest elevations are found in the central and northern sections of the AOI. There are three population 

centers within the AOI: Ruyi Du Ab in the northeast, Tala Wa Barfak in the east, and Kahmard in the 

south. 

Figure 17B–3. Elevations and topography of the Baghlan area of interest. 

17B.3.2 Lithology and Structure

Rocks in the Baghlan area range in age from Ordovician to Recent. The southeastern region of 

the AOI contains Paleozoic age rocks that are overlain by Triassic, Jurassic, and Cretaceous sedimentary 

rocks, which are in turn overlain in the central parts of the AOI by Eocene and Neogene age sedimentary 

rocks. Triassic granitic plutons and stocks intrude the older rocks in the eastern part of the AOI. 

Gypsum, clay, and bauxite deposits are most abundant in the Jurassic sedimentary rocks associated with 

coal (Peters and others, 2007). Gypsum also occurs in some Eocene age sedimentary rocks (fig. 17B–4; 

Abdullah and Chmyriov, 1977; Doebrich and Wahl, 2006; Peters and others, 2007).

17B.3.3 Known Mineralization

Figure 17B–5 shows 23 locations where mineralization with a potential for mineral resource 

development may exist (Peters and others, 2007). A number of different types of mineral prospects, 

particularly gypsum, clay, and bauxite prospects are present within the Baghlan AOI. The mineralogical 
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1289

characteristics of the mineralized prospects are summarized in table 17B–1. There are also prospects of 

copper skarns, polymetallic veins, and sulfur, but these do not correlate well to the imaging spectroscopy

data or are too small to be resolved. 

The main known bauxite prospect is the Nalag prospect near lat 35°25'16''N., long 68°09'20''E. 

The prospect occurs in the weathering crust of Upper Triassic extrusive rocks at the base of a Jurassic 

coal-bearing sequence (Peters and others, 2007). Ten bauxite bodies, as thick as 4 m and as long as 

200 m, have been identified in the area (Abdullah and others, 1977, Doebrich and Wahl, 2006; Peters 

and others, 2007). The main bauxite prospect is the Eshpushta prospect near lat 35°25'16''N., long 

68°09'20''E. The prospect, ranging in thickness from 1 to 3 m and extending for 300–400 m, also occurs 

in the weathering crust of Upper Triassic extrusive rocks. The bauxites are light gray and pinkish 

(Abdullah and others, 1977, Doebrich and Wahl, 2006; Peters and others, 2007). A small occurrence of 

bauxite (Estoma Bauxite prospect) is present in the weathering crust of Upper Triassic extrusive rocks at 

the base of Jurassic coal-bearing sequence (Abdullah and others, 1977, Doebrich and Wahl, 2006; Peters 

and others, 2007).

Figure 17B–4. Geologic map of the Baghlan area of interest from 1:500,000-scale geologic map of Afghanistan 

(Abdullah and Chmyriov, 1977; Doebrich and Wahl, 2006; Peters and others, 2007).

The main known gypsum occurrence is the Dasht-i-Safed Gypsum prospect located near lat 

35°18'32"N., long 67°57'24"E. The prospect is a sulfur-bearing bed (1.0 to 1.5 m thick) containing 

celestite and lies between Upper Cretaceous–Paleocene marl and gypsum strata (Abdullah and others, 

1977, Doebrich and Wahl, 2006; Peters and others, 2007). Gypsum prospects include the Nadr, Kamard, 
1290 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Dasht-i-Safed, and Nalak prospects. The Nadr prospect near lat 35°26'25"N., long 67°48'02"E., is a 

12-m-thick bed containing 89 percent gypsum that occurs in Upper Cretaceous–Paleocene dolomite, 

clay, and limestone that crop out from beneath Eocene prospects (Abdullah and others, 1977, Doebrich 

and Wahl, 2006; Peters and others, 2007). The Kahmard prospect is located near lat 35°18'32"N., long 

67o54'E. This prospect contains beds consisting of massive gypsum, as much as 2.5 m thick, and 

stratified gypsum, 20 to 40 cm thick. The gypsum has been found in Upper Cretaceous–Paleocene clay 

and dolomite. The total thickness of the gypsum unit is 20 m and the average gypsum content is 

97.94 weight percent (Abdullah and others, 1977, Doebrich and Wahl, 2006; Peters and others, 2007).

The Dasht-i-Safed prospect is located near lat 35°17'09"N., long 67°53'08"E. This is a unit of stratified 

gypsum 30 m thick, occurring in Upper Cretaceous–Paleocene clay and limestone (Abdullah and others, 

1977, Doebrich and Wahl, 2006; Peters and others, 2007). The Nalak prospect is a bedded gypsum 

prospect within Upper Jurassic sandstones and clays (Abdullah and others, 1977, Doebrich and Wahl, 

2006; Peters and others, 2007). 

Figure 17B–5. Sites of known mineralization by deposit type (Abdullah and Chmyriov, 1977; Doebrich and Wahl, 

2006; Peters and others, 2007) on the geologic map of the Baghlan area of interest from 1:500,000-scale geologic 

map of Afghanistan (Abdullah and Chmyriov, 1977; Doebrich and Wahl, 2006; Peters and others, 2007).
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1291

Table 17B–1. Known sites of mineralization in the Baghlan area of interest.

[Data are from Abdullah and Chmyriov (1977), Doebrich and Wahl (2006), and Peters and others (2007)] 

Name Deposit type Major commodity Host lithology Alteration Mineralogy Gangue

Dasht-i-Safed Gypsum unknown gypsum Gyp Upper Cretaceous - Paleocene _ Gypsum No data

clays and limestones

Kamard Gypsum unknown gypsum Gyp Upper Cretaceous - Paleocene _ Gypsum No data

clays and dolostone

Unnamed unclassified Cu Upper Triassic acidic effusives, _ Chalcopyrite; malachite; No data

tuff- sandstones and sphalerite

conglomerates

Eshpushta Copper skarn Cu Cu Middle - Upper Triassic lime Skarn alteration Chalcopyrite; pyrite; No data

sandstones, gravelstones and arsenopyrite; sphalerite; 

conglomerates molybdenite

Eshpushta Bauxite laterite-type bauxite Al Weathering profile over Upper Laterization Bauxite No data

Triassic effusives

Eshpushta West sedimentary kaolin China clay Lower - Middle Jurassic Kaolinization No data No data

terrigenous rocks

Dasht-i-Safed Sulfur sulfur S Sulfur bed between Upper _ Sulfur native; celestite No data

Cretaceous - Paleocene marls 

and gypsum

Siwak limestone Limestone Upper Cretaceous - Paleocene _ No data No data

marls and marly limestones

Eshpushta East sedimentary kaolin China clay Middle - Upper Triassic rocks Kaolinization No data No data

Darra Alasang skarn Cu Cu Sn Pb A contact of Upper Triassic Skarn alteration Pyrrhotite; chalcopyrite; No data

granites and Upper Triassic sphalerite; galena; 

shales scheelite; cassiterite; 

ilmenite

Unnamed polymetallic vein Cu A contact of Upper Triassic Silicification; Pyrite Quartz

granodiorites and Upper Triassic pyritization

sandstones and volcanogenics

Talin sedimentary kaolin Fireclay Clays in Lower - Middle Jurassic _ No data No data

deposits

Tanghy-Eshpushta unclassified Cu Upper Cretaceous limestones and Silicification; Limonite; jarosite; copper Quartz

dolostone limonitization; pitch ore; fahlore

malachitization

Doab unknown Cu Cu

Tala-Barfak residual kaolin China clay Kaolines in weathering profile over Kaolinization Kaolin No data

Upper Triassic quartz porphyry 

subvolcanic body

Unnamed skarn Cu Cu A contact of Upper Cretaceous Skarn alteration of Chalcopyrite; pyrite; No data

limestones magnetite facies magnetite

Nalak Gypsum bedded gypsum Gyp Upper Jurassic sandstones and _ Gypsum No data

clays
1292 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Name Deposit type Major commodity Host lithology Alteration Mineralogy Gangue

Nalag (Tala) laterite-type bauxite Al Weathering profile over Upper 

Triassic effusives in the bottom 

of overlaying Jurassic coalbearing deposits

Laterization Bauxite No data

Nadr bedded gypsum Gyp Upper Cretaceous - Paleocene 

dolostone, clays and limestones 

exposed among Eocene deposits

_ Gypsum No data

Nalag Clay sedimentary kaolin Fireclay Clays on Upper Triassic diorites 

porphyry

_ Not data No data

Estoma Bauxite laterite type bauxite Al Weathering profile over Upper 

Triassic effusives in the bottom 

of overlying Jurassic coalbearing deposits

Laterization Bauxite No data

Unnamed polymetallic vein Cu Middle - Upper Triassic deposits Silicification Pyrite; hematite; limonite; 

quartz

Quartz

Rafak sedimentary kaolin Fireclay clays among Lower Cretaceous 

siltstones

_ No data No data
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1293

The main known kaolinite occurrence is the Tala-Barfak prospect near lat 35°21'49"N., long 

68°10'40"E. The prospect consists of three small kaolin relics in the weathering crust on a Late Triassic 

subvolcanic body of quartz porphyry (Peters and others, 2007; Abdullah and others, 1977). The kaolin 

relics extend for more than 1 km, their widths reaching 250 m, and thicknesses as much as 20 m. The 

kaolin is white, relatively compact, and at places includes patches of slightly weathered rock. Other 

kaolinite and clay prospects include the Eshpushta East prospect, which is a zone of slightly kaolinized 

rocks of Middle–Late Triassic age, 20 to 25 m thick that extends for 0.5 km (Abdullah and others, 1977, 

Doebrich and Wahl, 2006; Peters and others, 2007). The Eshpushta West prospect is a zone of slightly 

kaolinized rocks of Early–Middle Jurassic age that is 20 m thick and extends for 300 m (Abdullah and 

others, 1977, Doebrich and Wahl, 2006; Peters and others, 2007). The Rafak prospect is a 5-m-thick 

clay bed that occurs in Lower Cretaceous siltstone (Abdullah and others, 1977, Doebrich and Wahl, 

2006; Peters and others, 2007). Other small prospects include the Nalag Clay and Talin prospects. 

17B.4 Mineral Maps of the Baghlan Area of Interest

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

methods resulted in the identification of a wide variety of surficial minerals. 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 prospects. The presence of abundant vegetation, which masked the surficial minerals in 

significant parts of the area, has reduced the utility of the imaging spectroscopy data for overall site 

characterization in several regions within the Baghlan AOI.

Figure 17B–6 depicts the results of the MICA analyses of the HyMap data for the Baghlan AOI 

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

other materials. Carbonates cover most of the Baghlan AOI, primarily indicated by pixels containing 

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

large contiguous areas in the central and southwestern areas. In the southwestern section, the muscovites 

and illites occur along a river basin. Distinct patterns of kaolinitic clays occur in bedded units primarily 

in the Early–Middle Jurassic stratified rock units. Bedded units, 30 km long and as much as 3 km wide, 

occur in the south-central and southeastern areas of the AOI along the river basin in Early–Middle 

Jurassic stratified units. Localized areas of kaolinite occur in the east-central, west-central and 

northwestern portions of the AOI mainly in Early–Middle Jurassic stratified rocks with smaller 

occurrences in Eocene and Rhaetian (Upper Triassic) stratified units. Large areas of epidote or chlorite 

were found throughout the AOI in Triassic and Carboniferous stratified units (see fig. 17B–6). 

Montmorillonite does map throughout the AOI in localized patterns, mainly in Eocene rocks, in the 

west-central portion of the AOI. Dolomite, serpentine or calcite + dolomite, and serpentine 

concentrations were mapped together throughout the AOI in what appears to be bedded units in many 

different lithologies. 
1294 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

 

Figure 17B–6. Map of carbonates, phyllosilicates, sulfates, altered minerals, and other materials derived from 

HyMap data in the Baghlan area of interest.

Figure 17B–7 shows the results for the iron-bearing materials. The iron-bearing materials map is 

dominated by Fe2+ Fe3+, Type 2, goethites, Fe2+, Type 1, and hematite with smaller occurrences of 

epidote and Fe3+, Type 1. Fe2+ Fe3+, Type 2 dominate the Early–Middle Jurassic and Middle–Late 

Triassic rock units but also occur within the Eocene and Rhaetian strata. Fe2+ Fe3+, Type 2 are coincident 

with the location of the 2 μm materials muscovites and illites. Goethites occur in Early–Middle Jurassic 

and Middle–Late Triassic bedded units in the southeast region of the AOI. Hematites and Fe3+ minerals 

map within the Early Cretaceous and Pliocene age rocks. Jarosite pixels map in small spatially cohesive 

clusters in the Middle Triassic-Late Triassic stratified units in the south-central region of the AOI. 

Because of the large number of classes 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. 17B–8 to 17B–12). Figure 17B–8 shows the distribution of carbonate 

minerals in the Baghlan AOI, whereas figure 17B–9 shows where clay minerals and micas occur. The 

distribution of iron-oxide and iron-hydroxide minerals are displayed in figure 17B–10. Minerals 

commonly found in hydrothermally altered rocks are mapped in figure 17B–11, and secondary minerals 

often associated with mineralized and (or) weathered rocks are mapped in figure 17B–12. 

17B.4.1 Carbonate Minerals

Carbonate minerals, either calcite or dolomite, were mapped over a large portion of the Baghlan 

AOI (fig. 17B–8). In general, the carbonates are mapped throughout the AOI and within almost every 

geologic unit. Dolomite, serpentine or calcite + dolomite, and serpentine occurrences were mapped 
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1295

together throughout the southern region of the AOI in what appears to be bedded units in many different 

strata. The known limestone prospect of Siwak occurs within a calcite unit in the southwest region of the 

AOI.

Figure 17B–7. Map of iron-bearing minerals and other materials derived from HyMap data in the Baghlan area of 

interest. 

17B.4.2 Clays and Micas

Pixels matching pure muscovite or illite spectra occur over large contiguous areas in the central 

and southwest areas of the AOI. In the southwestern section, muscovites and illites occur along a river 

basin. Distinct patterns of kaolinite clays occur in localized patterns and in bedded units mainly in the 

Early Jurassic-Middle Jurassic stratified units. Extensive bedded units of kaolinite and muscovite 30 km 

long and as much as 3 km wide occur in the south-central and southeastern areas of the AOI along the 

river basin in Early–Middle Jurassic and Middle–Late Triassic age rocks. Localized areas of spatially 

related kaolinite occur in the east-central, west-central, and northwestern portions of the AOI mainly in 

Early–Middle Jurassic and Middle–Late Triassic age rocks with smaller occurrences in Eocene and 

Rhaetian stratified units. The Tala-Barfak, Eshpushta West, and Eshpushta East kaolinite prospects did 

map within units of kaolinite detected by HyMap data. Interestingly, Tala-Barfak, Eshpushta West, and 

Eshpushta East are considered China clay commodities and were mapped as kaolinite where the Talin, 

Nalag Clay and Rafak kaolinite prospects are described as fire-clay commodities and mapped mainly 

within calcite or calcite/dolomite units (Abdullah and Chmyriov, 1977; Doebrich and Wahl, 2006; 

Peters and others, 2007). Large areas of epidote or chlorite were found throughout the AOI in Triassic 

and Carboniferous age stratified units (see fig. 17B–6). Montmorillonite does map throughout the AOI 
1296 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

in localized patterns mainly in the Eocene unit in the west-central portion of the AOI. Alunite + kaolinite 

maps as individual pixels, but those pixels are limited to the southeast region of the AOI.

Figure 17B–8. Map of distribution of carbonate minerals derived from HyMap data in the Baghlan area of 

interest. 

17B.4.3 Iron Oxides and Iron Hydroxides

The Baghlan AOI contains large areas of hematite in the southern region of the area 

(fig. 17B–10) in Early Cretaceous strata. The description of the Early Cretaceous units includes redstone 

and is consistent with the HyMap hematite classes (Abdullah and Chmyriov, 1977; Doebrich and Wahl, 

2006; Peters and others, 2007). Goethite and Fe-hydroxide are observed across the AOI in bedded 

lithologies running parallel to the hematite with the largest concentration in the southern part of the AOI. 

Goethite in the Baghlan AOI approximately coincide with areas where kaolinites are mapped in the 

2-μm materials map. Jarosite is found in small concentrations but is consistently found within the 

Middle–Late Triassic age unit. Jarosite is bordered by the goethite classes in the iron-bearing map and is 

mainly associated with kaolinites in the clays, carbonates, phyllosilicates, sulfates, altered minerals, and 

other materials map (near lat 35°

18'26''N., long 68°04'48''E.). Occurrences of epidote are found dispersed 

over the AOI in several different geologic units. 

17B.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. 17B–11). Consequently, where they occur in distinct 

clusters is of great interest in terms of potential mineral deposits. However, the minerals do not occur in 

distribution patterns that are suggestive of such alteration in the Baghlan AOI. All of the mineral classes 
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1297

in this map with the exception of kaolinite (dickite may be present) occur over large areas with little 

spatial coherence in the AOI. Kaolinite (dickite may be present) did cluster in two locations; one near 

lat 35°

20'12''N., long 68°05'49''E., and the second near lat 35°19'27''N., long 68°07'50''E., which should 

be examined in more detail in future studies. 

Figure 17B–9. Map of distribution of clay and mica minerals derived from HyMap data in the Baghlan area of 

interest. 

17B.4.5 Common Secondary Minerals

Secondary minerals, in the epidote and chlorite or epidote classes (fig. 17B–12), are distributed 

throughout the AOI. Serpentine and serpentine or calcite + dolomite occur in association with dolomites 

in the southeast and west-central regions of the AOI. 

17B.4.6 Gypsum

A specialized MICA analysis to enhance the detection and map the spatial distribution of 

gypsum was completed for the AOI. The result of that mapping is shown in figure 17B–13, in which 

gypsum is most prominent in the center of the Baghlan AOI. Small groupings and single pixel detections 

occur south-southwest and north-northeast of the central concentration in similar geologic units.

Gypsum was detected near the known gypsum prospects of Kamard, Dasht-i-Safed, Nadr, and Nalak.

With the exception of Nalak, only a few pixels of gypsum are detected near the known mineral 

occurrences. At Nalak, the analysis of imaging spectrometer data revealed an area containing gypsum 

more than 110 hectares in size. Additional concentrations of pixels with strong gypsum-related 

absorption features in their spectra occur near lat 35°22'28"N., long 68°05'57"E., within an area greater 

than 100 hectares and near lat 35°19'50"N., long 68°01'03"E., in a narrow zone 3 km in length. These 
1298 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

previously unreported gypsum concentrations in the center of the AOI are discussed in more detail in 

King, Johnson, and others (2011). 

Figure 17B–10. Map of distribution of iron oxide and iron hydroxide derived from HyMap data in the Baghlan area 

of interest. 

17B.5 Summary 

Carbonate minerals and vegetation cover most of the Baghlan AOI. Muscovites and illites were 

detected in greatest concentration in the mapped units of Triassic and Jurassic rocks in the central to 

southeastern region of the Baghlan AOI and in smaller patches to the northwest. Epidote and chlorite 

were found in spatially consistent patterns in the central and southeast regions. Kaolinites were 

distributed within the Early–Middle Jurassic and Middle–Late Triassic age stratified units. A large 

occurrence of kaolinite was mapped in the southern part of the AOI. In the iron-bearing materials map, 

the goethites approximately coincide with areas where kaolinites are mapped in the 2-μm map, and the 

Fe2+ Fe3+, Type 2 are coincident with the location of the 2-μm muscovites and illites. The hematites 

consistently map within geologic units described as red sandstone. Jarosite is found in small 

concentrations throughout the goethite classes in the Middle–Late Triassic age geologic unit. In most 

locations jarosite correlates to kaolinite in the 2-μm map. A customized MICA analysis for gypsum was 

performed to better define their spatial distribution. The analysis yielded detections consistent with 

known gypsum occurrences at Kamard, Dasht-i-Safed, Nadr, and Nalak and identified several 

previously unknown concentrations of pixels that warrant additional investigation. The bauxite mineral 

occurrences did not seem to correlate to specific minerals detected by HyMap, but the addition of 

bauxite minerals to the spectral library could improve our detections. Kaolinite detections were 
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1299

consistent with the China clay-type kaolinites in the Tala-Barfak, Eshpushta West, and Eshpushta East 

prospects.

Figure 17B–11. Map of distribution of common alteration minerals derived from HyMap data in the Baghlan area 

of interest. 
1300 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 17B–12. Map of distribution of common secondary minerals derived from HyMap data in the Baghlan area 

of interest. 
Chapter 17B. Analysis of Imaging Spectrometer Data for the Baghlan Area of Interest 1301

Figure 17B–13. Map of gypsum distribution derived from HyMap data in the Baghlan area of interest. 

17B.6 References Cited

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