Chapter 21A. Summary of the Mineral Information Package for 

the Khanneshin Carbonatite Area of Interest

Contribution by Robert D. Tucker, Harvey E. Belkin, Klaus J. Schulz, Stephen G. Peters, and Kim P. Buttleman 

Abstract

The Khanneshin carbonatite is a deeply dissected igneous complex of Quaternary age that rises 

approximately 700 meters above the flat-lying Neogene sediments of the Registan Desert, Helmand 

Province, Afghanistan. The complex consists almost exclusively of carbonate-rich intrusive and 

extrusive igneous rocks, crudely circular in outline, with only three small hypabyssal plugs of leucite 

phonolite and leucitite outcropping in the southeastern part of the complex. The complex is broadly 

divisible into a central intrusive vent (or massif), approximately 4 kilometers in diameter, consisting of 

coarse-grained sövite and brecciated and agglomeratic barite-ankerite alvikite; a thin marginal zone (less 

than 1 kilometer wide) of outwardly dipping (5°–45°). Neogene sedimentary strata; and a peripheral

apron of volcanic and volcaniclastic strata extending another 3–5 kilometers away from the central 

intrusive massif. Small satellitic intrusions of biotite-calcite carbonatite, no larger than 400 meters in 

diameter, crop out on the southern and southeastern margin of the central intrusive massif.

In the 1970s several teams of Soviet geologists identified prospective areas of interest for 

uranium, phosphorus, and light rare earth element (LREE) mineralization in four regions of the 

carbonatite complex. High uranium concentrations are reported in two regions; the greatest 

concentrations are confined to silicified shear zones in sandy clay approximately 1.1 kilometers

southwest of the peripheral part of the central vent. An area of phosphorus enrichment, primarily 

occurring in apatite, is present in coarse-grained agglomeratic alvikite, with abundant fenite xenoliths, 

approximately 750 meters south of the periphery of the central vent. Lastly, an area of prospective 

LREE mineralization was identified within extensively veined and dike-intruded ankerite-barite alvikite 

in the outer portion of the central vent near its contact with Neogene sedimentary rocks.

Three reconnaissance missions to the Khanneshin carbonatite were completed by scientists of the 

U.S. Geological Survey. Two of these were to the area of light rare earth element (LREE) enrichment,

which is the primary subject of this summary.

Two types of REE mineralization occur. Type 1 REE mineralization consists of semiconcordant, 

symmetrically banded veins and discontinuous seams, up to 0.5 to 0.7 meters thick and several tens of 

meters long. These occur throughout a vertical thickness of 150 meters in ankerite-barite alvikite of the 

LREE area. The symmetrically banded veins and seams are defined by yellow-weathering zones, 

symmetric around a dark central zone, that are enriched in khanneshite-(Ce), barite, strontianite, and 

secondary REE minerals (synchysite-(Ce) and parisite-(Ce)). The dark central zone, consisting primarily 

of ankeritic dolomite, barite, apatite, and strontianite, also has trace khanneshite-(Ce). These symmetric 

banded veins and seams alternate with dark, meter-thick layers of ankerite-barite alvikite that is the wall 

rock. In some veins the REE carbonate minerals form dense crystal aggregates, presumably crystallizing 

from immiscible droplets, which comprise up to 30 percent by volume of the vein. Type 1 mineralized 

rocks average 19.9 weight percent Ba, 3.61 weight percent Sr, and 2.78 weight percent total LREE

(∑ LREE = sum of La, Ce, Pr, Nd). The values of ∑ LREE for eight average whole-rock analyses range 

between 6.23 and 1.83 weight percent.

Type 2 REE mineralization occurs in discordant dikes and tabular sheets, up to tens of meters 

thick and hundreds of meters long, which are filled with primary igneous minerals that crystallized 

directly from magma or a late-stage hydrothermal fluid. These REE-enriched igneous rocks are of two 

types: those enriched in fluorine and those enriched in phosphorus. The igneous rocks enriched in 
1456 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

fluorine have as their REE-bearing minerals idiomorphic phenocrysts of khanneshite, together with 

synchysite-(Ce), bastnäsite-(Ce), and calkinsite-(Ce) of likely secondary origin. The igneous rocks 

enriched in phosphorus have as their REE-bearing minerals idiomorphic phenocrysts of carbocernaite-

(Ce), together with parisite-(Ce) of secondary origin. The Type 2 mineralized rocks average 11.1 weight 

percent Ba, 5.36 weight percent Sr, and 3.28 weight percent ∑ LREE (sum of La, Ce, Pr, Nd ). The 

values of ∑ LREE for 14 average whole-rocks range between 5.98 and 0.49 weight percent.

A magmatic origin is indicated for the Type 2 discordant dikes and tabular sheets. Based on 

textural and field evidence, the semiconcordant veins and discontinuous seams (Type 1 mineralization)

may have formed in the presence of REE-rich hydrothermal fluids. It is possible that both types of REE 

mineralization may be penecontemporaneous, having formed in the marginal zone of a carbonate-rich 

magma, highly charged with volatile constituents, carbon dioxide, fluorine, and phosphorus, and 

strongly enriched in barium, strontium, and the LREE. 

Both types of REE-enriched rocks are comparable in grade to the world-class Bayan Obo 

(China) and Mountain Pass (California, USA) deposits, which are also greatly enriched in the LREE.

Based on several assumptions, and employing a simple geometry for the mass, we estimate that at least 

1 million metric tons of LREE may be present in the Khanneshin Carbonatite Area of Interest. . This 

comports well with the probabilistic estimate of 1.4 Mt (million metric tons of undiscovered REE 

resources in all of south Afghanistan (Peters and others, 2007). In addition to the LREE, the Khanneshin 

carbonatite is greatly enriched in barium (>10 weight percent), strontium (>6 weight percent), 

phosphorus (~2 weight percent), and uranium (>0.05 weight percent). A resource calculation of these 

elements was not attempted.

21A.1 Introduction

China’s dominance as the producer of more than 95 percent of world output of rare earth 

elements (REE), its decision to restrict exports of rare earth product, and the rapid increase in worldwide 

consumption of rare earth products have heightened concern about the future availability of REE. As a 

result, countries such as the United States, Japan, and member nations of the European Union face a 

future of limited supplies and high prices for rare earth products unless other sources are found.

Carbonatites are intrusive alkaline igneous rocks composed of more than 50 volume percent 

calcite or other carbonate minerals. They are a highly prospective source for the REE (model 10, Singer, 

1986 a,b).

In southern Afghanistan, the primary area of interest is centered within the Khanneshin 

carbonatite complex with its U-Th, P, and REE mineral occurrences (Abdullah and others, 1977). Based 

on the aeromagnetic data from Sweeney and others (2006), a larger permissive tract was delineated to 

include the north- to northwest-striking carbonatite dikes to the east and west of the Khanneshin, which 

follow the shape of the aeromagnetic anomalies beneath sand and gravel of the Sistan Basin (fig. 21A-1; 

Sweeney and others, 2006). A favorable tract, cb01, was identified by Peters and others (2007) to 

include the carbonatite dikes and central volcanic zone of the Khanneshin as well as the area outlined by 

the aeromagnetic anomaly.

21A.2 Previous Work

The Khanneshin carbonatite is the primary area of interest for three prospective non-fuel 

resources: REE, uranium, ,and phosphorus . The prospective resources were first identified and 

delineated by Soviet geologists (Abdullah and others, 1975; Yeremenko, 1975; Cheremitsyn and 

Yeremenko, 1976; Alkhazov and others, 1978). Rare earth element mineralization occurs mostly within 

the northeast marginal zone of the central intrusive stock. High uranium concentrations have been 

reported in many rocks throughout the carbonatite complex, but the greatest concentrations are confined 

to silicified shear zones in sandy clay approximately 750 meters (m) southwest of the peripheral part of 

the central vent. A secondary zone of uranium mineralization is located in the northern marginal zone of 

the central massif. Finally, phosphorus is present in significant amounts, principally as apatite in 
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1457

rudaceous agglomerate, fenite xenoliths, and alvikite. Other commodities that may be present in 

significant, but as yet undiscovered, amounts include barite, fluorite, nepheline, niobium, tantalum, 

zirconium, and copper. In addition to the Khanneshin carbonatite, alkali syenite intrusive igneous rocks, 

consisting of volcanoes and intrusive plugs and dikes, occur throughout south Afghanistan (Abdullah 

and others, 1975; Vikhter and others, 1976, 1978). Based on the regional geology, and Monte Carlo 

calculations, Peters and others (2007) estimated a 50-percent probability of one or more undiscovered 

deposits of REE and niobium in south Afghanistan. The mean estimated tonnage of these undiscovered 

resources is 1.4 Mt (million metric tons) REEand 3.5 Mt Nb, respectively (Peters and others, 2007). 

Figure 20A–1. Aeromagnetic map (Sweeney and others, 2006) showing permissive tract of U-P-REE 

mineralization (cb01) in the Helmand Basin in southern Afghanistan. Numbers one thru eight refer to possible 

alkaline igneous centers within the tract. These targets formed the basis for the probabilistic estimate of U, P, Nb, 

and REE resources in Peters and others (2007). The Khanneshin complex is the only exposed carbonatite in south 

Afghanistan. Additionally, to the north, an aeromagnetic anomaly was designated by the U.S. Geological SurveyAfghanistan Geological Survey Assessment Team as a secondary area of interest for undiscovered REE resources 

(Peters and others, 2007). 
1458 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

21A.3 Metallogeny

Common economic deposits in carbonatite (model 10, Singer, 1986a) are apatite-magnetite and 

REE deposits in zoned igneous complexes. The zonation is defined by a central plug of carbonatite or 

syenite breccia surrounded by ring dikes and cone sheets of carbonatite-related rock types (Hogarth, 

1986; Woolley, 1989). Apatite-magnetite and REE-enriched rocks tend to occur in iron- and 

magnesium-rich carbonatites bearing abundant dolomite, ankerite, and siderite. Associated rocks with 

these include pyroxenite, feldspathic pyroxenite, picrite porphyrites, dunite, ijolite, nepheline syenite 

and their volcanic equivalents. Alkalic fenitized wall rocks may also be common. Igneous textures are 

typically hypidiomorphic-granular and poikiloblastic, but breccia may also be abundant, particularly 

where magma of the central vent is highly charged with volatile constituents.

Carbonatites range in age from Archean to Holocene. Typically they exhibit a complex history of 

igneous crystallization with several episodes of injection and eruption of multiple magma types. These 

magmas are commonly enriched in alkali- and alkali-earth elements, but other elements, such as 

uranium, thorium, barium, strontium and the rare earth elements, may be present in high concentrations 

as well. Owing to the high enrichments of incompatible elements and volatile constituents, late deuteric 

and metasomatic alteration commonly accompanies their emplacement and crystallization. Carbonatites 

are typically emplaced into continental shields undergoing regional extension, and they are usually 

related spatially to regional-scale faults and lineaments such as the East African rift system. 

Accessory ore minerals in common carbonatite may include pyrrhotite, ilmenite, molybdenite, 

chalcopyrite, pyrite, pyrochlore, sphalerite, galena, anatase, and brookite. Rarely, such as in the Palabora 

carbonatite, copper and gold are reported. In carbonatites enriched in phosphorus and iron, important ore 

minerals are apatite, magnetite, pyrochlore, columbite, and perovskite. In contrast, carbonatites highly 

enriched in the REE also have high concentrations in barium, strontium, and iron or magnesium. In 

these rocks, common accessory minerals include barite, strontianite, siderite, rhodochrosite, ankerite, 

bastnaesite, parisite, monazite, and breunnerite. In many carbonatites, the economic ore minerals are 

typically disseminated and banded. 

The alteration of wall rock and xenoliths associated with carbonatites is accompanied by growth 

of alkali feldspar, aegerine, alkali hornblende, chlorite, and sphene. This fenitization, or alkali 

metasomatism, is a result of the passage of alkali-rich fluids through the wall rock during magma 

emplacement. The ores associated with carbonatites are commonly restricted to carbonatite dikes, sills, 

breccias, sheets, and veins, but they may also be present in satellitic intrusions associated with the 

complex. Deep chemical weathering may also form goethite- and clay-rich soils highly enriched in 

phosphate, niobium, and REE. Geophysical signatures typically consist of radiometric anomalies, 

magnetic anomalies, and high gravity anomalies. Geochemical signatures are elevated concentrations of 

Ba, Ce, Cu, Eu, La, Mn, Mo, Nb, P, Pb, S, Sm, U, V, Th, Ti, Y, Zn, and Zr; high concentrations of B, 

Be, Hf, Li, Sn, Ta, and W are rare. According to Singer (1986b) carbonatite complexes may contain 

economic grades of U,Th, Ti, Fe, Cu, vermiculite, Zr, or P, and these commodities may be in different 

parts of the complex than the Nb-rich parts. Mean tonnage for most deposits is 60 million metric tons, 

and most deposits contain between 16 and 220 million metric tons. Mean niobium grade (weight percent 

Nb2O5) is 0.58, and mean rare earth oxide grade (weight percent RE2O5) is 0.35 (Singer, 1986b). 

In Afghanistan, carbonatite and alkali syenite intrusive igneous rocks are present as small 

volcanic plugs, minor intrusive stocks, and dikes in the Helmand Basin (fig. 21A–1). The largest and 

most important igneous center is the Khanneshin carbonatite, situated 5 kilometers (km) south of the 

Helmand River. 

21A.4 Geology The Khanneshin carbonatite, first described by Yeremenko (1975), occurs within the Early 

Quaternary volcanic rocks south of the Helmand River. The igneous complex is broadly divisible into 

four parts (figs. 21A–2, 21A–3): a central vent, approximately 4 km in diameter; a thin marginal zone 

(< 1 km wide) of outwardly dipping (5-40°) Neogene sedimentary strata that comprise the basement to 
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1459

the igneous complex (fig. 21A–4a); a peripheral apron of volcanic and volcaniclastic strata extending 

another 3–5 km away from the central vent; and small satellitic intrusions of subvolcanic origin, no 

larger than 400 m in diameter, that crop out on the southern and southeastern periphery of the central 

intrusive massif. 

The following petrogenetic history is taken from Cheremitsyn and Yeremenko (1976) with 

modification by Vikhter and others (1978). 

The Khanneshin complex consists of igneous rocks of several generations. The initial phase was 

explosive eruption of ankerite alvikite from the central vent. This was followed by forceful emplacement 

of coarse-grained sövite in the same vent. The presence of strongly metasomatized “glimmerites” and 

fenites within and around the central vent (fig. 21A–4c) suggests extensive fluorine, sulfate, and 

phosphate enrichment at depth, concurrent with extensive fracturing and emplacement of carbonatite 

radial dikes (fig. 21A–4d). This phase ended with emplacement of REE-enriched ankerite-barite 

carbonatite in the northeast margin of the central vent (fig. 21A–2). 

The succeeding phases commenced as explosive eruption of common alvikite of the satellitic 

extrusive stocks and vents. These include various agglomerates, lava flows, and tuffs, including 

fine-grained carbonatites. The final phase of activity was the eruption and emplacement of critically 

undersaturated silicate magma. These are represented by the flows of leucite phonolite and brecciated 

plugs of leucitite in the southeastern part of the complex (figs. 21A–2, 21A–3).

The rocks of the Khanneshin complex are assigned an early Quaternary age because they intrude 

fossiliferous sedimentary rocks of Neogene age, and they are overlain by unconsolidated deposits of 

Middle-Upper Quaternary age. An unpublished K-Ar age of 610,000 years, cited as personal 

communication by Whitney (2006), supports this contention. 

21A.4.1 Rocks of the Central Vent

The bulk of the igneous massif is made up of rocks of the central vent. They consist of mediumand coarse-grained carbonatite (sövite) confined to a central stock approximately 2-3 km in diameter.

Also present is fine- to medium-grained ankerite-barite carbonatite (alvikite) agglomerate that forms a 

nearly continuous ring, 0.8-1.5 km wide, surrounding the central stock of sövite. At the margin of the 

central vent, where the intrusive rocks are in contact with Neogene sedimentary rocks, the Neogene 

strata are strongly altered, brecciated, and invaded by dikes that form an outwardly dipping sequence of 

discolored and metasomatized albite- and calcite-rich fenites (figs. 21A–4a,c,d). 

21A.4.2 Rocks of the Volcanic Apron

Pyroclastic and volcaniclastic sedimentary rocks of the Khanneshin area are variegated and 

banded in their structural and textural features. They form an extensive apron, thickest in the northeast 

and southeast part of complex, and nearly absent in the west and northwest part of the complex 

(fig. 21A–4e). At least three major eruptive sequences are recognized, some of them linked to intrusive 

rocks of the central vent (Alkazov and others, 1978), but in general the chemistry and petrography of the 

volcanic rocks is not well known. In a broad sense, the volcanic formations of the Khanneshin complex 

are similar to many of the world’s carbonatite associations, both in mineralogy and chemistry. An 

interesting feature of the Khanneshin complex, however, is the overwhelming abundance of carbonatite 

and the paucity of silicate-rich igneous rocks. Based on discordant field relations with the volcanic 

apron, the few plugs of leucitite that are present at Khanneshin were emplaced very late in the 

petrogenetic cycle during the last phase of igneous activity. 

The lowest part of the volcanic sequence, near the central vent, consists of dark-red coarse- to 

medium-grained poorly indurated volcanigenic tuff and sandstone. Within these are abundant thick 

layers of ferruginous carbonate and carbonate-rich ash. The higher parts of the volcanic sequence are, in 

general, composed of bright orange-red rocks characterized by a noticeably lower degree of iron 

enrichment of carbonate, on the whole, by finer grain size. The highly sorted nature of these rocks, and 

abundant cross-bedding, suggests a significant amount of sedimentary reworking. 
1460 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 21A–2. Geologic map of the Khanneshin carbonatite, after Cheremitsyn and Yeremenko (1976), showing 

the principal bedrock divisions of the complex: (1) The central intrusive vent (or massif), composed of sövite and 

medium- to fine-grained alvikite agglomerate. The LREE prospect is located in the northeast portion of the central 

intrusive vent. (2) Neogene sedimentary strata, partly metasomatized, upturned away from the central intrusive 

vent. (3) The apron of volcanic and volcano-sedimentary strata. (4) Small satellitic intrusive rocks and volcanic 

plugs, mostly on the southern peripheral margin of the complex, which includes alvikite, sövite, and leucite 

phonolite. Cross-sectional lines shown in figure 21A-3.

Figure 21A–3. Two lines of cross section (fig. 21A-2) through the Khanneshin carbonatite. Line A-B-C: A 

northeast-southwest line of section through the REE-enriched area and the zone of uranium mineralization. Line 

D-E-F : A northwest-southeast line of section through the central intrusive vent and plugs of leucite phonolite.
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1461

Figure 21A–4. Field photographs of the key rock types and their relations within the central intrusive vent and 

volcanic apron. (a) View to the northwest from the zone of LREE enrichment showing the Neogene strata 

(background) dipping modestly north and away from the intrusive rocks of the central vent (foreground). Note the 

rugged relief and person for scale. (b) Unconformable relation between alvikite of the REE-enriched rocks (above) 

and normal carbonatite-intruded alvikite (below) of the marginal zone, central intrusive vent. Pen for scale. 

(c) Common agglomeratic alvikite of the central vent. Here, in the eastern margin of the central vent, the marginal 

fine-grained alvikite rocks contain abundant xenoliths of fenitized country rock (“glimmerite”) and sövite. Hammer for 

scale. (d) Common alvikite of the central vent, here with few xenoliths, intruded by fine-grained dikes of carbonatite 

(alvikite). Compare with (c), above. (e

Coarse-grained breccia is present in volcanic agglomerate immediately north of the central vent.

These deposits contain blocks of sövite and ankerite-barite carbonatites, several centimeters to several 

meters in diameter, cemented with green-brown carbonate. In some localities, the blocks of sövite and 

alvikite are weakly banded, indicating a very crude stratification within the breccia. The presence of 

fragmental ankerite-barite alvikite suggests that the breccia is a tuffaceous product of the intrusion, 

perhaps linked to explosive eruption of the REE-enriched alvikites described below.

) View of the volcanic rocks of the southwest apron (1) showing their relation 

to older Neogene strata (2) and younger Recent gravels (3). Photographs by Robert D. Tucker, U.S. Geological 

Survey. 

The southeastern part of the volcanic apron consists of orange-red tuffs that are overlain by 

massive green tuffs and tuffaceous sediments with pronounced lenticular laminations. The latter rocks 

are poorly cemented, crystal-lithic tuffs with fragments of ankerite sövite (30–70 volume percent), 

calcite (5–10 volume percent), phlogopite (2–8 volume percent), and apatite (2–3 volume percent).
1462 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

21A.4.3 Satellitic Vents, Dikes, and Minor Intrusive Rocks

Six large plugs and several small intrusive masses of coarse-grained carbonatite crop out in the 

south, southeast, and west part of the complex (figs. 21A–2, 21A–3). These are heterogeneous in 

composition and texture but, in general, banded and spotted biotite-calcite sövites dominate. The largest 

of the intrusive plugs contains coarse- and very coarse-grained xenoliths of sövite, biotite-rich 

“glimmerites” (mica-rich inclusions), and potassium feldspar-rich country rock (fenites). In rare 

instances, very large (>1 m diameter) inclusions of coarse-grained sövite and “glimmerite” are very 

abundant, and outcrops have the appearance of giant intrusive breccias. 

Three small plugs of leucitite and leucite phonolite crop out in the southeast part of the volcanic 

apron. These are the only bodies of silicate rock in the Khanneshin complex. The leucite phonolites are 

dense, massive green-gray rocks with a thinly banded, finely spotted structure and porphyritic texture.

Locally they exhibit a spheroidal parting. The phenocrysts (50–70%) consist of idiomorphic leucite 

crystals measuring 0.2–0.5 millimeters (mm) in diameter. The groundmass consists of sanidine, fine 

acicular aggregates of aegerine, and minute crystals of nepheline, leucite, and carbonate. 

21A.5 Prospects and Anomalies

Carbonatites are of economic interest because they may contain major and unique deposits of 

several commodities including iron, phosphorus, the rare earth elements, barium, strontium, niobium, 

uranium, thorium, fluorine, and lead. Studies by Soviet geologists in the 1970s showed that the 

Khanneshin complex is enriched in high levels of barium and strontium and thus highly favorable for 

hosting major deposits of phosphorus, uranium, and the rare earth elements. The Soviet teams identified 

three such prospective areas of phosphorus, uranium, and REE enrichment (fig. 21A–2).

21A.5.1 Uranium Prospect in the Southwest 

The uranium contents of the Khanneshin igneous rocks are quite high, typically ranging between 

50 to 100 parts per million (ppm). Two zones of uranium mineralization were first identified by Soviet 

field teams in 1975 (Cheremitsyn and Yeremenko, 1976). The largest zone, most enriched in uranium, is 

situated 700 to 800 m southwest of the central vent within tuffaceous sandstone of Neogene age. There, 

uranium mineralization occurs as a north-northeast-trending zone of intense brecciation approximately 

200 m wide and 500 m long. Within this zone, the tuffaceous sandstones are intensively brecciated with 

thin veins of aragonite and chalcedony. Individual lode veins, up to 8 m wide and 100 m long, are 

impregnated with bright-yellow autuntite (Ca(UO2)2(PO4)2 · 10-12 H2O). Whole-rock analyses of the 

load veins yield assays of 8.04 to 9.63 weight percent uranium, and 0.0036 to 0.0003 weight percent 

thorium. 

21A.5.2 Uranium Prospect in the North 

The second zone of uranium mineralization is located 2 to 3 km north of the central vent, also 

within Neogene sandstone near the periphery of the cone. This zone, too small to be shown in figure 

25A–2, is also characterized by extensive silicification (chalcedony); the largest vein is a 1- to 

1.5-m--thick zone approximately 100 m long. In this zone, uranium assays of 0.1 weight percent and 

0.5 weight percent were determined. Verification of these data by X-ray fluorescence analysis indicates 

actinide concentrations between 0.0058 and 0.0152 weight percent uranium and 0.0018 and 

0.0115 weight percent thorium. 

21A.5.3 Phosphorus Prospect in the South 

Apatite is the principal phosphorus-bearing mineral in rocks of the Khanneshin complex. It is 

common in most intrusive igneous rocks, and especially in agglomeratic alvikite with abundant 

xenoliths of metasomatized country rocks (that is, fenite). Apatite is concentrated in the broken and 

disaggregated xenoliths, commonly with the assemblage magnetite-apatite-forsterite ± aegerine-acmite, 

and also as a matrix mineral in agglomerate. Apparently fenitization was a metasomatic process that 
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1463

involved the complexing and transportation of phosphorus, iron, and REE. According to Cheremitsyn 

and Yeremenko (1976), the apatite in these rocks is a rare-earth fluoro-apatite (britholite family). The 

xenoliths assay 8.3 weight percent P2O5 and contain 1.0 to 1.5 weight percent LREE (mostly Ce). The 

rudaceous agglomerate assays 1.55 to 2.29 weight percent P2O5.

Eight zones of apatite enrichment were delineated by the Soviet field teams; all are in alvikite 

agglomerate on the southern flank of the central vent. The principal area of phosphorus enrichment is 

indicated in figure 21A–2. 

Soviet scientists also assayed alluvial gravel and sand in intermittent streams of the northern and 

eastern part of the central vent. The assays averaged approximately 1 weight percent P2O5, and thus

placer phosphorus prospects are unlikely to be present. 

21A.5.4 The LREE Prospect

A high content of REE is characteristic of the sövitic rocks, as well as the barium- and strontiumrich ankerite-barite alvikites. In the 1970s, Soviet geologists identified a polygonal area having extreme 

LREE enrichment in the northeast margin of the central vent (Qisf ; fig. 21A–2). Two traverses were 

completed by USGS scientists across the northern and southern corners of the zone of REE enrichment. 

The traverses are indicated in figure 21A–2. The traverse of August 2010 just touched the southern edge 

of the REE zone of mineralization, and the traverse of February 2011 crossed the northern corner of the 

REE mineralization zone. In the course of this work, extremely unusual rocks and minerals were 

observed, some of them highly enriched in strontium, barium, and LREE (table 21A–1), and more than

50 rock samples, representing the principal rocks of the mineralized zone, were collected for 

geochemical analysis and scanning electron microscopy. The result of our field and analytical work is 

summarized below and reported in Tucker and others (2011).

21A.5.4.1 REE Mineralization

Two styles of REE mineralization occur. 

Type 1.—Concordant, symmetrically banded veins and seams (fig. 21A–5). Type 1 REE 

mineralization consists of concordant, symmetrically banded, veins and discontinuous seams, up to 0.5 

to 0.7 m thick and several tens of meters long. The layers of REE enrichment consist of two outer bands 

of yellow-weathering minerals symmetrically disposed about a dark central band. The bands of 

yellow-weathering minerals consist of khanneshite-(Ce), barite, strontianite and secondary synchysite-

(Ce), and parisite-(Ce). The central, dark-colored band consists primarily of ankeritic dolomite, barite, 

apatite, and strontianite, as well as trace khanneshite-(Ce). These symmetric bands of highly mineralized 

rock are layered with weakly mineralized ankerite-barite alvikite (that is, the host wall rock) for more 

than 150 m of exposed vertical section. 

Texturally, there is abundant evidence that the REE carbonates formed late in the petrogenetic 

history, possibly from immiscible fluid droplets (fig. 21A–6). Backscattered electron images 

demonstrate that khanneshite-(Ce), the primary REE mineral, forms spheroidal mineral aggregates or 

late fibrous overgrowths on interstitial dolomite and calcite. The average diameter of the spheroidal 

aggregates, interpreted as REE-rich droplets of immiscible liquid, is 100 micrometers. In still other 

instances, REE-rich bands of barite, strontianite, and khanneshite-(Ce) appear to have crystallized from 

a fluid which was introduced into brecciated dolomitic ankerite of the host alvikite. In all examples, the 

REE minerals crystallized late in the mineral petrogenesis. In some veins the REE carbonate minerals 

form dense crystal aggregates comprising 50 percent (by volume) of the vein. 

Type II.—Discordant tabular sheets (fig. 21A–7). Type 2 REE mineralization occurs in 

discordant dikes and tabular sheets, up to tens of meters thick and hundreds of meters long, which are 

filled with primary igneous minerals that crystallized directly from magma or a late-stage hydrothermal 

fluid. These REE-enriched igneous rocks are of two types; those enriched in fluorine, and those enriched 

in phosphorus. The igneous rocks enriched in fluorine have as their REE-bearing minerals idiomorphic 
1464 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

phenocrysts of khanneshite-(Ce), together with synchysite-(Ce), bastnäsite-(Ce), and calkinsite-(Ce) of 

likely secondary (alteration) origin. The igneous rocks enriched in phosphorus have as their 

REE-bearing minerals idiomorphic phenocrysts of carbocernaite-(Ce), together with parisite-(Ce) of 

secondary origin. 

Figure 21A–5. Examples of concordant REE mineralization (Type 1) in the marginal zone of the central intrusive 

vent, February 2011 traverse (fig. 21A-2). (a) Photograph of common alvikite in the REE-enriched zone showing the 

pitted nature and abundant yellow-weathering indicating the presence of REE carbonate minerals. (b) Photograph 

of the concordant symmetric bands of mineralized alvikite at outcrop RT-11K-2, February 2011 traverse.

(c) Photograph of a partially rotated concordantly mineralized band implying high fluidity of the mineralized rocks. 

Outcrop near RT-11K-3, February 2011 traverse. (d) Photograph of alvikite showing the mineralized bands at 

station RT-11K-5. The concordant bands of mineralized alvikite alternate with common dolomite-ankerite alvikite at 

the scale of centimeters. Photographs by Robert D. Tucker, U.S. Geological Survey.
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1465

Figure 21A–6. Mineralogy and crystallization sequence of the concordantly REE-mineralized rock, RT-11K-2, 

February 2011 traverse. (a) Photograph of the concordant symmetric bands of mineralized alvikite. (b) Slab of the 

symmetrically zoned band, outlined in 6a, showing the (approximate) location of the false-colored backscattered 

electron images (c-f). (c) False-colored backscattered electron image of box c, dark band of apatite, dolomite, and 

calcite: apatite (ap), apatite-(Ce) (ap-(Ce)), dolomite (dol), khanneshite (kh), and calcite (cc). Calcite and 

khanneshite appear as late, interstitial minerals after early-formed phenocrysts of dolomite and apatite. 

(d) False-colored backscattered electron image of box d: dolomitic ankerite (dol-ank), apatite (ap), barite (ba), 

strontianite (str) and, khanneshite (kh). Barite, strontianite, and khanneshite appear as an infilling of late minerals 

into brecciated dolomitic ankerite of the host alvikite. (e) False-colored backscattered electron image of box e, 

light-colored band: Sr-rich orthocarbonate (Sr >Ca carbonate), barite (ba), dolomitic-ankerite (dol-ank), calcite (cc), 

and khanneshite (kh). (f) False-colored backscattered electron image of box f, dark-colored band: barite (ba), 

dolomitic-ankerite (dol-ank), apatite (ap), strontianite (str), and khanneshite (kh). The dark bands consist mostly of 

dolomitic ankerite and barite, with interstitial strontianite, apatite, and immiscible droplets of khanneshite and 

strontianite. Photographs by Robert D. Tucker, U.S. Geological Survey.
1466 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 21A–7. Examples of discordant REE mineralization (Type 2) in the marginal zone of the central intrusive 

vent, February 2011 traverse, (fig. 21A-2). (a) The apatite-rich discordant carbonatite dike, with local pegmatitic 

texture, at outcrop RT-11K-6. The carbonatite dike, approximately 75 centimeters thick and steeply dipping, has 

relic igneous texture and demonstrable intrusive contacts with the concordantly banded alvikite (to the left). (b) An 

example of a fluorine-rich carbonatite dike, Khanneshin igneous complex (RT-11K-4), showing its intrusive nature 

into the banded alvikites of the marginal zone, central intrusive vent. (c) A thin apatite-rich dike (under the foot of 

the hiker) intruding yellow-weathering REE-enriched alvikite of the marginal zone, central intrusive vent (RT-11K3B). (d) Slab of the apatite-rich carbonatite dike at RT-11K-3B showing the large phenocrysts of carbocernaite in a 

matrix of dolomitic-ankerite, apatite, barite, and strontianite. (e) Slab of the apatite-rich carbonatite dike at RT-11K-6 

showing the large phenocrysts of carbocernaite in a matrix of dolomitic-ankerite, apatite, barite, and strontianite. 

(f) Slab of the fluorine-rich carbonatite dike at RT-11K-4 showing the large yellow-weathering phenocrysts of 

REE-carbonate in a fine-grained matrix of dolomite, barite, strontianite, and calcite. Also present, but too small to 

see at this scale, are phenocrysts of a former fluorine-bearing mineral now pseudomorphed by a strontium-rich 

orthocarbonate and an unidentified compound with potassium, magnesium, and fluorine. (g) Hand specimen of a 

fluorite- and khanneshite-bearing carbonatite dike (RT-10K-3) that has intruded discordantly across the volcanic 

layering of the layered volcanic tuffs (alvikite). (h) Close-up of the fluorine-rich dike and its contact with the layered 

volcanic tuff. Photographs by Robert D. Tucker, U.S. Geological Survey.
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1467

A magmatic origin is clearly indicated for Type 2 discordant dikes and tabular sheets 

(fig. 21A–8). Based on textural and field evidence, we suggest that the semiconcordant veins and 

discontinuous seams (Type 1 mineralization) may have formed in the presence of REE-rich 

hydrothermal fluids. It is possible that both types of REE mineralization may be penecontemporaneous, 

having formed in the marginal zone of a carbonate-rich magma, highly charged with volatile 

constituents (for example, carbon dioxide and fluorine), and strongly enriched in barium, strontium, and 

the LREE (La, Ce, Pr, and Nd). 

21A.5.4.2 Grade of Barium, Strontium, and REE Enrichment

The grades in both types of REE-mineralized rocks are extraordinarily high and comparable to 

the world-class ores from Mountain Pass, California (USA) and Bayan Obo (China) (figs. 21A–9, 

21A–10). Like both of these REE deposits, the barite-alvikites at Khanneshin are highly enriched in the 

light rare earth elements (LREE), over heavy rare earth elements (HREE). In contrast, the alvikites of 

the northeast part of the central vent are also highly enriched in barium and strontium (table 21A–1).

Type 1 mineralized rocks average 19.92 weight percent Ba, 3.61 weight percent Sr, and 

2.78 weight percent ∑ LREE (the sum of La, Ce, Pr, and Nd). The average values of ∑ LREE for eight 

of our samples range between 6.22 and 1.83 weight percent (table 21A–2).

Type 2 mineralized rocks average 11.1 weight percent Ba, 5.46 weight percent Sr, and 

3.28 weight percent ∑ LREE (the sum of La, Ce, Pr, and Nd). The average values of ∑ LREE for 14 of 

our samples range between 5.98 and 0.49 weight percent (table 21A–2).

Table 21A–1. Minerals containing rare earth elements, strontium, or barium as 

complex. 

major elements at the Khanneshin 

Mineral Formula Theoretical REE2O3 (weight percent)

carbocernaite (Ca,Na)(Sr,Ce,Ba)(CO3)2 18.64

ancylite-(Ce) Sr(Ce) (CO3)2 (OH) · H2O 47.98

calkinsite-(Ce) (Ce,La)2 (CO3)3 . 4H2O 61.62

synchysite-(Ce) Ca(Ce,La)(CO3)2F 52.64

parisite-(Ce) Ca(Ce,La)2(CO3)3F2 60.89

bastnäsite-(Ce) (Ce, La) CO3 F 74.81

apatite-(Ce) (Ca,Ce)5PO3F < 5

strontianite SrCO3

barite BaSO4

celestine SrSO4

1

Belovitskaya and others, 2 2002; Yeremenko and Bel'ko, 1983; 3 Mandarino, 1995.

21A.5.4.3 Preliminary Resource Estimation

Tucker and others (2011) calculated a new estimation of the REE resource at Khanneshin based 

on field and analytical work conducted from 2009 to 2011. Because rocks in the Khanneshin Carbonatite 

Area of Interest have not been mapped in detail, drilled for exploration, or investigated using modern 

geophysical methods, the estimation is necessarily preliminary with various inferred assumptions. The 

calculation to convert rock volume to LREE resource involves converting volume to mass, via a density 

conversion factor, and then mass to a theoretical quantity of recoverable resource using an average grade 

of total LREE content (tables 21A–2 and 21A–3).
1468 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 21A–8. Mineralogy and crystallization sequence of the apatite-rich intrusive dikes, Khanneshin complex. 

(a) Outcrop of intrusive dike RT-11K-6. The rectangle of image b shows the approximate location of the hand 

specimen pictured in b. (b) Rock slab of sample RT-11K-6 showing the phenocrysts of carbocernaite-(Ce) in a 

matrix of dolomitic-ankerite, siderite, apatite, and barite. Location of images c, d, and e are shown as the inset 

boxes. (c) False-colored backscattered electron image showing the textural relationships among carbocernaite-(Ce) 

(c-cer), dolomite-ankerite (dol-ank), apatite (ap), siderite (sid), barite (ba), and parisite-(Ce) (par). Dolomitic 

ankerite, with siderite rims, and carbocernaite-(Ce) are early phenocrysts; apatite and barite are interstitial minerals; 

and parasite-(Ce) is a late-stage alteration mineral of carbocernaite-(Ce). (d) False-colored backscattered electron 

image showing the textural relationships among carbocernaite-(Ce) (c-cer), dolomite-ankerite (dol-ank), siderite

(sid), barite (ba), and apatite (ap). Dolomitic ankerite, with siderite rims, and carbocernaite-(Ce) are early 

phenocrysts; apatite, and barite are interstitial minerals; and parasite-(Ce) is a late- stage alteration mineral of 

carbocernaite-(Ce). (e) False-colored backscattered electron image showing the textural relationships among 

carbocernaite-(Ce) (c-cer), dolomite-ankerite (dol-ank), siderite (sid), barite (ba), strontianite (str), apatite (ap), and 

parasite-(Ce) (par). Dolomitic ankerite, with siderite rims, and carbocernaite-(Ce) are early phenocrysts; apatite, 

barite, and strontianite form interstitial minerals; parasite-(Ce) is a late-stage alteration mineral of carbocernaite-

(Ce). Photographs by Robert D. Tucker, U.S. Geological Survey.
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1469

Figure 21A–9. Variations in major- and trace-element concentrations between normal alvikite and sövite of the 

Khanneshin carbonatite and the light rare earth element (LREE)-enriched rocks of the marginal central vent. Red 

circles are volcanic tuffs and dikes from the southwest part of the complex (Traverse 1, September 2009). Blue 

circles, filled and unfilled, are LREE-enriched rocks from the LREE zone. The shaded orange area is the field for 

Khanneshin intrusive and volcanic rocks sampled in 2009 and 2010. Also shown is average calcio-carbonatite (CC, 

yellow star), ferro-carbonatite (FC, red star), and magnesio-carbonatite (MC, blue star) from Woolley and Kempe 

(1989). (a) MnO (weight percent) versus Fe2O3 (weight percent). Note the strong enrichment in MnO of the

REE-enriched rocks over the common alvikites of the Khanneshin carbonatite complex. (b) CaO (weight percent) 

versus barium (parts per million). Note the very high concentrations of barium, relative to CaO, in the REE-enriched 

rocks of the Khanneshin carbonatite. One percent (parts per hundred) equals 10,000 ppm (parts per million). 

Symbols same as figure 21A-9a. (c) Strontium (parts per million) versus barium (parts per million). Note the very 

high concentrations of barium, relative to strontium, in the REE-enriched rocks of the Khanneshin carbonatite. Also 

shown are concentrations in carbonatite dike at Bayan Obo (China) (data from Yang and others, 2009). One 

percent (parts per hundred) equals 10,000 ppm. Symbols same as figure 21A-9a. (d) Ytterbium (parts per million) 

versus log P2O5 (weight percent). Note the strong correlation between ytterbium and P2O5 in the REE-enriched 

rocks of the Khanneshin carbonatite, suggesting control by apatite. The concordantly banded rocks, and those 

intrusive dikes having modal apatite and carbocernaite, are enriched in ytterbium, a proxy for the HREE. The 

fluorine-rich intrusive dikes, bearing either fluorite or the unnamed potassium, magnesium, fluorine phase, are poor 

in apatite (lower P2O5 values) and hence they have lower HREE concentrations. Symbols same as figure 21A-9a. 
1470 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Figure 21A–10. Diagrams illustrating the magnitude and significance of REE enrichment in the marginal zone, 

central intrusive vent, Khanneshin complex. Red circles are volcanic tuffs and dikes from the southwest part of the 

complex (Traverse 1, September 2009). Blue circles, filled and unfilled, are LREE-enriched rocks from the LREE 

zone. The shaded orange area is the field for Khanneshin intrusive and volcanic rocks sampled in 2009 and 2010 

(Traverses 2 and 3). Also shown is average calcio-carbonatite (CC, yellow star), ferro-carbonatite (FC, red star), 

and magnesio-carbonatite (MC, blue star) from Woolley and Kempe (1989). (a) Lanthanum (parts per million) 

versus strontium (parts per million). The positive correlation of the LREE and strontium in the REE-enriched rocks

indicates the propensity of the LREE to substitute for strontium in khanneshite (burbankite group) and 

carbocernaite, the primary carbonate minerals, of the Khanneshin complex. Also shown are mineralized carbonate 

and carbonatite dikes from Byan Obo (data from Yang and others, 2009) and average ores from Mountain Pass, 

California (data from Castor, 2008). (b) Lanthanum (parts per million), representative of the LREE, versus ytterbium

(parts per million), representative of the HREE. Common alvikites of the Khanneshin complex have LREE and 

HREE concentrations similar to average ferro-, magnesio-, and calcio-carbonatites worldwide. However, the 

ankerite-barite alvikites of the marginal central vent, Khanneshin complex, are highly enriched in the REE and 

comparable in grade to the world-class REE deposits of Bayan Obo (data for average Bayan Obo ores from Yuan 

and others, 1992) and Mountain Pass (data from Castor, 2008). (c) The Khanneshin whole-rock concentrations, 

February 2011 traverse, normalized relative to chondrite values. Same symbols as b, above. Also shown are the 

minimum, mean, and maximum grades of the REE ores from Mountain Pass and Bayan Obo (data sources as in b).
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1471

Table 21A–2.

[ppm, parts per million; wt. %, weight percent]

Barium, strontium, and rare earth element (REE) concentrations in whole rocks from the zone of light rare earth element (LREE) enrichment 

from the February 2011 scoping mission at the Khanneshin carbonatite area of interest.

Occurrence 

type

Ba

wt.%

Sr

wt.%

La

ppm

Ce

ppm

Pr

ppm

Nd

ppm

Sm

ppm

Eu

ppm

Gd

ppm

Tb

ppm

Dy

ppm

Ho

ppm

Er

ppm

Tm

ppm

Yb

ppm

Lu

ppm

La

wt. %

Ce

wt. %

Pr

wt. %

Nd

wt. %

∑ LREE

wt. %

RT-11K-1A1 2 19.62 3.05 10,300 14,600 1,110 2,880 258 40109 6.9 26.4 3.4 8.3 1.01 5.8 0.86 1.030 1.460 0.111 0.288 2.889

RT-11K-1A2 2 21.51 3.90 11,400 15,800 1,190 3,040 267 42115 7.5 28.4 3.6 8.5 1.06 6.1 0.91 1.140 1.580 0.119 0.304 3.143

RT-11K-1B2 2 18.74 3.36 10,000 14,700 1,160 3,050 278 43109 7.7 28.7 3.5 8.4 1.02 5.7 0.88 1.000 1.470 0.116 0.305 2.891

RT-11K-2A2 1 19.04 2.21 5,820 8,880 840 2,740 390 75223 27.4 124 15.8 30.5 3.03 14.3 1.64 0.580 0.888 0.084 0.274 1.826

RT-11K-2B1 1 20.70 3.85 8,620 11,700 1,010 3,090 415 85271 36.5 162 20.8 40.4 3.84 17.1 2.06 0.860 1.170 0.101 0.309 2.440

RT-11K-2B2 1 21.01 3.64 7,980 11,200 992 3,060 417 85267 36.2 160 20.9 39.8 3.83 16.9 2.11 0.790 1.120 0.099 0.306 2.315

RT-11K-3B31 2 23.63 4.43 10,400 12,200 945 2,710 445 107367 47.5 181 18.6 30.9 2.47 11.2 1.36 1.040 1.220 0.095 0.271 2.626

RT-11K-3B32 2 28.57 6.05 16,000 16,600 1,180 3,040 328 65221 27 118 13.0 20.7 1.72 7.1 0.81 1.600 1.660 0.118 0.304 3.682

RT-11K-4AO1 2 4.99 4.75 5,550 7,940 720 2,160 231 38 91.7 6.1 22.8 3.1 8.6 1.24 8.4 1.34 0.550 0.794 0.072 0.216 1.632

RT-11K-4AO2 2 12.92 8.24 18,800 17,600 1,170 2,770 217 34108 6.1 23.1 3.3 8.3 1.16 7.4 1.21 1.880 1.760 0.117 0.277 4.034

RT-11K-4B3 2 10.63 7.05 14,500 14,500 1,020 2,540 216 34 95.8 5.7 23.1 3.4 9.0 1.23 7.9 1.30 1.450 1.450 0.102 0.254 3.256

RT-11K-4C1A 2 10.61 7.20 14,100 13,900 995 2,470 210 33 90.1 5.3 20.2 3.1 8.4 1.25 8.5 1.43 1.410 1.390 0.100 0.247 3.147

RT-11K-4C1B 2 3.98 1.91 1,440 2,360 244 838 189 49166 24.4 120 18.6 44.3 5.23 27 3.53 0.144 0.236 0.024 0.084 0.488

RT-11K-5A2 1 24.59 2.57 5,990 13,000 1,240 3,690 507 110349 44.1 181 19.9 32.8 2.83 12.6 1.57 0.599 1.300 0.124 0.369 2.392

RT-11K-5A3 1 22.44 2.91 5,870 12,400 1,190 3,580 512 112369 47.8 201 22.3 36.7 3.29 14 1.67 0.587 1.240 0.119 0.358 2.304

RT-11K-5B1B 1 23.73 3.77 5,380 11,900 1,180 3,600 508 109352 46.2 201 23.8 42.3 3.7 15.8 1.80 0.538 1.190 0.118 0.360 2.206

RT-11K-5B3B 1 22.79 4.95 6,400 13,300 1,270 3,990 626 136431 55.5 236 25.5 38.2 3.01 12.7 1.52 0.640 1.330 0.127 0.399 2.496

RT-11K-5B6A 1 5.03 4.98 21,000 31,500 2,600 7,090 657 102274 15.8 46.5 5.0 11.0 1.36 8.3 1.36 2.100 3.150 0.260 0.709 6.219

RT-11K-6A2A 2 3.25 2.37 5,790 9,030 870 2,810 397 84279 46.4 266 43.3 98.1 9.48 40.4 4.33 0.579 0.903 0.087 0.281 1.850

RT-11K-6A2B 2 8.70 6.82 20,900 29,100 2,480 7,300 816 140376 37.5 175 25.7 54.6 5.32 23.4 2.59 2.090 2.910 0.248 0.730 5.978

RT-11K-6B2 2 7.49 5.62 16,600 23,000 1,980 5,800 615 102279 22.5 90.8 11.4 22.0 2.16 9.7 1.12 1.660 2.300 0.198 0.580 4.738

RT-11K-6B3 2 7.00 5.61 16,700 22,400 1,890 5,680 660 120358 38.5 180 26.2 56.0 5.43 23.1 2.60 1.670 2.240 0.189 0.568 4.667

∆ Ba

wt.%

∆ Sr 

wt.%

∆ La 

wt.%

∆ Ce 

wt.%

∆ Pr 

wt.%

∆ Nd 

wt.% ∆ LREE

15.50 4.51 Total collection 1.091 1.491 0.125 0.357 3.063

19.92 3.61 Type 1 mineralized rocks (# 2,5) 0.837 1.424 0.129 0.386 2.775

11.07 5.46 Type 2 mineralized dikes (# 3,4,6) 1.279 1.533 0.123 0.347 3.282

19.96 3.44 Fluorine-rich dikes (#1) 1.057 1.503 0.115 0.299 2.974
1472 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

Table 25A–3. Estimated LREE resources of the Khanneshin complex.

3 [g/t, grams per cubic centimeter; km, kilometers; m , cubic meters; Mt, million metric tons; wt. %, weight percent]

Rock ∆ LREE Mt LREE Mt LREE Length Width Depth Volume Density, quantity grade† (before 10:1 (after 10:1 (m3 3 (km) (km) (km) ) (g/cm ) Mt # (wt.%) dilution) dilution)

LREE enriched box

Type 1. Concordant veins and seams:

0.750 0.550 0.150 0.061875 2.94 181.913 2.775 5.048 0.505

0.330 0.250 0.150 0.012375 2.94 36.383 2.775 1.010 0.101

Total LREE box 0.074250 2.94 218.295 2.775 6.058 0.606 * Type 2. Discordant veins and seams

#1 0.050 0.020 0.150 0.000150 2.94 0.441 3.282 0.014

#2 0.500 0.040 0.150 0.003000 2.94 8.820 3.282 0.289

#3 0.400 0.035 0.150 0.002100 2.94 6.174 3.282 0.203

Total discordant sheets 0.005250 2.94 15.435 3.282 0.507

$ $ Total LREE box 1.113

Remote sensing polygons

Northwest of the Soviet-defined box 0.071176 2.94 209.257 2.775 5.807 0.581

Within the Soviet-defined box 0.073124 2.94 214.985 2.775 5.966 0.597

Total remote sensing polygon 1.178

†Taken from table 21A–2.

#

Wall rock is 10 times more abundant than mineralized seams, hence 10:1 dilution factor

*

Estimated from mineral content in dikes, not affected by wall rock dilution

$

Sum of Type 1 and Type 2 tonnage

Soviet geologists delineated an area (fig. 21A–2), approximately 0.64 km2, within which 

ankerite-barite carbonatite is macroscopically enriched in REE-bearing carbonate minerals. Within this 

area the total LREE concentrations in many rocks approach several percent, with barium and strontium 

concentrations averaging 15.5 and 4.51 weight percent, respectively (table 21A–2). 

21A.5.4.3.1 Concordant Layers of Mineralization 

Concordant mineralization consists of yellow-weathering REE-carbonates (± fluorine) that form 

layer-parallel, centimeter-thick bands, which alternate with dark, meter-thick layers of ankerite-barite 

alvikite (wall rock). Based on USGS field observations and the Soviet work, whose field teams 

accurately described the geology and mineralogy of the entire igneous complex, we assert this style of 

mineralization is common throughout the area of REE enrichment. This assumption is borne out by the 

many samples of “REE ore” recovered and analyzed by Soviet geologists in the area and by our own 

collection that confirms their data. The volume of REE mineralization, however, must be diluted by a 

factor of 10, which is approximately the ratio of concordantly mineralized rock to weakly mineralized 

wall rock (fig. 21A–5d). This dilution factor is a conservative value because, in some sections, 

concordant mineralization is ubiquitous, whereas, in other sections, surface exposures are poor or 

covered by alluvium. The proper way to determine directly this dilution factor is to drill and assay 

recovered rock core throughout the area. It was not possible to do this for our study because of 

budgetary, logistical, time, and security concerns. 

Because drilling, core analysis, and geophysical exploration were not possible, the depth of 

mineralization throughout the REE zone is estimated from ground observations. We assert a value of 

150 m based on the vertical dimension of mineralized rock observed over the rugged relief of the region 

(approximately 170 m). In essence, we assume a depth of mineralization that roughly mimics the surface 

topography of the area of REE enrichment. This assumption is justified because the topography is young 

( less than 5 million years), the valley walls are steep, and hence the mass of eroded rock is small 

relative to the unexhumed mass at depth. We believe, moreover, our estimate is conservative if, as seems 
Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest 1473

likely, the zone of REE enrichment extends to depths well beyond the arbitrary value of the local relief 

(fig. 21A–3). The proper means to determine the depth of mineralization is to drill and assay core 

throughout the region of REE enrichment.

Using an average density of mineralized carbonatite (2.94 grams per cubic centimeter, g/cm3), an 

average grade of LREE concentration (2.775 weight percent, table 21A–2), and a dilution factor of 10:1 

(wall rock: mineral bands), we calculate approximately 0.505 Mt (million metric tons) of LREE are 

present in the concordantly mineralized rocks of the Soviet-defined zone (table 21A–3).

21A.5.4.3.2 Discordant Tabular Sheets 

Within the zone of REE enrichment, Soviet geologists identified more than 50 “ore bodies” of a 

stockwork-type with widths between 60 and 0.5 m and lengths between 500 and 20 m. The vertical 

dimension of the stockwork bodies is not given, but they are likely to be hundreds of meters deep, as 

they form near-vertical dikes (fig. 21A–7) across the rugged relief of the region. These bodies 

correspond to the discordant, steeply dipping tabular sheets of this report, which are decimeters to 

meters thick and meters to hundreds of meters long.

Three major stockwork bodies of this type were trenched and sampled by the Soviet teams 

(Cheremitsyn and Yeremenko, 1976): 

Stockwork dike # 1, located in the northwest part of the REE zone, is 20 m by 50 m with a 

northwest strike and near-vertical dip. Ten small trenches, each 2 m long, were dug across the dike. The 

LREE concentration (La plus Ce) for all of the Soviet samples averages more than 1.5 weight percent 

(Cheremitsyn and Yeremenko, 1976).

Stockwork dike #2, located in the northern part of the REE zone, is 10-60 m wide and 500 m 

long; it has a north-south strike and near-vertical dip. Three trenches were dug across the dike, in its 

northern, central, and southern part. The average concentration for La plus Ce for all of the trench 

samples is 1.5 weight percent (Cheremitsyn and Yeremenko, 1976).

Stockwork dike # 3, located in the southeast part of the REE zone, is ~35 m wide and 400 m 

long; it has a northeast strike and near-vertical dip. One trench across its central part yielded an average 

concentration for La and Ce of greater than 1.5 weight percent (Cheremitsyn and Yeremenko, 1976).

The Soviet analyses of the stockwork dikes yield LREE concentrations that are compatible with 

the average ∑LREE concentrations of the discordant dikes in our collection (3.282 average weight 

percent ∑LREE, table 21A–2). 

Our estimate of LREE resources within the discordant tabular dikes (table 21A–3) is a 

conservative estimate because the calculation is only for the three largest dikes, and more than 50 such 

bodies are recognized. As with the resource calculation for the concordantly mineralized rocks, we 

assume the discordant dikes extend to 150 m depth and that LREE concentrations are uniform 

throughout the mass of rock. 

Assuming an average density for carbonatite (2.94 g/cm3

) and an average grade of ∑LREE 

concentration (3.282 weight percent, table 21A–2), we estimate approximately 0.507 Mt of LREE are 

present in the three largest dikes (discordant sheets) of the Soviet-defined zone (table 21A–3). 

Thus, together with the concordantly mineralized rocks, we estimate a LREE resource of 1.1 Mt

in the entire Soviet-defined REE zone. This estimate comports well with the probabilistic estimate of 

1.4 Mt of undiscovered REE resources in all of south Afghanistan (Peters and others, 2007). In addition 

to the LREE, the Khanneshin carbonatite is greatly enriched in barium (> 10 weight percent), strontium 

(> 6 weight percent), phosphorus (~ 2 weight percent), and uranium (> 0.05 weight percent). A resource 

calculation of these elements was not attempted.

21A.6 Summary of Potential

The presence of relatively well-explored REE and uranium prospects at the Khanneshin 

Carbonatite Area of Interest and its subareas is an important positive indicator for this area. The 
1474 Summaries of Important Areas for Mineral Investment and Production Opportunities of Nonfuel Minerals in Afghanistan

petrologic characteristics of the associated igneous rocks and the available assays suggest that a REE 

deposit of significant size may be present. 

The USGS assessment team (Peters and others, 2007) estimated that there is a 90-percent chance 

of 0 or more undiscovered porphyry copper deposits at Khanneshin, a 50-percent chance of 1 or more, 

and a 10-percent chance of two or more deposits. The amounts of contained metal that result from a 

Monte Carlo simulation based on this estimate are illustrated and summarized in table 21A–4. This is a 

relatively optimistic estimate for a relatively small area.

Table 21A–4a. The statistical parameters 

[Data are from Peters and others (2007)] 

for the assessment 

deposits

of the Khanneshin permissive tract. 

Probability (percent) Estimated number of 

90 0

50 1

10 2

5 3

1 5

Table 21A–4b. Estimated mean metric tons of undiscovered mineralized rock, phosphate, rare earth elements 

(REE), and niobium in undiscovered deposits of the Khanneshin complex. [Data are from Peters and others (2007). Values are rounded to no more than three significant digits. Nb, niobum; 

P, phosphorus]

Rock (metric tons) P (metric tons) REE (metric tons) Nb (metric tons)

251,000,000 6,200,000 1,400,000 3,500,000

These estimates were used to generate probabilistic estimates of the amounts of phosphorus, 

REE, and niobium in the undiscovered deposits using Monte Carlo simulation (table 21A–4b). 

Based on several assumptions, and employing a simple geometry for volume of mineralized 

rock, the present report estimates at least 1 Mt (million metric tons) of LREE are present in the 

Khanneshin Carbonatite Area of Interest (Tucker and others, 2011). 

Future discoveries and delineations of resources with the Khanneshin Carbonatite Area of 

Interest require aeromagnetic and aeroradiometric surveys flown at low elevation, coupled with detailed 

geologic mapping,, explatory drilling, and ground geochemical surveys. 

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