1. Antony Benham, Stan Coats, Fiona McEvoy British Geological Survey
Aynak – a world-class sediment-hosted stratiform copper deposit in Afghanistan
Antony Benham, Stan Coats, Fiona McEvoy
British Geological Survey

2. Structure Introduction Afghanistan and the BGS project
Mineral potential of Afghanistan
The Aynak copper deposit
Geology of the area
Style of mineralisation
Past mining/exploration activities
Current and future activity
Summary

3. Introduction to Afghanistan
Turbulent recent history
Since the fall of the Taliban in 2001:
Hamid Karzai elected
President
Peaceful elections in
2004 and 2005
Return to stability
Afghanistan is situated in a strategic position in south-central Asia and borders Iran to the west, Pakistan to the south, and Turkmenistan, Uzbekistan and Tajikistan to the north.
A small part of the country also borders China in the so called Pan Handle of Afghanistan in the extreme east of the country.
Afghanistan has had a very turbulent recent history with decades of war and internal conflict since the Soviet occupation in 1980.
In more recent times however, since the fall of the Taliban in 2001, the country has seen a gradual progression towards democracy with peaceful elections being held in 2004 and 2005, and there is a strong desire for most Afghanis to start to rebuild their country.
BGS’s role in Afghanistan
Three year DFID-funded project to strengthen the capability of the Afghan Geological Survey (AGS)
Promoting mineral resources of Afghanistan
Intention is to provide the AGS with the skills to perform the functions of a national survey and provide assistance to mining companies
The most promising mineral deposit that could be developed in the foreseeable future is the Aynak copper deposit which is the focal point of this talk
However, the talk is based almost exclusively on reports and data produced from Soviet geologists during the occupation until 1989 and BGS have not yet done any primary exploration or analytical work on Aynak and therefore only limited interpretation can be made at this stage.

4. Mineral occurrences in Afghanistan
Afghanistan is world famous for its Lapis Lazuli and gem quality emeralds, however it also has significant amounts of other minerals and the country has not generally been well explored using modern exploration techniques.
There are >1000 mineral occurrences identified in Afghanistan including:
Major sediment-hosted copper deposits e.g. Aynak (click once)
Copper-gold skarn deposits (click TWICE)
Gold placer deposits (currently worked by artisanal miners) (click once)
Precious gemstones including ruby, emerald, lapis lazuli (click once)
Sediment-hosted iron deposits e.g. Hajigak
Chromite deposits e.g. Logar
Vast industrial mineral deposits
Detailed mapping and exploration from mid 19th century
Afghanistan Geological Survey established 1955
German, Italian, French and Soviet involvement from 1955
Detailed exploration work during Soviet occupation from
Little work carried out since Soviet withdrawal

5. Location of the Kabul Block
Thought to be a terrane accreted to margins of Laurasia 250 Ma
Hosts numerous copper occurrences and old workings
Afghanistan has a very complex geological history and sits astride the collision zone of the Indo-Pakistan and Asian crustal plates, which has given rise to the Himalayas.
This slide shows the outline of Afghanistan in red with the high terrain of the Hindu Kush mountains leading into the Himalayas further to the east.
You might be able to make out some major fault lines some of which are believed to represent the boundaries of small blocks or ‘terranes’ which split off around 250 million years ago from the margin of the Gondwana supercontinent.
These terranes then successively accreted on to the southern margin of the Asian continent. The Kabul Block is interpreted to be a one of these fragments and it hosts many copper occurrences together with evidence that copper has been worked in the area since ancient times.
Location of the Kabul Block

6. Tectonic map of Afghanistan
This slide shows the major tectonic domains and position of the Kabul Block a bit more clearly.
The Kabul Block is bound by two major faults, on the west by the Pagman Fault and on the east by the Altimur Fault.
Aynak is one of a number of copper prospects that occur in the Kabul block and it is situated 35 km south-south-east of Kabul.
Area shown in next slide

7. Geological map of Aynak
The deposit occupies an area of 7.0 km2 and is divided into two prospects, Central Aynak and Western Aynak.
The structure at Aynak is dominated by the Aynak anticline. The anticline is asymmetrical and approximately 4 km in length and up to 2.5 km wide. The southeastern limb dips gently to the south-east but the northwestern limb is steeply dipping and, in places overturned, with dips of 45–70° to the south- east.
The periclinal closure of the anticline at its western end is asymmetrical. Here, the southern limb is overturned and the axial plane is inclined towards the north-north-east. Several sets of later faults cut across the folds.

8. Cross sections through Aynak
The oldest rocks exposed in the area belong to the metavolcanic Welayati Formation, composed of gneiss and amphibolites, and are exposed in the core of the anticline.
This formation is overlain by the thick metasedimentary sequence of the Loy Khwar Formation, which is a cyclical sequence of dolomite marble, carbonaceous quartz schist and quartz-biotite-dolomite schist and hosts the copper mineralisation
The Loy Khwar Formation is post-dated by basaltic to dacitic metavolcanic rocks of the Gulkhamid Formation, which are also of Vendian–Cambrian age.

9. Stratigraphic column at Aynak
The copper mineralisation at Aynak is stratabound and characterised by bornite and chalcopyrite disseminated in dolomite marble and quartz-biotite-dolomite schists of the Loy Khwar Formation. The mineralisation is mainly concentrated in members 3-5 of the Formation.
The main zone of mineralisation at Central Aynak is dominated by bornite. Chalcopyrite occurs in only minor amounts in the middle and lower parts of the body, but increases in the upper parts. Cobalt concentrations are very low but, like zinc, increase peripherally in some parts of the deposit.
The oxidised zone varies between m depth beneath Neogene cover. This zone contains chalcocite and native copper and passes downwards into a mixed zone of oxidised and primary sulphides. No evidence for a supergene-enriched zone occurs.

10. Mineralisation at Aynak
Left: Bornite mineralisation within dolomite marble of the Loy Khwar Formation.
1cm
Near right: Porphyroblastic dolomite marble with chalcopyrite.
This slide shows samples of some of the mineralisation from Aynak, including bornite mineralisation from the Loy Kwhar Formation as well as dissemination and stringer chalcopyrite mineralisation in this biotite-feldspar-quartz schist.
Far right: Finely laminated biotite-feldspar-quartz schist with disseminations and stringers of chalcopyrite.
1cm
1cm

11. Central Prospect, Aynak
These two slides show what some of the area at Aynak looks like.

12. Central Prospect, Aynak

13. Other occurrences in the Kabul Block
In addition to Aynak, numerous other occurrences are found within the region.
Notable amongst these are Darband and Jawkhar, which are situated a short distance to the north and north-east of Aynak. Considerable exploration was undertaken by Soviet geologists on both prospects, although most information about Jawkhar was lost in recent years during the rise of the Taliban.
Both of these deposits are reported to be fairly sizeable and consist of similar geology and mineralogy, and the close proximity of them to Aynak suggests that they may be part of a larger “copper belt” that occurs within the Kabul Block.

14. Past exploration at Aynak
Extensive and detailed exploration by Soviet geologists between and including:
>150 boreholes
70 trenches
9 adits
Surface geological and geophysical surveying
Soviet “drill-indicated” resource estimate of % Cu, however this does not conform to Western classification standards.
The work of the Soviet-Afghan geologists’ on Aynak and its neighbouring deposits is documented in a large number of reports in the Afghanistan Geological Survey archive. In total, the exploratory work included over 150 boreholes, 70 trenches, nine adits and surface geological and geophysical surveying.
Original resource estimations carried out by Soviet Geologists, at varying cut-off grades, delineated several large ore bodies and a number of smaller lenses.
At a 0.4 % Cu cut-off grade, the main orebody at Central Aynak extends 1850 m along strike and 1200 m down dip and has a maximum thickness of 210 m.
At Western Aynak the main body extends 2230 m along strike and 1640 m down dip, and has a maximum thickness of 214 m, based on a similar cut-off.

15. Current work at Aynak
The BGS have created a database from exploration boreholes
All reports relating to Aynak have been translated from Russian to English
A 3D model of Aynak has been created in Vulcan
Reports and borehole database available on request

16. Vulcan model of Aynak
The Aynak model created in Vulcan is primarily based on borehole data but also includes sections drawn by Soviet geologists
Left: Section through the western prospect at Aynak looking east through the steeply dipping anticline
Assays of the drillcore are recorded on the borehole logs and this information, combined with the detailed lithology from
boreholes, cross sections and geological plans, made it possible to produce a 3D model showing the distribution of copper in the orebodies

17. Vulcan model of Aynak
The mineralised Loy Khwar Formation is the dark green unit 5
Left: Section through the central prospect at Aynak looking west through the shallow dipping section of the Aynak anticline
The main ore body in the Central zone of the deposit, with its shallow dip down from near surface, is probably mineable from an openpit.
The depth of overburden increases to the south and the stripping ratio may be too high to extend mining further south.
The Western zone is steeply dipping and underground mining would be needed to exploit the main ore body.

18. This movie shows the Aynak deposit that has been modelled by the BGS in Vulcan.
The view is looking from the west to the east and starts at the shallow-dipping Central Prospect with the mineralised zone in dark green, and progresses through several faults to the Western Prospect with its much steeper dipping mineralisation around the anticline.
The BGS is assisting in bringing the Aynak deposit to Tender.
The initial pre-Tender stage, which commenced at the Mines and Money conference in November, will allow interested parties controlled access to information held by the AGS.
Following this, pre-qualified companies will be able to have access to data in order to prepare a bid which will then be weighed up against each other before making the award of the mining contract.
Vulcan model of Aynak

19. Vulcan model of Aynak

20. Possible Mineral Deposit Model
Very little interpretative work has been done by BGS on a metallogenic model for the Aynak deposit.
One of the simplest theories that fits the facts we know about the deposit at the moment involves the action of evaporitic brines and seawater circulating through the underlying volcanic rocks of the Welayati Formation.
The circulating fluids may have leached copper from the volcanics and gained heat until they began to rise up faults and fractures. Just beneath the surface they would have reacted with newly deposited limestones and marls, containing abundant organic matter and reduced sulphide ions, and precipitated copper sulphides and altered the limestone to dolomite.
This theory is however only one of several mechanisms for the formation of this deposit and alternative mechanisms for producing these deposits may involve a more syngenetic or epigenetic method.

21. Summary Main features of the Aynak deposit
World-class stratabound ore deposit (240 Mt at 2.3 % Cu)
Mineralisation hosted within dolomite marbles and calcareous-biotite schists
Mineralogy dominated by bornite, chalcopyrite
Consists of two prospects, the shallow dipping Central Prospect and the more steeply dipping Western Prospect
Central Prospect amenable to open-pitting
Other prospects close to Aynak include Darband and Jawkhar suggest Aynak is part of a larger “copper belt”
Aynak is a world-class stratabound copper deposit which, but for the upheavals of the last 25 years in Afghanistan, would surely have become an operating mine. Its main features are:
● Easy access and close to Kabul with its infrastructure
● Few environmental problems
● New Minerals Law (2005)
● Government favourable to mining development