Gold & Silver bearing boulangerite prospects of Chitral Dist. Khyber Pakhtunkhwa, Pakistan.

Boulangerite?is a sulphosalt group of minerals, normally bluish, dark grey to black colored mineral types mainly composed of lead and antimony that commonly occur with galena and stibnite in low to medium temperature hydrothermal veins and stock works. Some other minerals commonly associated with boulangerite are sphalerite, pyrite, arsenopyrite, siderite and quartz.

Existence of Gold and Silver bearing boulangerite, currently being mined for galena and antimony metals was discovered during 1974-75 in Chitral Dist. of Khyber Pakhtunkhwa, Pakistan. This occurrence was further investigated in the field during 1980-81 by the USGS geologists in Awireth and Sewakht Valleys. The two Sub-valleys are located opposite to each other across the Lutkho Valley near Shoghore village where boulangerite mineralization in form of hydrothermal veins and lenticular bodies are reported to have been emplaced along the fault zone/s of Reshun Fault as well as in branch faults zones on its either sides.

Reshun Fault in turn is a regional thrust longitudinally ?intersecting the entire Karakorum terrain and separates Devonian-Jurassic rocks (constituting a wide variety of metavolcanic, metasedimentary and sedimentary rocks) from the Cretaceous rocks mainly composed of marble, limestone, red phyllite, conglomeratic phyllite and brown weathering conglomerates. Starting from Darosh in the southern most location at Chitral Dist; it passes through Awireth and Sewakht valleys for about 37 km and is traceable up to Shah Jinali pass in the extreme northeast of Chitral Dist. for about 165 km cumulative distance from its point of origin where it conceals under the soil cover towards Broghal valley in the east.

A 12 meter long and on the average1.2 meter wide boulangerite bearing vein emplaced along a local shear zone in Awireth gol valley was geologically examined in the field by the USGS geologists whereby presence of gold and silver was reported from these rocks that mainly composed of black, fine grained lead antimony sulphide with accessory chalcopyrite and pyrite. In some places the ore was also noticed as green colored malachite and yellow colored arsenic stained. According to the USGS report, published in 1981, samples taken at intervals across 1.2 meters width of the vein contain large amounts of gold and silver as well as smaller amounts of tin, vanadium and other metals. Results of partial chemical analyses of 5 numbers of such samples indicate that although lead and antimony constitute the bulk of the ore, the values of these and other metals is overshadowed by the gold and silver contents (Table-A).

Some more detailed field investigations were conducted by an Austrian Geologist, Dr. H.Gamerith during the years 1988-89. A total of 136 samples were analyzed from the area whereas the samples from the sulphide ore body’s average metal content was computed as: Antimony: 14%, Lead: 38%, gold: 50g/t, Silver: 470g/t. Concluding points of the aforementioned geological work were as under:

1-???Geological mapping of 12km long part of exposed Reshun fault zone in Awireth gol valley showed a few additional boulangerite lenticular bodies controlled by the main fault between Shoghor limestone in the east and Lun Shale of the Awireth green series in the west (Fig-1).

2-???Along the fault and in close relation with the Awireth Series, boulangerite mineralization occur in dolomitic zone which is interpreted as a border facies of the Shoghor limestone. Owing to the inherent physical characteristics it was found heavily fractured and in places mylonittized. Strong fracturing has made this “Contact dolomite” a preferred migration path for ascending hydrothermal solutions.?

3-???Boulangerite and related minerals of the high grade massive ore zone are emplaced in the dolomite, together with the disseminated and weakly auriferous pyrite mineralization.

4-???Along the outcrop there is usually a secondary gossan development mainly fracturing limonite.

5-???Gold was noted in the form of native gold (plus silver) as isolated grains in fractures of the sulphides.?

6-???The gold grains occur in sizes of 10 to 20 microns. Quartz, dolomite and calcite are the main gangue minerals.

7-???In a vertical sense the mineralization is exposed by underground workings over about 30 to 60 meters.

An impregnated altered pyrite disseminated zone and a quartz vein within showing weak boulangerite mineralization was recently sampled (Fig-2 & Fig-3) and got analyzed at SGS Pakistan as well as at CRL (Centralized Research Laboratories, University of Peshawar). Chemical analysis report of the same is portrayed vide table-B that strongly signals for occurrence of anomalous values of gold and silver even in the weakly boulangerite mineralized rocks of the area.???

In the light of compiled as well as fresh data already explained, the 2 oppositely facing valleys (Awirireth & Sewakht), where the Reshun Fault passes for a linear distance of about 37 km, seems to be highly potential area for occurrence of gold, silver and other precious metals. The gold and silver values already noticed in the rock units along the regional thrust fault (Reshun fault) by various workers loudly speaks of economic potentiality of gold and silver notwithstanding a ground reality of even overshadowing the higher contents of antimony and galena in rich boulangerite ores already discovered and being mined from this part of the world.

A pre-planned, fast track and cost effective detailed exploration work to be conducted at the outset, in Awireth and Sewakht valleys through applying modern geological exploration techniques by also using the findings of USGS and Dr. H. Gamerith already mentioned in this text as basic “Guide Lines” are therefore highly recommended. This proposed green field exploration program if successfully completed, may transform the entire region along the boundary zone of Reshun Thrust Fault that is traceable in the Chitral Dist. for about 165km in to a large theater for finding gold and precious metals.??