Geology and Mineral Potential of Chitral Region

Mineral Potential of Chitral Region

Northern Pakistan where is the RL area is located has a complex history of crustal evolution and a rich diversity of geological environments which compare favorably with geological similar mineral producing areas elsewhere in the world.

Regional Geological Setting

Geographically the Chitral region occupies the northeastern extremities of 1200 km long Hindukush range where it represents a diffuse boundary with the Karakorum range at Hindu Raj mountain chain, east of Yarkhun valley. Geotechnically the area represent the western extremities of Himalayan Orogenic belt. Geologically the region comprises thick upper Paleozoic to Mesozoic and Tertiary tectonostraitigraphic sedimentary and valcanoplutonic sequences.

Geology of the Chitral region, in a broad sense, is represented by the occurrences of thick Paleozoic to Mesozoic sedimentary series of Hindukush Karakoram (Asia) plate to the north, and a dominant Cretaceous volcano-sedimentary sequence to the south. The Paleozoic to Mesozoic rock belts were strongly compressed and tectonically folded and faulted during the Cretaceous-Teritiary orogenic activites and were subjected to the emplacement of subduction related volcano plutonic complexes.

With reference to the relevant literature and field observations, the Chitral region is subdivided into five major tectonostratigraphic domains. From north to south, these are (1) Wakhan Formtion, (2) Tirich Mir Fault Zone, (3) Chitral Central Complex, (4) Northern Suture Zone and (5) Kohistan Arc Batholith.

Wakhan Formation

The Wakhan Formation of Permian to Jurassic age extend from Wakhan (Afghanistan) toward south in the northwest of Chitral and comprising a continuous zone of dark black homogenous slate, silt stone with marker beds of light quartzite and intercalations of Calcareous schist and marble (Buchroithner and Gamerith, 1986) and thick bedded dolomite (Gaetani and Leven, 1993).

Tirich Mir Fault Zone

The Tirich Mir Fault Zone represents the most prominent tectonic lineament with in Hindukush Karakorum plate separating the Wakhan Formation in the north from the Chitral Central Complex in the south. The fault zone is observed to have been associated with basic ultrabasic rocks of tens of meters to hundreds of meters in thickness.

Chitral Central Complex

The Chitral Central Complex is characterized by regionally important NE-SW trending vertical to subvertical longitudinal faults system along contact zones of rock inhomogeneties. The most important and prominent of these faults is the Reshun Fault of Tipper (in Pascoe, 1923) and Calkins etal (1981) which passes along centre of the complex and separate the Upper Paleozoic series to the north from Mesozoic sequence, to the south in the western part of Chitral. The sedimentary sequence north of Reshun Fault comprises dark gray slate to silt stone with minor intercalations of quartzites, calcareous schist and at places volcano sedimentary green stone beds and is also characterized by presence of thick fossiliferous Devonian Carbonate of Hayden (1915) immediately along the north of Reshun fault. This part of the complex coincide with the Sarikal shale of Hayden (1915), lun shale and north-west unit of Pudsey etal (1985), lun shale of Desio (1966) and Devonian to Carboniferous rocks of Calkins etal (1981). Immediately south of Reshun Fault the complex is represented by a varied Mesozoic lithologies of massive limestone (Shoghore limestone) followed by polymictic red conglomerate, shale, slate and siltstone (Reshun Formation), dark grey slate and siltstone with intercalations of quartzites, calcareous schist, conglomerate grey wacks and green stone (Chitral slate), chloritic epidiote quartz schist (Koghozi green schist) and coarse grained marble (Gahirate Marble) in the south-western part of Chitral, and Permo-carboniferous dark grey slate to siltsotne and quartzite with intercalations of calcareous rocks (Darkat Group of Ivanac etal, 1956) in the eastern part of the region.

Northern Suture Zone

The Northern Suture Zone is the major known tectonic scare of Himalayan Orogeny in Chitral region which separates Hindukush Karakoram plate in the north from Kohistan Arc Batholith Terrains to the south. The suture zone is characterised by the occurrence of blocks of volcanic rocks, limestone, red shale, conglomerate, quartzite, and serpentinite in a shaly to slatty matrix mostly derived from the Kohistan Arc terrains and have preserved in the small back arc basin which closed 102-85 Ma (Treloar, 1989 b) and is interpreted as olistostromal in nature (Pudsey etal 1985, Pudsey 1986, Sear etal 1987, and Searl 1991).

Kohistan Arc Batholith

The Kohistan Arc Batholith represent late Jurassic to early Cretaceous tholeitic to clalcalkaline volcanics (Shalt-Drosh volcanic group) late early Cenozoic acidic lava flows and pyroclastic volcanics (Dir Shamran volcanic group) and Cretaceous to Tertiary intrusion of Kohistan Batholith.