Koh-i-Sultan is a volcano in Balochistan, Pakistan. It is part of the tectonic belt formed by the collision of the Eurasian Plate and Indian Plate: specifically, a segment influenced by the subduction of the Arabian plate beneath the Asian plate and forming a volcanic arc which includes the Bazman and Taftan volcanoes in Iran. The volcano consists of three main cones, with heavily eroded craters running west-northwest and surrounded by a number of subsidiary volcanic centres. Its summit is high, and the crater associated with the Miri cone has a smaller crater inside.
The volcano is formed by andesite and dacite rocks, with fragmentary rocks prevailing over lava flows. The rocks have typical arc-volcano chemistry and composition, with a progression from andesite to dacite in the eruption products with younger age. Potassium-argon dating has indicated an age range from 5,900,000 to 90,000 years. Subsequent erosion has generated a large debris apron around the base of the volcano and carved rock formations which impressed early explorers; one well-known rock formation is Neza e Sultan.
Geothermal activity and the emission of volcanic gases are ongoing, and the volcano has been prospected for the possibility of obtaining geothermal energy. The geothermal activity has resulted in widespread rock alteration and the formation of sulfur deposits, which were mentioned in a 1909 report and later mined. Koh-i-Sultan also has deposits of other minerals.
Geography and geology
Political geography and human history
Koh-i-Sultan is in the Chagai District of the Quetta Division, Baluchistan, Pakistan. A nearby settlement is the Nokkundi railway station, south. Henry Walter Bellew was the first to report the volcano's existence in 1862, and the Geological Survey of British India conducted mining and reconnaissance operations from 1941 to 1944. In 1961, a truck-accessible mining road was built from Nokkundi to the volcano's summit. Its name, translated as "Mountain of the King", is a reference to a saint in the local Baluchi religion.
Regional
Pakistan is part of the active tectonic belt which is responsible for the formation of the Himalayas following the collision of the Eurasian and Indian plates. As a result of this activity, hydrothermal alteration and hydrothermal activity are expected to be widespread in Pakistan. Koh-i-Sultan is the youngest volcano in Pakistan.
It is tectonically influenced by the Arabian Plate subducting beneath the Eurasian Plate, forming the Chagai volcanic zone. Tectonic activity related to this subduction is ongoing. Before the onset of volcanic activity at Koh-i-Sultan in the early Quaternary, tectonic uplift occurred in the region. Koh-i-Sultan and the Iranian volcanoes Bazman and Taftan form the Sultan volcanic arc. Also known as the Makran or Baluchistan volcanic arc, it is long and stretches in an east-northeast direction. Magma generated by the relatively shallow subduction of the Indian Plate rises to the surface and forms the andesitic rocks, among others, of Taftan and Koh-i-Sultan. The related Makran subduction zone is one of the few Cretaceous zones still active, and has formed a large accretionary prism.
Local
Koh-i-Sultan is a volcanic complex with at least three cones, named Kansuri, Abu and Miri after their respective summits. Each has a central crater—the largest of which is over wide—which have been heavily affected by erosion. The summit of Koh-i-Sultan is high. and the -high Miri is considered the youngest cone. Its crater is nested; the outer crater has a diameter of and the inner crater, formed by resurgent activity, has a diameter of . Miri's summit, south of the crater, is surrounded by a zone of altered rock. Subsidiary volcanic centres also exist in the form of volcanic plugs and satellite cones; those around Miri are named Bag Koh, Batal Koh, Chhota Dalil, Dam Koh, Koh-e-Dalil, Koh-e-Malik and Mit Koh. The volcanic pile covers an area of , and the volcanic complex has an area of running west-northwest. Although Koh-i-Sultan is considered dormant or extinct, ongoing fumarolic activity has been recorded.
The volcano consists of agglomerates, flows and tuff. Lava flows make up about 10 percent of the volcanic pile, and the remainder is volcaniclastic material. Other layers alternate between ash, lava and pyroclastic flows. Andesitic-dacitic materials dominate, including block-and-ash flows, lahars and tuff. Andesitic lava flows have thicknesses of ; two at Miri are and thick. The dacites form lava domes and subsidiary centres. Rock fragments are widely buried by long lava flows, and an Eocene mélange makes up part of the volcano's basement.