Dacht-i-Navar Group

In 1969, the history of volcanism in Afghanistan was poorly known.[4] Only a few volcanic fields of Pliocene-Quaternary age exist in Afghanistan.[5] Aside from orogen-associated volcanism, volcanism typical of rifting zones is also found. Magma production through the Pliocene-Pleistocene has been low and volcanoes cover only small areas.[6] These volcanoes are isolated as well; to the east one has to go for 4,000 kilometres (2,500 mi) to reach volcanoes, in Burma.[7]

Dacht-i-Navar is formed by over ten central volcanoes that form lava sheets and tuffs stacked on top of each other. These central volcanoes form heavily degraded stratovolcanoes, the largest of which (4,559 metres (14,957 ft) high Mamikala and 4,312 metres (14,147 ft) high Zarkadak[4]) are over 10 kilometres (6.2 mi) wide at the base,[5] and are cut by ravines that end in alluvial fans[8] and previously channelled nuee ardentes. They also display traces of glacial activity which bury most of the edifices.[9]

These two centres lie in the south of the group; Ghiftu, Khut and Sewak are also located in the south while 3,555 metres (11,663 ft) high Kotale Reg and 3,920 metres (12,860 ft) high Qaghkusta lie in the east. The Doni Yarchi massif lies in the north.[4] Other volcanic centres are Mount Burguk, Mount Hut and Mount Mohammad,[10] in total over 24 individual centres were found.[11]

The highest of these centres exceed 4,500 metres (14,800 ft) of altitude.[12] Some of these volcanoes still display craters. Extrusive bodies such as lava domes are also found,[5] as well as two calderas associated with stratovolcanoes.[11] Smaller centres sometimes also have central calderas with extrusive domes,[8] some of these calderas reach diameters of 2–3 kilometres (1.2–1.9 mi).[13]

The Dacht-i-Navar group lies mainly within the southern part of a geological depression with dimensions of 100 by 30 kilometres (62 mi × 19 mi).[5] The few more northern centres are separated from the main complex by the clay-filled Nawar basin and a surrounding Pleistocene terrace.[10] The infill, which includes volcanic material, is likely thicker than 100 metres (330 ft).[4] This basin has an altitude of 3,125 metres (10,253 ft),[12] but it is surrounded by higher summits.[4] Despite evaporation, a lake persists within the basin. Probably, the depression was once a valley cut into schists which are pre-Devonian and still crop out in some places. This valley drained southwestward towards the Arghandab River that was eventually blocked by volcanic activity. The Ab-i-Khanduli dry valley still connects Dacht-i-Navar to the Arghandab river.[14] Another possibility is that the valley originally drained eastward towards Qarabagh.[15]

Metamorphic rocks of Paleozoic age form the basement.[10] Additional volcanic centres are found both west and east of Dacht-i-Navar.[16] The volcanism appears to be associated with left-lateral strike-slip faulting in the area.[17]

The field has erupted andesite and dacite. The dacites are found in the lower parts and the andesites in the upper part of the volcanic deposits; some rhyodacites and rhyolites are found among the oldest rocks. The rocks have a porphyric nature and phenocrysts include amphibole, biotite, clinopyroxene, magnetite, olivine, orthopyroxene, plagioclase and quartz, with different rock types having different composition.[5] Chemically, the rocks belong to the calc-alkaline series.[2]

Dacht-i-Navar is a source of obsidian, one of the few in Southwest Asia. Some Paleolithic archeological sites in the area have used this obsidian.[18] This obsidian does not appear to have been transported to large distances from Dacht-i-Nawar.[19]