Abstract:The Kabul Block is an elongate crustal fragment which cuts across the Afghan Central Blocks, adjoining the Indian and Eurasian continents. Bounded by major strike slip faults and ophiolitic material thrust onto either side, the block contains a strongly metamorphosed basement consisting of some of the only quantifiably Proterozoic rocks south of the Herat-Panjshir Suture Zone. The basement rocks crop-out extensively in the vicinity of Kabul City and consist predominantly of migmatites, gneisses, schists and sm… Show more
“…III‐ shows Eocene metamorphism of the granitoids in the Salang and Panjshir valleys (Faryad et al, 2013, this work). K 1 and K 2 are P‐T conditions for the Paleoproterozoic and Neoproterozoic metamorphisms, respectively in the Kabul Block (Collett & Faryad, 2015; Collett et al, 2015)…”
Section: Discussionmentioning
confidence: 99%
“…Metamorphic rocks reaching granulite facies conditions in the Western Hindu Kush are known from Sare Sang (~160 km NW from the studied area), but these rocks indicate earlier high‐ P metamorphism that led to formation of whiteschists (Faryad, 1999, 2002; Kulke & Schreyer, 1973) and belong to the Afghan–Tajik Block. On the other hand, the Neoarchean rocks that experienced Palaeoproterozoic granulite facies and Neoproterozoic amphibolite facies metamorphism are exposed in the adjacent Kabul Block (Collett et al., 2015; Faryad et al., 2016). Based on the position of xenolith‐bearing metagranite (at close contact with the Kabul Block) and the estimated temperature for the xenolith (Figure 11), the Kabul Block was the most probable source of these xenoliths.…”
Section: Discussionmentioning
confidence: 99%
“…The Western Hindu Kush is part of a collision belt located between two crustal blocks with Proterozoic to Archean basement rocks, the Afghan–Tajik to the north and the Afghan Central Blocks, including Kabul Block, to the south (Faryad et al., 2016; Horeva, Iskanderova, & Shergina, 1971). High‐ P amphibolite to granulite facies conditions were estimated for the Afghan–Tajik Block at Sare Sang (Faryad, 1999, 2002) and multi‐stage granulite and amphibolite facies metamorphism of Palaeoproterozoic and Neoproterozoic ages for the Kabul Block (Collett & Faryad, 2015; Collett, Faryad, & Mosazai, 2015; Faryad et al., 2016). To the east, the Western Hindu Kush has a sharp tectonic contact with the Nuristan Block to the northeast (Andritzky, 1967), which is considered to be a continuation of the Karakoram and Qiantang to the west (Searle, Hacker, & Bilham, 2001; Wallis, Phillips, & Lloyd, 2014).…”
Basement rocks from the Western Hindu Kush preserve evidence of multiple metamorphic and magmatic events that occurred along the boundary between the Archean–Proterozoic Afghan Central and Afghan–Tajik Blocks. To verify the different metamorphic stages or events, mineral textures and phase equilibria in metamorphic basement rocks and their age relations to magmatic episodes have been investigated. Quartzofeldspathic gneiss and migmatite with lenses of amphibolite (with assumed Proterozoic age for their metamorphism) are intruded by the Triassic Hindu Kush granitoid batholith and small Cretaceous and Oligocene granite intrusions. The age of thermal overprint (210–170 Ma) by the Triassic batholith is confirmed by new monazite data. Both Triassic and Cretaceous granitoids and surrounding basement rocks underwent subsequent metamorphism up to epidote–amphibolite facies. The degree of this metamorphism increases southward at the contact to the Kabul Block, which under‐plates the Western Hindu Kush from the south. An early Miocene age was obtained by Pb–Th analyses in thorite and huttonite, which are close or slightly younger than the Oligocene granite in this area. The Cretaceous meta‐granodiorite near the border with the Kabul Block contains xenoliths of granulite facies rocks that could come from the Neoarchean granulite facies basement of the Kabul Block. The multi‐stage metamorphic and magmatic evolution classifies the Hindu Kush mountain belt as a long‐lived suture zone that was active since the early Palaeozoic. The results of this study support the interpretation about possible relations of the Afghan Central Blocks to the southern margin of Eurasia during the evolution of Para‐ and Neotethys.
“…III‐ shows Eocene metamorphism of the granitoids in the Salang and Panjshir valleys (Faryad et al, 2013, this work). K 1 and K 2 are P‐T conditions for the Paleoproterozoic and Neoproterozoic metamorphisms, respectively in the Kabul Block (Collett & Faryad, 2015; Collett et al, 2015)…”
Section: Discussionmentioning
confidence: 99%
“…Metamorphic rocks reaching granulite facies conditions in the Western Hindu Kush are known from Sare Sang (~160 km NW from the studied area), but these rocks indicate earlier high‐ P metamorphism that led to formation of whiteschists (Faryad, 1999, 2002; Kulke & Schreyer, 1973) and belong to the Afghan–Tajik Block. On the other hand, the Neoarchean rocks that experienced Palaeoproterozoic granulite facies and Neoproterozoic amphibolite facies metamorphism are exposed in the adjacent Kabul Block (Collett et al., 2015; Faryad et al., 2016). Based on the position of xenolith‐bearing metagranite (at close contact with the Kabul Block) and the estimated temperature for the xenolith (Figure 11), the Kabul Block was the most probable source of these xenoliths.…”
Section: Discussionmentioning
confidence: 99%
“…The Western Hindu Kush is part of a collision belt located between two crustal blocks with Proterozoic to Archean basement rocks, the Afghan–Tajik to the north and the Afghan Central Blocks, including Kabul Block, to the south (Faryad et al., 2016; Horeva, Iskanderova, & Shergina, 1971). High‐ P amphibolite to granulite facies conditions were estimated for the Afghan–Tajik Block at Sare Sang (Faryad, 1999, 2002) and multi‐stage granulite and amphibolite facies metamorphism of Palaeoproterozoic and Neoproterozoic ages for the Kabul Block (Collett & Faryad, 2015; Collett, Faryad, & Mosazai, 2015; Faryad et al., 2016). To the east, the Western Hindu Kush has a sharp tectonic contact with the Nuristan Block to the northeast (Andritzky, 1967), which is considered to be a continuation of the Karakoram and Qiantang to the west (Searle, Hacker, & Bilham, 2001; Wallis, Phillips, & Lloyd, 2014).…”
Basement rocks from the Western Hindu Kush preserve evidence of multiple metamorphic and magmatic events that occurred along the boundary between the Archean–Proterozoic Afghan Central and Afghan–Tajik Blocks. To verify the different metamorphic stages or events, mineral textures and phase equilibria in metamorphic basement rocks and their age relations to magmatic episodes have been investigated. Quartzofeldspathic gneiss and migmatite with lenses of amphibolite (with assumed Proterozoic age for their metamorphism) are intruded by the Triassic Hindu Kush granitoid batholith and small Cretaceous and Oligocene granite intrusions. The age of thermal overprint (210–170 Ma) by the Triassic batholith is confirmed by new monazite data. Both Triassic and Cretaceous granitoids and surrounding basement rocks underwent subsequent metamorphism up to epidote–amphibolite facies. The degree of this metamorphism increases southward at the contact to the Kabul Block, which under‐plates the Western Hindu Kush from the south. An early Miocene age was obtained by Pb–Th analyses in thorite and huttonite, which are close or slightly younger than the Oligocene granite in this area. The Cretaceous meta‐granodiorite near the border with the Kabul Block contains xenoliths of granulite facies rocks that could come from the Neoarchean granulite facies basement of the Kabul Block. The multi‐stage metamorphic and magmatic evolution classifies the Hindu Kush mountain belt as a long‐lived suture zone that was active since the early Palaeozoic. The results of this study support the interpretation about possible relations of the Afghan Central Blocks to the southern margin of Eurasia during the evolution of Para‐ and Neotethys.
“…This comprises garnetiferous gneisses, amphibolitic gneisses and schists containing staurolite, andalusite and sillimanite. Collett et al (2015) established that these rocks were metamorphosed to granulite facies followed by a subsequent amphibolite-facies overprint. Based on U-Pb dating of zircon and U-Th dating of monazite, Faryad et al (2016) established a Paleoproterozoic age of ~1.85-1.80 Ga for the granulite facies metamorphism.…”
Section: Geological Setting Of the Aynak Copper Depositmentioning
Aynak is the largest known copper deposit in Afghanistan, with indicated resources of 240 Mt grading 2.3% Cu placing it in the 'giant' category. Host rocks are Neoproterozoic metasediments comprising dolomitic marble, carbonaceous quartz schist and quartz-biotite-dolomite schist containing garnet, scapolite and apatite. Chalcopyrite and bornite dominate the hypogene ore with lesser pyrite, pyrrhotite, cobaltite and chalcocite, and rare sphalerite, molybdenite, uraninite and barite. Sulphides occur as bedding-parallel laminae, disseminations, metamorphic segregations and crosscutting veins. Sulphide δ 34 S ratios range-14.5 to +17.3‰ in bedded and disseminated sulphides (n = 34). This broad range favours biogenic reduction of seawater sulphate as a major source of sulphur, although thermochemical reduction processes are not precluded. The narrower δ 34 S range of-6 to +12.2‰ in vein and segregation sulphides (n = 21) suggests localized redistribution and partial homogenization during metamorphism. Geochemical associations suggest that Al, P, Ca, Ti and Fe were primary sedimentary constituents whereas Cu, Mg, S, Se, As, Co and Bi were introduced subsequently. We infer that Aynak originated as a shale-and carbonatehosted stratabound replacement deposit, resembling orebodies of the Central African Copperbelt, although underlying red-beds are absent at Aynak and mafic volcanics were the probable copper source. These giant deposits formed worldwide in the Cryogenian probably due to marine enrichment in copper, magnesium and sulphate coincident with profuse basaltic volcanism and ocean oxidation.
“… Fig. 1 (A) A simplified geologic map of Afghanistan (after Benham et al., 2009 and Collet et al., 2015 ). (B) Simplified geological map of the central part of the Kabul terrane outlined as red square in A ( Kafarsky et al., 1975 ).…”
Chromite is widely distributed in the east and southeast of Afghanistan, especially in Logar Province. Chromite mineralization is podiform-type and is hosted in the stratigraphically lowest ultramafic rocks of the Logar Ophiolite Complex. This ophiolite complex represents a remnant of an early Cretaceous oceanic crust that was thrusted over a late Permian to Mid-Jurassic platform-type sequence of the Kabul Terrane during the Himalayan Orogeny. The ultramafic rocks are composed mainly of dunite and harzburgite, which are variably serpentinized. Chromite mineralization of the Logar area ranges from massive chromitite pods to disseminated chromite crystals in the ultramafic rocks. Microscopically, the chromite exhibits granular texture and is generally fresh; however, some magnetite and/or ferritchromite are formed along the fractures of some chromite grains. The primary interstitial silicate minerals of the massive chromite and the silicate minerals surrounding the disseminated chromite grains are completely altered to serpentine along with some chlorite. Thus, serpentinite is most likely the host of the chromite in the Logar Province. The main aim of this study is discriminate serpentine using the Landsat 8 Operational Land Imager (OLI). The serpentinite of the Logar Province is separated by the combination of bands, principal components, band ratios, and supervised classification techniques. Using Landsat 8 and supervised classification with maximum likelihood classification as a tool for mineral exploration improve lithological mapping in the Logar Valley area.
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