Abstract The actual state of knowledge concerning the tectonic evolution of the Afghan orogenic segment is summarized in the context of the neighbouring regions. The segment can be divided into: (1) the Late Palaeozoic North Afghan Variscan domain, which forms the southern margin of the Turan Plate; (2) the Early Cimmerian (Late Triassic–Early Jurassic) Palaeotethys suture zone of Middle Afghanistan, with the associated magmatic arc and back-arc rift extending from the Parapamisos and western Hindu Kush to the northern Pamir Mountains; (3) the Late Cimmerian (Late Jurassic–Early Cretaceous) domain of the Central Afghan Block mosaic with Gondwana-derived terranes; and (4) the Cenozoic-age Himalayan domain, which fringes the Cimmerian domain along the transpressive boundary of the Indian Plate in the east and the accretionary complex of the Makran subduction zone in the south. This current review of the scattered literature of a country where geological fieldwork effectively ceased 35 years ago is intended to bridge the gap between the better-known regions to the west in eastern Iran, and to the east in the Pamir–Punjab syntaxis.

Abstract The left-lateral strike-slip Tirich Mir Fault, Chitral, NW Pakistan, is associated with a belt of peridotites, metagabbros and gneisses named the Tirich Boundary Zone (TBZ), separating the Late Palaeozoic-Mesozoic units of the East Hindu Kush from the Palaeozoic successions of the Karakoram block. These rocks were metamorphosed up to upper amphibolite facies conditions, followed by a greenschist facies overprinting, and then thrust on to very low grade metasediments; they were finally intruded at shallow levels by the mid-Cretaceous Tirich Mir pluton. Ultramafic rocks along the fault zone include well-preserved spinel lherzolites and harzburgites (Tirich Gol, Barum valley, Arkari Gol), whereas schistose serpentinites occur in the Rich Gol. Whole-rock analyses and mineral chemistry of olivine, clinopyroxene, orthopyroxene and spinel from these peridotites show a depleted signature. Microstructural and petrological features suggest a mantle origin for these ultramafic bodies, which equilibrated at temperatures ranging from 1000–1100 °C. Peridotites are faulted against partially metamorphosed igneous bodies including hornblende-gabbros, hornblende cumulates and quartz-diorites. Metamorphic rocks of the TBZ, which lay south of the ultramafic-mafic complex, include quartzites, amphibolites, garnet-sillimanite (± kyanite ± K-feldspar)-biotite gneisses and mica schists, locally displaying migmatitic textures. A sub-continental character of the peridotites indicated by low temperatures of equilibration and by the presence of a deep crustal sequence. These characters along with the absence of an ophiolitic sequence may suggest that the TBZ represents a fragmented crust-mantle boundary developed along a zone of attenuated continental crust. The TBZ is interpreted as a sheared lithospheric section of a Jurassic-Early Cretaceous orogenic complex, formed as a consequence of the accretion of the Karakoram terrane to the southern side of the Pamir belts, which were progressively accreted to the Asian margin.