Abstract In the Afghan Hindu Kush, the 223–209 Ma (≤800°C) Salang batholith is part of the Silk‐Road magmatic arc that was built on ∼40‐km‐thick Turan‐Karakum block continental crust. The batholith constitutes the hanging wall of the Herat‐Panjshir‐Badakhshan—the Paleo‐Tethys—suture zone, vestige of the subducted Paleozoic‐early Mesozoic Paleo‐Tethys oceanic lithosphere. It intruded Precambrian (≤∼610 Ma) paragneiss and Ordovician (∼480 Ma) orthogneiss. 208–180 Ma anorogenic leucogranites (≤700°C) along the suture formed by mica‐dehydration melting in ∼30‐km‐thick crust. Post‐emplacement cooling rates declined from ∼35 to 3°C/Myr. In the Afghan Pamir, 211–180 Ma anatectic leucogranites accompanied ≤750°C metamorphism in mostly Middle Triassic accretionary‐wedge sediments; this rock association cooled at ∼20°C/Myr. The wedge was built on 329–275 Ma continental‐arc and MORB‒island‐arc (IAB) rocks, and incorporated ocean‐island (OIB) and MORB rocks; their 1.02–1.15 Ga T (Nd) model ages indicate a significant contribution of juvenile crust, with one MORB ( ε Nd (i) = +8.59) recording a typical Paleo‐Tethys oceanic crust signature. Detrital zircons of the wedge rocks indicate both proximal and distal provenance. The magmatic rocks of the Afghan Pamir, NE Iran, and northwestern Tibet delineate a Carboniferous arc. The Salang‐batholith arc magmatism, the post‐collisional magmatism, and the related regional metamorphism suggest a ∼210 Ma closure of the Paleo‐Tethys ocean. A distinct plate configuration in the embayment between the Turan‐Karakum and Tarim blocks explains the proximity of sites with major accretion and back‐arc extension, weak accretion and accretionary‐wedge subduction associated with high‐grade metamorphism, and subduction erosion and wedge subduction along the Paleo‐Tethys suture in Afghanistan, Tajikistan, and western Tibet.
Ratschbacher et al. (Fri,) studied this question.