The Cimmerian obduction of the Bashgumbaz ophiolites (South Pamir, Tajikistan)

The Pamir belts, located NW of the Himalaya, formed in response to the Cenozoic collision and indentation of India with Eurasia resulting in strong deformation and bending of pre-existing Paleozoic to Mesozoic orogens. Several crustal blocks separated by complex and scarcely studied suture zones form the present day tectonic architecture of the Pamirs. The extreme crustal shortening experienced by the Pamirs during the indentation of India hinders straightforward correlations between tectonic terranes of the Himalaya-Tibetan area with their potential continuations through the Pamirs into Afghanistan and Iran. Existing stratigraphic and paleontological data suggest that Central and SE Pamir, together with Karakoram and Qiangtang blocks separated from the Gondwana margin in the Early Permian, drifted northward, following the closure of the Paleotethys and other minor oceanic branches, and diachronously collided with Northern Pamir and Tian Shan. The Central and South Pamir are now separated by the Rushan-Pshart Suture Zone that extends E-W from the E-Pamir Fault ??? to the valley of the Panj River. South Pamir is separated into two units (SE and SW Pamirs) by a crustal scale detachment system that brought in contact the Permian to Cenozoic sedimentary succession of the SE block with the gigantic basement domes of the SW block, made of Precambrian metamorphic rocks with an high-T overprint of Miocene age. In SE Pamir the occurrence of Cimmerian tectonics is proved by lowermost Jurassic deposits resting in unconformity on intensively folded and faulted Permian and Triassic units. On the base of available data the suggested collision age of SE Pamir with Central Pamir is roughly bracketed between Middle Triassic to Early Jurassic. Along the contact between the SE and SW Pamir, a small (a few tens of km2 wide) ophiolitic unit occurs: the Bashgumbaz ophiolites. They consist of a low-grade metamorphic association of serpentinized harzburgites and gabbros with minor bodies o