Abstract Reconstruction of the Western Himalaya requires three subduction systems operating beneath the Spong arc, Dras–Kohistan arc and the Asian continent during the Late Cretaceous–Paleocene. The timing of the closure of the Neo-Tethys Ocean along the Indus Suture Zone (ISZ) in Ladakh and south Tibet has been proposed to be as old as c. 65 Ma and as young as c. 37 Ma. The definition of the India–Asia collision can span >15 myr from the first touching of Indian continental crust with Asian crust to the final marine sedimentation between the two plates. There is good geological evidence for a Late Cretaceous–Early Paleocene phase of folding, thrusting and crustal thickening of Indian Plate shelf carbonates associated with obduction of ophiolites. There is no geological evidence of any oceanic ‘Greater Indian Basin’ separating the northern Tethyan and Greater Himalaya from India. There is clear evidence to support final ending of marine sedimentation along the ISZ at 50 Ma (planktonic foraminifera zone P7–P8). There is no evidence for diachroneity of collision along the Pakistan–Ladakh–South Tibet Himalaya. The timing of ultrahigh-pressure metamorphism cannot be used to constrain India–Asia collision, and the timing of high-grade kyanite- and sillimanite-grade metamorphism along the Greater Himalaya can only give a minimum age of collision.

Abstract Alkaline schorlitic tourmaline with domains of myrmekitic quartz and tourmaline intergrowths is reported for the first time from quartzo-feldspathic gneisses of the Tso Morari Crystalline Complex (TMCC), eastern Ladakh Himalaya. Except for schorlitic tourmaline, the brown-green dravitic tourmaline occurs in melanocratic layers of the gneiss. The schorlitic tourmaline contains REE-rich apatite, which is a typical mineral formed under high-pressure (HP) conditions. The observed myrmekite, marked by vermicular quartz and tourmaline intergrowths, was probably formed during decompression as a consequence of excess silica released from recrystallized tourmaline. The recalculated composition of the tourmaline with quartz myrmekite suggests that Si also occupied the tourmaline octahedral Z site during the HP regime. During decompression excess Si from this tourmaline was replaced by Mg and Fe 3+ . At an early stage of exhumation needle-shaped schorlitic tourmaline II and mosaic zoning were formed. The excess of silica and the structural disorder suggest that the Si-oversaturated tourmaline was stable at high-pressure–ultrahigh-pressure (HP–UHP) conditions. The greater stability of dravitic tourmaline compared to schorlitic tourmaline at HP conditions is evidently recorded at the TMCC. The tourmaline-bearing gneisses of the TMCC most probably shared the same metamorphic conditions during Tertiary collision of the Indian and Eurasian plates, similar to that observed for the associated UHP eclogites.