Timeline of the South Tibet – Himalayan belt: the geochronological record of subduction, collision, and underthrusting from zircon and monazite U–Pb ages

Abstract

The “exact timing” of collision between India and Eurasia is a recurring theme. Careful dating is critical for all tectonic events. With the example of the South Tibet – Himalaya collision system, a short review of arguments from different approaches suggests that this pursuit is in vain, but that our knowledge is already sufficient to provide an acceptably “precise” timing of the main events. We reviewed U–Pb ages of zircons and monazites, recognizing that major tectonic events can produce thermal effects strong enough to be recognized in high-temperature geochronology. This review also shows that precise timing is beyond the precision of the methods and the rock record. General consistency between geologic and thermochronologic records strengthens previous interpretations of the collisional orogenic system. We argue that the Tsangpo Suture in South Tibet results from two merged subduction zones and that island arcs may be part of the root of the Eurasian paleoactive margin, which is at variance with most tectonic interpretations. The two main collisional events closely followed each other at ca. 50 and 40 Ma.