Detrital zircon provenance of the Indus Group, Ladakh, NW India: Implications for the timing of the India-Asia collision and other syn-orogenic processes

Abstract

Abstract The timing of the India-Asia collision is greatly debated and is critical for elucidating early orogenic processes. This study documents, for the first time, evidence of India-Asia detrital mixing in the continental sedimentary rocks of the India-Asia collision zone of NW India at ca. 50 Ma and presents the largest detrital zircon (DZ) U-Pb age data set (n = 1225) from the region. Our DZ U-Pb age spectra from the early Eocene–late Oligocene continental Indus Group reveal a hybrid India-Asia provenance. The dominant Mesozoic–Cenozoic DZ peaks are ca. 107 Ma, 100–80 Ma, 60–50 Ma, 40 Ma, and 26 Ma, and they are mostly derived from Asia. The primary Precambrian DZ peaks are ca. 2.5 Ga, 1.2–0.95 Ga, 0.78–0.63 Ga, and 0.55 Ga and are representative of Tethyan Himalayan rocks on Greater India. Maximum depositional ages (MDAs) for four key Indus Group units, the Nurla, Hemis, Basgo, and Temesgam Formations, support syn-orogenic deposition in the Indus Basin from early Eocene to at least late Oligocene time. The Nurla Formation, with an MDA of ca. 50 Ma, records the first arrival of Greater Indian zircons on the Asian plate, thereby indicating uplift and erosion along the subducting Indian plate and collision of India with Asia by ca. 50 Ma. The ca. 27–26 Ma zircons in the younger late Oligocene Basgo and Temesgam Formations were contributed by the Lhasa terrane in south Tibet, which implies that the Indus River flowed from east to west across NW India at least by ca. 27 Ma.