The Gangdese retroarc thrust belt revealed

Abstract

The Cretaceous-early Tertiary Gangdese arc in southern Tibet is generally attributed to the northward subduction of Neotethyan oceanic lithosphere prior to Indo-Asian collision. However, the history and tectonic significance of deformation and sedimentation in Tibet during this time interval have remained enigmatic. We show that contractional structures and clastic rocks near the city of Lhasa can be attributed to the development of a northward-propagating retroarc thrust belt that was active between 105 and 53 Ma. A kinematic model shows that the thrust belt could have accommodated >230 km (>55%) of N-S shortening. An episode of large magnitude (>160 km) and rapid (>8 mm/yr) shortening predated the onset of a magmatic flare-up ca. 69 Ma, which is linked to removal of overthickened mantle lithosphere. This tectonic history implies that southern Tibet underwent substantial crustal thickening and elevation gain prior to the Indo-Asian collision.

Constraints on the early uplift history of the Tibetan Plateau

“…6). The northern edge of the Tanggula Shan formed the northern margin of the proto-Tibetan Plateau, whereas the Gangdese arc formed the southern boundary, consistent with the inferences of Kapp et al (11,47) and Spurlin et al (34). Oligocene-Early Miocene upper-crustal shortening within the HXB would have been driven by Indo-Asian collisional stresses from the south transmitted across this high proto-Tibetan Plateau and localized along its northern boundary.…”

High-pressure Tethyan Himalaya rocks along the India-Asia suture zone in southern Tibet

“…We suggest that between 40-38 Ma, a transition to shallow northward underthrusting of Greater Indian continental lithosphere occurred, resulting in northward displacement of the Asian mantle wedge and shutoff of Gangdese arc magmatism in southern Tibet ( Fig. 6c; Kapp et al, 2007). Shallowing in the dip of the subducting continental plate was also concomitant with the initiation of Lopu Range HP exhumation.…”

“…6B), as evidenced by our garnet Lu-Hf data. The most recent episode of Gangdese arc magmatism persisted from ~70 Ma to 38 Ma (Kapp et al, 2007), requiring the presence of a melt-fertile upper-plate mantle wedge during this time interval. We suggest that between 40-38 Ma, a transition to shallow northward underthrusting of Greater Indian continental lithosphere occurred, resulting in northward displacement of the Asian mantle wedge and shutoff of Gangdese arc magmatism in southern Tibet ( Fig.…”

Temporal–spatial distribution and tectonic implications of the batholiths in the Gaoligong–Tengliang–Yingjiang area, western Yunnan: Constraints from zircon U–Pb ages and Hf isotopes

“…This Cordilleran-style model involves contrational deformation and fold-and-thrust in the continental arc margin and in the hinterland crust, which are observed in the field. For instance, Kapp et al (2007b) identified a northward-propagating retroarc thrust belt operational between 105 and 53 Ma. They further estimated that the thrust belt could have accommodated >230 km (>55%) N-S shortening in the Lhasa Terrane.…”