Palaeolatitude and age of the Indo-Asia collision: palaeomagnetic constraints

Abstract

S U M M A R YOngoing controversies on the timing and kinematics of the Indo-Asia collision can be solved by palaeomagnetically determined palaeolatitudes of terranes bounding the Indo-Asia suture zone. We show here, based on new palaeomagnetic data from the Linzizong volcanic rocks (54-47 Ma) near the city of Lhasa, that the latitude of the southern margin of Asia was 22.8 ± 4.2 • N when these rocks were deposited. This result, combined with revised palaeomagnetic results from the northernmost sedimentary units of Greater India and with apparent polar wander paths of India and Eurasia, palaeomagnetically constrain the collision to have occurred at 46 ± 8 Ma (95 per cent confidence interval). These palaeomagnetic results are consistent with tomographic anomalies at 15-25 • N that are interpreted to locate the Tethyan oceanic slab that detached following collision, and with independent 56-46 Ma collision age estimates inferred from the timing of slowing down of India, high pressure metamorphism, the end of marine sedimentation and the first occurrence of suture zone and arc detritus on the Greater Indian margin. When compared with apparent polar wander paths of India and Eurasia, the ∼46 Ma onset of collision at 22.8 ± 4.2 • N implies 2900 ± 600 km subsequent latitudinal convergence between India and Asia divided into 1100 ± 500 km within Asia and 1800 ± 700 km within India.

Insights on the kinematics of the India‐Eurasia collision from global geodynamic models

“…New paleomagnetic data, corrected for sediment compaction and inclination shallowing [Tan et al, 2010], suggest that models such as Lee and Lawver [1995] place the Lhasa terrane, forming the active pre-collision margin, up to $10 too far south, indicating that early contact at $55 Ma between a maximum extent Greater India and southward-displaced Lhasa may be problematic. Paleomagnetic studies which show an initial overlap between apparent polar wander paths of India with respect to Asia suggest contact at 46 AE 8 Ma [Dupont-Nivet et al, 2010] or as late as $43 Ma [Tan et al, 2010], indicating that collision timing derived from paleomagnetic data has large inherent uncertainties and cannot be used alone to define the initial timing of continent-continent collision. Reconstructing the geometry of Greater India and Lhasa as proposed by Lee and Lawver [1995] shows that initial contact occurs between 54 and 49 Ma across the five different rotation models (italic values in Table 1 and Figure 3), which highlights the model-dependence of interpretations based on rotation models to infer collision timing (Figure 2).…”

Zircon U‐Pb Age and Geochemistry of Rhyolite in Jianshui, Yunnan and Its Geological Implications

“…While there is disagreement about the timing of the initial India-Asia collision, there is growing consensus that the Tethyan Himalaya collided with Asia in the early Eocene (Zhu et al, 2005;Dupont-Nivet et al, 2010;Najman et al, 2010;van Hinsbergen et al, 2012). Models with an early Eocene collision differ in their interpretation of the arc's geochemical response after the initial collision and an Eocene slab breakoff event.…”

Did high Neo-Tethys subduction rates contribute to early Cenozoic warming?

“…Subduction below Tibet in the Early Cretaceous occurred simultaneously with Indian separation from eastern Antarctica and Australia ∼ 130 Ma ago (Guillot et al, 2008;van Hinsbergen et al, 2011a). Collision between the northernmost continental crust of the Indian plate and Eurasia is commonly stated to have started between ∼ 60 and ∼ 50 Ma (e.g., Dupont-Nivet et al, 2010;Najman et al, 2010;Orme et al, 2014;Hu et al, 2015) (Fig. 1).…”