Indian plate paleogeography, subduction and horizontal underthrusting below Tibet: paradoxes, controversies and opportunities

Abstract

The India-Asia collision zone is the archetype to calibrate geological responses of continent-continent collision, but hosts a paradox: there is no orogen-wide geological record of oceanic subduction after initial collision around 60-55 Ma, yet thousands of kilometers of post-collisional subduction occurred before arrival of unsubductable continental lithosphere that currently horizontally underlies Tibet. Kinematically restoring incipient horizontal underthrusting accurately predicts geologically estimated diachronous slab break-off, unlocking the Miocene of Himalaya-Tibet as natural laboratory for unsubductable lithosphere convergence. Additionally, three end-member paleogeographic scenarios exist with different predictions for the nature of post-collisional subducting lithosphere but each is defended and challenged based on similar data types. This paper attempts at breaking through this impasse by identifying how the three paleogeographic scenario each challenge paradigms in geodynamics, orogenesis, magmatism, or paleogeographic reconstruction and identify opportunities for methodological advances in paleomagnetism, sediment provenance analysis, and seismology to conclusively constrain Greater Indian paleogeography.

Constraints on the timing of the India‐Asia collision and unroofing history of the Himalayan orogen using detrital zircon U‐Pb‐Hf and whole‐rock Sr‐Nd isotopes in Cretaceous‐Miocene Lesser Himalayan sedimentary rocks

“…The reversal of 'sedimentary polarity' from cratonic sources to orogenic belt and cratonward migration of a flexural forebulge in foreland basin systems are common, both in collisional (Himalaya-type) (DeCelles et al, 2014;Ding et al, 2009) and retroarc (Andean-type) systems (Horton, 2018, 2022 andreferences therein). Finally, we agree with the statement that either significant Cenozoic crustal shortening within Asia and the Himalaya or one or more Cenozoic suture zones has not been identified (Kapp & DeCelles, 2019), and those disputes will continue until we confidently find the 'missing' Indian continental crust or new oceanic crustal remnants within the Himalayan orogen or southern margin of the Asian continent (Ding et al, 2022;Kapp & DeCelles, 2019;Parsons et al, 2020;van Hinsbergen, 2022). We appreciate the assistances from Weilin Zhang, Tao Zhang, Dawen Zhang, Fuli Wu and Dhan Bahadur Khatri in the field and Xiaoli Yan and Wanfeng Chen in the laboratory.…”

“…Parsons et al (2020) and van Hinsbergen (2022) compared the abovementioned collision models associated with their strengths and weaknesses and pointed out that none of the present models for the India‐Asia collision are entirely satisfactory with current provenance constraints, palaeomagnetic datasets and magmatic records at the same time. It is worth noting that the current palaeomagnetic datasets concerning the India‐Asia collision are controversial, and each collision model has supportive palaeomagnetic datasets.…”

“…Knowledge of the timing of India‐Asia collision and unroofing history of the Himalayan orogen are critical to improving our understanding of the crustal shortening budget for geodynamics involved in the evolution of the Tibetan Plateau (Ingalls et al, 2016; Parsons et al, 2020; van Hinsbergen, 2022; van Hinsbergen et al, 2011), tectonic‐climatic interactions related to orogenic growth (Molnar et al, 2010; Raymo & Ruddiman, 1992), oceanic geochemistry (Colleps et al, 2018; Richter et al, 1992) and development of peripheral foreland basins (DeCelles & Giles, 1996; Stockmal et al, 1986). Current opinions for the age of India‐Asia collision onset span from 70 to 65 Ma (Cai et al, 2011; Ding et al, 2005; Yin & Harrison, 2000) to as late as ca.…”

A timeline of the Cenozoic tectonic–magmatic–metamorphic evolution and development of ore resources in the Himalayas

“…Therefore, the Himalayas have become a typical area for studying orogeny and metallogenic processes (Cao, Pei, et al, 2022). Although considerable research has been performed in the Himalayas in the past (van Hinsbergen, 2022; Yin, 2006), new geological evidence and the development of new analytical techniques in recent years have substantially clarified the geological evolutionary process of the Himalayas and many new ideas have been proposed. For example, (1) in terms of tectonic evolution, palaeomagnetic evidence suggests that there was a “Great India Basin” on the northern margin of the Indian continent during the Cretaceous period, which led to two collisions between the India and Lhasa blocks (van Hinsbergen et al, 2012) circa 58 Ma and 25–15 Ma (van Hinsbergen et al, 2019).…”

Subduction and Slab Detachment Under Moving Trenches During Ongoing India‐Asia Convergence

“…The mantle below India and the Indian Ocean was among the first regions where deep mantle structure was correlated to subduction history (Hafkenscheid et al, 2006;Replumaz et al, 2004;van der Voo et al, 1999). These studies identified multiple detached slabs, and the shallowest of these are identified hundreds to more than 1,500 km to the south of the modern northern extent of the Indian continental lithosphere which is imaged sub-horizontally below Tibet over a distance of 300-800 km north of the modern plate boundary, the southern Himalayan front (Agius & Lebedev, 2013;Chen et al, 2017;van Hinsbergen, 2022;van Hinsbergen et al, 2019) (Figure 2). Clearly, these geodynamic constraints differ completely from those used for the past numerical models simulating slab detachment and from which the currently perceived diagnostic geological signatures of slab detachment are derived.…”