Timing of collision of the Kohistan–Ladakh Arc with India and Asia: Debate

Abstract

The Kohistan-Ladakh Arc in the Himalaya-Karakoram region represents a complete section of an oceanic arc where the rocks from mantle to upper crustal levels are exposed. Generally this arc was regarded as of Jurassic-Cretaceous age and was welded to Asia and India by Northern and Southern Sutures respectively. Formation of this arc, timings of its collisions with Asia and India, and position of collision boundaries have always been controversial. Most authors consider that the arc collided with Asia first during 102-75 Ma and then with India during 55-50 Ma, whereas others suggest that the arc collided with India first at or before 61 Ma, and then the India-arc block collided with Asia ca 50 Ma. Recently published models of the later group leave several geological difficulties such as an extremely rapid drifting rate of the Indian Plate (30 Ϯ 5 cm/year) northwards between 61-50 Ma, absence of a large ophiolite sequence and accretionary wedge along the Northern Suture, obduction of ophiolites and blueschists along the Southern Suture, and the occurrence of a marine depositional environment older than 52 Ma in the Indian Plate rocks south of the Southern Suture. We present a review based on geochemical, stratigraphic, structural, and paleomagnetic data to show that collision of the arc with Asia happened first and with India later.

Varieties of the Himalayan eclogites: A pictorial review of textural and petrological features

“…The Himalayan mountain range is composed of a collage of rocks of the Indian and Asian plates, sandwiching an intra‐oceanic Cretaceous island arc namely the Kohistan–Ladakh arc (KLA). The area presents a classical example of continent–continent collision where the northern margin of the Indian plate subducted to mantle depths beneath the Asian plate, underwent high‐pressure (HP) and ultrahigh‐pressure (UHP) metamorphism before its final exhumation to the earth's surface (Rehman, Seno, Yamamoto, & Khan, ; Tahirkheli, Mattauer, Proust, & Tapponnier, ; and references therein). Major lithological units (mainly Proterozoic to Tertiary in age) of the Indian plate, to the south of the island arc, form the Higher Himalayan Crystalline (HHC) sequence, the Lesser Himalayan sequence (LHS), and the Tertiary foreland Siwalik molasse sediments of the Sub‐Himalayas (Figure ).…”

The Cretaceous and Cenozoic tectonic evolution of Southeast Asia

“…However, plate motion reconstructions tend to differ in key areas, including (1) the subduction polarities, (2) the number of active subduction zones bounding southern Eurasia, and (3) the tectonic driving forces related to the opening and closure of the proposed back-arc basins. Previous studies argued for Shyok Suture (Karakoram-Kohistan) closure in the Late Cretaceous, between 102 and 75 Ma, well before the approach of India to the Eurasian margin (Molnar and Tapponnier, 1975;Petterson and Windley, 1985;Beck et al, 1995;Rowley, 1996;Bignold and Treloar, 2003) based on the review of Rehman et al (2011). Subduction beneath Kohistan was interrupted between ∼ 95 and 85 Ma, and was replaced by arc rifting (Burg, 2011), suggestive of a new pulse of back-arc generation in the Neo-Tethys at this time, much like the multi-phase back-arc generations in the Mariana Arc system on the eastern margin of the Philippine Sea plate (Sdrolias and Müller, 2006;Sdrolias et al, 2004).…”

Evidence of Eocene high-temperature/high-pressure metamorphism of ophiolitic rocks and granitoid intrusion related to Neotethyan subduction processes (Doğanşehir area, SE Anatolia)

“…The Doganşehir granulite facies rocks can be compared with the granulite facies rocks of the Jijal complex, northern Pakistan, which forms the lowest unit of the mid-Cretaceous (c. 110 Ma) Kohistan island arc (Peterson & Windley 1995;Burg et al 1998;Garrido et al 2006;Rehman et al 2011). These granulites are inferred to have formed by intrusion of arc-related magmatic rocks into the core of an intra-oceanic magmatic arc (Tahirkheli et al 1979;Bard et al 1980;Bard 1983;Yamamoto 1993).…”