RbSr dating of the Kohistan arc-batholith in the Trans-Himalaya of north Pakistan, and tectonic implications

40Ar–39Ar dating of volcanic rocks of the Shyok suture zone in north–west trans-Himalaya: Implications for the post-collision evolution of the Shyok suture zone

“…These formations could not be traced to the east of Ladakh sector in Lhasa and southern Tibet region and remain a peculiarity of the northwestern Himalaya. However, tectonic models proposing two subduction zones in general assume two sutures along the entire south Asian boundary (Brookfield and Reynolds, 1981;Rai, 1983;Reynolds et al, 1983;Coward and Butler, 1985;Petterson and Windley, 1985;Srimal, 1986;Sharma, 1987;Treloar et al, 1989;Searle et al, 1997;Weinberg and Dunlap, 2000;Dunlap and Wysoczanski, 2002;Robertson and Collins, 2002;Dubois-Cote et al, 2005;Dupuis et al, 2005). This has resulted in various attempts of correlating older sutures present in Lhasa-Tibet block with the Shyok suture (Dunlap and Wysoczanski, 2002;Lacassin et al, 2004).…”

“…Brookfield and Reynolds (1981), and Reynolds et al (1983) suggested that the Shyok suture closed in Miocene after the Late Cretaceous suturing along the Indus suture. However, Coward and Butler (1985), Petterson and Windley (1985), Treloar et al (1989) and Searle et al (1997) proposed that the Shyok suture is older than the Indus suture. Rai (1983) reported upper Cretaceous to Eocene marine fossils from the flysch of the Shyok suture zone.…”

“…Presently it is widely believed that the Shyok suture presents a site of ocean closure probably in Early-Late Cretaceous (Coward and Butler, 1985;Petterson and Windley, 1985;Treloar et al, 1989 Upadhyay et al, 1999;Bhutani et al, 2003) showing volcano-sedimentary formations of Shyok suture zone sandwiched between Ladakh batholith in the south and Karakoram batholith in the north. Sample locations are of earlier study (Bhutani et al, 2003) along with the present study (samples LK 88 and LK90).…”

TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

“…Following the classification of Streckeisen (1974), the sampled rocks are gabbros, diorites, monzodiorites, quartz diorites, quartz monzonites, tonalites, granodiorites and granites. Quartz diorite and granodiorite compositions are dominant in all visited parts of the Kohistan batholith that was estimated to be composed of 5 % mafic rocks (gabbro/diorite), 30 % quartz and quartz monzodiorite, 13 % tonalites, 25 % granodiorites, 12 % I-type granites and 15 % leucogranite dikes and stocks (Petterson and Windley 1985;Jagoutz and Schmidt 2012). In the following, we summarize the textures of the samples used for geobarometry; details for each sample including the modal mineralogy are presented in the electronic appendix.…”

The nature and origin of orbicular rocks from near Deshai, Swat Kohistan, Pakistan

“…Owing to the relief, the exact position and nature of the eastern contact of the major outcrop of orbicular rocks is not known, and the position of the contact has been mapped on the basis of surface morphology and weathering pattern alone. The orb-bearing (host) rocks are diorites and norites intrusive into gneissose quartz diorites probably of Cretaceous age (Petterson and Windley, 1985). The orbicular diorites, in which the majority of the orbs occur, are composed of plagioclase, clinopyroxene, hornblende, biotite, quartz and minor ilmenite and/or magnetite, apatite and sphene.…”