The age and nature of Mesozoic-Tertiary magmatism across the Indus Suture Zone in Kashmir and Ladakh (N. W. India and Pakistan)

Abstract

Eine tektonisch ruhige Phase auf der 5rtlichen indischen Kontinentalplatte im Paliioz~n und frtihen Eoz~in wiihrend der Subduktion im asiatischen Randgebiet.Ein weiterer Schub des Indischen Kontinental-Randes nach Siiden in Zusammenhang mit der Bildung eines Anden-~ilmlichen Bogens (des Ladak_h-Deosai-Batholithen) im nSrdlichen indischen Randgebiet ira Eoz~in.Ein oligoz~iner andischer Bogen (die Karakorum-Batholithen) im asiatischen Randgebier, gefolgt yon einer mioziinen KoUision der zwei Kontinente sowie der Intrusion yon ,,echten Graniten", die durch teilweises Verschmelzen der Kontinentalkruste verursacht wurden. Abstract We report t]~e following new 4~ages: 180--150 and 90--100 Ma from monzodiorite and tremolite-actinolite schist of the Kohistan Complex; 44 + 0.5, 39.7 +-_ 0.2 Ma from dikes cutting the Ladakh-Deosai Batholith Complex; 130-145 Ma from a diorite in the Shyok melange; and 7.8 + 0.1 Ma from a late stage monzogranite of the Karakorum Batholith. A 261 ___ 13 Ma age from gneiss of the Karakornm Batholith is of uncertain significance.These dates, previously published ones which we summarize here, and some Sr isotope data suggest the following, (due to subduction switching between the Indian and Asian margins during closing of the Tethys ocean):Late Cretaceous emplacement of the Dras-Kohistan Cretaceous Island arc, followed by rapid cooling between abut 85 and 45 Ma.A quiet phase tectonically on the northern Indian plate during the Palaeocene to early Eocene, when subduction was occurring on the Asian margin. Further southward thrusting of the Indian continental margin associated with the development of an Andean-type arc (the Ladakh-Desosai Batholiths) on the northern Indian margin during the Eocene.An Oligocene Andean arc (the Karakorum Batholiths) on the Asian margin, followed by Miocene collision of the two continents and intrusion of 'true' granites derived from partial melting of continental crust. R&um6Nous raisons 6tat ici des nouvelles datations 4~suivantes Phase tranquille, sur le plan tect0nique, sur la plaque N. de l'Inde allant du Pal~o-c@ne h l'Eoc@ne ancien, lots de la subduction de la marge asiatique.Pouss@e vers le sud de la marge continentale de l'Inde associ@es au d6veloppement d'un arc de type andin (les batholites du Ladakh-Deosai) sur la marge N. de l'Inde l'Eocbne.Arc andin oligoc6ne (les batholites du Karakoram) sur la marge asiatique, suivi d'une collision au Mioc@ne des deux continents et de l'intrusion de << v@ritables >> granites provenant de la fonte partielle de la crofite continentale.

A tectonic model reconciling evidence for the collisions between India, Eurasia and intra-oceanic arcs of the central-eastern Tethys

“…Burg (2011b) suggests that the (Kohistan) intra-arc rifting, attributed to trench rollback (Burg et al, 2006;Treloar et al, 1996), may have removed the need for subduction along the southern Karakoram margin as India's faster northward motion i.e., faster subduction of the Tethys, then formed most of the Kohistan Batholith. Continued closure between India and Eurasia resulted in locking of the intervening Kohistan Arc (or KLA) during the Eocene-Miocene (Brookfield and Reynolds, 1981;Reynolds et al, 1983), as convergent thrusting created unconformable Eocene lavas, 30 Ma old plutons, and mainly north-vergent/south-dipping structures in the KKSSZ (Burg, 2011b).…”

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.…”

Tectonic and magmatic evolution of the eastern Karakoram, India

“…Brookfield and Reynolds [8] and Reynolds et a1. [9] suggested that the Shyok suture did not close before the Miocene and therefore considered it to be younger than the Indus suture. Srimal [10], however, suggested that the tectonic units accompanying the Shyok ophiolites were part of a collage between the northern margin of India and the southern margin of the Asian plate.…”