LATE MIOCENE TO EARLY PLIOCENE TECTONOMETAMORPHISM AND COOLING IN SOUTH-CENTRAL KARAKORAM AND INDUS-TSANGPO SUTURE, CHOGO-LUNGMA AREA (NE PAKISTAN)

The Chogo Lungma glacier is located at the northeastern edge of the Na nga Parbat-Haramosh spur where the Ladakh-Kohistan are formations are laminated between the Karakorum and High Himalaya units. In the Karako rum metamorphic complex, metamorphism of a pelitic and granitic protol ith took place in two tectonometamorphic phases. Isoclinal folds (simi lar to 700 degrees C, 1 GPa) were followed by doming (similar to 630-7 00 degrees C, 400-750 MPa) in a compressional climax (Lemennicier et a l., 1996). One hornblende and two biotites associated to syntectonic m agmatism with mantle affinities, contemporaneous of doming, give cooli ng ages between 3.0 and 7.7 Ma. A muscovite from an orthogneiss in the Karakorum gives an age of 5 Ma. Fast cooling (70-110 K/Ma) has prevai led ever since. Two muscovites from a foliated intrusion emplaced on t he thrust of the Ladakh-Kohistan are over the High Himalaya Crystallin es have ages of 8.2 and >9 Ma (despite being collected in the same loc ality), dating the thrust at just before 9 Ma. All this points to a co eval tectonometamorphism and thrusting in that area during the Tortoni an.