摘要:

ABSTRACTCrustal thickening along the northern margin of the Indian plate, following the 50 Ma collision along the Indus Suture Zone in Ladakh, caused widespread high‐temperature, medium‐pressure Barrovian facies series metamorphism and anatexis. In the Zanskar Himalaya metamorphic isograds are inverted and structurally telescoped along the Main Central Thrust (MCT) Zone at the base of the High Himalayan slab. Along the Zanskar valley at the top of the slab, isograds are the right way‐up and are also telescoped along northeast‐dipping normal faults of the Zanskar Shear Zone (ZSZ), which are related to culmination collapse behind the Miocene Himalayan thrust front. Between the MCT and the ZSZ a metamorphic‐anatectic core within sillimanite grade rocks contains abundant leucogranite‐granite crustal melts of probable Himalayan age. A thermal model based on a crustal‐scale cross‐section across the Zanskar Himalaya suggests that M1isograds, developed during early Himalayan Barrovian metamorphism, were overprinted during high‐grade MCT‐related anatexis and folded around a large‐scale recumbent fold developed in the ha

ISSN:0263-4929    

DOI:10.1111/j.1525-1314.1989.tb00579.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe pressure‐temperature and temperature‐time paths derived for rocks in the Kohistan arc and adjacent Nanga Parbat‐Haramosh massif record the dynamics of the collision between the island arc and the Indian plate. Studies ofP‐T‐tpaths show that the Kohistan arc was thrust over the Nanga Parbat‐Haramosh massif at least 25 Ma ago, but not more than 30–35 Ma ago. Rocks in the Kohistan arc followed decreasing pressure paths, with the early metamorphism beginning at high pressures (9.5 kbar) and later metamorphism occurring at 8.0 kbar. In contrast, rocks in the Nanga Parbat‐Haramosh massif (Indian plate) experienced increasing pressure and temperature paths. Prior to thrusting, the massif was at low pressures (4.0 kbar) and low temperatures (450°c). Later, the pressure and temperature increased to 8 kbar and 580°c. The authors interpret the convergence (to approximately the same pressure and temperature) of theP‐Tpaths in the two terranes as being the result of thrusting and thermal equilibration between the thrust sheets.40Ar/39Ar cooling ages of hornblendes and other geochronological data suggest that the time of peak metamorphism and hence the completion of thickening was approximately 30–35 Ma ago.Temperature‐time paths show that after thrusting, during the period 25–10 Ma, the Kohistan arc and Nanga Parbat‐Haramosh massif were uplifted at similar rates (0.5 km Ma). However, in the past 10 Ma the Nanga Parbat‐Haramosh massif has been uplifted more rapidly than the adjacent Kohistan arc. Rapid uplift has been accommodated by late faults

ISSN:0263-4929    

DOI:10.1111/j.1525-1314.1989.tb00580.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0263-4929    

DOI:10.1111/j.1525-1314.1989.tb00581.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY