Magmatism and metamorphism in the Ladakh Himalayas (the Indus-Tsangpo suture zone)

摘要: Abstract Ladakh (India) provides a complete geological section through the northwestern part of Himalayas from Kashmir to Tibet. Within this magmatic, metamorphic and geotectonic evolution northern Himalayan orogeny has been studied using petrographic, geochemical isotope analytical techniques. The beginning cycle was marked by large basaltic extrusions (Panjal Trap) Permian Lower Triassic age at “northern” margin Gondwana continent (Indian Shield). These continental type tholeiitic basalts were followed more alkaline volcanism within Jurassic Lamayuru unit margin. Cretaceous oceanic crust sediments (ophiolitic melange s.s.) accompany flysch deposits Indus-Tsangpo suture zone, major structural divide between Indian Shield (High Himalaya) Tibetan Platform. So far, no relic Paleozoic found. Subduction Tethyan during Upper time produced an island arc represented calc-alkaline volcanic rock series (Dras volcanics) related intrusives accompanied volcaniclastic towards Subsequent subduction crust, volumes plutons (Trans-Himalayan or Kangdese plutons) intruded over distance 2000 km partly Dras in region. collision Platform started middle upper Eocene caused large-scale, still active intracrustal thrusting as well piling up nappes. tectonically highest these nappes is built huge slices peridotitic mantle (Spongtang klippe). In High tectonic activity outlasted Barrovian-type metamorphism that affected Kashmir-Nun-Kun synclinorium kyanite/staurolite grade deeper-seated units sillimanite grade. Cooling ages micas are around 20 m.y. (muscovite) 13 (biotite). Towards zone decreases with obvious discontinuity greenschist, prehnite-pumpellyite zeolite Remnants possibly Eo-Himalayan blueschist have found thrust zones accompanying ophiolitic zone.