Abstract
The Karakoram metamorphic Complex (KMC) in the southern Karakoram block is one of the best examples of Barrovian type metamorphism that comprises numerous exhumed metapelite units where a series of low to high grade (green schist to sillimanite facie) rocks are exposed. This sequence shows a complex polyphase history of metamorphism and deformation which offer deeper understanding of collision orogeny. Karakoram metamorphic Complex contains metapelites, meta-carbonates, meta-igneous and amphibolite layers, cross-cut by granite sheets in the northern part. This complex is bounded to the north by the Hunza plutonic unit which is the central portion of the massive east-west trending Karakoram axial batholith and to the southwest by the Main Karakoram thrust (MKT). In this contribution, we provide detail geological mapping, petrography, geochemistry and micro-analytical work using Electron Prob-micro analysis in the central Hunza Valley.
Highlights
Since detachment from the Gondwana supercontinent at c. 150 Ma, the Indo-Australian plate has drifted in northward anti-clockwise path, covering c. 5000 km before colliding with Asia [1]
Oceanic and continental platform sediments of the Asian margin were subjected to low-pressure–hightemperature (LP–HT) andalusite–sillimanite grade metamorphism due to collision and emplacement of subduction related calc-alkaline granitoids of Karakoram axial batholith [4,6]
On a chondrite diagram the trace-element contents are minor enriched in light rare earth element (LREE) except Hu-Gd-11 which shows unusually higher HREE with observable Eu anomaly Fig. 5)
Summary
Since detachment from the Gondwana supercontinent at c. 150 Ma, the Indo-Australian plate has drifted in northward anti-clockwise path, covering c. 5000 km before colliding with Asia [1]. 50–55 Ma [2,3], with both events causing Barrovian-type metamorphism and magmatism on both plates This collision resulted in crustal thickening, magmatism, polyphase metamorphism and deformation both along the northern margin of India (forming the Himalaya) and along the southern margin of Asia (forming the Hindu Kush, Karakoram and the Tibetan plateau) [6]. Oceanic and continental platform sediments of the Asian margin were subjected to low-pressure–hightemperature (LP–HT) andalusite–sillimanite grade metamorphism due to collision and emplacement of subduction related calc-alkaline granitoids of Karakoram axial batholith [4,6]. This sequence comprises of late-Paleozoic and earlyMesozoic sedimentary rocks that have been metamorphosed during and following collision.
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