tübinger geowissenschaftliche arbeiten (tga) - TOBIAS-lib ...

66
The Permo-Triassic volcano-siliciclastic sediments of the Lake Karakul area constitute
the Karakul-Mazar/Sonpan-Ganze accretionary wedge rocks. The Late Triassic/Jurassic
Karakul lake batholith is stitching together the Kunlun arcs and are correlated to the
western Kunlun (Akarz mountain pluton, (?)Sailiyak magmatic belt) and to the western
Badakshan, western Hindu Kush, and Feroz Koh regions (e.g. at Salang pass).
South of the northern Pamirs/Kunlun, the cryptic Tanymas/Jinsha suture evidence
mainly Triassic southward subduction of the Karakul-Mazar/Sonpan-Ganze ocean
beneath the Central Pamirs/Qiangtang block. The basement antiforms of the Central
Pamirs and Qiangtang, formerly interpreted to be of Precambrian age, are mainly
composed of exhumed medium to high-grade metamorphic Tanymas/Jinsha ocean floor
and Triassic/Jurassic basin associations. Eventually, in the Safed Khers related
basement domes are exposed and the Band-e Bayan and Farah Rod can be correlated
with the Central Pamirs and Qiangtang.
The southern margin of the Central Pamirs and the Rushan Pshart zone are intruded by
several granitoids of diverse composition and with distinct age groups or age
components from 250-200 Ma and 200-150 Ma. The first group is attributed to the
southward subduction along the Jinsha suture, whereas the latter group represent the
Rushan Pshart arc, which developed by Jurassic northward subduction of oceanic
lithosphere of the Rushan Pshart basin. A similar zone is found along the Bangong-
Nujiang zone in Central Tibet. As in the Pamirs, the closure of scattered oceanized
basins along the Rushan Pshart and Bangong-Nujiang zones led to the collision of the
Central Pamirs/ Qiangtang block with the SE Pamirs/Lhasa blocks. South of the SE
Pamirs/Lhasa terranes, a new active margin established. Probably upper Lower
Cretaceous (~120 Ma) collision of the Karakorum with the eastern Hindu Kush and SE
Pamirs along the Tirich Mir/Kilik (?)suture and Late Cretaceous (~80 Ma) collision of
the Kohistan/Ladakh arc with the Karakorum along the Shyok suture caused bimodal
intrusion of granitoids as far as to the northern Central Pamirs.
This study suggests a relatively simple first-order crustal structure for the Pamirs and
Tibet. From the Kunlun arc in the north to the southern Qiangtang block in the south,
the Pamirs and Tibet have a dominantly (meta)sedimentary crust, characterised by the
Karakul-Mazar/Sonpan-Ganze accretionary wedge rocks. The crust south of the
southern Qiangtang block is likely of granodioritic composition, reflecting long-lived
subduction, arc formation and Cretaceous-Cenozoic underthrusting of arc segments
beneath the Qiangtang block.