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Tethyan ocean between them (Kapp & Cowgill 2001; chap. 3; Schwab et al. in press). In
Late Permian/Early Triassic the closure of these ocean basins started and resulted in
Triassic/Early Jurassic accretion of the Qiangtang terrane to the southern Eurasian
margin. Several slices of oceanic crust and mélange rocks were subducted beneath the
Qiangtang block and exhumed in fault-bounded basement domes in the Central
Pamirs/Qiangtang block. In the Qiangtang, exhumation of these basement rocks was
already in the Mesozoic, whereas in the Central Pamirs in the Tertiary. It is not
published if Tertiary central Qiangtang sediments derived Triassic ages probably
related to the Mesozoic exhumation of the basement domes.
Grain ages of the Palaeogene sediment sample A96K1e cluster around 165 Ma and are
comparable with a major age component in Triassic/Jurassic granitoids of the southern
margin of the Qiangtang block and may record Rushan Pshart arc activity.
(2) Cretaceous magmatic rocks and contact metamorphic hornfelses occur at the
northern margin of the Qiangtang block. Sample A96S1b, a subvolcanic latite-andesite,
is cropping out in the Saseksu valley (Fig. 4.2); it’s lower intercept U/Pb zircon age is at
~74 Ma (Fig. 3.7k, chap. 3) and the zircon fission track cooling age is about 64 Ma. A
similar zircon fission track age was also found at the southern margin of the Qiangtang
block; monzogranite 96A10b yielded an apparent zircon fission track age of about 59
Ma. Both the Late Cretaceous magmatic intrusions and their low-T cooling ages thus
give evidence for the regional distribution of a Late Cretaceous thermal influence, likely
caused by flat-slab subduction of the Shyok suture. If this thermal overprint reached as
far as to the northern part of the Qiangtang block and may explain the Late Cretaceous
ages determined there, is debatable.
Shyok ocean basin subduction and Kohistan-Ladakh arc accretion caused high-grade
metamorphism in the Hindu Kush-Karakoram blocks south of the South Pamirs at 80 to
50 Ma (Fraser et al. 2001). As no apatite fission track ages are on hand, it can not be
inferred if the Late Cretaceous/Palaeocene cooling in the Qiangtang block led to
cooling of the rocks to near surface temperatures. Additionaly, intracontinental
deformation caused by the approaching India may have caused renewed lithosphere
subduction of the Karakul-Mazar belt beneath the northern Qiangtang margin. This
may be evidenced by the geochemical signiture of sample A96S1b close to the Karakul-
Mazar substratum. In the light of such Late Cretaceous thermal influences, it would be
interesting to determine whether the Early Eocene apatite cooling age of the
southernmost sample of the Karakul-Mazar belt is also a result of a Late
Cretaceous/Palaeocene heat source.
Muzkol and Sares domes, Central Pamirs
The Muzkol and Sares domes expose fault bound greenschist to upper amphibolite
facies metamorphic rocks of Tertiary age. Monotonous, mainly siliciclastic and mafic
rocks with subordinate carbonatic sequences (see chap. 3) are interpreted to
characterise the Karakul-Mazar-Sonpan-Ganze accretionary wedge rocks, associated
with the subduction of Jinsha oceanic crust (chap. 3, Schwab et al. in press). Whereas
these rock associations were formed in Triassic/Early Jurassic times, the exhumation of
the domal structure is a Tertiary feature. Metamorphic hornblende and biotite Ar/Ar
ages range from 28 to 14 Ma (Appendix A, Tab. A3). Two Rb/Sr whole rock-muscovite