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elt likely operated as an out-of-sequence thrust, causing exhumation during the
Middle Miocene as reflected by the fission track ages of 18 Ma. The age pattern may be
explained by piggy-back thrust tectonics, in which footwall burial and hanging wall
exhumation propagates towards the foreland, i.e. towards the north in the Pamirs. The
evidence that the Ar/Ar biotite ages mirror a similar younging towards north trend is
only weak, but could argue either for the activity of a predecessor of the Markansu fault
in the Jurassic/Triassic or for a ‘rotation’ of the whole Markansu-Mazar belt around a
horizontal E-W trending axis. The latter my be explained in terms of normal faulting in
the south, probably induced by the dome exhumation, and thrusting in the north, due
to the ongoing compression between India and Asia. So far, the Karakul-Mazar belt is
the only region in the Pamirs where Eocene apatite fission track ages are preserved.
Similar Early to Middle Eocene ages were found in the eastern Kunlun range by Jolivet
et al. (2001); these authors interpreted the ages by a change of the deformation style
from compressive to extensive as indicated by pull-apart basin formation in e.g. the
Hexi corridor (Vincent and Allen 1999). At least since Quaternary times the Karakul
basin is a pull-apart basin, but whether basin formation already started in Eocene time
is not clear detected.
Qiangtang block, Central Pamirs
Zircon fission track results from a Tertiary sediment sample with peak ages around
371 Ma, 242 Ma, and 165 Ma as well as from Cretaceous magmatic rocks describe the
thermal evolution of the Qiangtang block: (1) Palaeogene sediment sample A96K1e
from an intramontane basin along the northern margin of the Qiangtang block and the
Muzkol dome possibly defines the Palaeozoic and Mesozoic history of the Qiangtang
basement (Fig. 4.2, Appendix C, Tab. C7, Fig. C4). The oldest peak age is at ~371 Ma
and can be interpreted in two ways: (a) The age might reflect low-T cooling of the
Qiangtang basement. In chapter 3 and Schwab et al. (in press), inherited zircons (575-
425 Ma) from the Parmiran Qiangtang block granitoid P17 and published zircon ages
from Qiangtang basement rocks of Central Tibet (Gangma Co gneiss, Kapp et al. 2000)
were interpreted to characterise the Qiangtang basement. The results from U/Pb zircon
dating of Tertiary intrusions and dykes from the Muzkol and Sares domes (P15 and
96A6b) yielded upper intercept ages of 540 Ma and 570 Ma, respectively. The
interpretation is that all Tertiary melts contain inherited zircons of the Qiangtang
basement. Ar/Ar amphibole ages from the same Gangma Co basement rocks of central
Tibet range from 380 to 355 Ma (Kapp & Cowgill 2001). The amphibole ages are
consistent with high-grade metamorphism prior to Carboniferous time (Kapp & Cowgill
2001). Assuming a similar tectono-metamorphic evolution for the Pamiran Qiangtang
block, the zircon peak age of ~371 Ma from sample A96K1e may reflect the low-T
cooling of the Qiangtang basement; anyhow, it is speculative whether such basement
was exposed in Tertiary. (b) The second interpretation of the ~371 Ma age population
is that the zircons derived from the Kunlun arc to the north. Granite intrusions around
380 Ma are known from the Kunlun of north-western Tibet (Matte et al. 1996) and 370-
320 Ma old metavolcanic rocks occur in the Kunlun range of the northern Pamirs
(Altyndara section). Deposition of Carboniferous to Permian passive margin strata
within both, the Kunlun and Qiangtang terranes, resulted from opening of the Palaeo-
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