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Coward et al. (1988) pointed
out some problems concerning
the BNZ as Mid-Late
Jurassic collisional suture
because typical collision
related deformation, thickening,
mountain building, as
well as related molasse
formation are lacking.
Schneider et al. (2003) found
an interpretation for the
eastern BNZ solving most of
these problems. Based on
detailed basin analyses of
the Dongqiao Naqu basin
(DNB), one of several scattered basins along the BNZ, Schneider et al. (2003) explain
the DNB as a polycyclic basin. The rift flank sequences indicate transtensional basin
formation (Permian to Late Triassic) with rifting via oceanisation (Late Triassic to Early
Jurassic) to transpression of a remnant basin. Partial basin closure of the DNB,
indicated by ophiolite thrusting to the south, was during the early Mid- to Late
Jurassic. Whether the eastern Qiangtang block was affected by arc magmatism is
unclear; thus Schneider et al. (2003) characterise the Late Jurassic to Early Cretaceous
DNB as a remnant basin. In summary, their model explains the occurrence of similar
prerift sequences on the Lhasa and Qiangtang blocks and the regional linear ophiolite
belts distribution pattern within strike-slip zones and between continental blocks as
parautochthonous rather than allochthonous units (Schneider et al. 2003). Some of the
transpressional and transtensional strike-slips which are suppositional for their model,
were probably initiated in the Late Jurassic and are evident for the Late Cretaceous to
Tertiary. During Neogene and Quaternary some faults were reactivated (Schneider et
al. 2003).
Coming back to the Rushan Pshart zone and the in this study preferred correlation with
the BNZ, the following concept can be drawn: The revised (Leven 1995), isolated, lensshaped
tectonic blocks of the Rushan, Pshart and Dunkeldyk may be considered as
transtensional basins accompanied by rifting associated basaltic volcanism on the
northern Gondwana margin. Only in the (?)Rushan block, East Pshart, and southeastern
Pamirs is the Carboniferous and Lower Permian recorded. Like in the
Qiangtang and Lhasa it is dominated by clastic deposits (Leven 1995, Schneider et al.
2003). The Upper Permian is charcetrised by siliceous sediments interbedded with
calcereous sediments in the East Pshart, and south-eastern Pamirs. Basalts occur in the
Upper Permian of the East Pshart, whereas basaltic tuffs, probably derived from the
East Pshart are deposited in the south-eastern Pamirs. The Upper Permian/(?)Triassic
of the Rushan block contains fusulinids and corals, proposing a carbonate platform.
According to Leven (1995) the Permian of the Central Pamirs and West Phart are
characterised by limestones and dolomite which may be part of a former carbonate
platform. The same facies is recorded from the Central Qiangtang and Lhasa blocks