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

54
Kara Kunlun or Mazar accretionary prism formed by subduction-accretion processes
during closure of the Palaeotethyan ocean and the final docking of the Gondwana
Karakoram-Qiangtang block to the Eurasian Kunlun block.
Granitic intrusions into the Bazar Dara and Qitai complexes yielded Rb/Sr biotite
isochron ages of 190 Ma (Zhang & Xie 1989), suggesting that by the Late Triassic to
Early Jurassic the locus of magmatism had migrated from north (Sailiyak magmatic arc)
to south. 40 Ar/ 36 Ar plateau ages of biotite, determined by Xu et al. (1992), range
between 215 and 185 Ma, whereas the lower interception U/Pb zircon ages for different
intrusions in the Kara Kunlun range between 199 and 192 Ma. A K/Ar biotite cooling
age of 171.5±5.4 Ma was reported by Gaetani et al. (1991) for the Mazar pluton located
west of Mazar. The emplacement and cooling ages of the Karakul lake batholith
presented in this study, are very well correlatable to ages of the western Kunlun range
and are herein summarised as the Karakul-Mazar belt.
Correlation of the Karakul lake batholith to the west leads to the eastern and southeastern
margin of western Badakshan and western Hindu Kush, and to the southern
margin of Feroz Koh in Afghanistan (Fig. 3.1, 3.13). Extensive granite intrusions of Early
Mesozoic age are documented in the area of the Salang pass (Stöcklin 1977). The lateral
extent of such Triassic intrusions, mainly granodiorites of calc-alkaline character, is
more than 500 km along strike and associated with volcanic activity (Debon et al. 1987).