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The granodiorites of western Badakshan and western Hindu Kush have Sr (i)-ratios of
0.7044±4 and a whole rock Rb/Sr isochron age (9 samples) of 234±12 Ma (Debon et al.
1983). Rb/Sr biotite ages of 8 samples are in the range of 224-192 Ma (Desio et al. 1964).
Samples from the Feroz Koh region gave K/Ar ages on biotite of 212 Ma (Wittekindt
1973) and K/Ar on whole rock of 247-192 Ma (Debon et al. 1986). Debon et al. (1983)
suggested that the magmatic arc intrusions have been formed by ocean subduction to
the south. Other authors inferred northward subduction, either of the Palaeotethys
located immediately south of the western Badakshan and western Hindu Kush
(remnants of which being assumed to occur along the Herat fault (e.g. Mattauer et al.
1980, Tapponnier et al. 1981) or south of the Farah Rod ocean (e.g., Bassoullet et al.
1980).
The Late Triassic/Early Jurassic transitional I- to S-type intrusions of the Lake Karakul
area find widespread correlatives to the east and west and are interpreted as syn- to
late-collisional intrusions stitching together the Late Palaeozoic Kunlun arc formed by
northward subduction of the Palaeotethys and the mid-Jurassic Jinsha suture formed
by southward subduction of the Palaeotethys along the northern margin of the
Qiangtang terrane. The Late Palaeozoic to Triassic volcanoclastic successions around
the Lake Karakul area are interpreted in this study as equivalents to the Mazar
accretionary prism in the western Kunlun (Xiao et al. 2002). Further eastward, these
rock associations are correlatives to the Songpan-Ganze melange of northern Tibet.
Central Pamirs
In the Central Pamirs, different tectono-stratigraphic units are constrained by
diverse intrusions of different age and geochemical composition. As pointed out from
the discussion in chapter 3.2, no unique and complete geological description exists
from the Central Pamirs. Formerly, three main structural units were characterised,
namely (1) Precambrian basement, covered by (2) Mesozoic units and overlain by
several (3) Tertiary intra-montane molasse basins.
Central Pamiran basement rocks
Ratschbacher et al. (1999), Schwab et al. (2000) and this thesis could demonstrate,
that the basement antiforms are a young Cenozoic feature. The regional structure is a
normal fault bounded anticlinorium exposed in the Muzkol and Sares domes. The
metamorphic rocks cropping out in these windows are metamorphosed to greenschist
or amphibolite facies conditions with local migmatisation. The rocks are mainly biotitegneiss,
phyllitic quarzite, flysch-like metaclasitic rocks, amphibolite, and greenschist.
The oldest intrusion of the Central Pamirs dated in this study, is an aplitic dike (sample
P17) cutting high-grade biotite-gneiss in the Muzkol dome. The upper interception
U/Pb zircon age of this sample is about 535 Ma and SHRIMP spot ages range from 561
to 424 Ma (see chapter 3.3).
Similar extensional metamorphic core complexes to a much larger extend with like
aged basement rocks are found in the Central Qiangtang block (Kapp et al. 2000). The
metamorphic rocks are interpreted to represent the Songpan-Ganzi accretionary wedge
system created by southward subduction of the Palaeotethys along the Jinsha suture
and below the Qiangtang block. Mélange-exhumation was triggered by Late Triassic-
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