Page 331 - Global Tectonics

314 CHAPTER 10

36 N Kohistan Transhimalayan batholiths
Kohistan
Arc Kohistan arc
Arc
Indus-Zangbo suture zone/ophiolite
MMT
35 MMT Tethyan zone
Karakorum Fault
Karakorum Fault
Higher Himalaya/Miocene leucogranite
Ladakh Batholith
Ladakh Batholith
34 IZS Lower Himalaya
IZS
SubHimalaya
MBT
MBT
STDS
STDS
Gneiss dome
33 IZS BNS
BNS
IZS
MCT
32 MCT STDS
STDS
31
Gangdese
Gangdese
Batholith
Batholith
0 100 IZS
MCT
MCT
MBT
MBT
IZS
Gangdese
30 km STDS Gangdese
Batholith
Batholith
STDS
STDS
STDS
IZS
IZS
29 MCT
MCT
Thrust fault MBT
MBT
STDS
STDS
STDS
28 High-angle normal fault MCT STDS STDS
STDS
MCT
Low- to moderate-angle normal fault
MCT
MCT
MCT
Strike-slip fault MCT
27 Fault with unknown displacement MBT
MBT
74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 E

Figure 10.19 Geologic map of the Himalaya (modified from Hodges, 2000, with permission from the Geological
Society of America). BNS, Bangong–Nujiang suture; IZS, Indus–Zangbo suture; MBT, Main Boundary Thrust; MCT, Main
Central Thrust; MMT, Main Mantle Thrust; STDS, South Tibetan Detachment System.
detachment dips gently-moderately to the north and cored by Precambrian metamorphic basement sur-
separates the high-grade gneisses of the Greater Hima- rounded by a mantle of less metamorphosed Carbonif-
laya from low-grade Cambrian–Eocene rocks of the erous–Triassic rocks (Burg et al., 1984). A few of the
Tethyan zone (Fig. 10.19). These latter rocks were largest gneiss domes preserve eclogite-facies metamor-
deposited on the passive margin of northern India prior phic assemblages that are overprinted by amphibolite-
to its collision with Eurasia. The basal detachment facies assemblages (Guillot et al., 1997). The domes are
records Miocene and, possibly, Pliocene north-directed dissected by normal faults and bear some resemblance
normal displacements of at least 35–40 km that occurred to the extensional metamorphic core complexes in the
contemporaneously with south-directed motion on the western USA and elsewhere (Section 7.3). However,
Main Central Thrust (Hodges, 2000). In its hanging their origin is not well understood and several different
wall, Tethyan rocks are dissected by complex arrays of mechanisms have been proposed to explain them,
splay faults (Fig. 10.19) whose cumulative displacement including thrust faulting and folding in addition to
probably approaches that of the basal detachment normal faulting and lower crustal fl ow.
(Searle, 1999). At the northern end of the Tethyan Zone the Indus–
Throughout the Tethyan zone are a discontinuous Zangbo suture separates rocks that once formed part
series of metamorphic culminations called gneiss of the Indian Plate from Paleozoic–Mesozoic rocks of
domes. The most extensively studied of these is the the Lhasa terrane (Section 10.4.2). The suture is defi ned
Kangmar gneiss dome, which forms part of an antiform by a deformed mixture of components derived from