The document summarizes the six primary lithotectonic zones of the Himalayas from west to east. These include: 1) the Trans-Himalayan batholith consisting of igneous rocks representing an island arc environment in the west and Andean-type environment in the east, 2) the Indus-Tsangpo suture zone marking the zone of collision and subduction of the Tethys Ocean, 3) the Tethyan Himalaya zone containing unmetamorphosed marine sediments deposited on the Indian continental shelf, 4) the Higher Himalaya zone comprised of metamorphosed rocks representing multiphase deformation, 5) the Lesser Himalaya zone containing sedimentary rocks from

1. MORPHO-STRUCTURAL UNIT

2. WEST HIMALAYA
The Himalayas can be divided into six primary lithotectonic
zones that occur in parallel belts.
1. These zones consist of the Trans-Himalayan batholith,
2. Indus-Tsangpo suture zone,
3. Tethyan(Tibetan) Himalaya,
4. Higher(Greater) Himalaya,
5. Lesser(Lower) Himalaya, and
6. Sub-Himalaya.
Tectonic environments within these zones also vary. The
emense collision of plates at 45 million years gave rise to
an island-arc margin in the western Himalayas.

3. WEST HIMALAYA

4. WEST HIMALAYA
1. Trans-Himalayan batholith-
Linera plutinic complex, Cont molsse, uplifted magnetic rock
(igneous) –Gabbro, Diorite, Granite-several phase, 110-40mya
Partial melting of a subducting NeoTethyan slab beneath the
Asian plate is thought to have resulted in these magmas
(Sorkhabi 1999). This zone varies in a west-east direction. To
the west, plutons were emplaced into an area, called the
Kohistan-Ladakh region, and represent an island arc
environement. Contrastly, eastern igneous rocks represent an
Andean-type environment(Windley 1995).
Western Trans-Himalaya
An island arc formed on the northern side of the NeoThethys
and became trapped in between Asia and India. This allowed
for two stages of deformation. The first consisted of collision
of the arc with Eurasia, followed by collision with India, as the
Tethys began to subduct under Asia.

6. Indus-Tsangpo Suture Zone
 (ITZS) defines the areas of collision between the Indian plate and the Kohistan-Ladakh arc in
the western Himalayas and the Tibetan Lhasa block in the east
 It also marks the zone along which the Tethys Ocean was consumed by subduction processes.
 The ITSZ can be traced for more than 2000km between these regions and host a variety of
rock types that tell us quite a bit about the orogen. Complete successions of ophiolites occur,
some containing diamonds as well,
 high pressures during subduction and rapid extrusion along the suture zone. Glaucophane
schists also occur in narrow belts along the ITSZ in Pakistan.
 Olistoliths occur in northwestern India
 Mafic to felsic lavas as well as cherts, serpentinites, and dunites are also observed.
 Limestones and red sandstones are associated with Tethys Ocean sediments and found in the
Ladakh region (Windley 1995).
Their one commonality is that this great structure separates Asian lithosphere from the Indian
plate.

8. Tethyan(Tibetan) Himalaya
 To the south of the ITSZ. They consist of thick, 10-17km, marine
sediments that were deposited on the continental shelf and slope of the
Indian continent.
 Occured as India was drifting but still in the southern hemisphere
 Sediments are largely un-metamorphosed, which has made for
excellent preservation of fossils and occur in synclinorium-type basins.
 Fossils occur in this east-west zone within strata that are very clearly
known. The large variety of size and distribution of fauna suggest that
life was flourishing in this area before the orogen. Such success in
biological diversity is accounted for by the relatively stationary position
of the Tehthyan Zone between mid-Proterozoic and Eocene time.

9. Higher(Greater) Himalayas
 The Higher Himalayas are also known as the Central Crystalline zone, comprised of ductily
deformed metamorphic rocks and mark the axis of orogenic uplift.
 Mica schist, quartzite, paragneiss, migmatite, and leucogranite bodies characterize this
uppermost Himalayan zone.
 They represent a multiphase deformation event, the first being Barrovian type, or normal
geothermal gradient conditions. There was then a shift to Buchan-type metamorphism, low
pressure and high temperature conditions, with temperatures greatly exceeding normal gradient
temperatures.
 Analyses show that peak orogenic temperatures and pressures were 475-825 degrees Celsius and
500-800 megapascals. Corresponding minerals assemblages are dominated by biotite to
sillmanite, representing greenschist to amphibolite facies deformation.
 Deformation seems to have occured in a north to south direction and is associated with the
Main Central Thrust Fault (MCT), which brings the higher Himalayas on top of the lower
Himalayas-supercrustal rock.
 This idea states that upper crustal material of India accreted northward onto the Asian continent
and that crustal material was origanlly an appendage of India that was, itself, accreted to India
during Paleozoic time..
Lesser(Lower) Himalayas
The Lesser Himalayan zone is bounded the Main Central Thrust(MCT) in the north and Main
Boundary Thrust(MBT) to the south.
 Unlike the higher Himalayas, the lessers only experienced up to greenschist facies
metamorphism. T
 he rock types present here are also different. They are primarily sedimentary rocks from the
Indian platform. Rock units here also show a series of anticlines and synclines that are in many
cases quite sheared. Fossils have been documented in this zone, but they do not occur at the
same frequency as Tehtyan zone fossils

10. Sub-Himalaya
•This foreland zone consists of clastic sediments that were produced by the uplift and
subsequent erosion of the Himalayas and deposited by rivers.
•These rocks have been folded and faulted to produce the Siwalik Hills that are at the foot
of the great mountains. S
•Sub-Himalayan rocks have been overthrust by the Lesser Himalayas along the Main
Boundary Thrust Fault. This steep thrust flattens with depth, dveloped during the
Pliocene time and has been shown as active through the Pliestocene
•In turn, the Sub-Himalayas are bounded by a thrust fault to the south and are forced over
sediments on the Indian plate. This fault system is called the Himalayan Frontal thrust