Download The India

The India - Eurasia collision,
Himalaya and the Tibetan plateau.
Some important characteristics:
• Very long duration of continental
collision and shortening
• Thickest crust and highest
topography on earth
•
Bulge
Active tectonics include both
reverse, normal and strike-slip
deformation on a large scale
Well-constrained plate-motions
for the pre- and syn-collision
Movement histories
Indian ocean
since mid-early
Cretaceous
(Aptian)
until present
From; www.geodynamics.no
(Patriat and Achache, 1984)
Le Pichon et al., 1993
2-D cartoon of plate - tectonic evolution, top speed of India at
ca. 60 Ma.
70-80 Ma
50-60 Ma
Ca 50 Ma-present
Geological cross-section interpreted based on surface observation
across the Himalayas,
•THE FORELAND SEQUENCE
MFT
MBT
30 km
50 km
MCT
STDS
ITS
FORELAND FOLD- AND THRUST BELT: Notice the
decollement surface in the Eocambrian evaporite
sequence. Notice also the negative Bouguer anomaly
and the infilling of Tertiary molasse.
Thrust loading Pb (see next page)
The flexure of a broken plate is given by :
Where
Pb = applied line load / unit width (downward acting
loads are negative - upward acting loads are positive).
The load is applied at the end of the plate, at the break.
y = flexure(negative downwards, positive upwards)
m = density of material beneath the plate
infill = density of material above the plate
g = average gravity
x = horizontal distance
= flexural parameter given by:
D = flexural rigidity of the plate given by:
Where
E = Youngs Modulus
v = Poisson's Ratio
Te= Elastic thickness of the lithosphere
Low Himalaya
High Himalaya
HIGH HIMALAYA
LOW HIMALAYA
SOUTH TIBETAN
DETACHMENT
SEISMIC IMAGE
OF THE
CRUSTAL
STRUCTURE
INDUS-TSANG PO
SUTURE
SCHEMATIC
N-S PROFILE ACROSS
THE HIMALAYAS
STDS
ITS
MBT
MCT
MFT
MHT
NB!
INTER-PLAY BETWEEN
CONTRACTION AND
EXTENSION DURING
A LONG PERIOD OF
COLLISION
MCT
Low-Himalaya
From: Hodges et al. 1997
STDS
High-Himalaya
THE TRANS-HIMALAYAN-BATHOLITH
REMNANT OF THE ANDEAN MARGIN WHICH PRE-DATE
THE CLOSURE OF TETHYAN OCEAN (AGE ≈ 95-45 Ma)
STDS
ITS
MBT
THB
MCT
MFT
MHT
HIMALAYAN REGIONAL METAMORPHISM,
• NORMAL AND INVERTED METAMORPHIC GRADIENTS
• “HOT-IRON” (HOT ON COLD) HYPOTHESIS
• TRANSPORTED OLDER METAMORPHISM HYPOTHESIS
• FRICTIONAL HEATING HYPOTESIS
Staurolite
Kyanite
Sill-Musc
Sill-Kspar
Leucogranites
FOLDED METAMORPHIC
ISOGRADS INDICATING
TRANSPORTED OLDER
METAMORPHISM
HIMALAYAN LEUCO-GRANITES AND PATIAL MELTING
THE SUTURE(S):
INDUS TSANG PO
KOHISTAN ARC
SPONTANG
OPIOLITE
DEEP
SUBDUCTION
OF CONTINETAL
LITHOSPHERE
(SEISMIC EVENTS)
AND REFRACTION
STUDIES
THE KOHISTAN ARC, AN ALMOST COMPLETELY
PRESERVED ISLAND ARC COMPLEX EXPOSED FROM
BASE TO TOP!
NOT PRESERVED
CONTINUE WITH PRESENT DAY
TECTONICS OF
THE HIMALAYAN TIBETAN
COLLISION ZONE