The India - Eurasia collision, Himalaya and the Tibetan plateau.
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The India - Eurasia collision, Himalaya and the Tibetan plateau. Some important characteristics: • Very long duration of continen collision and shortening • Thickest crust and highest topography on earth • Active tectonics include both reverse, normal and strike-sl deformation on a large scale Well-constrained plate-motions for the pre- and syn-collision Movement histories Bulge
description
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 Active tectonics include both reverse, normal and strike-slip - PowerPoint PPT Presentation
Transcript of The India - Eurasia collision, Himalaya and the Tibetan plateau.
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
• Active tectonics include both reverse, normal and strike-slip deformation on a large scale
Well-constrained plate-motionsfor the pre- and syn-collisionMovement historiesBulge
Indian oceansince mid-earlyCretaceous(Aptian)until present
From; www.geodynamics.no
(Patriat and Achache, 1984)
Le Pichon et al., 1993
70-80 Ma
50-60 Ma
Ca 50 Ma-present
2-D cartoon of plate - tectonic evolution, top speed of India at ca. 60 Ma.
30 km
Geological cross-section interpreted based on surface observation across the Himalayas,•THE FORELAND SEQUENCE
50 km
ITSMCTMBTMFT STDS
FORELAND FOLD- AND THRUST BELT: Notice thedecollement surface in the Eocambrian evaporitesequence. Notice also the negative Bouguer anomalyand 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 actingloads 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 plateinfill = density of material above the plateg = average gravityx = horizontal distance= flexural parameter given by:
D = flexural rigidity of the plate given by:
WhereE = Youngs Modulusv = Poisson's RatioTe= Elastic thickness of the lithosphere
Low Himalaya High Himalaya
LOW HIMALAYA
HIGH HIMALAYA
SOUTH TIBETANDETACHMENT
INDUS-TSANG POSUTURE
SEISMIC IMAGE OF THE CRUSTAL STRUCTURE
INDIAN CONTINENTAL CRUST
SCHEMATICN-S PROFILE ACROSS THE HIMALAYAS
MHT
ITS
MCT
MBT
MFT
STDS
High-Himalaya
NB! INTER-PLAY BETWEENCONTRACTION AND EXTENSION DURINGA LONG PERIOD OFCOLLISION
Low-Himalaya
MCT STDS
From: Hodges et al. 1997
THE TRANS-HIMALAYAN-BATHOLITHREMNANT OF THE ANDEAN MARGIN WHICH PRE-DATETHE CLOSURE OF TETHYAN OCEAN (AGE ≈ 95-45 Ma)
MHT
ITS
MCT
MBT
MFT
STDS
THB
HIMALAYAN REGIONAL METAMORPHISM, • NORMAL AND INVERTED METAMORPHIC GRADIENTS• “HOT-IRON” (HOT ON COLD) HYPOTHESIS• TRANSPORTED OLDER METAMORPHISM HYPOTHESIS• FRICTIONAL HEATING HYPOTESIS
FOLDED METAMORPHIC ISOGRADS INDICATING TRANSPORTED OLDERMETAMORPHISMStaurolite
Kyanite
Sill-Musc
Sill-Kspar
Leucogranites
HIMALAYAN LEUCO-GRANITES AND PATIAL MELTING
THE SUTURE(S):INDUS -TSANG POKOHISTAN ARC
DEEP SUBDUCTIONOF CONTINETALLITHOSPHERE(SEISMIC EVENTS)AND REFRACTIONSTUDIES
SPONTANGOPIOLITE
THE KOHISTAN ARC, AN ALMOST COMPLETELY PRESERVED ISLAND ARC COMPLEX EXPOSED FROMBASE TO TOP!
NOT PRESERVED
CONTINUE WITH PRESENT DAY TECTONICS OF
THE HIMALAYAN TIBETAN COLLISION ZONE
