Large-scale
geometry, offset and kinematic evolution of the Karakorum fault, Tibet
|
The total offset, lifespan and slip rate of the
Karakorum
fault zone (KFZ) (western Tibet) are debated. Along the southern fault
half, ongoing oblique slip has exhumed dextrally sheared gneisses
intruded by synkinematic leucogranites, whose age (V23 Ma, U/Pb on
zircon) indicates that right-lateral motion was already in progress in
the late Oligocene. Ar/Ar K-feldspar thermochronology confirms that
rapid cooling started around 12 Ma, likely at the onset of the present
dextral normal slip regime. Correlation of suture zones across the
fault requires a total offset greater than 250 km along the active
"northern" fault branch. An average long-term slip rate of 1+-0.3 cm/yr
is inferred assuming that this offset accrued in a time span of 23-34
Ma. Southwest of the Ladakh-Karakorum Range, the large-scale boudinage
of ophiolitic units suggests that an offset of several hundreds of
kilometers exists along another "southern" branch of the KFZ. Towards
the southeast, in the Mount Kailas region, the fault zone does not end
at Gurla Mandatha, but continues eastwards, as a transpressive flower
structure, along the Indus-Tsangpo suture. Our new data thus suggest
that the KFZ contributed to absorb hundreds of kilometers of India-Asia
convergence.
|
Paper by
Lacassin, Valli et al. published in EPSL v.219 (2004) p.255-269
PDF of
this paper
PDF
of reply to M. Searle's comment. |
|
|