『Abstract
Focused denudation and mid-crustal flow are coupled in many active
tectonic settings, including the Himalaya, where exhumation of
mid-crustal rocks accommodated by thrust faults and low-angle
detachment systems during crustal shortening is well documented.
New structural and (U-Th)/He apatite data from the Mount Everest
region demonstrate that the trans-Himalayan Ama Drime Massif has
been exhumed at a minimum rate of 〜1 mm/yr between 1.5 and 3.0
Ma during orogen-parallel extension. The Ama Drime Massif offsets
the South Tibetan detachment system, and therefore the South Tibetan
detachment system is no longer capable of accommodating south-directed
mid-crustal flow or coupling it with focused denudation. Previous
investigations interpreted the NNE-SSW-striking shear zone on
the west side of the Ama Drime Massif as the Main Central thrust
zone; however, our data show that the Ama Drime Massif is bounded
on either side by 100-300-m-thick normal-sense shear zone and
detachment systems that are kinematically linked to young brittle
faults that offset Quaternary deposits and record active orogen-parallel
extension. When combined with existing data, these results suggest
that the Ama Drime Massif was exhumed during orogen-parallel extension
that was enhanced by, or potentially coupled with, denudation
in the trans-Himalayan Arun River gorge. This model provides important
insights into the mechanisms that exhumed trans-Himalayan antiformal
structures during orogen-parallel extension along the southern
margin of the Tibetan Plateau.
Keywords: exhumation; mid-crustal flow; extension; denudation;
Himalaya; Tibetan Plateau』
Introduction
Previous interpretations of the Ama Drime Massif
Structural evolution and exhumation of the Ama Drime Massif
Discussion and conclusions
Acknowledgments
References cited