Tectonic evolution of the Himalayan syntaxes

the view from Nanga Parbat

Research output: Contribution to journalArticle

Abstract

Current tectonic understanding of the Nanga Parbat–Haramosh massif (NPHM) is reviewed, developing new models for the structure and deformation of the Indian continental crust, its thermorheological evolution, and its relationship to surface processes. Comparisons are drawn with the Namche Barwa–Gyala Peri massif (NBGPM) that cores an equivalent syntaxis at the NE termination of the Himalayan arc. Both massifs show exceptionally rapid active denudation and riverine downcutting, identified from very young cooling ages measured from various thermochronometers. They also record relicts of high-pressure metamorphic conditions that chart early tectonic burial. Initial exhumation was probably exclusively by tectonic processes but the young, and continuing emergence of these massifs reflects combined tectonic and surface processes. The feedback mechanisms implicit in aneurysm models may have been overemphasized, especially the role of synkinematic granites as agents of rheological softening and strain localization. Patterns of distributed ductile deformation exhumed within the NPHM are consistent with models of orogen-wide gravitation flow, with the syntaxes forming the lateral edges to the flow beneath the Himalayan arc.
Original languageEnglish
Pages (from-to)215-254
Number of pages40
JournalGeological Society Special Publications
Volume483
Early online date30 Aug 2018
DOIs
Publication statusPublished - 2019

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Tectonics
tectonic evolution
tectonics
downcutting
ductile deformation
feedback mechanism
denudation
softening
exhumation
continental crust
Gravitation
Cooling
cooling
Feedback
young

Cite this

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title = "Tectonic evolution of the Himalayan syntaxes: the view from Nanga Parbat",
abstract = "Current tectonic understanding of the Nanga Parbat–Haramosh massif (NPHM) is reviewed, developing new models for the structure and deformation of the Indian continental crust, its thermorheological evolution, and its relationship to surface processes. Comparisons are drawn with the Namche Barwa–Gyala Peri massif (NBGPM) that cores an equivalent syntaxis at the NE termination of the Himalayan arc. Both massifs show exceptionally rapid active denudation and riverine downcutting, identified from very young cooling ages measured from various thermochronometers. They also record relicts of high-pressure metamorphic conditions that chart early tectonic burial. Initial exhumation was probably exclusively by tectonic processes but the young, and continuing emergence of these massifs reflects combined tectonic and surface processes. The feedback mechanisms implicit in aneurysm models may have been overemphasized, especially the role of synkinematic granites as agents of rheological softening and strain localization. Patterns of distributed ductile deformation exhumed within the NPHM are consistent with models of orogen-wide gravitation flow, with the syntaxes forming the lateral edges to the flow beneath the Himalayan arc.",
author = "Butler, {Robert W. H.}",
note = "Acknowledgements: I was introduced to the Himalayas by Mike Coward in the mid-1980s and remain indebted to him for inspiring a career studying orogenic tectonics. I also thank the numerous colleagues both from the UK and from Peshawar University who were companions on many field campaigns, especially around Nanga Parbat. This contribution has been greatly improved by incisive reviews by Tom Argles and Phaedra Upton, although, of course, the author takes full responsibility for the views presented here. Finally, I thank Peter Treloar for inviting this review and for his patience while I put it together. Funding: Over the years this research has been variously supported by the UK’s Natural Environment Research Council and the Royal Society. Published in: Himalayan Tectonics: A Modern Synthesis.",
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N1 - Acknowledgements: I was introduced to the Himalayas by Mike Coward in the mid-1980s and remain indebted to him for inspiring a career studying orogenic tectonics. I also thank the numerous colleagues both from the UK and from Peshawar University who were companions on many field campaigns, especially around Nanga Parbat. This contribution has been greatly improved by incisive reviews by Tom Argles and Phaedra Upton, although, of course, the author takes full responsibility for the views presented here. Finally, I thank Peter Treloar for inviting this review and for his patience while I put it together. Funding: Over the years this research has been variously supported by the UK’s Natural Environment Research Council and the Royal Society. Published in: Himalayan Tectonics: A Modern Synthesis.

PY - 2019

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N2 - Current tectonic understanding of the Nanga Parbat–Haramosh massif (NPHM) is reviewed, developing new models for the structure and deformation of the Indian continental crust, its thermorheological evolution, and its relationship to surface processes. Comparisons are drawn with the Namche Barwa–Gyala Peri massif (NBGPM) that cores an equivalent syntaxis at the NE termination of the Himalayan arc. Both massifs show exceptionally rapid active denudation and riverine downcutting, identified from very young cooling ages measured from various thermochronometers. They also record relicts of high-pressure metamorphic conditions that chart early tectonic burial. Initial exhumation was probably exclusively by tectonic processes but the young, and continuing emergence of these massifs reflects combined tectonic and surface processes. The feedback mechanisms implicit in aneurysm models may have been overemphasized, especially the role of synkinematic granites as agents of rheological softening and strain localization. Patterns of distributed ductile deformation exhumed within the NPHM are consistent with models of orogen-wide gravitation flow, with the syntaxes forming the lateral edges to the flow beneath the Himalayan arc.

AB - Current tectonic understanding of the Nanga Parbat–Haramosh massif (NPHM) is reviewed, developing new models for the structure and deformation of the Indian continental crust, its thermorheological evolution, and its relationship to surface processes. Comparisons are drawn with the Namche Barwa–Gyala Peri massif (NBGPM) that cores an equivalent syntaxis at the NE termination of the Himalayan arc. Both massifs show exceptionally rapid active denudation and riverine downcutting, identified from very young cooling ages measured from various thermochronometers. They also record relicts of high-pressure metamorphic conditions that chart early tectonic burial. Initial exhumation was probably exclusively by tectonic processes but the young, and continuing emergence of these massifs reflects combined tectonic and surface processes. The feedback mechanisms implicit in aneurysm models may have been overemphasized, especially the role of synkinematic granites as agents of rheological softening and strain localization. Patterns of distributed ductile deformation exhumed within the NPHM are consistent with models of orogen-wide gravitation flow, with the syntaxes forming the lateral edges to the flow beneath the Himalayan arc.

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