| Title | Inherited cross-strike faults and Oligocene-early Miocene segmentation of the Main Himalayan Thrust, west Nepal |
| |
| Author | Soucy La Roche, R ; Godin, L |
| Source | Journal of Geophysical Research, Solid Earth vol. 124, issue 7, 2019 p. 7429-7444, https://doi.org/10.1029/2019JB017467 |
| Image |  |
| Year | 2019 |
| Alt Series | Natural Resources Canada, Contribution Series 20190083 |
| Publisher | American Geophysical Union (AGU) |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf (Adobe® Reader®); html |
| Area | Himalayas; Nepal |
| Lat/Long WENS | 80.0000 84.0000 31.0000 27.0000 |
| Subjects | structural geology; tectonics; geochronology; geochemistry; igneous and metamorphic petrology; Nature and Environment; Science and Technology; Neogene; Miocene; Paleogene; Oligocene; bedrock geology;
basement geology; structural features; faults; klippen; orogenesis; structural controls; phase equilibria; radiometric dating; uranium lead dating; argon argon dating; tectonic elements; tectonic evolution; pressure-temperature conditions;
metamorphism; deformation; faulting; subduction; seismicity; thermal history; Main Himalayan Thrust; Greater Himalayan Sequence; Karnali Klippe; Jajarkot Klippe; Indian Plate; Tethyan Sedimentary Sequence; Phanerozoic; Cenozoic; Tertiary |
| Illustrations | geoscientific sketch maps; cross-sections; digital elevation models; phase diagrams; photomicrographs; time series; block diagrams |
| Program | GEM2: Geo-mapping for Energy and Minerals Western Cordillera, Stikine Terrane |
| Released | 2019 06 26 |
| Abstract | The geometry of orogenic basal detachments controls the location and partitioning of seismicity, yet how it influences past episodes of orogenesis is often overlooked. We integrate recently published
microstructural, phase equilibria modeling, monazite U-Th/Pb petrochronology, and white mica 40Ar/39Ar geochronology data from the Greater Himalayan sequence to characterize the geometry of the Himalayan basal detachment, the Main Himalayan thrust
(MHT), during the Oligocene and early Miocene. The Karnali and Jajarkot klippen, located at equivalent along-strike positions in the direction of tectonic transport in the foreland of west Nepal, record contrasting
pressure-temperature-time-deformation paths. Units in both klippen reached similar peak pressures with a 5- to 10-Myr time difference: Units in the Karnali klippe were exhumed while units in the Jajarkot klippe were buried. We interpret the
contrasting metamorphic pressures between 35 and 25 Ma to reflect the influence of a vertical or steeply east dipping lateral ramp (or tear fault) in the MHT between the two klippen. The location of this putative Oligocene MHT ramp coincides with
other evidence for a MHT lateral ramp since the Pleistocene to the present. Segmentation of the MHT in west Nepal is therefore an active and protracted phenomenon that started in the Oligocene or earlier. We interpret this offsetting of the MHT to be
linked to the Lucknow basement fault, a spatially coinciding inherited cross-strike structure in the subducted Indian lithosphere. Our study highlights the important applications of metamorphic petrology and petrochronology to seismotectonics by
illustrating the timescales of lateral segmentation of an orogenic basal detachment. |
| Summary | (Plain Language Summary, not published)
This manuscript presents a new model to explain the evolution of the Himalaya mountain belt. It explores how deep structures in the underthrust Indian
continent control the structural and metamorphic evolution of the overriding plate. The results of this study have wide applicability to mountain belts around the world including those that are preserved in Canada. |
| GEOSCAN ID | 314728 |
|
|