Detrital muscovite thermochronology in two drainage basins in western Bhutan

New reconnaissance data for a poorly characterized area in the western Bhutan Himalaya show distinction between the 40Ar/39Ar cooling age distributions of detrital minerals in the two river catchments of the Punatsang chu and the Wang chu. Muscovites from five samples of Wang chu river sands yield ages (corresponding roughly to the time of bedrock cooling through a temperature of ca.350°C) between 9.37± 0.08 Ma and 13.98 ± 0.08 Ma. The majority of ages are less than 13 Ma, and the data for all samples have a unimodal distribution with an average age of ca. 11.4 ± 1.5 Ma. In contrast, muscovites from 14 Punatsang chu samples yield ages with nearly the same total range but with a distinctively multi-modal distribution. Two modes predominate in the Punatsang chu data: one at ca. 11.4 Ma, which is statistically indistinguishable from the single mode of the Wang chu data, and one at ca. 14.5 Ma. The full explanation for this distribution must await further bedrock and detrital dating studies, but one hypothesis is that the out-of-sequence Kakhtang thrust fault system - which is thought to transect the upper reaches of the river catchments - has juxtaposed two bedrock terrains with different cooling histories.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Tshering, Peldon

Advisor dc:contributor.advisor

• Kip V. Hodges.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/39008

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/39008