Alexandria Digital Research Library

Time-scales of crustal anatexis in the Ama Drime Massif, southern Tibet

Author:
Willingham, Amanda Lee
Degree Grantor:
University of California, Santa Barbara. Geological Sciences
Degree Supervisor:
John M. Cottle
Place of Publication:
[Santa Barbara, Calif.]
Publisher:
University of California, Santa Barbara
Creation Date:
2012
Issued Date:
2012
Topics:
Asian Studies and Geology
Keywords:
Leucogranite
U(-Th)-Pb.
Ama Drime Massif
Himalaya
Geochronology
Anatexis
Genres:
Dissertations, Academic and Online resources
Dissertation:
M.S.--University of California, Santa Barbara, 2012
Description:

As an active continent-continent collision zone, the Himalayan orogen provides a superb natural laboratory to study a wide range of tectonic processes. One process inexorably linked to tectonism is melt generation, which can occur in a multitude of ways. Partial melting of continental crust, anatexis, typically produces migmatites and melts of granitic composition. Studying these granites in their geologic context allows placement of age maxima and minima for tectonic events, thus allowing evaluation of tectonic hypotheses. This study examines the timescales of anatexis and melt mobilization in the Ama Drime Massif (ADM), an exposure of mid-to-lower-crustal material in the Everest region. The ADM crosscuts a major Miocene fault system, the South Tibetan Detachment System (STDS), and is structurally lower than the GHS. Thus, it provides valuable information about post-STDS Himalayan tectonics. Using laser ablation inductively coupled mass spectrometry (LA-ICP-MS), U(-Th)-Pb geochronology of accessory minerals in leucogranite intrusions in the ADM demonstrates that, compared with the overlying GHS, melting in the ADM was short-lived---the entire range of granite crystallization occurred over ∼6 m.y. (8.5 +/- 0.1 Ma to 14.6 +/- 0.1 Ma)---after ductile deformation ceased in both the Everest region Greater Himalayan Series (GHS) and Northern Himalayan gneiss domes (NHGD). This study indicates that the ADM was largely unparticipatory in melting events that pervasively affect the GHS and NHGD, and records mid-crustal processes within the orogen after movement stopped on the STDS.

Physical Description:
1 online resource (138 pages)
Format:
Text
Collection(s):
UCSB electronic theses and dissertations
ARK:
ark:/48907/f3h41pcd
ISBN:
9781267649911
Catalog System Number:
990038916110203776
Rights:
Inc.icon only.dark In Copyright
Copyright Holder:
Amanda Willingham
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