Miocene collision related conglomerates, south Tibet
Abstract of thesis entitled
MIOCENE COLLISION RELATED CONGLOMERATES,
Angel On Kee Chan
for the degree of Master of Philosophy
at The University of Hong Kong
in October 2004
The Yarlung Tsangpo suture zone is located in southern Tibet and preserves a record of the history of the India-Asia collisional event. The objective of the research project is to use an integrated study of the Gangrinboche conglomerates to further constrain the timing of the India-Asia collision. The study investigates the sedimentology, petrography, geochemistry and paleontology of the conglomerates.
Clastic detritus within the Gangrinboche conglomerates came from all nearby terranes. The dominant source of detrital clasts exhibits a gradual change up-section from materials derived from the north (the Lhasa terrane) to sediment sourced from the south of the suture zone (the Indian and other nearby terranes). This indicates that the India-Asia collision had happened by the time of conglomerate deposition. Sedimentary facies analysis indicates that the depositional environment evolved with time from an alluvial fan developed along the southern flank of an uplifted chain of Lhasa terrane rocks through a proximal to distal braided river system.
The discovery of tuffaceous layers interbedded within the Dazhuqu Formation is a significant result of this study. These pyroclastic deposits have an adakitic geochemistry and developed through modification of subduction-processed magma. As the sedimentary succession in the Dazhuka section contains clastic detritus derived from either side of the suture zone it is clear that the India-Asia collision had initiated by the time the conglomerates were deposited. The discovery of the tuffs within the conglomerates provides the
potential for a direct constraint on the timing of their deposition and timing of collision-related events.
School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:conglomerate china tibet suture zones structural geology stratigraphic cenozoic
Date of Publication:01/01/2005