Sequential melting of deep crustal sources in a rift system: An example
from the Southern Tibet
Abstract
How the continental crust responds geochemically to progressive
extension is one of the interesting questions. The Southern Tibet Rift
System (STRS) is one of the active extensional structures. The Yardoi
gneiss dome, located within STRS, consists of at least four suites of
Miocene granites. As crystallization ages become younger, they are
characterized by decrease in Nd(t) and Sr/Y, but increase in
87Sr/86Sr(t) and Rb/Sr. Such temporal trends could be explained by
sequential partial melting of first the mafic lower crustal rocks and
then progressively shallower metasedimentary rocks. Together with
literature data, from north to south along STRS, as the extension
proceeds and the heat moves upward, sequential partial melting is common
to produce Miocene magmatic rocks. The processes documented in the
southern Tibet might be common in other extensional provinces and
provides a new insight to unravel the mechanisms for the generation of
geochemical variations in contemporaneous granites.