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Durham University

Department of Earth Sciences

Profile

Publication details for Professor Yaoling Niu

Song, S., Zhang, L., Niu, Yaoling, Su, L., Song, B. & Liu, D. (2006). Evolution from Oceanic Subduction to Continental Collision: a Case Study from the Northern Tibetan Plateau Based on Geochemical and Geochronological Data. Journal of Petrology 47(3): 435-455.

Author(s) from Durham

Abstract

Two apparently distinct, sub-parallel, paleo-subduction zones can
be recognized along the northern margin of the Tibetan Plateau: the
North Qilian Suture Zone (oceanic-type) with ophiolitic me´langes
and high-pressure eclogites and blueschists in the north, and the
North Qaidam Belt (continental-type) in the south, an ultrahighpressure
(UHP) metamorphic terrane comprising pelitic and granitic
gneisses, eclogites and garnet peridotites. Eclogites from both belts
have protoliths broadly similar to mid-ocean ridge basalts (MORB)
or oceanic island basalts (OIB) in composition with overlapping
metamorphic ages (480–440 Ma, with weighted mean ages of
464  6Ma for North Qilian and 457  7Ma for North
Qaidam), determined by zircon U–Pb sensitive high-resolution
ion microprobe dating. Coesite-bearing zircon grains in pelitic
gneisses from the North Qaidam UHP Belt yield a peak metamorphic
age of 423  6Ma, 40 Myr younger than the age of
eclogite formation, and a retrograde age of 403  9 Ma. These
data, combined with regional relationships, allow us to infer that
these two parallel belts may represent an evolutionary sequence from
oceanic subduction to continental collision, and continental underthrusting,
to final exhumation. The Qilian–Qaidam Craton was
probably a fragment of the Rodinia supercontinent with a passive
margin and extended oceanic lithosphere in the north, which was
subducted beneath the North China Craton to depths >100 km at
c. 423 Ma and exhumed at c. 403 Ma (zircon rim ages in pelitic
gneiss).