Premium
40 Ar/ 39 Ar Constraints on the tectonic history and architecture of the ultrahigh‐pressure Sulu orogen
Author(s) -
HACKER B. R.,
WALLIS S. R.,
MCWILLIAMS M. O.,
GANS P. B.
Publication year - 2009
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.2009.00840.x
Subject(s) - geology , plutonism , metamorphism , terrane , craton , geochemistry , zircon , isochron dating , cretaceous , metamorphic facies , paleontology , magmatism , tectonics , isochron , facies , structural basin
New 40 Ar/ 39 Ar ages are presented from the giant Sulu ultrahigh‐pressure (UHP) terrane and surrounding areas. Combined with U‐Pb ages, Sm‐Nd ages, Rb‐Sr ages, inclusion relationships, and geological relationships, they help define the orogenic events before, during and after the Triassic collision between the Sino–Korean and Yangtze Cratons. In the Qinling microcontinent, tectonism occurred between 2.0 and 1.4 Ga. The UHP metamorphism occurred in the Yangtze Craton between 240 and 222 Ma; its thermal effect on the Qinling microcontinent was limited to partial resetting of K‐feldspar 40 Ar/ 39 Ar ages. Subsequent unroofing at rates of 5–25 km Myr −1 brought the UHP terrane to crustal levels where it underwent a relatively short amphibolite facies metamorphism. The end of that metamorphism is marked by 40 Ar/ 39 Ar ages in the 219–210 Ma range, implying cooling at crustal depths at rates of 50–200 °C Myr −1 . Ages in the 210–170 Ma range may reflect protracted cooling or partial resetting by Jurassic or Cretaceous magmatism. Jurassic 166–149 Ma plutonism was followed by cooling at rates of c. 15 °C Myr −1 , suggesting relatively deep crustal conditions, whereas Cretaceous 129–118 Ma plutonism was succeeded by cooling at rates of c. 50 C Myr −1 , suggesting relatively shallow crustal depths.