Original paper
Extreme 18O depletion in eclogite from the Su-Lu terrane in East China
Zheng, Yong-Fei; Fu, Bin; Gong, Bing; Li, Shuguang
European Journal of Mineralogy Volume 8 Number 2 (1996), p. 317 - 324
62 references
published: Apr 22, 1996
manuscript accepted: Nov 23, 1995
manuscript received: Apr 20, 1995
DOI: 10.1127/ejm/8/2/0317
Abstract
Abstract The unusually low δ18O values of-10.3 to -6.8‰ are found in mineral separates from an eclogite pod (containing quartz-schist bands) in the Su-Lu terrane, East China. These are the lightest oxygen isotope compositions so far reported for metamorphic rocks in the world. Oxygen isotope equilibrium has been approached among the minerals within both eclogite and quartz-schist. This not only yields the concordant isotope temperatures of 655 to 765 °C, but also indicates that the rocks have exchanged oxygen isotopes with a very 18O-depleted fluid. A plausible interpretation for the anomalously low δ18O values of the eclogite pod is that it equilibrated isotopically with ancient meteoric water prior to eclogite-facies metamorphism and thus preserved the premetamorphic isotopic signature. The hydrothermally altered basaltic rocks kept this isotopic signature through all stages of progressive UHP metamorphism as well as subsequent exhumation and cooling. This provides insight into limited crust-mantle interactions under ultrahigh pressure metamorphic conditions in the suture zone of a continent-continent collision
Keywords
oxygen isotopes • water-rock interaction • isotope geothermometry • eclogite • UHP metamorphism • continental collision • Dabie Mountains