[Oberhänsli] 39Ar/40Ar in situ determination on local equilibrium domains: Exhumation history of UHP rock from the Chineese Continental Scientific Drilling (CCSD) drill hole in Donghai, China
German Title: 39Ar/40Ar in situ determination on local equilibrium domains: Exhumation history of UHP rock from the Chineese Continental Scientific Drilling (CCSD) drill hole in Donghai, China
Current Status: completed
Main Applicant:Prof. Dr. Roland Oberhänsli
The goal of this proposal is a more detailed definition of the retrogressive exhumation paths. Petrographic and petrologic investigations allow defining locally well preserved equilibria in shear bands. In situ 39Ar/40Ar dating of amphiboles and micas from these locally preserved equilibria in shear band from the Donghai main drill hole allows to better constrain the exhumation history of the UHP rocks from the Dabie - Sulu UHP belt. In the Donghai drill hole preliminary fission track work by Glasmacher and Wagner show juxtaposition of of several units along shear bands and shear zones. Apatite fission track ages on either side of these shear bands are reported as 30/50 Ma and 80/50 Ma. It is obvious that within the major shear zone described in from the Donghai main hole, shear bands of varying ages exist and that investigations of such petrologically and structurally discrete zones add to the understanding of the exhumation history. The exhumation history of the UHP crust in the Sulu belt is jet not well constrained. We got fresh samples from the drill hole. Furthermore, we think that in the core we can observe geometric constraints of deformation and crystallisation.
Wawrzenitz, Nicole, Romer, Rolf L., Oberhänsli, Roland, Dong, Shuwen (2006). "Dating of subduction and differential exhumation of UHP rocks from the Central Dabie Complex (E-China): Constraints from microfabrics, Rb–Sr and U–Pb isotope systems" Lithos 89 p174-201
Romer, R. L., Wawrzenitz, N., Oberhänsli, R. (2003). "Anomalous unradiogenic 87Sr//86Sr ratios in ultrahigh-pressure crustal carbonates – evidence for fluid infiltration during deep subduction?" Terra Nova 15 p330-336