Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published November 2006 | public
Journal Article

Thermal histories from the central Alborz Mountains, northern Iran: Implications for the spatial and temporal distribution of deformation in northern Iran

Abstract

We integrate new and existing thermochronological, geochronological, and geologic data from the western and central Alborz Mountains of Iran to better constrain the late Cenozoic tectonic evolution of northern Iran in the context of the Arabia-Eurasia collision. New data are presented for two granitic plutons north of the Alborz Range crest. Additional new apatite (U-Th)-He data are also presented for volcanic, intrusive, and detrital apatite grains from two transects south of the range crest. Our most definitive results include zircon and apatite (U-Th)-He and limited K-feldspar ^(40)Ar/^(39)Ar thermal history data from the Cretaceous (ca. 98 Ma) Nusha pluton that reveal that the Alborz basement underwent generally slow denudation (∼0.1 km/m.y.) as late as 12 Ma with more accelerated exhumation (∼0.45 km/m.y.) that likely began shortly after 12 Ma. The Lahijan pluton, a late Neoproterozoic–Cambrian basement exposure near the Caspian shore, records apatite (U-Th)-He closure at 17–13 Ma. Additional (U-Th)-He results from detrital apatites sampled along two separate horizontal transects all consistently yielded latest Miocene to Pliocene apparent ages that imply that even supracrustal cover rocks within the Alborz have undergone significant, regionally extensive exhumation. Overall, our data are consistent with ∼5 km of regionally extensive denudation since ca. 12 Ma. The onset of rapid exhumation in the Alborz at ca. 12 Ma appears to be consistent with other timing estimates that place the onset of the Arabia-Eurasia collision between 14 and 10 Ma.

Additional Information

© 2006 Geological Society of America. Manuscript received 11 March 2005; Revised manuscript received 5 May 2006; Manuscript accepted 2 June 2006. This study was supported by the Research Council, University of Tehran (J.H.); U.S. National Science Foundation (NSF) grants EAR-9903249 and EAR-0073966 (M.G.); and NSF grant EAR9902932 (B.G., D.F.S., G.J.A.). The U-Pb data presented in this paper were collected in the ion microprobe facility at UCLA. The ion microprobe facility at UCLA is partly supported by a grant from the Instrumentation and Facilities Program, Division of Earth Sciences, National Science Foundation. We thank Kenneth Farley for cost-free use of the Caltech (U-Th)-He lab and Lindsey Hedges for assistance with conducting (U-Th)-He analyses on the Nusha and Lahijan zircons. Peter Bird and Brian Horton provided insightful reviews of earlier versions of this manuscript. Charlie Verdel reviewed a presubmission version of this manuscript and provided helpful comments. Finally, we are very grateful to Jahandar Ramezani for his exhaustive review and written comments on this manuscript and to an anonymous reviewer for his/her comments.

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023