Multi-method chronometry of the Teletskoye graben and its basement, Siberian Altai Mountains: new insights on its thermo-tectonic evolution
Published:January 01, 2009
Johan De Grave, Mikhail M. Buslov, Peter Van den Haute, James Metcalf, Boris Dehandschutter, Michael O. McWilliams, 2009. "Multi-method chronometry of the Teletskoye graben and its basement, Siberian Altai Mountains: new insights on its thermo-tectonic evolution", Thermochronological Methods: From Palaeotemperature Constraints to Landscape Evolution Models, F. Lisker, B. Ventura, U. A. Glasmacher
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The Altai Mountains form an intracontinental, transpressive deformation belt in the NW Central Asian orogenic system. Using a multi-method chronometric approach, the thermo-tectonic history of the basement underlying the Teletskoye graben area is constrained in more detail. The results provide new insights into the Siberian Altai basement evolution from the Early Palaeozoic to the present. Zircon SHRIMP (sensitive high-resolution ion microprobe) U–Pb ages (Late Ordovician–Early Silurian, 460–420 Ma) indicate an earlier crystallization age for the basement granitoids than previously thought (Late Devonian–Early Carboniferous, 370–350 Ma), while new multi-mineral 40Ar/39Ar age spectra suggest continuous basement cooling throughout the Devonian–Carboniferous. Reactivation of long-lived Palaeozoic structures controls the Teletskoye graben formation since the Plio-Pleistocene as a distant effect of India–Eurasian convergence. Deformation is propagated through Central Asia and Siberia along an inherited structural network closely associated with its basement fabric. A similar reactivation affected the Altai during the Mesozoic. Modelled apatite fission-track data suggest Late Jurassic–Cretaceous (150–80 Ma) cooling, interpreted to be related to denudation and the tectonic reactivation that we link to the coeval Mongol–Okhotsk orogeny. From the Late Cretaceous until the Pliocene, the thermal history models indicate a period of stability. Roughly around 5 Ma ago renewed cooling is observed that possibly represents the denudation and growth of the present-day Altai, and provides the context for the Teletskoye graben formation. A modelled Late Cenozoic cooling can be a result of, or overemphasized by, a modelling artefact. Some caution should be taken not to overinterpret this cooling phase.
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Thermochronological Methods: From Palaeotemperature Constraints to Landscape Evolution Models
Thermochronology - the use of temperature-sensitive radiometric dating methods to reconstruct the thermal histories of rocks - has proved to be an important means of constraining a wide variety of geological processes. Fission track and (U–Th)/He analyses of apatites, zircons and titanites are the best-established and most sensitive methods for reconstructing such histories in the uppermost kilometres of the crust, over time scales of millions to hundreds of millions of years.
The papers published in this volume are divided into two sections. The first section on ‘New approaches in thermochronology’, presents the most recent advances of existing thermochronological methods and demonstrates the progress in the development of alternative thermochronometers and modelling techniques.
The second section, ‘Applied thermochronology’, comprises original papers about denudation, long-term landscape evolution and detrital sources from the European Alps, northwestern Spain, the Ardennes, the Bohemian Massif, Fennoscandia and Corsica. It also includes case studies from the Siberian Altai, Mozambique, South Africa and Dronning Maud Land (East Antarctica) and reports an ancient thermal anomaly within a regional fault in Japan.