A new method for the estimation of cooling and denudation rates using paramagnetic centers in quartz: A case study on the Eldzhurtinskiy Granite, Caucasus

Abstract

Abstract. We present a new method for the assessment of the most recent cooling and denudation rates using paramagnetic centers in quartz measured by electron spin resonance (ESR) spectroscopy. These centers have a relatively low thermal stability. For cooling rates of 40 ø and 1000øC Myr -•, effective closure temperatures vary between 55 ø and 82øC (Ti center) and 49 ø and 64 øC (A1 center), respectively. Samples were collected from two cores that were drilled into the Eldzhurtinskiy Granite, which has an emplacement age of ~2 Ma as measured by U/Pb analyses of zircons. One 1500 rn core was taken from a drill hole into the dome of the granite, a second core of 4000 rn from a drill hole at the base of the Baksan However, the ESR denudation rates underestimate the erosion rate of the Baksan Valley because the geothermal gradient is not equilibrated between the surface and the depth of the annihilation temperatures, 950 and 1800 rn for the A1 and Ti centers, respectively. We conclude that ESR measurements of paramagnetic centers in quartz will allow the reconstruction of landscape dynamics for the past 10-1000 kyr and that in conjunction with U/Pb, fission track, and Ar/Ar analyses it will be possible to develop dynamic models for Quaternary tectonic movements. Aim and Scope of This Study IntroductionThe aim of this study was to demonstrate that electron spin resonance (ESR) measurements of paramagnetic centers can be used for the estimation of denudation and cooling rates, to assess the potential of this method, and to identify the weaknesses on which future research has to be focussed. The cores of the Eldzhurtinskiy Granite were ideally suited for this study: samples could be collected from a very long core to study the thermal stabilities of all centers involved; the present day uplift rate is known (N6-8 mm a -• as measured by a nearby Global Positioning System (GPS) station using a Trimble 4000 SSE system); and it is a very young intrusion, suggesting that the paramagnetic centers would not be saturated.• Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia.

OSL-thermochronometry of feldspar from the KTB borehole, Germany

“…With the notable exception of Durrani et al (1972Durrani et al ( , 1973, the majority of later studies circumvented the time-consuming determination of laboratory kinetics by adherence to their standard literature values and/or simplifying approximations (e.g. Grün et al, 1999;Herman et al, 2010). Thus, although several studies produced pi-oneering and insightful qualitative results, their projection onto absolute scales may be seen as subject for further investigation (Guralnik et al, 2013).…”

“…Ikeya et al, 1982), and hydrocarbon exploration (e.g. Ypma and Hochman, 1991), was recently superseded by studies utilising ESR or OSL signals to derive orogenic exhumation rates (Grün et al, 1999;Herman et al, 2010).…”

Determining the cooling age using luminescence-thermochronology

“…6) is in the same form with that given by Debusyst et al (1984) and Grün (1999) except that the lifetime is replaced by , where . However, is usually much smaller than τ at ambient temperatures (e.g.…”

“…Grün et al, 1999).The cooling rate is determined from the apparent age (t a ) and the present temperature (T p ) of samples in the A-T plot. The A-T plot can be constructed based on Eq.11, provided that all parameters ( , D 0 and τ) are known.…”

“…A full review of thermochronology has been provided by Reiners et al (2005). In terms of low-temperature thermochronology, radiation damage dating techniques, such as electron spin resonance (ESR) dating (Grün et al, 1999) and thermoluminescence (TL), are applied (Johnson 1966). Recently, in the study of the relief evolution and exhumation rates within the last glacial cycle in the Southern Alps of New Zealand, a new low-temperature 2 thermochronology has been introduced using the technique of optically stimulated luminescence (OSL) dating of quartz (Herman et al, 2010) .…”