Stockli, Daniel F. and Farley, Kenneth A. (2004) Empirical constraints on the titanite (U–Th)/He partial retention zone from the KTB drill hole. Chemical Geology, 207 (3-4). pp. 223-236. ISSN 0009-2541 http://resolver.caltech.edu/CaltechAUTHORS:20121120-111334016
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We analyzed (U–Th)/He ages of titanite from both the initial pilot hole (4 km depth) and the main drill-hole (9 km depth) of the German Continental Deep Drilling Project (KTB), to empirically evaluate the titanite (U–Th)/He partial retention zone (HePRZ) and laboratory helium diffusion data. Laser (U–Th)/He ages on single titanite fragments from the KTB drill hole, uncorrected for α emission, range from ∼94 to ∼2 Ma with reproducibility better than ±9%. Nearly invariant titanite (U–Th)/He ages, concordant with reported apatite fission track data, suggest that rocks from the upper ∼3 km of the KTB drill hole rapidly cooled from temperatures >200 to <110 °C between ∼75 and 85 Ma, followed by protracted cooling. Below ∼3 km, mean titanite (U–Th)/He ages decrease systematically with increasing borehole depth and down-hole temperature in a pattern similar to the titanite HePRZ predicted on the basis of laboratory-determined He diffusivities. Our results demonstrate that experimental titanite He diffusion data are applicable in the natural setting and that titanite (U–Th)/He thermochronometry provides a means to reliably reconstruct and quantify thermal histories between ∼100 and 180 °C, bridging the temperature ranges constrained by other techniques such as ^(40)Ar/^(39)Ar K-feldspar multi-diffusion domain modeling (350–150 °C) and apatite fission track dating (<110 °C).
|Additional Information:||© 2004 Elsevier B.V. Received 17 February 2003; accepted 8 March 2004. This work was supported by the National Science Foundation and by a Texaco postdoctoral fellowship award to D. Stockli and a David and Lucille Packard Foundation fellowship award to K. Farley. We are grateful to R. Jonckheere and G. Wagner for providing KTB titanite separates. We also thank L. Hedges for assistance in the Caltech Noble Gas laboratory and L. Stockli for assistance with SEM inclusion imaging at UCLA. Helpful reviews by A. Warnock and P. Zeitler improved the manuscript. [PD]|
|Subject Keywords:||Titanite; (U–Th)/He; Thermochronology; KTB; Borehole; Calibration|
|Official Citation:||Daniel F Stockli, Kenneth A Farley, Empirical constraints on the titanite (U–Th)/He partial retention zone from the KTB drill hole, Chemical Geology, Volume 207, Issues 3–4, 16 July 2004, Pages 223-236, ISSN 0009-2541, 10.1016/j.chemgeo.2004.03.002. (http://www.sciencedirect.com/science/article/pii/S0009254104001068)|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||20 Nov 2012 19:36|
|Last Modified:||20 Nov 2012 19:36|
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