Carbonate clumped isotope thermometry in continental tectonics

Reconstructing the thermal history of minerals and fluids in continental environments is a cornerstone of tectonics research. Paleotemperature constraints from carbonate clumped isotope thermometry have provided important tests of geodynamic, structural, topographic and basin evolution models. The thermometer is based on the C-13-O-18 bond ordering in carbonates (mass-47 anomaly,Delta(47)) and provides estimates of the carbonate formation temperature independent of the delta O-18 value of the water from which the carbonate grew; Delta(47) is measured simultaneously with conventional measurements of carbonate delta C-13 and delta O-18 values, which together constrain the isotopic composition of the parent water. Depending on the geologic setting of carbonate growth, this information can help constrain paleoenvironmental conditions or basin temperatures and fluid sources. This review examines how clumped isotope thermometry can shed new light on problems in continental tectonics, focusing on paleoaltimetry, basin evolution and structural diagenesis applications. Paleoaltimetry is inherently difficult, and the precision in carbonate growth temperature estimates is at the limit of what is useful for quantitative paleoelevation reconstruction. Nevertheless, clumped isotope analyses have enabled workers to address previously intractable problems and in many settings offer the best chance of understanding topographic change from the geologic record. The portion of the shallow crust residing at temperatures up to ca. 200 degrees C is important as host to economic resources and records of tectonics and climate, and clumped isotope thermometry is one of the few proxies that can access this critical range with sensitivity to temperature alone. Only a handful of studies to date have used clumped isotopes to investigate diagenesis and other sub-surface processes using carbonate crystallization temperatures or the sensitivity of Delta(47) values to a sample's thermal history. However, the thermometer is sufficiently precise to answer many important questions in this area, making the investigation of sub-surface processes an excellent target for future investigations. (C) 2015 Elsevier B.V. All rights reserved.