Detrital zircon geochronology: enhancing the quality of sedimentary source information through improved methodology and combined U-Pb and fission-track techniques

Zircon is the most widely used mineral in detrital dating studies because it is common to multiple rock types, is chemically and physically resistant, and can endure successive cycles of burial, metamorphism and erosion. Zircon also has the advantage that single grains may be dated by either the fission-track (FT) or U-Pb method, which, because of their contrasting thermal sensitivities (total resetting occurs at temperatures > 320 degrees C for FT and > 700-900 degrees C for U-Pb), can provide unique information about both the age structure and the thermal evolution of a sediment source. However, single method-based bias and difficulties associated with interpreting measured ages can influence both the quality and the level of useful provenance information. For example, the zircon FT system is sensitive to metamorphic overprinting and hence measured ages alone cannot be interpreted as unambiguously dating formation age of the source rock. In contrast, U-Pb zircon data have high resistance (700-900 degrees C) to thermal overprinting and therefore recorded formation ages may not relate to an immediate source but may instead reflect a polycyclical history. The focus of this paper is to examine, from a practical standpoint, the provenance potential of detrital zircon fission track data and to investigate the method's complementary role as an aide to the interpretation of high-temperature detrital U-Pb zircon data by combining U-Pb and FT methods in a single study.