Zircon ages reveal dynamics of accretionary wedges

The detrital zircon geochronology has been increasingly used to analyze accretionary wedges over the past decade. A new study by Jiří Žák and others, stemming from collaboration of the Center with the Czech Academy of Sciences, explores the exciting potential of this method, with the key outcome being introduction of a new concept of the Age–Distance Curves (ADCs). The analysis of age variations across accretionary wedges may reveal a wealth of information on a variety of dynamic processes that occur above subduction zones: linear ADCs may track continuous accretion whereas variably sloping ADCs may reflect tectonic erosion, increase in the rate of deposition and accretion, or tectonic duplication; stepped ADCs may record the latter two processes, but also out-of-sequence thrusting while sawtooth ADCs may result from emplacement of older units within younger (olistoliths) or, vice versa, from tectonic underplating and exhumation. The new concept also outlined several issues that still remain poorly understood and would deserve attention in future research, for instance, quantifying temporal variations in the rates of accretion, estimating magmatic arc tempos, as well as rates of erosion and sediment supply from arc to trench.

Žák J., Svojtka M., Hajná J., Ackerman L. (2020): Detrital zircon geochronology and processes in accretionary wedges. Earth-Science Reviews 207, 103214 (DOI)