Abstract

The U-Pb thermochronology of titanite, apatite, and rutile from a crustal profile through a Mesozoic magmatic arc in Fiordland, New Zealand, is used to constrain the timing and duration of significant vertical movements during arc construction and evolution. Titanite data from deep-crustal (12–13 kbar) basement and cover rocks of central Fiordland imply that contractional arc thickening (∼25 km) occurred by 111.1–113.4 Ma, within a few million years of a major phase of mid- to deep-crustal magmatism. This finding suggests that this cycle of magmatism, arc thickening, and high-grade metamorphism occurred in ≤6.2 m.y. In contrast to rapid burial, significant unroofing of the central Fiordland granulites was more protracted, requiring an additional 40–45 m.y. These new data are consistent with continued residence of the granulites in thickened arc crust for 15–20 m.y., with subsequent major unroofing recorded by rutile cooling to <450 °C by ca. 70 Ma. Such temporal constraints are essential for comprehensive models of the growth, modification, and unroofing of magmatic arc systems.

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