Tempo of burial and exhumation within the deep roots of a magmatic arc, Fiordland, New Zealand

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 gran- ulites was more protracted, requiring an additional 40-45 m.y. These new data are con- sistent 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 8C by ca. 70 Ma. Such temporal constraints are essential for comprehensive models of the growth, modifi- cation, and unroofing of magmatic arc systems.