Thermochronology of the New Caledonian high-pressure terrane: Implications for middle Tertiary plate boundary processes in the southwest Pacific

Abstract

One of the youngest and best-preserved exposures of blueschist-and eclogite-facies rocks on Earth occurs in an elongate NW-SE-trending range in northeastern New Caledonia. This high-pressure (HP) terrane evolved within the Australia-Pacific plate boundary zone and records a middle Tertiary history of subduction burial, metamorphism, and exhumation. 40 Ar and fission track thermochronology was undertaken in the New Caledonian HP terrane to further constrain the timing and rates of cooling and exhumation, as well as to evaluate tectonic models. Oceanic and sedimentary protoliths were subducted at rates of 6-16 mm/yr and metamorphosed under HP conditions at ca. 44 Ma. Subsequently, rapid coolin..