Structural and metamorphic evidence from low-P, high-T metamorphic terranes within the northern Arunta Inlier, central Australia, indicates that two discrete tectonic cycles affected the region. Each cycle was associated with compressive deformation, coincident with peak granulite facies metamorphism and granite intrusion. SHRIMP U-Th-Pb analysis of zircons from early-, syn- and late-tectonic granitoids allows the age of the two tectonic cycles to be directly measured. The age of the first cycle (D-1) is determined by emplacement of the Mount Stafford Granite, dated at or before 1818+/-15 Ma, after the first two foliations of the cycle had formed, but before the axial-plane cleavage associated with later upright folding. The regional extent of this tectono-magmatic event is confirmed by an emplacement age of 1818+/-8 Ma measured on the large, discordant Harverson Granite, 40 km away. The second cycle (D-2) consisted of four distinct deformation stages (D-2a-2d), the ages of which are constrained by 1785-1775 Ma old, early-, syn- and late-tectonic granitoids. The Warimbi Granite (emplaced at or before 1785+/-22 Ma) and the granitic protolith to the Napperby Gneiss (inferred to be 1780+/-10 Ma) pre-date, or formed during, the earliest foliation (S-2a). Zircon considered to have grown at peak granulite facies metamorphic conditions, during generation of the dominant S-2b foliation, gives an age of 1774+/-6 Ma in the Possum Creek Charnockite, Leucogranite in the Napperby Gneiss, which post-dates S-2b and large-scale, upright, NW-SE-trending F-2d folds, yields an age of 1775+/-12 Ma and confirms that the entire tectonic cycle (D-2a-2d) formed in a rapid (similar to 10 Ma) period. Younger zircons, which formed at 1659+/-6 Ma in the Napperby Gneiss, cannot be related to any local structural event, but are similar in age to a major magmatic/metamorphic episode in the southern Arunta (Black and Shaw, 1992), similar to 150 km away. They may be the peripheral manifestation of that event, Further zircon growth at similar to 1600 Ma in the Napperby Gneiss and Possum Creek Charnockite was caused by hydrothermal fluid fluxing associated with post-tectonic pegmatite emplacement. These dykes were deformed by amphibolite facies, retrograde shear zones. Ion probe dating of zircon ''stratigraphy'' from the granitoids has confirmed the discrete successive tectonic cycles identified by earlier structural and metamorphic studies. For the northern Arunta Inlier at least, those cycles (or ''orogenies'') are associated with short-lived (similar to 10 Ma) thermal pulses related to granite magmatism, not prolonged thermal perturbations spanning 100 Ma or more (cf. Dirks and Wilson, 1990; Dirks and Hand, 1991). Such short-lived pulses are intimately associated with granite intrusion and may be a general feature of low-P, high-T metamorphism.
