U-Pb ages of metamorphic overgrowths on detrital zircons from the paragneisses indicate multiple events at ¡«1.76, 1.74, 1.70 and 1.67 Ga which documents a periodicity of tectonism through time. The oxygen isotope ratios of the metamorphic zircon overgrowths from the paragneisses remained relatively constant through time within each sample, consistent with growth during in situ partial melting. However, oxygen isotope ratios of zircons from 1.74 Ga leucocratic material are lower in ¦Ä18O, and therefore could not have been generated by partial melting of the adjacent paragneiss. Monazite from both igneous and metasedimentary rocks preserves two periods of growth at 1.75 and 1.67 Ga. In situ, U-Pb dating of monazite reveals that 1.67 Ga monazite inclusions are found in major rock-forming minerals, and therefore we interpret this as the timing of fabric formation and migmitization, which is younger than previously believed and is interpreted to be the dominant metamorphic pulse in the protracted middle crustal tectonism. Thermobarometry indicates peak metamorphic conditions of ¡«3.5 kb and ¡«740 ¡ãC, which is consistent with partial melting and the metamorphic mineral assemblage in these rocks (sillimanite + K-feldspar, muscovite absent). This paper shows (1) multiple pulses identified within 100 Ma orogeny, (2) zircon components and their overgrowths demonstrate mixing of Archean, 1.8 and younger reservoirs, (3) low pressure granulite facies metamorphism occurred at 1.67 Ga and may have been related to continental extension of a tectonically over-thickened crust.