Flemish Cap, a large isolated submarine knoll 600 km east of Newfoundland, consists of a central core of Hadrynian rocks and an onlapping sequence of undisturbed to disturbed Mesozoic–Cenozoic sediments. The central core of the cap, sampled with an electric rock-core drill, comprises pink, fine- to medium-grained granodiorite, dacite, and volcanic siltstone. The granodiorite samples, collected in six out of eight cores, are remarkably similar lithologically, despite a separation of up to 65 km, and probably represent a single pluton. The aphanitic dacite and laminated cherty volcanic siltstone have been metamorphosed to subgreenschist (prehnite) facies but show no evidence of contact metamorphism.U–Pb analyses of coarse and fine zircon fractions from a granodiorite core yielded upper intercepts of 751 and 833 Ma, respectively. Although not precise, these ages probably represent the age of intrusion sometime in the 750–830 Ma range and are older than those reported for similar Hadrynian granitic rocks of eastern Newfoundland. AK–Ar age of 657 ± 29 Ma on hornblende from the same core and a K–Ar age of 615 ± 20 Ma on biotite from a granodiorite core elsewhere in the body probably represent incomplete degassing during the superimposed subgreenschist metamorphism of uncertain age.Thus the Flemish Cap granodiorite and associated rocks are part of the Avalon Zone and may represent a much older part of the Avalon Terrane than parts toward the west on Avalon Peninsula and Burin Peninsula.

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Rb–Sr whole-rock and mineral isochron ages have been determined for metamorphic and granitic rocks of the Hida metamorphic belt. The results indicate that an extensive metamorphic event together with plutonic activity took place within the belt during the latest Paleozoic – early Mesozoic period. The older ages of 220–250 m.y. represent an earlier phase of the metamorphism, whereas the younger ages of 170–180 m.y. represent a later phase. The Funatsu granitic rocks yielded a whole-rock isochron age of 176 m.y. with an initial 87Sr/86Sr ratio of 0.7056. This age is believed to indicate the time of original emplacement, and the rocks are considered to represent late-kinematic intrusion in the Hida belt.Some information on the middle Paleozoic metamorphism in the Hida Mountains was obtained from the isochron study. The whole-rock isochron age of 412 m.y. for the metamorphic rocks of the Fujibashi area may be considered, although not confirmed, to indicate the time of older metamorphism. The Omi Schist of the Circum–Hida crystalline schist belt, which belongs to the glaucophanitic type of metamorphism, gave a mineral isochron age of 350 m.y. thereby providing evidence of mid-Paleozoic metamorphism.The initial 87Sr/88Sr ratios for the whole-rock samples of the Hida metamorphic belt are found to be generally low, i.e. 0.705–0.708. This is especially so for the metamorphic rocks from the northern part of the belt where the lowest values were found.

Forty-four new potassium–argon age determinations on minerals of metamorphic and igneous rocks from the Yukon Crystalline Terrane define the timing of the three most recent thermal events affecting this region. The oldest, 160 to 170 Ma ago, involved weak retrograde metamorphism of igneous and metamorphic rocks and coincides with the intrusion of batholiths of pink quartz monzonite. The next event, 90 to 100 Ma ago, reflects the emplacement of batholiths of the Coffee Creek quartz monzonite suite. The youngest thermal episode, 50 to 60 Ma ago, marks the time when the Nisling Range alaskite, with its porphyry dyke swarms and explosive acid volcanic rocks, was emplaced and when the K–Ar system of the Ruby Range Batholith was thermally reset. The data provide a younger limit to the age of the oldest Mesozoic plutonic rocks, the Klotassin suite, but they do not define its time of emplacement.