U-Pb geochronology of the Grenville Orogen of Ontario and New York: constraints on ancient crustal tectonics

The Robertson Lake shear zone section describes a boundary between domains with different thermal histories, and the Mooroton shear zone section reports different cooling ages and differential uplift across that fault (pages unavailable in our copy). But the paper explicitly says no age information is available for shearing along Robertson Lake; it does not establish 960–930 Ma displacement on both zones or identify both as essentially posttectonic normal faults. (LLM, conf=0.88)

In “Central Metasedimentary Belt Boundary Zone and Bancroft domain” (page unavailable), the paper reports sphene (titanite) ages from Bancroft-area skarns, but attributes their growth to igneous activity; it instead assigns regional metamorphism to sphene ages of 1045–1030 Ma from marbles and calc-silicate gneisses. Table 1 (page unavailable) lists a 1041 Ma monazite age, but the paper does not identify three Bancroft schist monazite ages or establish the stated 1041–1092 Ma metamorphic range. The zircon age is cited to Magnus, not Mezger, in the citing sentence. (LLM, conf=0.84)

The Central Metasedimentary Belt Boundary Zone and Bancroft domain section (page unavailable) reports sphene ages of 1074–1045 Ma, but identifies those grains as igneous; it dates regional metamorphism from metamorphic sphene ages of 1045–1030 Ma instead. The Closure temperatures section estimates about 650°C for most analyzed sphenes, not a universal maximum, while the Geological setting section reports about 6 kbar for Bancroft. Thus the paper supports the approximate temperature and pressure, but not the claim that 1.08–1.05 Ga titanite ages define the dominant Bancroft metamorphic stage. (LLM, conf=0.88)