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Titanite geochemistry is an effective petrogenetic and metallogenic indicator of Cu-Mo-Au mineralized magmatic systems. It forms in various geological environments, including igneous and low-medium grade metamorphic, and low-temperature hydrothermal veins. Titanite is a common accessory phase in oxidized I-type granitoid intrusions, occurring with quartz, plagioclase, K-feldspar, apatite, ± hornblende, ± biotite, and ± titanomagnetite, and is enriched in a variety of trace elements including halogens. Variably mineralized (Cu, Mo, and Au, i.e. fertile) Devonian oxidized adakitic I-type granodiorites to granites from the New Brunswick part of the northern Appalachians with magmatic titanite fromrelatively fresh magmatic assemblages were examined. The compositional data reveal that these titanites are variably enriched in high field strength elements (Ta = 6.76–750.7 ppm, Zr = 44.48–6879.9 ppm, Hf = 2.62–173.1 ppm, Th = 7.95–931.5 ppm, U = 5.25–458.3 ppm), light to heavy rare earth elements, and Sr (1.59–447.8 ppm). These titanites exhibit notably negative Eu and Y anomalies and slightly positive Ce anomalies. Larger negative Eu anomalies of some of the titanites imply more reduced magmatic crystallization conditions, at least locally. Varying degrees of negative Eu anomalies imply variable fractionation in the source and of plagioclase from these magmas. Typically, these fertile granitoids have high magmatic f O 2 , which promotes the incorporation of Ce 4+ into titanites, accounting for positive Ce anomalies. Zr-in-titanite thermometry indicates that crystallization temperatures of the investigated intrusions ranged from 737° to 899 °C, reflecting variability in their formation conditions. Crystallization pressures using the Al 2 O 3 content of titanite are estimated to be between 182 and 382 MPa. Titanite Sr isotopes record a progressive magmatic evolution from an early mantle-derived magma to later magmatic interaction during ascent through the crust. These magmas ascend and are emplaced in post-collisional settings following the break-off of a subducting oceanic slab and the onset of transtensional tectonics. Heat from upwelling asthenosphere entered the slab gap, raising temperatures and inducing melting of the oceanic crust and possibly partial thickened suprasubduction subcontinental lithospheric mantle. Like other fertile adakitic porphyries, these Devonian oxidized intermediate magmas formed during slab failure then ascended rapidly through the thickened lithosphere in response to the changed geodynamic regime during post-collisional tectonic reorganization and lithospheric weakening processes.
Yousefi et al. (Fri,) studied this question.