Granitic magmatism and metallogeny of southwestern North America

摘要: In southwestern North America, late Palaeozoic through Cenozoic granitoids and their related mineral deposits show consistent patterns that can be interpreted in terms of combined provincial, exposure process controls. Voluminous Cordilleran magmatism began the Permian continued with few major interruptions Mesozoic Cenozoic, reaching maximum fluxes mid-Jurassic, Late Cretaceous Oligocene. Two distinctive types broad-scale igneous suites formed. The first type consists calc-alkaline to alkaline vary regularly time from early intermediate-mafic centres felsic over intervals lasting 20–50 Ma. These formed during periods stable convergence compressional tectonics, most notably early–mid-Cenozoic. second is compositionally varied, but shows no obvious secular variation composition. This neutral extensional tectonics mid-Mesozoic mid- Cenozoic. Regional (west east) (old young) changes calcic alkalic compositions do not correspond basement types; they point tectonic rather than crustal controls on magmatic evolution, although signatures are clearly transmitted isotopic systematics. Contrasting intrusive same lithospheric columns, suggesting variability reflects thermal stress regimes, subcrustal magma flux thickness. Simple mechanical models limits assimilation uprise broadly these patterns. Igneous-related mineralisation ubiquitous where epizonal environments preserved, thus preservation (and exposure) form first-order filter metallogeny. Mineralisation includes porphyry, skarn, epithermal, replacement syngenetic widely varying styles, metal contents links heat materials. Metal alteration styles correlate closely independent setting, systematic regional variations ratios documented. Ore element Cu–Au–Fe associated (quartz) dioritic monzonitic Cu–Zn–Mo–Pb–Ag–W–Au granodioritic centres, finally F–Mo–Zn–W–Ag–Be metaluminous strongly peraluminous granitic centres. A model both composition rationalises this correlation lack strong control. Key features (1) mineralogical fluid (2) efficacy processes producing voluminous ore-forming aqueous fluids. interpretation supported by field relationships, petrographic data, theoretical considerations.