Geochemistry of the highly evolved Sn-W-Mo-bearing Mount Douglas Granite, New Brunswick, Canada: Implications for origin and mineralization

摘要

The Late Devonian (368 +/- 1 Ma) post-orogenic peraluminous Mount Douglas Granite, located in southwestern New Brunswick, Canada, forms the eastern part of the Saint George Batholith. The batholith was emplaced following the accretion of the Gander and Avalon zones of the northern Appalachians during the Neoacadian Orogeny. The Mount Douglas Granite is divided into three units, Dmdl, Dmd2, and Dmd3, that formed by progressive high degrees of fractional crystallization. The two most fractionated units, i.e., Dmd2 and Dmd3, are locally associated with greisen/sheeted veins-related endogranitic Sn-W-Mo mineralization. Whole-rock delta O-18 values of +6.0 to +7.3 parts per thousand, high initial Sr-87/Sr-86 ratios of 0.70550 to 0.71665, slightly positive epsilon(Nd(368 Ma)) values (+0.3 to +1.1), and Pb isotopic data indicate that the granite was derived dominantly from partial melting of juvenile Avalonian crust, contaminated by supracrustal rocks.