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The Petrological and Metallogenic Significance of the Alkaline Igneous Centre at the Springpole Gold Prospect, Northwestern Ontario [microform]

出版	Thesis (Ph.D.)--University of Western Ontario, 1996
ISBN	06122127779780612212770
URL	http://books.google.com.hk/books?id=N6upNwAACAAJ&hl=&source=gbs_api

註釋The Springpole alkaline complex is located in the Birch Lake greenstone belt, 116 km northeast of the town of Red Lake in NW Ontario. It dates at 2734 +23/$-$19 Ma. The complex is composed of coarsely phenocrystic alkali feldspar trachyte porphyry dykes and sills, sinuous intrusive breccia dykes and pipes, minette lamprophyre dykes and enigmatic massive carbonate-fluorite bodies. Evidence of explosive magmatic volatile exsolution is exemplified by porphyry-sourced breccias of fluidised, vertically-transported trachyte fragments, that intrude into stratigraphically higher carapace rocks. In one area a breccia pipe explosively vented, producing bedded deposits. The interpreted apex of the magmatic system is an intense zone of K-metasomatism with barian K-spar, fluor-mica ($\leq$5.1 wt.% F), fluorite, and anomalous levels of the LREE's. Lower in stratigraphy are porphyries of $>$95% modal albite and orthoclase end-member composition feldspar. Synneusis (oriented poikilitic) textures indicate feldspars are orthomagmatic and have crystallized together, below the solvus in the albite-orthoclase phase system at ${\leq}630\sp\circ$C. Such low temperatures are only attainable in high level systems with several wt.% F in the melt. Analyses of Fe-Mg micas from intrusive breccias indicate that HF fugacities were similar to Climax-type F-rich porphyry molybdenum systems.