A geological and geochemical study of the Skidder basalt and Skidder trondhjemites : and the geology, ore petrology and geochemistry of the Skidder Prospect and its accompanying alteration zone: Buchans area, central Newfoundland

• Main Author: Pickett, Jacob Wayne
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1988
• Subjects: Indian; Newfoundland
• Online Access: https://research.library.mun.ca/6835/; https://research.library.mun.ca/6835/1/JacobWaynePickett.pdf; https://research.library.mun.ca/6835/3/JacobWaynePickett.pdf

The Skidder Basalt, which outcrops in an area of central Newfoundland immediately to the northwest of Red Indian Lake and approximately 12 km southwest of the town of Buchans, is a spilitized, tholeiitic, sub-alkaline assemblage composed mainly of mafic yariolitic and non-variolitic pillow lava, mafic pillow breccia and massive mafic flows; these extrusive rocks are interlayered with lesser amounts of mafic pyroclastic rocks and chert, and are intruded by diabase dykes. Units typically strike northeast to east-northeasterly and dip steeply; facing directions are typically northwesterly, although local reversals, particularly in the vicinity of the Skidder Prospect, are noted. Foliations trend northeasterly and dip steeply. Several northeasterly, northerly and northwesterly trending lineaments are evident on aerial photographs, and many correspond to linear magnetic features. -- Rocks of the Skidder Basalt are dominated by secondary mineral assemblages. Typically, albitized plagioclase phenocrysts occur in an intergranular to intersortal groundmass of albite, chlorite, quartz, dense granular sphene, and variable amounts of subhedral to acicular opaque minerals. Primary clinopyroxene and chromite, and secondary calcite, amphibole and epidote are constituents of some samples. Clinopyroxene and albitized plagioclase in some low-Zr Skidder basalts exhibit quench-texture morphologies. Formation of varioles, present in some of the low-Zr Skidder basalts, is suggested to be a result of quenching. Spilitization of the Skidder Basalt has involved albitization of plagioclase, chloritization of basaltic glass, alteration of ferromagnesian minerals to chlorite and lesser amphibole, and alteration of opaque Fe-Ti oxides to dense intergranular sphene. Geochemically, spilitization has resulted in redistribution of SiO₂ and total iron, removal of K₂O and MgO, and extensive addition of Na₂O. The spilitization is suggested to have resulted from interaction of the rocks with circulating seawater under conditions of low ...