Physical Sciences and Mathematics Commons^™

The Shuksan Metamorphic Suite And Shuksan Thrust Mt Watson Area, North Cascades, Washington, Ralph Albert Haugerud

WWU Graduate School Collection

Rocks of the Shuksan Metamorphic Suite exposed on Mt Watson are metamorphosed pillow basalts, basaltic flows (?), basaltic tuffs, carbonaceous sediments, Mn-enriched cherty sediments, rare calcareous sediments and rare ferromanganese nodules.

Greenschist of the Suite records the following history: 1) early static hydrothermal metamorphism; 2) Early Cretaceous (about 125 ma ago) synkinematic blueschist-facies metamorphism at P~7 kb, T~350° C, ^Pfluid ^{near P}total, ^XCO₂ < 0.1, with production of S₁ and L₁ ; 3) late-metamorphic isoclinal folding (F₂) around axes commonly at high angles to L₁; 4) L₃ crenulation of S₁. Phyllite of the …

Geology And Petrology Of The Lake Ann Stock And Associated Rocks, Eric William James

WWU Graduate School Collection

The Lake Ann stock is a two pyroxene quartz monzodiorite to granodiorite epizonal intrusive emplaced into the Shuksan thrust fault in the latest Pliocene. It is similar to other Late Tertiary Cascade intrusives in mineralogy, texture, chemistry, and setting. These similarities are attributable to near surface emplacement, quick cooling and magmatic arc setting. Epizonal emplacement is indicated by fine, equigranular textures, granophyre, late stage alteration, late miarolitic dikes, plagioclase resorbed by alkali feldspar, and low pressure contact metamorphic assemblages. Temperature of emplacement was between 600°C and 925°C; pressure was less than 2 kb. Chemistry of individual samples and variation diagrams …