Physical Sciences and Mathematics Commons^™

Fabric Study And Structural History Of Deformed Plutonic And Metamorphic Rocks In The Holden Area, North Cascades, Washington, Gary K. Hurban

WWU Graduate School Collection

The Holden area, in the Crystalline Core of the North Cascades, contains deformed and undeformed plutons ranging from Triassic to Eocene in age.

Two deformational styles have been identified in the Holden area. Contractional deformation is indicated by steeply-plunging, down-dip, mineral and stretching lineations in the syn-tectonic Seven Fingered Jack pluton (estimated midLate Cretaceous), and in the pre-tectonic Dumbell Mountain pluton (220 Ma), associated with apparent flattened fabrics. Strike-slip shear deformation is represented by gently-plunging to subhorizontal, strike-parallel mineral and stretching lineations, which are commonly associated with constricted fabrics. These fabrics occur prominently in the Dumbell Mountain pluton, and crosscut …

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 …

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 …