GEOLOGY AND PETROCHEMISTRY OF THE KELLER BUTTE PLUTON AND ASSOCIATED INTRUSIVE ROCKS IN THE SOUTH HALF OF THE NESPELEM AND NORTHERN HALF OF THE GRAND COULEE DAM QUADRANGLES, AND THE DEVELOPMENT OF CATACLASITES AND FAULT LENSES ALONG THE MANILA PASS FAULT, NORTHEASTERN WASHINGTON (LENS STRUCTURES, COLVILLE BATHOLTH, BRITTLE FRACTURE).

摘要

This dissertation is divided into two parts, the first of which deals with the petrochemistry and evolution of the Keller Butte pluton (KBP) in the Colville batholith of northeastern Washington, and the second part describes the development of cataclasites and fault lenses along the high-level Manila Pass Fault which juxtaposes different phases of the KBP.;The Manila Pass Fault is a high-level fault that defines the western boundary of the Keller graben in northeastern Washington. Granitic rocks involved in the faulting exhibit brittle deformation features and show sequential development of cataclastic textures throughout the zone. The presence of low-angle conjugate fault sets which form rhombic and triangular fault patterns on both cross-sectional and map views, are similar to fracture patterns formed experimentally in a three-dimensional strain field. The low-angle conjugate fault sets are visible at all scales within the fault zone, from displaced albite twins in plagioclase feldspar to linears on aerial photographs. Where the conjugate sets from plan and cross-sectional views are in phase, and slip along the fault sets generates differential shear, lens-shaped fault blocks form. The lenses are confined to localized zones within the Manila Pass Fault, and may form in response to strain adjustments within areas of complex faulting.;The KBP is a high-level, zoned pluton that intruded by upheaval of its roof. Zonation in the KBP is defined by textural variation and by smooth major and rare earth element (REE) compositional gradients inward from a porphyritic grandiorite border to a core of garnet-bearing granite (glgr). An inward decrease in LREE, progressive development of a negative Eu anomaly, and enrichment of HREE in the glgr, suggest that the KBP differentiated by a combination of crystal fractionation, volatile loss, and retrograde boiling.