IGNEOUS PETROLOGY AND PETROCHEMICAL VARIATION IN THE COYOTE CREEK PLUTON, COLVILLE BATHOLITH AND ITS RELATION TO MINERALIZATION AT SQUAW MOUNTAIN, COLVILLE INDIAN RESERVATION, WASHINGTON.

摘要

The Coyote Creek Pluton (CCP) is one member of the large composite Colville Batholith of Northeast Washington. It crops out in the southwestern part of the Colville Indian Reservation and is cut by later rhyodacite dikes. Approximately thirty five square kilometers of the CCP was mapped on a 7 1/2 minute base map. Samples were analysed for the major and trace elements using the XRF technique, and for the Rare Earth Elements (REE) by INAA.;Field, petrographic and chemical evidence suggest that the CCP is zoned, with a biotite-bearing granodiorite border unit, a middle unit of leucocratic granodiorite and a central unit of equigranular quartz monzonite cut by aplite.;SiO(,2) and K(,2)O increase inward whereas the other major oxides decrease; resulting in a chemical gradient from border to the core. Rb and Rb/Sr follow K, increasing inward, while Ba, Sr, Zr, and Ti behave in the reverse sense. The chondrite normalized REE patterns depict strongly fractionated REEs with enriched light REEs and an increasing negative Eu anomaly from border to the core.;The gradational petrochemistry of the CCP, the smooth calc-alkaline trend, the antipathetic relation between Rb and Sr, the decrease in Ba and K/Rb and increase in Rb/Sr towards the core lead to the conclusion that: The units are consanguineous and are probably related by fractional crystallization involving a progressive removal from the melt: plagioclase (An(,45(+OR-)2)) + biotite + apatite + zircon + magnetite; plagioclase (An(,30(+OR-)3)) + biotite + apatite + magnetite + zircon; plagioclase (An(,27(+OR-)3)) + biotite + quartz + potassium feldspar; plagioclase (An(,20(+OR-)2)) + quartz + potassium feldspar; plagioclase (An(,19(+OR-)4)) + quartz + potassium feldspar. These phases are concentrated in the hidden border granodiorite; the exposed border granodiorite; the quartz monzonite; and the aplite units respectively.;Mineralization on Squaw Mountain is not of economic dimension. Primary sulfides are pyrite, sphalerite, chalcopyrite, galena and molybdenite. Sulfide textures represent sulfide crystalloblastic series. The primary textures have been erased by post depositional recrystallization.