The Early Oligocene Oregon Coast Range Intrusions (OCRI) consist of gabbroic rocks and lesser alkalic intrusive bodies that were emplaced in marine sedimentary units and volcanic sequences within a Tertiary Cascadia forearc basin. The alkalic intrusions include nepheline syenite, camptonite, and alkaline basalt. The gabbros occur as dikes and differentiated...
The Three Sisters region of the Oregon High Cascades has developed three compositionally
and petrogenetically distinct silicic (i.e., SiO₂ ≥ 58%) magma systems within the last 600 k.y. These
silicic systems evolved from the same High Cascade mafic magma system and developed in the same
20x30 km area of the...
Understanding continental crust formation and modification is a fundamental and longstanding geologic problem. Influx of mantle-derived basaltic magma and partial melting of the crust are two ways to drive crustal differentiation. This process results in a low density upper crust and denser, more refractory lower crust, creating significant and vastly...
The Clarno Formation is a series of volcanic, volcaniclastic, and related intrusive rocks located in central Oregon. It is the westernmost extent of a broader Eocene magmatic belt that covers much the western United States. The magmatic belt stretches eastward from Oregon to western South Dakota, and from the Canadian...
