The composite Sunrise Butte pluton, in the central part of the Blue Mountains Province, northeastern Oregon, preserves a record of subduction-related magmatism, arc-arc collision, crustal thickening, and deep-crustal anatexis. The earliest phase of the pluton (Desolation Creek unit) was generated in a subduction zone environment, as the oceanic lithosphere between the Wallowa and Olds Ferry island arcs was consumed. Zircons from this unit yielded a 206 Pb/ 238 U age of 160.2 ± 2.1 Ma. A magmatic lull ensued during arc-arc collision, after which partial melting at the base of the thickened Wallowa arc crust produced siliceous magma that was emplaced into metasedimentary rocks and serpentinite of the overthrust forearc complex. This magma crystallized to form the bulk of the Sunrise Butte composite pluton (the Sunrise Butte unit; 145.8 ± 2.2 Ma). The heat necessary for crustal anatexis was supplied by coeval mantle-derived magma (the Onion Gulch unit; 147.9 ± 1.8 Ma). The lull in magmatic activity between 160 and 148 Ma encompasses the timing of arc-arc collision (159–154 Ma), and it is similar to those lulls observed in adjacent areas of the Blue Mountains Province related to the same shortening event. Previous researchers have proposed a tectonic link between the Blue Mountains Province and the Klamath Mountains and northern Sierra Nevada Provinces farther to the south; however, timing of Late Jurassic deformation in the Blue Mountains Province predates the timing of the so-called Nevadan orogeny in the Klamath Mountains. In both the Blue Mountains Province and Klamath Mountains, the onset of deep-crustal partial melting initiated at ca. 148 Ma, suggesting a possible geodynamic link. One possibility is that the Late Jurassic shortening event recorded in the Blue Mountains Province may be a northerly extension of the Nevadan orogeny. Differences in the timing of these events in the Blue Mountains Province and the Klamath–Sierra Nevada Provinces suggest that shortening and deformation were diachronous, progressing from north to south. We envision that Late Jurassic deformation may have collapsed a Gulf of California–style oceanic extensional basin that extended from the Klamath Mountains (e.g., Josephine ophiolite) to the central Blue Mountains Province, and possibly as far north as the North Cascades (i.e., the coeval Ingalls ophiolite).

Abstract This paper summarizes the current knowledge on the nature, kinematics and timing of movement along major tectonic boundaries in the Bohemian Massif and demonstrates how the Variscan plutonism and deformation evolved in space and time. Four main episodes are recognized: (1) Late Devonian–early Carboniferous subduction and continental underthrusting of the Saxothuringian Unit beneath the Teplá–Barrandian Unit resulted in the orogen-perpendicular shortening and growth of an inboard magmatic arc during c. 354–346 Ma; (2) the subduction-driven shortening was replaced by collapse of the Teplá–Barrandian upper crust, exhumation of the high-grade (Moldanubian) core of the orogen at c. 346–337 Ma and by dextral strike-slip along orogen-perpendicular NW–SE shear zones; (3) following closure of a Rhenohercynian Ocean basin, the Brunia microplate was underthrust beneath the eastern flank of the Saxothuringian/Teplá–Barrandian/Moldanubian ‘assemblage’; this process commenced at c. 346 Ma in the NE and ceased at c. 335 Ma in the SW; and (4) late readjustments within the amalgamated Bohemian Massif included crustal exhumation and mainly S-type granite plutonism along the edge of the Brunia indentor at c. 330–327 Ma, and peripheral tectonothermal activity driven by strike-slip faulting and possibly mantle delamination around the consolidated Bohemian Massif's interior until late Carboniferous–earliest Permian times.