Plutonic rocks of the Klamath Mountains, California and Oregon

Formation and emplacement of the Josephine ophiolite and the Nevadan orogeny in the Klamath Mountains, California‐Oregon: U/Pb zircon and 40Ar/39Ar geochronology

“…The proximity of the data for the oeme fraction to concordia strongly constrains the lower intercept at 139-•2 Ma, which is taken to be a close approbation to the igneous age of the sample. This age is concordant with a previous K/At hornblende age of 139*-4 Ma from a quartz monzonite located several km to the northwest [Hotz, 1971 ] The m'mimum westward displacement along the Orleans thrust is >40 km based on its outcrop pattern (Figures 1 and 2), and Jachens et al [1986] have estimated >110 km displacement based on geophysical data. Structural evidence for west or northwest directed thrusting of the older Klamath terranes over the Western Klamath terrane has been presented by many workers [Snoke, 1977;Harper, 1980Harper, , 1992Gray, 1985;Wyld, 1985;Jones, 1988;Harper, 1992 The numerous dikes and sills intruding the Josephine ophiolite and Galice Formation were previously considered to be pre-Nevadan because they are regionally metamorphosed and many are deformed [Harper, 1980;Saleeby et al, 1982;Harper and Wright, 1984;Wyld, 1985].…”

“…Nevertheless, the pluton is apparently syntectonic as evident from the dynamic contact aureole and high-temperature deformation in the pluton, implying that Nevadan deformation continued after movement on the Orleans thrust ceased. The Grants Pass pluton is mostly quartz diorite and quartz monzonite, but varies from diorite to granodiorite [Hotz, 1971, Barnes et al, 1992. Much of the pluton has an igneous foliation and lineation, and subsolidus fabrics are locally present.…”

“…This thrust has received little study, but the following evidence suggests it is a continuation or splay of the Madstone Cabin thrust: (1) the Chetco complex forms the footwall of both thrusts, (2) rocks beneath both tlm•._sts were strongly deformed under amphibolite facies conditions and have a north-northeast mineral lineation [Ramp, 1975;Dick, 1976;Loney and Himmelberg, 1977;Yule and Saleeby, 1993], and (3)muscovite from deformed granitic rocks beneath both thrusts have yielded ages of -•150 Ma [Hotz, 1971;Dick, 1976;Ramp, 1984; this study].…”

Mineral resource potential of the Wild Rogue Wilderness (NF105), Coos and Curry Counties, Oregon

“…Subsequent faulting and intrusive activity have truncated the base of the ophiolite suite. Both the basalt and the sheeted dikes are intruded by diorite which has yielded a potassium-argon age of 155 m.y., similar to ages of a number of widespread intrusive bodies in the Klamath Mountains (Hotz, 1971;Gray and McKee, 1981).…”

Preliminary geochemical and age data from postsubduction intrusive rocks, northwest Borneo

“…Granodioritic and dacitic terrains are common in late orogenic, accretionary environments such as southeastern Australia and western North America (e.g. Hine et al 1978;Hotz 1971). Because the bulk of the suite in West Kalimantan and Sarawak is acidic (Fig.…”