Contact metamorphism of the White Mountain Peak metavolcanic complex, eastern California

Abstract

The NNW-trending White-Inyo Range represents the eastern continuation of the Sierran volcanic-plutonic arc along the central California-Nevada state line. South of White Mountain Peak, the NE-trending, steeply SE-dipping Barcroft structural break transects the orogenic belt. This high-angle reverse fault downdropped deformed, weakly recrystallized, mid-Mesozoic, mildly alkaline, White Mountain Peak mafi c and felsic metavolcanic fl ows, interlayered volcanogenic metasedimentary strata, and minor subvolcanic plugs against a folded Neoproterozoic-lower Paleozoic quartzite and carbonate metasedimentary section on the south. The Middle Jurassic Barcroft granodioritic pluton later intruded the Barcroft break; the Middle Jurassic Cottonwood, and Late Cretaceous McAfee Creek + Pellisier Flat granitoids also invaded the superjacent section on the NE. Heating of the White Mountain Peak metavolcanic complex by the Barcroft and nearby plutons caused a southeastward progressive increase in metamorphic grade, producing neoblastic biotite, epidote, and hornblende in mafi c volcanic rocks + minor hypabyssal stocks, and biotite + epidote ± andalusite in felsic volcanic rocks + volcaniclastic strata. Gradual increases in biotite Ti and plagioclase An contents refl ect this SE metamorphic zonation. Utilizing hornblende-actinolite, muscovite-celadonite, and biotite solid solutions, thermobarometry indicates lithostatic pressures of 2-3 kbar during recrystallization, with temperatures ranging from a background value of ~350 °C far from the Barcroft pluton, to >500 °C along the intrusive contact. Physical conditions were similar to those developed in the Neoproterozoic-lower Paleozoic platform strata directly south of the Barcroft granodiorite. The region constitutes a typical example of the P-T evolution of the late Mesozoic Californian crustal margin, where episodic magma emplacement caused widespread contact metamorphism.

Detrital zircon geochronology of Neoproterozoic–Lower Cambrian passive-margin strata of the White-Inyo Range, east-central California: Implications for the Mojave–Snow Lake fault hypothesis

“…Pluton emplacement over the period from ca. 80 to 180 Ma caused localized contact metamorphism of White-Inyo country rocks (Barton and Hanson , 1989;Dollase, 1994;Ernst, 1996Ernst, , 2005Kontny and Dietl, 2002).…”

Geologic implications of new zircon U‐Pb ages from the White Mountain Peak Metavolcanic Complex, eastern California

“…The structural‐stratigraphic interpretation by Hanson et al [1987] is supported by our new SHRIMP‐RG dating of zircons from the three White Mountain Peak volcanogenic metasedimentary rocks and the metafelsite from the Millner Canyon section. The new U‐Pb age data necessitate local correction of the structural‐metamorphic map in Millner Canyon by Ernst et al [2002] and Ernst [2005]. For descriptions of geologic relationships as well as phase chemistry and mineral parageneses other than the specific changes presented below, the reader is referred to these earlier works.…”

“…Only the northern parts of the Jurassic Barcroft and Cottonwood plutons, and Cretaceous McAfee Creek granitoids, and the southern arm of the Cretaceous Pellisier Flat pluton are shown [ McKee and Conrad , 1996]. Isograds for the neoblastic index minerals biotite (±epidote), and hornblende are progressively developed in layered rocks of the White Mountain Peak Metavolcanic Complex, based on modes listed by Ernst [2005]. The hypothesized northeastern extension of the Sacramento Canyon fault is shown, but its inferred minor slip does not influence location of the isograds.…”

“…This major break juxtaposes Mesozoic White Mountain Peak metavolcanic and volcanogenic metasedimentary rocks and several comagmatic hypabyssal plugs on the north against a well‐stratified uppermost Proterozoic‐Lower Cambrian carbonate and siliciclastic metasedimentary series on the south [ Crowder and Ross , 1972; Stevens and Olson , 1972; Dunne et al , 1978; Stern et al , 1981]. The latter, and the older part of the volcanogenic section on the north, were folded and penetratively deformed prior to emplacement of the Barcroft Granodiorite [ Ernst , 1996, 1997, 2005]. This crosscutting pluton contact metamorphosed and disturbed earlier folds and faults in the superjacent units; structures apparently produced during Antler, Sonoma, and/or East Sierran deformation events [ Stevens and Greene , 1999; Coleman et al , 2003].…”

“…These geologic relationships, as well as small inclusions of mafic volcanic rocks mapped by Ernst et al [2002], demonstrate that the Barcroft Granodiorite intruded the southern margin of the volcanic pile. Contact metamorphism of interlayered mafic and felsic volcanic rocks also shows that a major part of the White Mountain Peak Metavolcanic Complex formed prior to the intrusion of the Barcroft pluton [ Hanson , 1986; Ernst , 2005]. Detecting no lithologic hiatus in the section, Ernst et al [2002] mapped the entire volcanogenic pile as older than the Barcroft pluton.…”