The Orocopia Schist in southwest Arizona: Early Tertiary oceanic rocks trapped or transported far inland

Haxel, Gordon B.; Jacobson, Carl E.; Richard, S.M.; Tosdal, Richard M.; Grubensky, M.J.

doi:10.1130/0-8137-2365-5.99

Cited by 20 publications

(73 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A key observation is that relative proportions of the major rock types are broadly similar in all areas (~90-99% metagraywacke, 1-10% mid-ocean ridge basalt (MORB) metabasite, and trace amounts of Fe-Mn metachert, marble, and serpentinite; Haxel and Dillon, 1978;Haxel et al, 1987Haxel et al, , 2002Dawson and Jacobson, 1989). Moreover, many of the schist bodies exhibit inverted metamorphic zonation; i.e., peak temperature of metamorphism decreases structurally downward (Ehlig, 1958;Graham and England, 1976;Jacobson, 1983bJacobson, , 1995.…”

Section: Correlation Of the Schistsmentioning

confidence: 99%

“…Referred to collectively in this paper as the "schists," these rocks comprise a distinctive eugeoclinal assemblage that was metamorphosed from epidote-blueschist to oligoclase-amphibolite facies at pressures of ~700-1000 MPa ( Fig. 1; Ehlig, 1958Ehlig, , 1968Ehlig, , 1981Crowell, 1968Crowell, , 1981Yeats, 1968;Haxel and Dillon, 1978;Jacobson, 1983aJacobson, , 1995Graham and Powell, 1984;Jacobson et al, 1988Jacobson et al, , 1996Jacobson et al, , 2002aDillon et al, 1990;Malin et al, 1995;Wood and Saleeby, 1997;Haxel et al, 2002). The schists are juxtaposed beneath an upper plate of Precambrian to Mesozoic igneous and metamorphic rocks, with essentially no evidence of intervening lithospheric mantle.…”

Section: Introductionmentioning

confidence: 99%

“…They underlie a series of low-angle faults known as the Vincent-Chocolate Mountains fault system. A few of these faults may be remnants of the thrust(s) beneath which the schists underwent prograde metamorphism (Ehlig, 1981;Jacobson, 1983bJacobson, , 1997, but most are retrograde or postmetamorphic features responsible for exhumation of the schists (Haxel et al, 1985(Haxel et al, , 2002Silver and Nourse, 1986;Jacobson et al, 1988Jacobson et al, , 1996Jacobson et al, , 2002aMalin et al, 1995;Wood and Saleeby, 1997;Yin, 2002).…”

Section: Introductionmentioning

confidence: 99%

“…These models were motivated by early structural studies that indicated top-to-northeast sense of shear along the Chocolate Mountains fault in southeastern California (Dillon, 1976;Haxel, 1977). While it is now generally accepted that this shear sense was imparted during exhumation of the schist (Simpson, 1990;Jacobson et al, 1996Jacobson et al, , 2002aOyarzabal et al, 1997;Haxel et al, 2002;Yin, 2002), two distinct models involving southwest-dipping thrusts were born out of the early work. One of these that held that the schists formed during collision between North America and an exotic microcontinent ( Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Overall, the backarc model has proven diffi cult to reconcile with the geology of southern California and western Arizona in that independent evidence for either the opening of the necessary rift basin or the suture that would have formed when it was closed is lacking (Burchfi el and Davis, 1981;Crowell, 1981;Hamilton, 1987Hamilton, , 1988. Very recently, Haxel et al (2002) dealt with the apparent absence of a suture by proposing that all remnants of the closed backarc basin and the suture itself were restricted to a tectonic window beneath counterposed thrust faults (Fig. 2D).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Temporal and spatial trends of Late Cretaceous-early Tertiary underplating Pelona and related schist beneath southern California and southwestern Arizona

Grove¹,

Jacobson²,

Barth³

et al. 2003

Tectonic Evolution of Northwestern Mexico and the Southwestern USA

Self Cite

159

View full text Add to dashboard Cite

The Pelona, Orocopia, and Rand Schists and the schists of Portal Ridge and Sierra de Salinas constitute a high-pressure/temperature terrane that was accreted beneath North American basement in Late Cretaceous-earliest Tertiary time. The schists crop out in a belt extending from the southern Coast Ranges through the Mojave Desert, central Transverse Ranges, southeastern California, and southwestern Arizona. Ion microprobe U-Pb results from 850 detrital zircons from 40 metagraywackes demonstrates a Late Cretaceous to earliest Tertiary depositional age for the sedimentary part of the schist's protolith. About 40% of the 206 Pb/ 238 U spot ages are Late Cretaceous. The youngest detrital zircon ages and post-metamorphic mica 40 Ar/ 39 Ar cooling ages bracket when the schist's graywacke protolith was eroded from its source region, deposited, underthrust, accreted, and metamorphosed. This interval averages 13 ± 10 m.y. but locally is too short (<~3 m.y.) to be resolved with our meth- ods. The timing of accretion decreases systematically (in palinspastically restored coordinates) from about 91 ± 1 Ma in the southwesternmost Sierra Nevada (San Emigdio Mountains) to 48 ± 5 Ma in southwest Arizona (Neversweat Ridge). Our results indicate two distinct source regions: (1) The Rand Schist and schists of Portal Ridge and Sierra de Salinas were derived from material eroded from Early to early Late Cretaceous basement (like the Sierra Nevada batholith); and (2) The OrocopiaSchist was derived from a heterogeneous assemblage of Proterozoic, Triassic, Jurassic, and latest Cretaceous to earliest Tertiary crystalline rocks (such as basement in the Mojave/Transverse Ranges/southwest Arizona/northern Sonora). The Pelona Schist is transitional between the two.

show abstract

Section: Correlation Of the Schistsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Temporal and spatial trends of Late Cretaceous-early Tertiary underplating Pelona and related schist beneath southern California and southwestern Arizona

Grove¹,

Jacobson²,

Barth³

et al. 2003

Tectonic Evolution of Northwestern Mexico and the Southwestern USA

Self Cite

159

View full text Add to dashboard Cite

show abstract

Transfer of Metasupracrustal Rocks to Midcrustal Depths in the North Cascades Continental Magmatic Arc, Skagit Gneiss Complex, Washington

et al. 2017

View full text Add to dashboard Cite

The metasupracrustal units within the north central Chelan block of the North Cascades Range, Washington, are investigated to determine mechanisms and timescales of supracrustal rock incorporation into the deep crust of continental magmatic arcs. Zircon U‐Pb and Hf‐isotope analyses were used to characterize the protoliths of metasedimentary and metaigneous rocks from the Skagit Gneiss Complex, metasupracrustal rocks from the Cascade River Schist, and metavolcanic rocks from the Napeequa Schist. Skagit Gneiss Complex metasedimentary rocks have (1) a wide range of zircon U‐Pb dates from Proterozoic to latest Cretaceous and (2) a more limited range of dates, from Late Triassic to latest Cretaceous, and a lack of Proterozoic dates. Two samples from the Cascade River Schist are characterized by Late Cretaceous protoliths. Amphibolites from the Napeequa Schist have Late Triassic protoliths. Similarities between the Skagit Gneiss metasediments and accretionary wedge and forearc sediments in northwestern Washington and Southern California indicate that the protolith for these units was likely deposited in a forearc basin and/or accretionary wedge in the Early to Late Cretaceous (circa 134–79 Ma). Sediment was likely underthrust into the active arc by circa 74–65 Ma, as soon as 7 Ma after deposition, and intruded by voluminous magmas. The incorporation of metasupracrustal units aligns with the timing of major arc magmatism in the North Cascades (circa 79–60 Ma) and may indicate a link between the burial of sediments and pluton emplacement.

show abstract

Protolith age of the Swakane Gneiss, North Cascades, Washington: Evidence of rapid underthrusting of sediments beneath an arc

2004

View full text Add to dashboard Cite

The metamorphic core of the North Cascades largely comprises island arc and oceanic terranes juxtaposed prior to circa 96 Ma magmatism. However, the tectonic affinity of the structurally deepest terrane, the 9–12 kbar Swakane Gneiss, is distinctly different from other terranes in the core; it is not intruded by arc‐related plutons and contains abundant Precambrian zircons. New U‐Pb analyses of detrital zircons from the Swakane Gneiss yield dates from 73 Ma to 1610 Ma with a dominant Late Cretaceous population. These data indicate that the Swakane protolith was deposited as late as 72.5 ± 0.6 Ma, the 206Pb/238U date of the youngest detrital grain. Following deposition, the gneiss was intruded by peraluminous leucogranite sheets that may represent partial melt derived from the gneiss at near‐ to postpeak P‐T conditions. One sheet yielded a U‐Pb crystallization age of 68.36 ± 0.07 Ma, which indicates that the gneiss was deeply buried within 5 Myr of deposition. Two possible mechanisms considered for this rapid burial (∼7 mm/yr) are overthrusting of a forearc or back arc basin by older crystalline rock or underthrusting of trench sediments during low‐angle subduction. The model involving overthrusting of a forearc or back arc basin is most consistent with thermobarometric and isotopic data and the regional geologic setting of the Cascades core. Rapid burial of the Swakane protolith is coincident with burial of sediments that formed the Pelona, Orocopia and Rand schists of southern California; however, differences in peak metamorphic temperatures indicate that conditions of burial must have varied along the plate margin.

show abstract

The Orocopia Schist in southwest Arizona: Early Tertiary oceanic rocks trapped or transported far inland

Cited by 20 publications

References 0 publications

Temporal and spatial trends of Late Cretaceous-early Tertiary underplating Pelona and related schist beneath southern California and southwestern Arizona

Temporal and spatial trends of Late Cretaceous-early Tertiary underplating Pelona and related schist beneath southern California and southwestern Arizona

Transfer of Metasupracrustal Rocks to Midcrustal Depths in the North Cascades Continental Magmatic Arc, Skagit Gneiss Complex, Washington

Protolith age of the Swakane Gneiss, North Cascades, Washington: Evidence of rapid underthrusting of sediments beneath an arc

Contact Info

Product

Resources

About