Geology of the older Precambrian rocks of the Grand Canyon

Clark, Malcolm D.

doi:10.1016/0301-9268(79)90032-9

Cited by 43 publications

(8 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4b). The massive amphibolites have a tholeiitic character and trace element compositions consistent with an island-arc environment (Clark, 1976).…”

Section: Granite Gorge Metamorphic Suitementioning

confidence: 85%

“…1) and cross section (Fig. 2) of the Upper Granite Gorge were compiled from detailed field mapping (Ilg, 1992;Ilg and Karlstrom, 1992, 1993, 1994, from photogeologic interpretation of high-resolution (1:4800 and 1:10 000) aerial photographs of the river corridor, and from previous work (Walcott, 1890(Walcott, , 1894(Walcott, , 1895Noble and Hunter, 1916;Campbell, 1936Campbell, , 1937Maxson, 1933-1938;Pasteels and Silver, 1965;Maxson, 1968;Ragan and Sheridan, 1970;Lingley, 1973;Walen, 1973;Livingston et al, 1974;Babcock et al, 1974Babcock et al, , 1979Clark, 1976Clark, , 1979Brown et al, 1979;Billingsley et al, 1980;Huntoon et al, 1980;Babcock, 1990). This section discusses new insights regarding lithostratigraphy and the nature of protoliths.…”

Section: Rock Unitsmentioning

confidence: 98%

“…The petrology and geochemistry of Brahma Schist amphibolites were studied by Clark (1976), who divided the amphibolites and mafic schists into five groups based on field occurrence and mineral assemblage:…”

Section: Granite Gorge Metamorphic Suitementioning

confidence: 99%

“…The Vishnu Schist consists of pelitic schist and quartz + biotite + muscovite schists interpreted as meta-lithic-arenites, metagraywackes, and calc-silicate lenses and pods. Meta-lithic-arenite and metagraywacke sequences show thick sections (kilometre-scale) of rhythmically banded (centimetre-to metre-scale) coarser and finer layers, with locally well-preserved bedding and graded bedding (Walcott, 1894;Clark, 1976;Fig. 4c).…”

Section: Granite Gorge Metamorphic Suitementioning

confidence: 99%

“…1). Clark (1976) named these rocks the "Zoroaster Plutonic Complex," modifying the term "Zoroaster Granite" (Maxson, 1968), which in turn was modified from the original "Zoroaster Gneiss" (Campbell and Maxson, 1933). However, in the Upper Granite Gorge, these granitoids have a range in age of at least 1840-1662 Ma , in composition from gabbro to granite, in morphology from large plutons to stocks to dikes and sills, and in tectonic significance from volcanic arc-related plutons to syncollisional plutons to postdeformational dikes and sills.…”

Section: Plutonic Rocksmentioning

confidence: 99%

See 4 more Smart Citations

Tectonic evolution of Paleoproterozoic rocks in the Grand Canyon: Insights into middle-crustal processes

Ilg

Karlstrom

Hawkins

et al. 1996

Geological Society of America Bulletin

View full text Add to dashboard Cite

Paleoproterozoic supracrustal rocks of the Upper Granite Gorge are divided into three mappable units: the Rama, Brahma, and Vishnu Schists, here collectively named the "Granite Gorge Metamorphic Suite." The Brahma Schist consists of mafic to intermediate-composition metavolcanic rocks that have yielded an age of 1750 Ma. The Rama Schist consists of felsic metavolcanic rocks that have yielded an age of 1742 Ma. On the basis of the presence of relict pillow structures, interlayering of metavolcanic units, and the large volumes of metavolcanic rocks, the combined volcanic package is interpreted to be metamorphosed, island-arc-related, submarine volcanic rocks. The metavolcanic units are locally overlain by the metamorphosed, arcbasin, submarine sedimentary rocks of the Vishnu Schist.The term "Zoroaster Plutonic Complex," previously used for all Paleoproterozoic and Mesoproterozoic plutonic rocks in the Grand Canyon, is abandoned in favor of use of names for individual plutons. Plutons are classified into two genetically and temporally separate intrusive suites: (1) 1740-1713 Ma plutons that are typically concordant to foliation, range in composition from gabbro to granodiorite, have calc-alkalic chemistry, and are interpreted to be arc-related plutons and (2) 1698-1662 Ma granite plutons, stocks, and pegmatite and aplite dikes that have textures and intrusive geometries indicating they were emplaced synchronously with peak metamorphism and northwestsoutheast shortening.The dominant tectonic fabric is a northeast-striking, subvertical, variably developed foliation (S 2 ) that is axial planar to plunging, open to isoclinal, upright, asymmetric folds (F 2 ) of an early, penetrative, apparently initially northwest-striking foliation (S 1 ). F 2 folds have wavelengths of kilometres and cause repetition of rock units across the transect. Partitioning of deformation in space and perhaps in time was strongly influenced by crustal heterogeneity. For example, plutons, pegmatite networks, and fold-hinge zones acted as buttresses, and S 2 high-strain domains and shear zones are localized at the margins of these features. Generally northeast-striking, S 2 -related shear zones segment the transect into blocks. Shear zones last moved late during shortening and postdate the metamorphic peak. One of these, the Crystal shear zone, may be a fundamental crustal province boundary.Paleoproterozoic rocks in the Grand Canyon record the accretion of 1750-1713 Ma island-arc rocks and their assembly to Laurentia via dynamic interaction of deformation, metamorphism, and magmatism over ≈20 m.y. Changes in styles of deformation from F 1 -related thrusting and penetrative S 1 fabric development to F 2 -related upright folding and variable S 2 fabric development coincided with changes in styles of magmatism. The 1740-1730 Ma arc-related mafic to intermediatecomposition plutons preserve strong S 1 foliation. The 1717-1713 Ma arc-related plutons preserve weak S 1 tectonic layering and locally strong S 2 strain. The 1698-1685 Ma granitic plutonism lo...

show abstract

“…4b). The massive amphibolites have a tholeiitic character and trace element compositions consistent with an island-arc environment (Clark, 1976).…”

Section: Granite Gorge Metamorphic Suitementioning

confidence: 85%