Geology of the older Precambrian rocks of the Grand Canyon Part I. Petrology and structure of the Vishnu Complex

Brown, E. H.; Babcock, R. S.; Clark, Malcolm D.; Livingston, Donald E.

doi:10.1016/0301-9268(79)90030-5

Cited by 50 publications

(15 citation statements)

References 15 publications

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“…This section reviews the structural geology of the Upper Gorge transect ( Fig. 1) and builds upon the structural studies done by Lingley (1973), Walen (1973), and Brown et al (1979). These workers documented several fold generations based on mesoscopic overprinting relationships, including an early compositional tectonic layering (S 1 ), a second-generation vertical cleavage (S 2 ), and late-stage kinks and crenulations (S 3 ).…”

Section: Structural Geology and Deformational Historymentioning

confidence: 82%

“…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%

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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

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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...

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Section: Structural Geology and Deformational Historymentioning

confidence: 82%

Section: Rock Unitsmentioning

confidence: 98%

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

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“…The relative enhancement in lime and silica concentrations of the amphibolites is portrayed on SiO 2 vs CaO discriminate plot ( Figure 6). Samples from both areas plot within the field of basalts of the Vishu complex (Brown et al, 1979). The tholeiitic chemical character of the amphibolites was revealed on the Na 2 O + K 2 O vs SiO 2 discriminant plot (Figure 7).…”

Section: Resultsmentioning

confidence: 99%

“…Plot of SiO 2 vs CaO for Wonu-Apomu and Ilesa amphibolites(Brown et al, 1979) Figure 7. Plot of Na 2 O+K 2 O vs SiO 2 for Wonu-Apomu and Ilesa amphibolites (Irvine and Baragar, 1971) Fe 2 O 3 -Na 2 O+K 2 O-MgO ternary plot for Wonu-Apomu and Ilesa amphibolites The Fe 2 O 3(t) contents are high for both amphibolites of Wonu-Apomu (13.31%) and Ilesa (12.44%) areas.…”

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confidence: 99%

Nature and Origin of the Amphibolites in the Precambrian Basement Complex of Iseyin and Ilesha Schist Belts, Southwestern Nigeria

Bolarinwa¹,

Adeleye²

2015

JGG

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Petrographic and geochemical studies of amphibolites from Wonu-Apomu area in Iseyin-Oyan schist belt and Ife-Ilesa area in Ilesha schist belt, southwestern Nigeria, were carried out with a view to unravel their nature and petrogenesis. The amphibolites in Wonu-Apomu are associated with quartzite, quartz schist, talc-schist, granite and pegmatites, while those of Ife-Ilesha area are associated with anthophyllite schist, talc tremolite and talc chlorite schists.Chemical data of the amphibolites showed high Al 2 O 3 (>14%), Fe 2 O 3 (>12.40%), CaO (>8.10), Na 2 O (>3.10%) and K 2 O (>5.0%) contents. Trace element data showed that the amphibolites are enriched in Ba (>137ppm), Sr (>122ppm), Rb (>33ppm), Zr (55pm) and Y (>37ppm), but impoverished in Cr (<62ppm), Ni (<57ppm) and Zn (<83ppm). Petrogenetic indices and discriminant plots of Na 2 O + K 2 O vs SiO 2 , Ga vs Y, Zr/Y vs Zr, Cr vs Ni, Fe 2 O 3 -Na 2 O + K 2 O -MgO, indicated tholeiitic basalt affinity of the amphibolites and emplacements of the precursor basaltic rocks within continental crust.Most of these investigations on the amphibolites occurrences within the Precambrian basement complex of southwestern Nigeria tend to emphasize their field relations, petrological descriptions, mineralogical attributes and chemical compositions. Various efforts to unravel the petrogenetic affinity have been dogged with controversy. Therefore, this present investigation largely seeks to generate chemical data to unravel the nature and origin of the amphibolites around Wonu-Apomu in the Iseyin-Oyan schist belt and those of Ilesa in the Ife-Ilesa schist belt, southwestern Nigeria.

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“…When the chemical data of the phyllite are plotted on an SiO2 vs. CaO variation diagram (Fig. 4), the phyllite plots in the field of Franciscan greywackes of BRowN et al (1979). In Fig.…”

Section: Phyllitementioning

confidence: 99%

Geochemistry of metasedimentary rocks of Uwet area, Oban Massif, southeastern Nigeria

Ekwueme

Onyeagocha

1986

Geol Rundsch

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Geology of the older Precambrian rocks of the Grand Canyon Part I. Petrology and structure of the Vishnu Complex

Cited by 50 publications

References 15 publications

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

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

Nature and Origin of the Amphibolites in the Precambrian Basement Complex of Iseyin and Ilesha Schist Belts, Southwestern Nigeria

Geochemistry of metasedimentary rocks of Uwet area, Oban Massif, southeastern Nigeria

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