Chemical composition and evolution of the upper continental crust: Contrasting results from surface samples and shales

Condie, Kent C.

doi:10.1016/0009-2541(93)90140-e

Cited by 2,073 publications

(1,137 citation statements)

References 61 publications

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“…Geochronological data suggest crustal formation rates have been nonuniform, perhaps quasiperiodic, throughout geologic time [Moorbath, 1977[Moorbath, , 1978Taylor and McLennan, 1981, 1985Anderson, 1994;Condie, 1993]. Large regions, such as the Superior Province in North America, have been assembled in rather short periods of time (circa 150 Ma [Hoffman, 1988] has been argued that geologic history is punctuated by episodes of enhanced exchange between the upper (d < 670 km) and lower (d > 670 km) mantle during which rapid continental growth takes place [Stein and Hofmann, 1994].…”

Section: Introductionmentioning

confidence: 99%

Simulations of crustal anatexis: Implications for the growth and differentiation of continental crust

Raia¹,

Spera²

1997

J. Geophys. Res.

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Abstract. Them is overwhelming and incontrovertible petrological and geophysical evidence for the significant role played by mantle-derived mafic magma in the generation and growth of continental crust. Likewise, intrusion of mafic magmas beneath or into continental crust is very likely the major source of enthalpy that drives intracrustal differentiation. A simple dynamical model has been constructed to examine the critical factors that govern the evolution and timescale of crustal anatexic events when driven by basaltic magma underplating or injection into crust. Critical factors include the intensity of the enthalpy input (i.e., the power dissipated) and the rheological propertie.s, bulk composition and compositional structure of the source rocks undergoing partial fusion. We have performed numerical simulations to evaluate these factors using phase equilibria and thermochemical and transport property data applicable to the binary eutectic system CaA12Si2Oa-CaMgSi20 6 as a rough analog to study anatexis of mafic lower crust. In distinction, forfscrit small, more enthalpy is stored in the solid and less melt is produced. However, the compositional spectrum of liquids generated within the anatexic region is significantly larger for smallfscrit. Because of the sensitive dependence of solidi and liquidi on bulk composition, melt productivity is related to bulk composition given a particular enthalpy power input and rheological model. There is a factor of 2 difference in volume of melt generated when the bulk composition of the source is 10 modal percent less refractory. Compositionally zoned melts form by melting of either homogeneous or layered sources, although compositionfrequency relations are sensitive to the initial (subsolidus) compositional structure. The effects of anatexic events are to fundamentally reorganize the pattern of compositional structure within the crust. Intracrustal differentiation is a long-term inevitable process associated with the underplating or injection of mafic magma into preexisting crust.

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Section: Introductionmentioning

confidence: 99%

Simulations of crustal anatexis: Implications for the growth and differentiation of continental crust

Raia¹,

Spera²

1997

J. Geophys. Res.

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“…Six samples, four from the Safa Formation and two from the Bir Maghara Formation, which yielded low CIA values (<61), are excluded as they are enriched in calcite. The high CIA values in the studied shales probably Phan Sh: Phanerozoic Shales (Condie, 1993), UCC: Upper Continental Crust (Taylor and McLennan, 1985), Pierre Shale (Schultz et al, 1980), NASC: North American Shale Composites (Gromet et al, 1984) and RMCS: Russian Mesozoic and Cenozoic Shales (Ronov and Migdisov, 1971 (Condie, 1993) and in the UCC (14 ppm) (Taylor and McLennan, 1985). Similar to Zr, samples 12 and 24 gave extremely high Sc concentrations -268 and 296 ppm respectively.…”

Section: Geochemistrymentioning

confidence: 97%

“…Their concentrations in sediments are used as a measure of detrital input. The average Al 2 O 3 concentration of the studied shales is 23 wt% (Table 4), whereas the average Al 2 O 3 concentrations in the Phanerozoic Shales and the Upper Continental Crust (UCC) are 17.8 and 15 wt%, respectively (Condie, 1993;Taylor and McLennan, 1985). Manju et al (2001) detected high Al 2 O 3 concentrations-up to 37.3 wt%-in the kaoliniterich Madayi deposits in India.…”

Section: Factors Controlling Chemical Compositionmentioning

confidence: 98%

“…Loss on ignition (LOI) was not determined. The data obtained from the studied shales are compared with the average chemical composition of the Phanerozoic Shale (Condie, 1993), Upper Continental Crust (UCC) (Taylor and McLennan, 1985), Normal Pierre Shale (Schultz et al, 1980), North American Shale Composite (NASC) (Gromet et al, 1984), and Russian Mesozoic and Cenozoic Shales (RMCS) (Ronov and Migdisov, 1971). To test the role of chemical weathering in the formation of the studied shales, the Chemical Index of Alteration (CIA) was calculated using the method of Nesbitt and Young (1982).…”

Section: Analytical Techniquesmentioning

confidence: 99%

“…For comparison, the chemical composition of the studied shales is plotted against the chemical composition of previously studied common shale composites (Schultz et al, 1980;Gromet et al, 1984;Condie, 1993) and the Upper Continental Crust (UCC) (Taylor and McLennan, 1985); see Table 3 and Fig. 5.…”

Section: Geochemistrymentioning

confidence: 99%

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Mineralogical and chemical characteristics of Bajocian-Bathonian shales, G. Al-Maghara, North Sinai, Egypt: Climatic and environmental significance.

2003

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Clay mineral assemblages in relation to the chemical characteristics of Bajocian-Bathonian shales at G. Al-Maghara, North Sinai, Egypt, have been determined to infer the climatic conditions and the factors regulating their distribution. Mineralogical analyses using XRD revealed the dominance of kaolinite relative to illite and smectite. Quartz, calcite, goethite, feldspars and plagioclase represent the non-clay minerals encountered. Chemical data reflect the enrichment of chemically immobile elements (Al, Ti, Zr and Sc) and the depletion of mobile elements (Fe, Ca, Na, K and Mg). Major element concentrations reflect the dominant mineralogical composition and the weathering history of the source area. Moreover, the enrichment of trace elements (Sc, Zr and partially Cr) could be attributed to the source rock chemistry and its weathering history. High values of the Chemical Index of Alteration (CIA) (Al 2 O 3 /(Al 2 O 3 + CaO + K 2 O + Na 2 O) × 100) were found. The high proportion of kaolinite associated with the enrichments of immobile particularly major elements (Al and Ti) and the high values of CIA suggest intensive chemical weathering of the source rock under tropical to subtropical humid climatic conditions. The abundance of kaolinite relative to smectite was also influenced by hydraulic sorting and relative sea level changes.

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Tectonics, topography, and river system transition in East Tibet: Insights from the sedimentary record in Taiwan

Lan

Yan

Huang

et al. 2014

Geochem. Geophys. Geosyst.

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The Cenozoic in East Asia is marked by major changes in tectonics, landscapes, and river systems, although the timing and nature of such changes remains disputed. We investigate the geochemistry and neodymium isotope character of Cenozoic mudstones spanning the breakup unconformity in the Western Foothills of Taiwan in order to constrain erosion and drainage development in southern China during the opening of the South China Sea. The La/Lu, Eu/Eu*, Th/Sc, Th/La, Cr/Th, and eNd values in these rocks show an abrupt change between 31 and 25 Ma. Generally the higher eNd values in sediments deposited prior to 31 Ma indicate erosion from Phanerozoic granitic sources exposed in coastal South China, whereas the lower eNd values suggest that the main sources had evolved to inland southern China by 25 Ma. The SHRIMP U-Pb ages of zircons from a tuff, together with biostratigraphy data constrain the breakup unconformity to be between 39 and 33 Ma, suggesting that the seafloor spreading in the South China Sea commenced before 33 Ma. This is significantly older than most of the oceanic crust preserved in the deeper part of the basin. Diachronous westward younging of the breakup unconformities and provenance changes of basins are consistent with seafloor spreading propagating from east to west. Initial spreading of the South China Sea prior to 33 Ma corresponds to tectonic adjustment in East Asia, including extrusion of the Indochina block and the rotation and eastward retreat of the subducting Pacific Plate.

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Chemical composition and evolution of the upper continental crust: Contrasting results from surface samples and shales

Cited by 2,073 publications

References 61 publications

Simulations of crustal anatexis: Implications for the growth and differentiation of continental crust

Simulations of crustal anatexis: Implications for the growth and differentiation of continental crust

Mineralogical and chemical characteristics of Bajocian-Bathonian shales, G. Al-Maghara, North Sinai, Egypt: Climatic and environmental significance.

Tectonics, topography, and river system transition in East Tibet: Insights from the sedimentary record in Taiwan

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