The Cr/Th ratio in Precambrian pelites from the Kaapvaal Craton as an index of craton evolution

Condie, Kent C.; Wronkiewicz, David J.

doi:10.1016/0012-821x(90)90046-z

Cited by 262 publications

(88 citation statements)

References 24 publications

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“…The enrichments of Al 2 O 3 and MgO are in favor of the occurrence of sapphirine, osumilite, sillimanite, garnet and cordierite in the pelitic and psammitic gneisses under the UHT metamorphic conditions. Such enrichments of MgO, Cr and Ni have been reported from the sedimentary rocks in other Archaean terrains (Condie, 1997) such as the Kaapvaal craton in southern Africa (Condie and Wronkiewicz, 1990) where enrichment in these components is suggested to reflect the existence of komatiite -high Mg basalt sources. This suggestion is consistent with the occurrence of komatiitic basalts and komatiites in the Napier Complex as described above.…”

Section: Protolith and Agesupporting

confidence: 71%

Protoliths of the Napier Complex in Enderby Land, East Antarctica; an overview and implication for crustal formation of Archaean continents

Ishizuka

2008

Journal of Mineralogical and Petrological Sciences

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Field and geochemical studies overviewed here reveal that the precursors of ultrahigh -temperature (UHT) metamorphic rocks of the Napier Complex in Enderby Land, East Antarctica, consist of mantle protolith (serpentinite and depleted peridotite), magmatic protolith (tonalite -trondhjemite -granodiorite (TTG) suite, basaltic to komatiitic rocks and anorthosite), and sedimentary protolith (MgO -, Ni -, Cr -and Co -rich sediments, impure quartzite, banded iron formation (BIF) and calc -silicate rock). This assemblage of protoliths, especially the komatiite -TTG association with minor anorthosite, is reminiscent of the Archaean greenstone -granite belts. The U -Pb SHRIMP or SIMS dating of zircons with oscillatory zoning and magmatic Th/U ratio from the TTG protoliths shows four age clusters such as ~ 3.8, 3.3, 3.0 and 2.6 Gyr ago, suggesting the multi -stages of protolith formation. The modern analogy for the genesis of TTG suite suggests that the tectonic setting of the protolith formation and emplacement can be considered in the framework of the present -day intra -oceanic island -arc and related subduction regime. Subsequently, the Napier Complex was stabilized during the UHT metamorphism at ~ 2.59 -2.55 or ~ 2.50 -2.45 Gyr ago.

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Section: Protolith and Agesupporting

confidence: 71%

Protoliths of the Napier Complex in Enderby Land, East Antarctica; an overview and implication for crustal formation of Archaean continents

Ishizuka

2008

Journal of Mineralogical and Petrological Sciences

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“…For example, La and Th are enriched in felsic rocks, whereas Sc, Cr, and Co are more concentrated in basic rocks relative to felsic rocks. These elements are relatively immobile during weathering [6,[16][17][18]. Hence, the ratios of La or Th to Co, Sc, or Cr are sensitive indicators of source rock compositions.…”

Section: Introductionmentioning

confidence: 99%

Geochemistry of sandstones and shales from the Ecca Group, Karoo Supergroup, in the Eastern Cape Province of South Africa: Implications for provenance, weathering and tectonic setting

2017

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Geochemical compositions of twenty-four sandstone and shale samples from the Ecca Group were analysed to decipher their provenance, paleoweathering conditions and tectonic setting. The shales have high Fe 2 O 3 , K 2 O, TiO 2 , Ce, Cu, Ga, La, Nb, Nd, Rb, Sc, Sr, Th and Y content more than the sandstones, whereas, sandstones are higher in SiO 2 , Hf and Zr than the shales. The positive correlations of Al 2 O 3 with other elements as well as the abundance of Ba, Ce, Th, Rb, Zn and Zr suggest that these elements are primarily controlled by the dominant clay minerals. Tectonic discrimination diagrams revealed that the sandstones and shales are mostly of quartzose sedimentary provenance, suggesting that they were derived from a cratonic interior or recycled orogen. The binary plots of TiO 2 versus Ni, TiO 2 against Zr and La/Th versus Hf as well as the ternary diagrams of V-Ni-Th*10 indicate that the shales and sandstones were derived from felsic igneous rocks. A-CN-K (Al 2 O 3 -CaO-K 2 O) ternary diagram and indices of weathering (CIA, CIW and PIS) suggest that the granitic source rocks underwent moderate to high degree of chemical weathering. The CIA values range between 24.41% and 83.76%, indicating low to high weathering conditions. The CIW values for the studied sandstones and shales range from 25.90 to 96.25%, suggesting moderate to high intensive chemical weathering. ICV values for the sandstones and shales vary from 0.71 to 3.6 (averaging 1.20) and 0.41 to 1.05 (averaging 0.82), respectively. The K 2 O/Na 2 O ratios for the studied samples vary from 0.71 to 8.29, which reveal moderate to high maturity. The plot of CIA against ICV shows that most of the shales are geochemically mature and were derived from both weak and intensively weathered source rocks. The tectonic setting discrimination diagrams support passive-active continental margin setting of the provenance.

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“…Therefore, the ratios of the elements serve as useful indicators of sediment source rocks (e.g. the works of Cullers et al [36], Wronkiewicz and Condie [37], Condie and Wronkiewicz [38] and Cullers [39]). The usefulness of REEs, Sc and Th in inferring sedimentary rocks provenance is highly favoured by the minimal effect of fractionation of heavy minerals and processes of diagenesis and metamorphism, as compared with trace elements such as Zr, Hf and Sn [2,37,40].…”

Section: Provenancementioning

confidence: 99%

Geochemistry of Fluvial Sediments from Geregu, Southwest Nigeria

Adiotomre

Ejeh

Adaikpoh

2017

Materials and Geoenvironment

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Geochemical analysis of fluvial sediments on the banks of River Ero using inductively coupled plasma mass spectrometry illustrates their maturity, provenance and tectonic setting. The analysed sediment samples show low SiO 2 /Al 2 O 3 ratios of 2.92-2.99 (units FL_A, FL_B and FL_E) and high SiO 2 /Al 2 O 3 ratios of 4. FL_D, FL_F and FL_G). Sediments were geochemically classified as shales (units FL_A, FL_B and FL_E) and greywackes (units FL_C, FL_D, FL_F and FL_G). Ključne besede: rečni sedimenti, Eu anomalija, SW Nigerija, izvor, tektonska uvrstitev

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The Cr/Th ratio in Precambrian pelites from the Kaapvaal Craton as an index of craton evolution

Cited by 262 publications

References 24 publications

Protoliths of the Napier Complex in Enderby Land, East Antarctica; an overview and implication for crustal formation of Archaean continents

Protoliths of the Napier Complex in Enderby Land, East Antarctica; an overview and implication for crustal formation of Archaean continents

Geochemistry of sandstones and shales from the Ecca Group, Karoo Supergroup, in the Eastern Cape Province of South Africa: Implications for provenance, weathering and tectonic setting

Geochemistry of Fluvial Sediments from Geregu, Southwest Nigeria

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