Journal ArticleDOI
Geochemical classification of terrigenous sands and shales from core or log data
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In this article, a means of relating geochemical concentrations to existing sandstone classification schemes is proposed based on three chemical parameters: the SiO2/Al2O3 ratio, the Fe 2O3/K2O ratio, and the Ca content.Abstract:
A means of relating geochemical concentrations to existing sandstone classification schemes is based on three chemical parameters: the SiO2/Al2O3 ratio, the Fe2O3/K2O ratio, and the Ca content. In terrigenous sands and shales, the SiO2/Al2O3 ratio separates Si-rich quartzarenites from Al-rich shales, with other sand types showing intermediate values. The ratio of total iron (as Fe2O3) to K2O separates lithic sands (litharenites and sublitharenites) from feldspathic sands (arkoses and subarkoses). In addition, very high Fe2O3/K2O ratios indicate Fe-rich shales (e.g., pyritic, sideritic, hematitic) or Fe-rich sands (e.g., gl uconitic) depending on the silica/alumina ratio. The Ca content is used to differentiate noncalcareous from calcareous sandstones and shales and to separate siliciclastic from carbonate rocks. Sandstones are classified the same by this scheme as by petrographic analysis about 84% of the time, and shales are effectively discriminated from sandstones. The requisite input data can be accurately supplied by geochemical well-logging measurements, enabling unbiased sandstone classification to be displayed on a continuous basis with depth.read more
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Journal ArticleDOI
Geochemistry of Upper Birimian sediments (major and trace elements and Nd–Sr isotopes) and implications for weathering and tectonic setting of the Late Paleoproterozoic crust
TL;DR: The Upper Birimian (Paleoproterozoic) formations consist mainly of a detrital sedimentary pile intercalated with calc-alkaline volcanites that were accreted during the Eburnean orogeny as discussed by the authors.
Journal ArticleDOI
Geochemistry of sandstones from the Upper Cretaceous Sillakkudi Formation, Cauvery Basin, southern India: Implication for provenance
TL;DR: In this article, the major, trace and rare earth elements (REE) composition of sandstones from the Upper Cretaceous Sillakkudi Formation, Ariyalur Group, Cauvery Basin were studied to decipher their weathering and provenance history.
Journal ArticleDOI
Middle to late Eocene exhumation of the Greater Himalayan Sequence in the Central Himalayas: Progressive accretion from the Indian plate
Rodolfo Carosi,Chiara Montomoli,Salvatore Iaccarino,Hans-Joachim Massonne,Daniela Rubatto,Daniela Rubatto,Antonio Langone,Lorenzo Gemignani,Dario Visonà +8 more
TL;DR: In this article, the authors investigated a contractional shear zone located in central Nepal, known as Kalopani shear Zone, and found that the high-temperature shear zones triggered the early exhumation of the metamorphic core in the Himalayan belt and deeply affected the tectono-metamorphic history of the crystalline rocks soon after the collisional stage.
Journal ArticleDOI
Iron and sulphur isotopes from the Carajas mining province (Para, Brazil) : implications for the oxidation of the ocean and the atmosphere across the Archaean-Proterozoic transition
Sébastien Fabre,Anne Nédélec,Franck Poitrasson,Harald Strauss,Christophe Thomazo,Christophe Thomazo,Afonso César Rodrigues Nogueira +6 more
TL;DR: In this article, major and trace element geochemistry combined with iron and sulfur isotopes were applied to banded iron formations (BIFs) and pyrite-bearing sandstones from the Carajas mineral province, Brazil.
Journal ArticleDOI
Geochemistry of sandstones from the Pliocene Gabir Formation, north Marsa Alam, Red Sea, Egypt: Implication for provenance, weathering and tectonic setting
TL;DR: The Gabir Formation is composed mainly of sandstones alternating with limestone and shale beds, and the Gabir sandstone is yellowish gray to yellowish brown color, calcareous and fossiliferous.
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