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Magmatism in the Context of the Present-Day Tectonic Settings
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
O.A. Bogatikov, V.I. Kovalenko, E.V. Sharkov, V.V. Yarmolyuk
According to Zeil and Pichler (1967) the petrography, along with unusually high copper (1,880 ppm on average) and aluminium (up to 8.7 normative corundum) content suggests that these rocks were generated by crystal anatexis. The strontium isotopic data agree with the above statement. The assemblage is characterized by a high initial 87Sr/86Sr ratio (0.7052–0.7091 for northern Chile; 0.7125 for Bolivia). In addition, they are much higher than those in rocks of the andesite assemblage. The ignimbrites are enriched in LREE and have a distinct europium anomaly.
Evolution of Ore Fluids and Hydrocarbons in the Benue Trough Lead-Zinc Deposits, Nigeria
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
Rare earth elements (REE) analyses of fluorite in the middle Benue ores indicate a total REE values of 586–790 ppm. A significant enrichment of light REE and positive europium anomaly were noted in the chondrite normalized plots. The REE data are consistent with a source of the ore components especially calcium from feldspar rich arkosic sediments in the trough.
Zebra rock and other Ediacaran paleosols from Western Australia
Published in Australian Journal of Earth Sciences, 2021
Rare earth elements show modest enrichment toward the surface with only slight rare earth enrichment in a Wajing profile (Figure 9), as in many other Precambrian arid land paleosols (Retallack, 2018; Retallack & Mao, 2019). Comparable enrichment slightly favouring light rare earth elements is also seen in modern aridland loessial soils (Compton et al., 2003; Ramakrishnan & Tiwari, 1999), unlike depletion seen in humid granitic soils (de Sá Paye et al., 2016; Kurtz et al., 2001). There is a slight negative europium anomaly, as in sediments from granitic (Foden et al., 1984), rather than basaltic rocks (Bavinton & Taylor, 1980). There is no marked enrichment in europium as in hydrothermally altered rocks (Bolhar et al., 2005; Sugahara et al., 2010). Nor are rare earth elements unchanged within the bed as in marine deposition and halmyrolytic alteration of marine beds (Clauer et al., 1990; Setti et al., 2004).
Mineralogical and geochemical characterisation of kaolin deposit from Debre Tabor area northwestern, Ethiopia
Published in Applied Earth Science, 2021
Alemu Mesele, Teklay Gidey, Tilahun Weldemaryam, Wuletaw Mulualem, Tamrat Mekuria, Yahya Ali, Gizachew Mulugeta, Betelhem Tesfaye, Mulgeta Brihan
The parent rocks contain higher concentrations of Rb but are depleted in Sr as compared to kaolin samples (Table 5 and Figure 8(b)). The occurrence of these high-value elements indicates that the deposit has still preserved feldspar minerals or the degree of weathering is minimal (Misra 2012). In the weathering process, the REE cations and minerals are released by hydrolysis from the parent rocks. Through the process of migration in water, the REE becomes concentrated in the clay minerals and afterward released from the unstable REE rich minerals. The LREEs (La, Ce, Pr, and Nd) are more insoluble to hydrolysis than HREEs (Yunhua and Lipu 1987; Oyebamiji et al. 2017). The chondrite normalised trace element patterns show steep slope LREEs than HREEs. The HREEs also show a gentle slope and all the parent and kaolin samples have nearly parallel patterns (Figure 8(a)). The patterns also represent a slightly negative europium anomaly. This negative anomaly of Eu can be associated with an atmospheric or hydrothermal origin and the weathering effect of acidic source rocks for the kaolin deposit (Rollison 1993; Oyebamiji et al. 2017).
Crustal and thermal structure of the Thomson Orogen: constraints from the geochemistry, zircon U–Pb age, and Hf and O isotopes of subsurface granitic rocks
Published in Australian Journal of Earth Sciences, 2018
C. Siégel, S. E. Bryan, C. M. Allen, D. J. Purdy, A. J. Cross, I. T. Uysal, D. A. Gust
Two granitic rocks were sampled (BAL-01 and VAL-01) from cores drilled at the eastern edge of the Thomson Orogen, ∼100 km west of the Nebine Ridge, a basement high separating the Surat and Eromanga basins (Figure 3). BAL-01 from AOP Balfour 1 drill core was collected at a depth of ∼1.7 km depth, 20 m beneath the top of the intrusion. The granitoid is unconformably overlain by the lowermost Permian (300 Ma) Joe Joe Group of the Galilee Basin, indicating a minimum late Carboniferous age for the granite. BAL-01 is a red, fine-grained, porphyritic, hornblende–biotite tonalite with enclaves and calcite veins (Table 3; Figure 4). The rock has been significantly altered as shown by elevated LOI (3.7 wt%, see Table 6) and secondary mineralogy (plagioclase and hornblende partially replaced by calcite and chlorite, respectively). Accessory minerals recognised in thin-section and using SEM are fluorapatite, titanite, zircon, secondary rutile (a by-product from titanite) and pyrite. BAL-01 is a magnesian and alkali-calcic granitoid, and plots in the peraluminous field of Maniar and Piccoli (1989), but the strong degree of alteration may have reduced its Na2O and K2O contents, thereby increasing the Alumina Saturation Index (ASI). When normalised to the upper continental crust (UCC) using the values of Taylor and McLennan (1985), BAL-01 exhibits a flat REE pattern and a small negative europium anomaly (Figure 5). BAL-01 has a heat production of 1.3 µW m–3, a value that is lower than the UCC (1.65 µW m–3).