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Magmatism of Phanerozoic Fold Belts
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
V.V. Yarmolyuk, V.I. Kovalenko
This zone correlates with the rear (intracontinental) part of the marginal volcanic– plutonic belt (Yarmolyuk and Kovalenko, 1991). It includes masses of nepheline syenites, alkaline gabbroids (ijolite–urtites, juvites and foyaites), alkali granites and syenites (Yashina, 1982). Volcanics associated with basanites, phonolites, trachytes, trachyrhyolites, pantellerites and comendites, as well as teschenite, mariupolite and pantellerite sills, are also very common (Table 3.8). Apart from the alkaline series, assemblages also contain rocks of the K–Na moderately alkaline series. They are dominated by moderately alkaline olivine basalts and alkali-feldspar trachyrhyolites. The 87Sr/86Sr(0) in basic rocks of the zone varies from 0.7033 to 0.706 and is independent of the volcanics (Vorontsov, 1994).
Strain and energy parameters of burst-prone rocks: Study and analysis
Published in Charlie C. Li, Xing Li, Zong-Xian Zhang, Rock Dynamics – Experiments, Theories and Applications, 2018
N.N. Kuznetcov, I.V. Fedotova, A.K. Pak
As is seen (Figure 2), the stress-strain curves of apatite-nepheline ore, urtite and ijolite samples are close to each other. The graphs for apatite-carbonate-magnetite ore and carbonatite are more different. In the first case we observe an almost perfect elastic strain, which is proved by an insignificant size of a formed loop and low values of relative strains.
A review of the geological settings, ages and economic potentials of carbonatites in the Democratic Republic of Congo
Published in Applied Earth Science, 2021
Georges M. Kasay, Anthony T. Bolarinwa, Olawale K. Aromolaran, Charles Nzolang, Vikandy S. Mambo
Ijolites are located in the eastern part of the carbonatite. They contain feldspars and are classified into four categories. The first category is the nepheline–pyroxene rocks, which do not have feldspar (called ijolite sensu-stricto). The second is a heterogeneous rock with patches of ijolite sensu-stricto surrounded by feldspar-rich ijolite or nepheline syenite. The third is a rock with euhedral nepheline crystals in a fine-grained pyroxene matrix, nepheline and alkali-feldspar. The fourth is an ijolitic rock having different proportions of alkali-feldspar and nepheline (Woolley et al. 1995). - Fenites