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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
If the above-mentioned variations in composition reflect general trends in the development of rift magmatism in time and space, the pattern of evolution of the separate magma chambers is displayed in the structure of differentiated igneous series related mainly to central-type volcanoes. The general sequence of compositional variations in these volcanoes is a replacement of basic by younger acid rocks. Different rift zones can provide examples of such series; their evolutionary trend actually is not affected by the composition of the initial melt. In Afar, in the Erta Ale Ridge and in the Boina volcanic centre, we can see the following sequence: moderately alkaline basalt (hawaiite) — moderately alkaline ferrobasalt–mugearite–trachyte–comendite–pantellerite with the abundance of rocks decreasing in the same direction (Barberi et al., 1975).
Petrogenetic links between the Dunedin Volcano and peripheral volcanics of the Karitane Suite
Published in New Zealand Journal of Geology and Geophysics, 2018
Oliver E. McLeod, James D. L. White
Hawaiite: Hawaiites from Seaward Hill are fine-grained, porphyritic rocks with very large phenocrysts and glomerocrysts of plagioclase (up to 6 mm) and smaller phenocrysts of titanian augite, diopside and olivine (up to 3 mm). The groundmass texture is felted and contains microlites of plagioclase, augite and ilmenite, and trace amounts of nepheline and sanidine (detected by XRD). Some olivine phenocrysts are moderately embayed and surrounded by radial microlitic haloes of augite. Plagioclase phenocrysts have well-developed sieve textures with opaque and glassy inclusions. Titanian augite phenocrysts have green diopside zoned cores, which are moderately resorbed and associated with fine magnetite at the zone boundary, and coarse magnetite at the crystal rim (Figure 5).