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The Sources and Origin of Magmas
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
E.V. Sharkov, O.A. Bogatikov, V.I. Kovalenko
The isotopic data for the Crater Lake volcano area (see Chapter 2) require sources of primitive magmas to consist of depleted mantle and a subduction component, introduced in variable quantity to the depleted mantle wedge (Bacon et al, 1994). Variable degrees of melting of this heterogeneous mantle, possibly at different depths, produced the diversity of isotopic compositions and LILE abundances in primitive magmas. Trace element ratios do not indicate the presence of an ocean island basalt source component.
Petrogenesis of the Hoy lava field, a long-lived continental mafic volcanic province in eastern Australia
Published in Australian Journal of Earth Sciences, 2023
T. J. Crossingham, T. Ubide, P. M. Vasconcelos, K. M. Knesel
Interestingly, the depth at which magma stagnates in the crust has been linked to magma production rates (e.g. Gleeson et al., 2021; Smith & Németh, 2017). In ocean island basalt intraplate settings, where magma production has been shown to be high (e.g. Hawaii), magmas mostly experienced stagnation and modification at shallow depth (Smith & Németh, 2017, and references therein). In contrast, volcanic provinces with lower magma production rates, such as the Azores, experienced stagnation at depths at or below the Moho (e.g. Smith & Németh, 2017 and references therein), with volatile saturation at subcrustal depths potentially triggering eruption (Ubide et al., 2022). The depth of magma stagnation appears to be the main difference between Hoy and the larger, shorter-lived central volcanoes. Estimates of eruptive volumes are not available for Hoy, as estimating magma production rates for the scattered small volcanoes is challenging owing to variable degrees of erosion. On average, however, estimated volumes of individual lava fields are substantially lower (∼186 km3) than those of central volcanoes (678 km3; Duncan & McDougall, 1989, and references therein).
Mid-Devonian basaltic magmatism and associated sedimentation: the Ooloo Hill Formation, central-eastern South Australia
Published in Australian Journal of Earth Sciences, 2023
C. Wade, A. J. Reid, E. A. Jagodzinski, M. J. Sheard
Ooloo Hill Formation basalts and andesite sit above the mid-ocean ridge basalt (MORB)–ocean island basalt (OIB) array and below the metasomatised mantle array on the Th/Yb–Nb/Yb diagram (Figure 12a). Eruptive sequences #1, #2 and #4 form a trend parallel to the MORB–OIB array, consistent with within-plate evolution of mantle sources (e.g. Liu et al., 2021), whereas eruptive sequence #3 has an apparent, although tenuous, vertical trend toward the metasomatised mantle array (Elliott et al., 1997; Hawkesworth et al., 1997). Differing evolutionary trends are also highlighted on Figure 12b, suggesting eruptive sequences #1 and #2 had an asthenospheric mantle source, possibly derived from OIB, and potentially share a common source region to eruptive sequence #4 that underwent differentiation. The separate but parallel offset in eruptive sequence #3 suggests it was derived from a more enriched OIB-like intraplate parent (Figure 12b). The lithospheric component in this eruptive sequence may be linked to slab-melt contributions into the mantle source or lithospheric contamination of a plume-derived source (Xia & Li, 2019). The mantle source components for Ooloo Hill Formation were therefore likely to be a heterogeneous OIB-like intraplate parent magma derived from the asthenospheric mantle. Different magma sources for Ooloo Hill Formation are demonstrated by incompatible element ratios (Figure 12b, c) suggesting a dynamic magmatic plumbing system.
The Alpha-Mendeleev ridge, a large igneous province with continental affinities
Published in GFF, 2019
The samples on the Northwind Rise and north of it comprised three groups with 40Ar/39Ar ages of ca. 112 Ma, ca. 100 Ma and ca. 83 Ma. Two younger samples of rock are (low-Ti tholeiitic basalts – LT, and high-Ti alkaline basalts – HT). Such a distribution of low- and high-Ti rock varieties is typical for plume-related continental flood basalts (CFB). Trace element compositions for this group and the Alpha Ridge sample are also similar to CFB (Mukasa et al. 2009). All the studied volcanic rocks belong to the intraplate volcanic associations whose petrological, geochemical and isotopic parameters are consistent with their emplacement in a continental setting (Table 2). Taken together, geochemical and isotopic attributes of the studied volcanic rocks are similar to those of CFB provinces originating from deep-seated hot spot sources and often associated with continental break-up (Andronikov et al. 2008). Furthermore, the chemical affinity of the basalt dredged from the Alpha Ridge (Fig.1) (Williamson & Larsen 2007) is consistent with the alkaline compositions reported for igneous rocks of the onshore Sverdrup Basin. It is noteworthy that the data from the dredged rocks have compositions that exclude typical ocean-island basalt (OIB), normal mid-ocean-ridge basalts (N-MORB), or even Gakkel Ridge enriched mid-ocean-ridge basalts (E-MORB) (Mukasa et al. 2009).