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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
Back-arc basins are part of a destructive plate margin. They are areas of back-arc spreading where generation of new crust takes place, in a similar way to that beneath mid-oceanic ridges. Based on three types of destructive environment (island-arc, ACM and continental plate collision zone), three types of back-arc basins are recognized: back-arc seas, mainly along the western periphery of the Pacific (the Sea of Okhotsk, the Japan Sea and Lau, etc.) and to a lesser degree in the Atlantic (the Caribbean and the Scotia Sea);back-arc sedimentary basins at active continental margins marked by active basalt volcanism as in western USA and South America (marginal rifts) andthe back-arc basins of collision zones in the Alpine–Himalayan Belt, where they form back-arc seas (Western Mediterranean, Aegean, Black and Caspian Seas) and sedimentary basins (the Pannonian Basin and the Po Valley). In the Pannonian Basin, the eruption of moderately alkaline basalts, containing spinel lherzolite xenoliths, took place during the Pliocene and Pleistocene.
Tectonics and Sedimentation
Published in Supriya Sengupta, Introduction to Sedimentology, 2017
Thick sedimentary piles are stacked rn the form of accretionary prisms in the forearcs. As the subduction zone migrates towards the sea the forearc sediments are successively thrust upwards (Fig. 7.8). Small sedimentary basins may develop over these accretionary prisms. Those lying between the volcanic arc and the trench slope break are generally very wide (50–100 km). These are the forearc or outer-arc basins. Behind the volcanic arc occur the back-arc basins.
The origin of mafic–ultramafic rocks and felsic plutons along the Clarke River suture zone: implications for porphyry exploration in the northern Tasmanides
Published in Australian Journal of Earth Sciences, 2023
A. Edgar, I. Sanislav, P. Dirks
The ca 456 Ma, I-type, Falls Creek Tonalite is a silica-rich, calc-alkaline, syntectonic pluton suite of continental-arc affinity (Dirks et al., 2021). This magmatic belt is situated southeast of, and parallel to, the Clarke River Fault (suture), and it probably formed in response to southeastwards facing subduction below the Charters Towers Province (Thomson Orogen; Figure 7; Edgar et al., 2022a, 2022b). Evidence for early Paleozoic, Thomson Orogen-facing subduction has been recorded by the Cambro-Ordovician Seventy Mile Range Group, which was interpreted as an east–west-trending, back-arc basin assemblage, deposited atop of continental crust (Henderson, 1986). Our interpretation of an approximately northeast–southwest-trending subduction complex, and associated magmatism, provides an alternative explanation for the east–west trend of the Seventy Mile Range Group back-arc basin and its distal position to the northern margin of the Charters Towers Province (Figure 7).
Cambrian ocean floor crust preserved in the Takaka Terrane, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2023
Carsten Münker, Frank Wombacher, Christopher Siebert
Based on the above considerations, we argue that the Mataki Volcanics sampled the asthenosperic mantle composition along the SE margin of Gondwana. In Figure 9, Nb/La ratios are plotted against La/Yb and Sm/Nd ratios in order to discriminate between contributions from subduction components (Nb/La < 1, high La/Yb and low Sm/Nd), contributions from depleted mantle (Nb/La > 1, low La/Yb and high Sm/Nd) and from enriched mantle (Nb/La > 1, high La/Yb and low Sm/Nd). It becomes evident that all three endmembers are required to explain the full compositional spectrum of the Mataki Volcanics. Hence, prior to addition of subduction components, the depleted mantle in the back-arc basin forming the Mataki Volcanics must have undergone addition of enriched components that were similar to the sources of present-day intraplate basalts.
Early Jurassic felsic and associated mafic meta-igneous rocks in Otago Schist, Central Otago, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2018
James K. Mortensen, J. Anthony Coote, David Craw, Douglas J. MacKenzie
We present middle Early Jurassic (191–190 Ma) U–Pb zircon crystallization ages for two samples of felsic metavolcanic rock from the North Rough Ridge area of Central Otago. We interpret these units to have been derived from a tuffaceous protolith; hence their age also provides the first direct depositional age for the metagreywackes of the Torlesse Terrane in this part of South Island. The felsic metavolcanic rocks yield phonolitic compositions with a within-plate tectonic affinity. Greenschists that are spatially closely associated with the felsic metavolcanics at North Rough Ridge are basaltic in composition and have a mid-ocean ridge or back-arc basin basalt petrotectonic affinity. Despite the close spatial association of the felsic metavolcanics and greenschists, it is still uncertain what the original relationship, if any, was between these rock units. We speculate that mafic to intermediate intrusive rocks from the Torlesse Terrane northwest of Christchurch (the Pember Diorite of Jongens et al. 2009), which has been dated at 185.6 Ma, may also be part of a previously unrecognised regionally developed Early Jurassic magmatic event in the Torlesse Terrane. Many other felsic metavolcanic rock units may be present within the Torlesse Terrane but have not been recognised or have been mapped as metacherts.