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General Features of Magmatic Evolution Throughout the Earth’s History
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
Paired metamorphic belts are characteristic of many fold regions combining units regionally metamorphosed under low- and high-pressure conditions. The studies of Miyashiro et al. (1982) have demonstrated that, in Alpine regions, low-pressure, high-temperature belts, followed by abundant granitoid magmatism, are confined to the back-arc zones of island arcs, for example Japan, whereas high-pressure low-temperature metamorphism (the glaucophane-schist facies) occur in the fore-arc zones of these structures. These blue-schists are thought to have been generated by subduction, and they indicate the presence of a Benioff zone. Therefore the presence of similar units in Phanerozoic and Late Precambrian fold belts (the Palaeozoic Kiyama, Omi and Sangun belts of Japan, the Palaeozoic Kyrento Series in Chile and NW Kamchatka, and, in the Mesozoic-Cenozoic, the Alps and California, and the Sanbagava belt of Japan, as well as those of New Caledonia and Central Kamchatka) provides further evidence that these structures were once island arcs.
Where is the boundary between New Zealand’s western and eastern provinces? A case study in describing terrane relationships using cladistic methods.
Published in New Zealand Journal of Geology and Geophysics, 2020
Bernard Michaux, Elizabeth M. Dowding, Malte C. Ebach
The nature of the boundary between the Western and Eastern Provinces has undergone a series of revisions since Landis and Coombs (1967) first introduced the concept of a Median Tectonic Line (MTL) separating the two. Landis and Coombs (1967) interpreted the MTL as a steeply dipping fault system separating a high temperature/low pressure metamorphic belt in the west (i.e. the modern Western Province) from a high pressure/low temperature belt in the east (i.e. the modern Eastern Province). Subsequent work showed the concept of a paired metamorphic belt to be oversimplified and that the MTL represented a tectonic boundary between terranes (Bishop et al. 1985). The term Median Tectonic Zone (MTZ) was introduced by Frost and Coombs (1989) when the MTL was reinterpreted as a complex magmatic belt rather than a narrow fault zone (Bradshaw 1993). The MTZ is composed of a suite of Palaeozoic to Mesozoic plutons and arc-related sedimentary terranes that are thought to represent a dismembered Carboniferous volcanic arc/pluton complex (Kimbrough et al. 1993). Fragments of the arc are found in Nelson (Rotoroa Complex, Drumduan Terrane, Teetotal Group (Figure 1)), Fiordland (Darran Complex, Loch Burn Formation, Largs Terrane) and Stewart Island (Paterson Group) (Scott 2013; Table 1). While the contact between the Jurassic metasedimentary units and Carboniferous basement is unseen in Nelson, the evidence for such a relationship is clearer in Fiordland and Stewart Island (Allibone and Tulloch 2004; Ewing et al. 2007; Scott et al. 2008). Drumduan Terrane fragments can be correlated across the Alpine Fault because each conforms to a generalised structure of arc-related sediments overlying Carboniferous granites and juxtaposed with Mesozoic plutons.