From: Geology and Landscape Evolution (Second Edition), 2018, David London, in Reference Module in Earth Systems and Environmental Sciences, 2020. In the central and eastern North Sea, basalt, trachyandesite, and rhyolite flows and tuffs occur interbedded with Rotliegend-facies mudstones and sandstones. Five eruptive stages have been recognized, and the total volume has been estimated at ∼48 000 km3, approximately 70% of which are rhyolitic lavas and ignimbrites that predominate in the eastern part of the basin. The lesson learned is that the three dynamic regimes of magma, characterized by large chambers, sills, and lava flows, each shows different aspects of the same spectrum of physical and chemical processes common to magma. 3 Nature of Magma • Composed of three portions – liquid, solid and gas • Liquid portion = melt ... • Partial melting and magma formation • Incomplete melting of rocks is known as partial melting • Formation of basaltic magmas – Most originate from partial melting of mantle The lower SF, including any cumulates, was locally disrupted time and again by these injections. Smaller volumes of mafic and felsic volcanic rock have been drilled in the central and eastern North Sea, and the Midland Valley of Scotland is known for its large number of alkaline mafic sills, vents, and subvolcanic intrusions that often contain megacrysts and xenoliths of mantle material and high-grade metamorphic crust. The texture in which elongate crystals of feldspar, micas, beryl, tourmaline, and a few others (e.g., columbite) are oriented perpendicular to the substrate surface goes by several names in petrology, including stockscheider and comb layering, but the most widely used term today is unidirectional solidification texture, or UST. Syenite is an igneous rock that solidified slowly in the crust in a similar manner to granite.A true syenite (sensu stricto) is also compositionally resembling granite.The most notable difference is the absence or very low quantity of quartz while it is an essential component of granite. (1989). The Lupar Formation, including the Pakong Mafic Complex, may also be accepted as accretionary prism material (Figure 66). The Schwaner Mountains are dominated by Lower to Upper Cretaceous I-type plutonic and volcanic rocks (Williams et al., 1988; Bladon et al., 1989; Haile et al., 1977). Depictions of the final rock records from three idealized magma chambers. (B) The thin border (~ 4 mm) transitions sharply into coarse-grained UST with skeletal gray quartz and creamy K-feldspar. For medium-grained gabbroic rocks the term microgabbro may be used: dolerite and diabase, however, are synonyms of long-standing usage which the Subcommission recognized as so entrenched as to require retention. Nov 6, 2016 - Explore Susanne Janecke's board "Geology: Plutonic Rocks", followed by 136 people on Pinterest. According to the trace element compositions and rare earth element patterns of the volcanic rocks, these rocks belong to the typical calc-alkaline volcanic rocks related to the subduction (Kim et al., 1991b; Park et al., 2006b; Yun et al., 2000). Those that fit into the former category are known as intrusive (or plutonic) rocks, while those that fit into the latter are known as extrusive (or volcanic) rock. The two most incompatible elements for which there are extensive bulk-rock data are Zr and Y. Coupling the distribution of the fast lower crust with known occurrences of Paleoarchaean rocks and minerals, we postulate that a >80,000 km2 craton existed by at least 3.4–3.2 Ga, stretching from the Oregon Trail structural belt in south-central Wyoming, north to the Paleoproterozoic Great Falls tectonic zone, and east to the Dakotan orogen, immediately east of the Bighorn Mountains. The Wyoming Craton is characterized by widespread Meso- to Neoarchaean plutonic and metasedimentary rocks that have Nd isotopic compositions that require the incorporation of Paleoarchaean to Hadean crust. That isotropy arises from the randomness of their mineral distributions and from the absence of preferred orientation of those minerals. The prefix leuco- implies that the rock is lighter colored than is normal, and mela- that it is darker than normal. 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