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Mainland Europe, Turkey and Cyprus
Published in Ian Sims, Alan Poole, Alkali-Aggregate Reaction in Concrete: A World Review, 2017
Isabel Fernandes, Özge Andiç-Çakir, Colin Giebson, Katrin Seyfarth
Almost the entire ‘Sheeted Dyke Complex’ of the Troodos Ophiolite (Upper Cretaceous) is basaltic to doleritic in composition. The dolerite (diabase) occurs in the form of dykes that are parallel and contiguous, with thicknesses varying from 0.30 m to more than 3 m. After emplacement, the dykes have undergone hydrothermal alteration resulting in local modification of the original composition of the dolerite. The varieties that have been recognized are quartz-dolerite, epidote-dolerite (diabase), amphibole-dolerite and albite-dolerite. Therefore, the quality of the dolerite used for the production of concrete aggregate depends on the degree of alteration that the sheeted dykes have undergone.
Structure of an accreted intra-oceanic arc: potential-field model of a crustal cross-section through the Macquarie Arc, Lachlan Orogen, southeastern Australia
Published in Australian Journal of Earth Sciences, 2022
Studies of the magnetic susceptibility of MORB have largely been based on dredge and core samples of present-day oceanic crust. Fox and Opdyke (1973) reported seafloor basalts from the North Atlantic, ranging from fresh to altered and metamorphosed, to have a mean magnetic susceptibility of 586 × 10−5 SI, and a geometric mean Königsberger ratio of 3.40. Johnson and Atwater (1977) found MORB away from the spreading ridge, with crustal ages exceeding 1 Ma, to have a magnetic susceptibility of about 3700 × 10−5 SI, and a mean Königsberger ratio of about 3. Smith (1985) found that the sheeted-dyke complex that makes up the lower part of seismic zone 2 and the upper part of seismic zone 3 in oceanic crust (Detrick et al., 1994) has magnetic susceptibility of about 600 × 10−5 SI and a Königsberger ratio >2. At depths exceeding 10 km the elevated temperatures (likely to exceed 200°C, assuming a low geothermal gradient of 20°C/km) are likely to have resulted in the acquisition of a viscous remanent magnetisation from relaxation of much of the remanence towards the ambient field (Pozzi & Dubuisson, 1992). This will have had the effect of aligning the remanence and induction vectors, so that the effective susceptibility needed to model MORB bodies should exceed the actual susceptibility by at least a factor of 2, suggesting an effective magnetic susceptibility when modelling by induction alone of about 2000 × 10−5 SI.
Use of Ultrafine Mafic Rocks for the Enhancement of Carbonation Reaction in Lime Renders
Published in International Journal of Architectural Heritage, 2020
Loucas Kyriakou, Ioannis Rigopoulos, Ioannis Ioannou
The dolerite (DOL) sample was a waste material (quarry fines) collected from a quarry located in Sia village, Nicosia District. Field observations indicated that this specific dolerite exposure is slightly to moderately weathered. It should be underlined that the dolerite exposures, which constitute the sheeted dyke complex of the Troodos ophiolite, cover an area of about 1/3 of the total area of the ophiolite. The sample used in the present study is an aliquot of exactly the same quarry waste sample that was characterized in detail by Rigopoulos et al. (2016a). Powder XRD analysis of this specific sample indicated that its mineralogical composition includes augite, anorthite, chlorite, actinolite, epidote, albite, quartz, calcite and magnetite (for further details see Rigopoulos et al. 2016a). Augite and anorthite, in particular, are rich in Ca, Mg and Fe cations, which are needed for the mineralization of CO2 (Oelkers, Gislason, and Matter 2008).
Seve terranes of the Kebnekaise Mts., Swedish Caledonides, and their amalgamation, accretion and affinity
Published in GFF, 2018
Per-Gunnar Andréasson, Ann Allen, Oskar Aurell, Daniel Boman, Jonas Ekestubbe, Ute Goerke, Anders Lundgren, Patrik Nilsson, Stefan Sandelin
From a thickness of c. 1000 m in the east, the Kebnekaise terrane wedges out rapidly westwards to a few tens of metres along the Tjäktavagge valley; in the Rombak–Sjangeli Window, the overlying Virisen terrane rests directly on the window basement. The Kebne Dyke Complex (Andréasson & Gee 1989a, 1989b) is dominated by amphibolites and subordinate granitoid dykes or sheets. In a few places, the amphibolites preserve a network of several generations of massive mafic dykes. Repeated injection of magma within single dykes occurred, but a sheeted dyke complex sensu stricto has not been observed so far. The reader is referred to Kirsch & Svenningsen (2016) for a detailed description of intrusive relations within a single outcrop in the Tarfala valley. Towards the contact with the underlying Mårma terrane, the amphibolite carries garnet and large sparkling porphyroblasts of hornblende aligned with the transport lineation. In contrast, the amphibolite along the roof thrust is fine-grained and fissile (Fig. 12A). The thickness of pervasively foliated amphibolites normally reaches 300–400 metres below eroded peak plateaus. Internal large-scale folding locally raised the pervasive foliation to steep angles. Local preservation of less deformed dolerite and gabbro may be related to the hinge zones of such folds. Primary intrusive relationships between dykes can often be inferred also when the rocks are deformed and amphibolitized (Fig. 9A–C). Evidence of contact metamorphism of rare calcareous rocks is preserved as thin bands of skarn composed of plagioclase, diopside, scapolite, phlogopite and poikiloblasts of amphibole. A small (c. 30 × 50 m) body of ultramafic rocks and gabbro cut by narrow mafic dykes occurs at Tjäktjatjåkka (N68.009936°/E18.323375°). A single thin section obtained from this body displays enstatite replaced by tremolite, phlogopite and seams of serpentine.