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Natural aggregate sources and production
Published in Mark Alexander, Sidney Mindess, Aggregates in Concrete, 2005
Mark Alexander, Sidney Mindess
a In terms of their origin. In this system, rocks are classified into the three broad groups already discussed: igneous, sedimentary, or metamorphic. b In terms of physical characteristics such as particle size or bulk density. Coarse aggregate is used to describe particles larger than 4.75 mm (usually), while fine aggregates are particles equal to or smaller than 4.75 mm. Regarding density, most natural aggregates have granular bulk densities (density of a confined mass of particles) in the region of 1500-1700 kg/m3, referred to as normal weight aggregates, while those with bulk densities less than about 1120 kg/m3 and greater than about 2000 kg/m3 are termed lightweight and heavyweight aggregates respectively (alternative terms are low density and high density respectively). c Petrologically, that is, in terms of the types and relative proportions of the minerals present. For example, a dolerite will be composed of mainly plagioclase and pyroxene, with smaller amounts of olivine or quartz and minor amounts of other minerals. Table 2.2 gives a list of the most common minerals found in aggregates. This classification scheme is not directly useful for concrete aggregates, but can serve as a starting point. Minerals alone cannot be used as a basis for predicting aggregate performance in concrete, and in any event aggregate particles are normally composed of several minerals. The techniques of petrological and mineralogical characterization of aggregates are, however, very useful in arriving at an informed assessment of likely performance of an aggregate in concrete, and these are discussed in Chapter 3.
Formation and physical properties of soils
Published in Fethi Azizi, Applied Analyses in Geotechnics, 1999
- igneous rocks such as granite, dolerite and basalt are formed as a result of magma cooling either on or below the surface of the Earth. Rocks which have resulted from the cooling of magma on the ground surface are called extrusive, the basalt blocks of the Giant's Causeway in Northern Ireland being a well known example. On the other hand, rocks made from the slow cooling of magma within the Earth crust, in other words below the ground surface, are known as intrusive, dolerite and granite being typical examples of this type of rocks.
Igneous Rocks
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
The chemistry of this intrusive rock corresponds to gabbro but its texture is finer. Dolerite forms dykes, sills, and other intrusions. The rock is dark grey in colour, except where its content of feldspar is greater than average. Dolerite is important as a road-stone for surfacing because of its toughness, and its capacity for holding a coating of bitumen and giving a good ‘bind’. In its unweathered state dolerite is one of the strongest of the building stones and used for vaults and strong-rooms, as in the Bank of England.
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
The Vássačorru igneous complex (Mårma magmatic complex of Paulsson & Andréasson 2002; Mårma complex of Paulsson 1996 and Sandelin 1997) is a network of gabbroic and doleritic mafic rocks and granite (Fig. 4A, B). In addition to the main occurrence in the Kebnekaise massif, smaller bodies of the VIC occur scattered from Singis in the south (Manak gabbro; Page 1993, and Aurek gabbro; Tilke 1986) to Lake Torneträsk (Kålkuktjåkkå; N68.236058°/E19.231625°) in the north. Mafic rocks are cut by granitic dykes, some quartz-monzonitic; these are in turn cut by dolerite dykes. Narrow, very fine-grained mafic dykes with pilotaxitic plagioclase occur. Aphanitic dykes lacking chilling against country rock are interpreted as quenched liquids. Mingling and mixing between felsic and mafic magmas took place (Fig. 4). Fig. 4D shows a hybrid rock with xenoliths of metasedimentary rocks and with mafic fragments in different stages of hybridization. Fragments of all generations are rich in garnet and some are rimmed by garnet porphyroblasts and biotite. Scattered, sometimes mantled, xenocrysts of feldspar occur in both fragments and hybrid host rocks. Hybrid rocks occur also as narrow, fine-grained dykes of monzogabbroic composition. Rare evidence of igneous layering includes horizons of rusty-weathering olivine-rich gabbro, anorthositic gabbro and hornblendites. The gabbro is medium- to fine-grained, granular and composed of plagioclase, augite, hypersthene and olivine. Olivine crystals with narrow inner coronas of orthopyroxene and outer coronas of amphibole occur. Olivine-absent, orthopyroxene predominates among mafic minerals, often as hypersthene stained by iron-oxides. The dolerite is ophitic, often plagioclase porphyritic and dominated by plagioclase and augite with pigeonite exsolution lamellae. Hypersthene and inverted pigeonite are subordinate and mantled by clinopyroxene. Pyroxenes are always rimmed by hornblende. The plagioclase of some dykes is clouded by iron oxide. The clouding is confined to central parts of plagioclase laths, and the boundary to clear rims of laths is very sharp, suggesting magmatic origin (Johansson 1992). Towards the overriding Kebnekaise terrane, gabbros and dolerites of the VIC pass into amphibolites, often garnetiferous.
Constraints on the nature of metamorphism in the Kalgoorlie gold camp (Yilgarn Craton, Western Australia) and implications for genetic models of gold mineralisation
Published in Australian Journal of Earth Sciences, 2021
J. A. McDivitt, S. G. Hagemann, N. Thébaud, M. P. Roberts
The Kalgoorlie gold camp (Figure 1a) is located in the Kalgoorlie terrane of the eastern Yilgarn Craton (Cassidy et al., 2006). An estimated ∼2300 t Au endowment is represented primarily by the Golden Mile (∼1780 t Au produced), Mt Charlotte (∼155 t Au produced), and Mt Percy (∼8 t Au produced) deposits as well as the recently discovered lower Hidden Secret orebody (∼1.4 t Au resource; McDivitt et al., 2020; Mueller, 2015, 2020b ?>). Lower stratigraphic units belong to the Kambalda Sequence and comprise the Hannan’s Lake Serpentinite (2708 ± 7 Ma; Nelson, 1997), the Devon Consols Basalt, the Kapai Slate (2692 ± 7 Ma; Claoué-Long et al., 1988), and the Paringa Basalt (Figure 1b). These units are overlain by the Black Flag Group sedimentary and volcanic rocks of the Kalgoorlie Sequence (Mueller, 2015; Mueller et al., 2020; Squire et al., 2010). Dolerite sills intruded the volcano-sedimentary pile; these include the 2696 ± 5 Ma Williamstown Dolerite (Fletcher et al., 2001), the undated Federal and Eureka dolerites, and the 2685 ± 4 Ma Golden Mile Dolerite (Tripp, 2013), which is the primary host rock to gold mineralisation. Late-stage porphyry dykes cross-cut the aforementioned stratigraphic units and comprise ca 2675 Ma quartz–feldspar porphyries and ca 2675–2640 Ma hornblende porphyries and lamprophyres (McDivitt et al., 2020). The Fimiston Au–Te lodes account for the majority of gold production and are dominant in the Golden Mile deposit. Fimiston lodes occur as banded, brecciated, colloform, and crustiform carbonate–quartz veins containing sulfides (predominantly pyrite), sulfosalts (tennantite–tetrahedrite ± enargite), magnetite, hematite, telluride minerals and native gold. Fimiston lodes are surrounded by proximal sericite–ankerite–siderite–quartz–hematite–pyrite–telluride alteration zones and distal ankerite–sericite–quartz–pyrite alteration zones (Bateman & Hagemann, 2004; Clout et al., 1990; Godefroy-Rodriguez et al., 2020; Mueller, 2007). Oroya Au–Telode mineralisation is dominant in the Oroya shoot area of the Golden Mile (Figure 1a) and comprises carbonate–quartz veins and breccias with ‘Green Leader’ quartz–sericite–carbonate–pyrite–telluride–nolanite–titanium vanadate–vanadium muscovite alteration (Eaton, 1986; Mueller, 2020a, 2020b; Nickel, 1977; Tomich, 1958). Mt Charlotte stockwork veins are a structurally late mineralisation type that is dominant in the Mt Charlotte deposit; the veins consist of a carbonate–sericite–albite–scheelite–sulfide–gold assemblage and are enveloped by ankerite–sericite–albite–pyrite–siderite–rutile ± pyrrhotite alteration halos (Bateman & Hagemann, 2004; Clark, 1980; Clout et al., 1990; Mernagh et al., 2004; Mueller, 2015; Ridley & Mengler, 2000).