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Published in Ian Sims, Alan Poole, Alkali-Aggregate Reaction in Concrete: A World Review, 2017
A further example of type of structures affected by AAR is an arch bridge (Figure 14.8), in which precast arch units, as well as the main body of the arches exhibited cracking. The aggregate was an acid igneous rhyodacite rock.
Zircon U–Pb age, whole-rock geochemistry and Nd–Sr–Pb isotope constraints on petrogenesis of the Eocene Zajkan gabbro–monzogranite intrusion, Tarom-Hashtjin magmatic belt, NW Iran
Published in Australian Journal of Earth Sciences, 2022
M. A. A. Mokhtari, H. Kouhestani, K. Z. Qin
In the Zajkan area, the major geological units are Eocene volcanic–volcaniclastic rocks (>2000 m in thickness; Hosseiny et al., 2016) that were intruded by the Zajkan intrusion (Figure 2). Volcanic rocks are andesite, trachyandesite and porphyritic andesite with local olivine basalt, andesitic basalt and rhyodacite lava flows (Hosseiny et al., 2016; Kouhestani et al., 2019a, 2019b). Andesites and trachyandesites comprise plagioclase, hornblende and biotite phenocrysts within fine-grained groundmass. Porphyritic andesite is composed of centimetre-sized plagioclase phenocrysts along with hornblende and minor small clinopyroxene phenocrysts set in a fine-grained to glassy matrix (Hosseiny et al., 2016). The olivine basalts consist of olivine, plagioclase, and clinopyroxene phenocrysts set in an intersertal and fine-grained groundmass (Hosseiny et al.,2016). Andesitic basalts show a porphyritic texture and consist principally of distinctive zoned phenocrysts of plagioclase and pyroxene (Hosseiny et al., 2016). The rhyodacite lavas are composed of largely plagioclase, sanidine, and quartz phenocrysts and rare biotite with a porphyritic texture (Hosseiny et al., 2016). The volcaniclastic strata is mainly tuff (i.e. crystal tuff, crystal lithic tuff, lapilli tuff, and tuff breccia), ignimbrite, agglomerate, sandy tuff and tuffaceous sandstone, with minor conglomerate intercalations (Hosseiny et al., 2016).
Early Devonian volcanic facies, central Lachlan Orogen, New South Wales: implications for tectonic and metallogenic models
Published in Australian Journal of Earth Sciences, 2022
A distinctive felsic coherent unit that crops out southwest of the Mirrool rhyolite (Figures 7 and 9), the Rowallen rhyodacite contains phenocrysts of 5% quartz, 5–7% plagioclase, 3–7% orthopyroxene, 1–2% biotite (some quite red), 2–3% garnet, and 5–7% of a needle-shaped, slightly purplish opaque mineral interpreted to be ilmenite. K-feldspar is absent suggesting rhyodacite (low-silica rhyolite) composition. Orthopyroxene is also locally associated with fine-grained plagioclase–ilmenite glomerophyric clusters, and here displays no edenite reaction rims in contact with the plagioclase–ilmenite (Figure 9a, b). In most cases, garnet is rimmed by plagioclase (albite?), although in one thin-section garnet is adjacent to and in textural equilibrium with orthopyroxene. Plagioclase crystals are zoned, and commonly resorbed.
Geochronology and geochemistry of the Devonian Gumbardo Formation (Adavale Basin): evidence for cratonisation of the Central Thomson Orogen by the Early Devonian
Published in Australian Journal of Earth Sciences, 2018
P. Asmussen, S. E. Bryan, C. M. Allen, D. J. Purdy
Recovered core material containing volcanic and epiclastic rocks of the Gumbardo Formation was inspected and logged in five wells (Table 1; Figure 4). From the available core, three main rock types were identified (Table 2): (1) ignimbrites of rhyodacitic composition, (2) coherent porphyritic rhyodacite, and (3) epiclastic sandstones (lithic arkose to arkose). Formational thickness is constrained by well log interpretations (McKillop et al., 2007) and has been verified based on cutting descriptions and core logs from the associated well completion reports (Kyranis, 1966; Leslie, 1971; Lewis, 1961; Lewis & Kyranis, 1962; Phillips Petroleum Company and Sunray DX Oil Company, 1963). Our revision of this material confirmed formational thickness for PPC Gumbardo-1 (755.5 m), PPC Carlow-1 (140 m) and PPC Cothalow-1 (273 m). For two wells, only minimum thicknesses are constrained (Figure 4, BEA Allandale-1, >236 m; PPC Etonvale-1, >206.1 m). Epiclastic sandstones of the upper Gumbardo Formation are intersected in PPC Cothalow-1 (∼110 m) and PPC Etonvale-1 (∼100 m) in the central part of the Adavale Basin.