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Volcanoes and Their Products
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Figure 7.41 shows a porphyritic latite. Latite is a kind of volcanic rock that contains about equal amounts of plagioclase and K-feldspar, and sometimes a small amount of quartz. The largest, somewhat blocky crystals in this photo are phenocrysts of gray plagioclase. This rock also contains phenocrysts of black clinopyroxene, which are just barely visible. The dark colored groundmass, between the larger phenocrysts, is a mix of feldspars, augite, biotite, and magnetite. The combination of larger phenocrysts in a sea of fine-grained material reflects the rock’s two-stage cooling history. See also Figure 5.30 in Chapter 5 for another view of a porphyry.
Lithological distribution of rare earth elements in soils in the As-Sb-Tl Allchar mining area, North Macedonia
Published in Journal of Environmental Science and Health, Part A, 2023
Katerina Bačeva Andonovska, Robert Šajn, Claudiu Tănăselia, Trajče Stafilov
The volcanic intrusive rocks of Allchar include latite, quartz–latite, trachyte, sporadic andesite and dacite. The volcanism of Allchar contains varying amounts of REEs. It can be concluded that there is some enrichment of light REEs (Figure 4). The relative enrichment of La is characteristic of the volcanic rocks of Allchar, while the Ce content (140–157 ppm) and Ce/Y (about 6) indicate some depletion of heavy elements.[12,13] The Nd content is also high. From the analysis of Frantz et al.,[16] it can be inferred that the enrichment in light REEs elements indicates that the magma is of continental crustal origin and different from tholeiitic basalts. The slightly pronounced Eu minimum and the pronounced Dy minimum indicate the fractionation processes of the primary magma and its contamination by rocks from the upper and lower crust.[16,17]
Basaltic dykes and their xenoliths from the Gerroa–Kiama region, southern Sydney Basin, New South Wales: evidence for multiple intrusive episodes
Published in Australian Journal of Earth Sciences, 2022
S. Abu-Shamma, I. T. Graham, P. Lennox, G. Bann, A. Greig
The shoshonitic basaltic andesites (Five Islands, Bumbo and Calderwood latite members) are porphyritic, holocrystalline dark grey to black rocks. Phenocrysts comprise plagioclase, clinopyroxene, titanomagnetite and chlorite pseudomorphs after olivine (Carr, 1984). In some areas, the phenocrysts group together to form a glomeroporphyritic texture. The phenocryst-to-groundmass ratio varies from 1:1 to 1:9. Although some of these contain either vesicles or amygdales (lined with quartz, chlorite, hematite and laumontite), the vesicles and/or amygdales seldom surpass 10% by volume of rock. The groundmass displays a range of textures that vary from pilotaxitic, orthophyric, intergranular and more rarely intersertal. The primary groundmass phases consist of feldspar, clinopyroxene, apatite and titanomagnetite, whereas chlorite, hematite, calcite, sericite, kaolinite and epidote form the secondary minerals.
Occurrence and enrichment sources of cobalt, chromium, and nickel in soils of Mitrovica Region, Republic of Kosovo
Published in Journal of Environmental Science and Health, Part A, 2021
Milihate Aliu, Robert Šajn, Trajče Stafilov
The investigated area belongs to the Vardar Zone. The geotectonic unit is covered by metamorphic, sedimentary and magmatic rocks of the younger Paleozoic and Triassic ages, the Cretaceous flysch, the Miocene volcanic rocks with pyroclastites as well as younger Pliocene and Quaternary sediments. The younger Paleozoic consists of green schists, shales, marbles, quartzite and metamorphosed basic magmatic rocks successively alternate to the lover part of series, while the upper one is built up of limestones (Stan Tёrg), riche by lead-zinc mineralization (Trepça mine). The overlying Mesozoic rocks consist of lower Triassic metaconglomerates and metasandstones. The middle Triassic is represented by metamorphosed volcanogenic-sedimentary formation (shales schists, metasandstones, metadiabase) and serpentinite (northern part of investigated area). Upper Triassic rocks are represented by the Cretaceous limestones (western part of investigated area) and flysch formations (alevrolites, shales and sandstones with olistolites). The Tertiary formation is represented with the Lower Miocene conglomerate, sandstone and clay and Miocene latite, quartz-latite and their pyroclastites (north-eastern part of investigated area). The Quaternary is represented by Pleistocene fluvio-lacustrine sediments, gravel and sand deposits, river terraces and alluvium (central and southern-east part of investigated area).[14]