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Bio-solution for global sand crisis and sustainable organic agriculture in desert states
Published in Zoltán Bartha, Tekla Szép, Katalin Lipták, Dóra Szendi, Entrepreneurship in the Raw Materials Sector, 2022
D. Štyriaková, I. Štyriaková, J. Šuba, Felix Föhre
The petrography and heavy mineral content of various dune sands have been described in detail in an article by authors Pastore et al. (2021) with the following composition: Quartz, feldspar, plagioclase, lithic grains (volcanic, carbonate, other sedimentary and metasedimentary) and transparent heavy minerals, including: Zircon + Tourmaline + Rutile, Apatite, Titanite, Epidote, Prehnite + Pumpellyite, Garnet, Staurolite, Kyanite, Amphibole, Pyroxene, Olivine and others (Anatase, Sillimanite, Andalusite, Monazite, Topaz, Brookite). The chemical composition of the raw quartz sands (especially the content of SiO2, Fe2O3 and Al2O3) is most important for their use and physical properties. The sand in the desert is formed by weathering and accumulation, and the pollutants cannot be removed as in river or sea sand, resulting in a high pollutant content in the sand, which is very slippery and does not meet the standards and limits for industrial use. To increase the purity of quartz and reduce the content of impurities to the desired levels, various physical and chemical processes are used industrially (Tuncuk & Akcil 2014).
Metamorphic Rocks
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
High pressure (labeled high P/T in Fig. 10.29) metamorphism is associated with subduction zones where descending cold and wet lithosphere cools the mantle below (Fig. 10.4). Rock is a good insulator, so temperatures in a subducting slab increase slowly as the slab descends. Consequently, temperatures are not as great as they would be otherwise and metamorphism follows a high P/T path. So, in these environments, metamorphism begins with the zeolite and prehnite-pumpellyite facies and subsequently might continue to the blueschist and eclogite facies (Fig. 10.28). Rocks that form at blueschist and eclogite conditions are relatively rare at Earth’s surface.
Cambrian ocean floor crust preserved in the Takaka Terrane, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2023
Carsten Münker, Frank Wombacher, Christopher Siebert
While equivalent rocks in the Cobb valley area have been subjected to prehnite-pumpellyite facies conditions, mafic igneous rocks in the upper Baton River area contain abundant chlorite, epidote, albite, actinolite and clinozoisite, which are characteristic of greenschist facies metamorphism. Rocks of the Mataki Volcanics mainly consist of massive flows of fine-grained, mostly aphyric dark grey to green volcanic rocks. Rarely, euhedral and partially chlorite-altered phenocrysts of clinopyroxene vary from 0.5-2 mm in size but never exceed 2 vol. %. Vesicles are often filled with secondary carbonate, chlorite or quartz. Metamorphic epidote is the main constituent of the matrix in pillow breccias. Likewise, glassy rims of pillows are altered to epidote. Gabbros of the Mataki Volcanics in the study area are generally medium to coarse grained, and primary minerals are partially replaced by the greenschist facies minerals given above. Fresh primary minerals that remain in the gabbros include subhedral plagioclase varying from 15 vol. % to 20 vol. % in abundance and 1 to 4 mm in length, and subhedral to euhedral clinopyroxene crystals reaching 5 mm in length and up to 25 vol. % in abundance.
Reconnaissance composition of river sand from northern South Island, New Zealand: a modern analogue for southern Taranaki Basin
Published in New Zealand Journal of Geology and Geophysics, 2020
Linda M. Doran, Kathleen M. Marsaglia, Greg H. Browne
Other differences are related to the percentages of quartz and types of lithic fragments. Of the two Caples Terrane samples, Sample NZ-11-45 exhibits higher proportions of monocrystalline quartz, quartz-biotite tectonite fragments, pumpellyite-bearing metasiltstones in the finer sand fractions, and quartz-chlorite tectonite fragments, along with a decrease in the proportion of pumpellyite-bearing metamudstone fragments. This is consistent with the observations of Turnbull (1980) who identified pumpellyite-actinolite and prehnite-pumpellyite metamorphic facies in the Caples terrane in northern Southland, New Zealand. Sample NZ-13-25 provides the clearest example of fragments of low-grade, prehnite-pumpellyite-facies metamorphic rocks. It has the most pumpellyite, the largest number of unmetamorphosed argillite and siltstone fragments, the lowest number of quartz-mica tectonite fragments, and almost no feldspar except for highly altered plagioclase grains in the very fine-sand fraction (Supplementary Tables 3 and 4, https://doi.org/10.1080/00288306.2019.1618881). Many individual clasts in metasiltstone fragments appear to have been replaced by pumpellyite and sericite. On occasion, the colourful birefringence of epidote is visible through the pumpellyite. Relict microlitic textures define some metavolcanic clasts.
Long distance kelp-rafting of rocks around southern New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2018
Mafic volcaniclastic rocks with prehnite–pumpellyite facies metamorphism occur in isolated outcrops of Brook Street Terrane along the northern coast of Foveaux Strait and locally on Ruapuke Island (Figure 2a; Turnbull and Allibone 2003). The most prominent coastal locality for these rocks is at Riverton (Figure 2a), and the large rafted mafic volcaniclastic cobble (Figure 7a; Figure S2a) strongly resembles some rocks at the Riverton outcrops. The rock is not sufficiently distinctive to specify an exact locality, but a general Brook Street Terrane source is most likely. The hydrothermally altered volcaniclastic pebble has the same low metamorphic grade as the Foveaux Brook Street Terrane rocks, and also was probably derived from the Foveaux Strait area. Similarly, the only highly mafic plutonic rocks in the Foveaux Strait area are in Brook Street Terrane, principally at Bluff and at Pahia Point to the west of Riverton (Figure 2a; Turnbull and Allibone 2003), and the pyroxenite veneer (Figure 10a) was probably derived from one of those localities.