Abstract:This paper reports the composition and alteration products of pyroclasts in the Holocene Paredão volcano (pyroclast 1) and Late Quaternary Morro Vermelho Formation (pyroclasts 2 and 3) of Trindade Island, South Atlantic, Brazil using combined macromorphological, micromorphological, mineralogical and geochemical techniques.The pyroclasts 1 and 2 are interpreted as volcanic tuff breccia deposits, whereas pyroclast 3 is a lapilli deposit. They are dark gray in color with some altered reddish regions and show vesi… Show more
“…The presence of ferromagnesian minerals such as olivine, pyroxene and amphibole explain the high content of Ni, Cr, Co, Zn and V. According to Hawes and Webb (1962), Ni, Cr, Co, Cu, Zn and V have similar chemical characteristics and occur in ferromagnesian minerals. Cr contents is high for all soils due to the deep mantelic origin of the pyroclasts and tend to concentrated in the olivine nuclei (Mateus et al 2020b). This fact explains the high exchangeable levels of Cr in soils from the Morro Vermelho Formation (Clemente et al 2012).…”
Section: Discussionmentioning
confidence: 96%
“…K 2 O, Na 2 O and MnO occur in small quantities and are mainly related to volcanic glass (sideromelane), which constitutes approximately 50% of the rock. The quantification of volcanic glass was obtained by description of rocks previously impregnated in a Zeiss microscope fitted with a digital camera (Mateus et al 2020a(Mateus et al , 2020b. The pyroclasts from profile 3 contain K 2 O values greater than Na 2 O due to the higher amounts of Ti-biotite.…”
Section: Geochemistrymentioning
confidence: 99%
“…For Cu, Th, V, Zn, Zr, S, Pb, Ca, Ga and U, there is a decrease from the rock to C2 Table 1. Physical and mineralogical characteristics of the profiles (Mateus et al 2020a(Mateus et al , 2020b and Mateus et al (2018). Table 2.…”
“…The presence of ferromagnesian minerals such as olivine, pyroxene and amphibole explain the high content of Ni, Cr, Co, Zn and V. According to Hawes and Webb (1962), Ni, Cr, Co, Cu, Zn and V have similar chemical characteristics and occur in ferromagnesian minerals. Cr contents is high for all soils due to the deep mantelic origin of the pyroclasts and tend to concentrated in the olivine nuclei (Mateus et al 2020b). This fact explains the high exchangeable levels of Cr in soils from the Morro Vermelho Formation (Clemente et al 2012).…”
Section: Discussionmentioning
confidence: 96%
“…K 2 O, Na 2 O and MnO occur in small quantities and are mainly related to volcanic glass (sideromelane), which constitutes approximately 50% of the rock. The quantification of volcanic glass was obtained by description of rocks previously impregnated in a Zeiss microscope fitted with a digital camera (Mateus et al 2020a(Mateus et al , 2020b. The pyroclasts from profile 3 contain K 2 O values greater than Na 2 O due to the higher amounts of Ti-biotite.…”
Section: Geochemistrymentioning
confidence: 99%
“…For Cu, Th, V, Zn, Zr, S, Pb, Ca, Ga and U, there is a decrease from the rock to C2 Table 1. Physical and mineralogical characteristics of the profiles (Mateus et al 2020a(Mateus et al , 2020b and Mateus et al (2018). Table 2.…”
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