TY - JOUR
T1 - Chromium-bearing clays in altered ophiolitic rocks from Crommyonia (Soussaki) volcanic area, Attica, Greece
AU - Mitsis, I.
AU - Godelitsas, A.
AU - Goettlicher, J.
AU - Steininger, R.
AU - Gamaletsos, P. N.
AU - Perraki, M.
AU - Abad-Ortega, M. M.
AU - Stamatakis, M.
PY - 2018
Y1 - 2018
N2 - Chromium-bearing clays occurring at Crommyonia (Soussaki), Greece, are studied in detail. In this area Mesozoic ultramafic ophiolitic rocks were affected by a Pliocene volcanic activity continuing, nowadays, with intense post-volcanic phenomena. Particularly, the Cr-bearing clays were formed at the margins of the ophiolite into highly altered serpentinized peridotite. These clays were studied by means of x-ray diffraction (powder-XRD), microscopic (SEM-EDS), nanoscopic (TEM-EDS/STEM-HAADF), and spectroscopic (FTIR, XANES) techniques. The XRD and SEM-EDS studies confirmed smectites and halloysites, with average Cr2O3 content ca 6.2 wt % and 4.3 wt%, respectively. The mineralogy and mineral-chemistry of the above unique Cr-clays was also confirmed by TEM-EDS/STEM-HAADF measurements. Subsequent FT-IR investigation indicated the relation of chromium ions with structural hydroxyls whereas a XANES study showed the presence of only Cr(III) in both phases and the absence of Cr(VI). According to the above data, Cr(III) ions should occupy octahedral sites in the structure of the studied clays. Geochemical data indicated high enrichment in Cr, and also in As, Se, Ni, V, Sc, Tl, when compared to Upper Continental Crust (UCC), and in Cr when compared to average global peridotite and primitive mantle. The formation of Cr-bearing clays is attributed to additional alteration of serpentinized peridotite minerals (such as Cr-spinels), due to hydrothermal fluids leaching different elements from the volcanic, sedimentary, and ophiolitic rocks of the area.
AB - Chromium-bearing clays occurring at Crommyonia (Soussaki), Greece, are studied in detail. In this area Mesozoic ultramafic ophiolitic rocks were affected by a Pliocene volcanic activity continuing, nowadays, with intense post-volcanic phenomena. Particularly, the Cr-bearing clays were formed at the margins of the ophiolite into highly altered serpentinized peridotite. These clays were studied by means of x-ray diffraction (powder-XRD), microscopic (SEM-EDS), nanoscopic (TEM-EDS/STEM-HAADF), and spectroscopic (FTIR, XANES) techniques. The XRD and SEM-EDS studies confirmed smectites and halloysites, with average Cr2O3 content ca 6.2 wt % and 4.3 wt%, respectively. The mineralogy and mineral-chemistry of the above unique Cr-clays was also confirmed by TEM-EDS/STEM-HAADF measurements. Subsequent FT-IR investigation indicated the relation of chromium ions with structural hydroxyls whereas a XANES study showed the presence of only Cr(III) in both phases and the absence of Cr(VI). According to the above data, Cr(III) ions should occupy octahedral sites in the structure of the studied clays. Geochemical data indicated high enrichment in Cr, and also in As, Se, Ni, V, Sc, Tl, when compared to Upper Continental Crust (UCC), and in Cr when compared to average global peridotite and primitive mantle. The formation of Cr-bearing clays is attributed to additional alteration of serpentinized peridotite minerals (such as Cr-spinels), due to hydrothermal fluids leaching different elements from the volcanic, sedimentary, and ophiolitic rocks of the area.
KW - Clays
KW - Smectite
KW - Chromium
KW - Nanoscopy
KW - Synchrotron
KW - Greece
U2 - 10.1016/j.clay.2018.06.016
DO - 10.1016/j.clay.2018.06.016
M3 - Journal article
SN - 0169-1317
VL - 162
SP - 362
EP - 374
JO - Applied Clay Science
JF - Applied Clay Science
ER -