A scanning and transmission electron microscopy study has been performed on Oligocene glaci-marine sediments, Devonian sandstones, and dolerites recovered during CRP-3 drilling along the western margin of the Victoria Land Basin, Ross Sea (Antarctica). Newly-formed clay minerals occur in the rock matrices and as fillings in veins and faults which crosscut the whole sequence. Authigenic clays in sediments consist of beidellite-montmorillonites, berthierine/chlorite intergrowths, and illite. Smectites with a muscovitic composition and kaolinite occur in the Devonian sandstone. Saponite, berthierine/chlorite intergrowths, and Fe-hydroxides grow in the weathered dolerites. Hence, the composition of the secondary phases depends on the geochemistry of the rock they grow in. In each sample, the same authigenic minerals form in the matrix and in the vein/fault. Clays precipitated from fluids which circulated in the system during contemporaneous diagenetic and faulting events. Possibly, the fluids were a mix of glacial melt waters and hydrothermal fluids with variable fO2 values
Syntectonic Growth of Clays in Veins, Victoria Land Rift Basin, Antarctica: An Electron Microscopy Study
Aghib FS;
2005
Abstract
A scanning and transmission electron microscopy study has been performed on Oligocene glaci-marine sediments, Devonian sandstones, and dolerites recovered during CRP-3 drilling along the western margin of the Victoria Land Basin, Ross Sea (Antarctica). Newly-formed clay minerals occur in the rock matrices and as fillings in veins and faults which crosscut the whole sequence. Authigenic clays in sediments consist of beidellite-montmorillonites, berthierine/chlorite intergrowths, and illite. Smectites with a muscovitic composition and kaolinite occur in the Devonian sandstone. Saponite, berthierine/chlorite intergrowths, and Fe-hydroxides grow in the weathered dolerites. Hence, the composition of the secondary phases depends on the geochemistry of the rock they grow in. In each sample, the same authigenic minerals form in the matrix and in the vein/fault. Clays precipitated from fluids which circulated in the system during contemporaneous diagenetic and faulting events. Possibly, the fluids were a mix of glacial melt waters and hydrothermal fluids with variable fO2 valuesI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
