RED JASPEROIDS FROM THE AREA OF THE UKRAINIAN ANTARCTIC RESEARCH STATION

Red jasper-like rocks from the area of the Akademik Vernadsky Station are known since the time of the first Ukrainian Antarctic expeditions. But until now, all the published information about them was limited to only one brief mention in the abstract of the report by Mytrokhyn and Bakhmutov (2017). This article summarizes all available data about these jasperoids with the aim of clarifying their origin and systematic position among other rocks of essentially siliceous composition. The authors studied the manifestations of the jasperoids on the Argentine Islands and Jalour Islands near the western coast of the Kyiv Peninsula (Graham Coast of the Antarctic Peninsula). It was found that small vein-like bodies of the jasperoids occur in Jurassic-Cretaceous strata of the Antarctic Peninsula Volcanic Group. According to their geological position, mode of occurrence and petrographic features, they are quite similar to hematite jasperoids found in many parts of the world in association with hydrothermal deposits of Au, Cu, Pb, Zn, Sb and Hg. The authors prove a hydrothermal origin for new localities of hematite jasperoids discovered in the Antarctica. Results of the studies indicate that the jasperoids were formed from silica-enriched hydrothermal fluids. Low temperature hydrothermal process was taking place at a shallow depth. Silica was mainly in a form of colloidal solution namely as silicic acid gel. The presence of hematite as well as some other minor minerals (calcite, pyrite, epidote, sericite and chlorite) can be explained by the interaction of the hydrothermal fluids with host rocks. It is assumed that the fluids were of juvenile origin. They could separate from the granitoid intrusion which lies at depth below hydrothermally altered volcanogenic strata. Zones of increased fracturing in the host volcanites were feeding channels for rising fluids.