NATURALLY PRODUCED ANATASE NANOSTRUCTURED FILMS DURING THE HYDROTHERMAL ALTERATION OF BIOTITE

摘要

Hydrothermally altered volcanic rocks extended over an area of about 1 km~2 in the Southwestern part of Limnos, island, Northeast Aegean sea, Greece, were found and studied using XRPD, SEM, SEM-EDS and FT-Raman techniques. The alteration of the parent rocks resulted from the circulation of hydrothermal fluids through faults and fractures. Mineralogical data indicate that the temperature prevailed during the hydrothermal alterations were about 80-100 °C. Anatase is mainly the alteration product of ilmenite. The layer structure of micas, especially biotite, seems to be the main factor controlling the morphology of the newly formed anatase. Anatase nanoparticles are found between and on micas layers. With increasing alteration anatase nanostructured films are formed which are parallel to mica layers. Preliminary experimental studies, on mixtures of biotite and anatase at 95 °C and various pH values showed that the formation of anatase nanostructured films between biotite layers in the laboratory is possible and that during this nanofabrication a small part of biotite can be transformed to anatase pillared mica, depending on the pH. Hydrothermally altered volcanic rocks extended over an area of about 1 km2 in the Southwestern part of Limnos, island, Northeast Aegean sea, Greece, were found and studied using XRPD, SEM, SEM-EDS and FT-Raman techniques. The alteration of the parent rocks resulted from the circulation of hydrothermal fluids through faults and fractures. Mineralogical data indicate that the temperature prevailed during the hydrothermal alterations were about 80-100 °C.