SEM study of authigenic rutile, anatase and brookite in Proterozoic sandstones from Sweden

Scanning electron microscopic examinations revealed interstitial rutile, anatase and brookite to be common in Upper Proterozoic sandstones of the Visingsö Group in southern Sweden. Anatase is observed as either single discrete crystals or as numerous crystals filling and lining pore space. Rutile and brookite occur predominantly as clusters of crystals within interstitial cements, on detrital grains (e.g. feldspar and quartz) or as overgrowths on detrital and authigenic titanium oxides. These titanium oxides have been formed diagenetically from percolating pore solutions rich in titanium ions. The source of titanium ions is suggested to be mainly detrital Fe-Ti oxides, sphene and biotite grains.