Leucoxene-calcite-quartz aggregates in sandstones and the relation to decomposition of sphene.

The texture and mineralogy of aggregates made up of leucoxene (rutile, anatase and brookite)-quartz-calcite, leucoxene-quartz and leucoxene-calcite in Proterozoic sandstones of the Visingso group in S Sweden suggest that they are pseudomorphous after detrital sphene. The sphene has been decomposed into these phases due to its instability in the diagenetic environment. The dominance of either calcite or quartz with the leucoxene phase is proposed to be mainly controlled by the pH of the pore solutions. (Authors' abstract)-E.v.P.