Multiple authigenesis of K-feldspar in sandstones: evidence from the Cretaceous Areado Formation, Sao Francisco Basin, central Brazil

Feldspar authigenesis occurred in two major episodes. 1) In the Early Cretaceous K-feldspar precipitated as overgrowths, healing of microfractures, and replacement of detrital K-feldspar and plagioclase at very shallow depths. Authigenesis was related to meteoric dissolution of detrital volcanic feldspars, volcanic vitric rock fragments, and micas in a hot semiarid climate. 2) In the Late Cretaceous, while still at shallow depths, K-feldspar precipitated as abundant fine crystals associated with opal-CT, hematite, and mixed-layer illite/smectite. -from Authors