Feldspar albitization and feldspar cementation in the Albert Formation reservoir sandstones, New Brunswick, Canada

Abstract

Feldspar albitization and feldspar cementation (especially albite) are common in the Carboniferous fluvio-lacustrine Albert Formation reservoir sandstones of the Moncton subbasin, New Brunswick. Both albitization and albite cements occur in early and late diagenesis. Burial diagenetic origin of albite is supported by: (1) the chemical purity of albite; (2) the growth of euhedral albite on numerous sites of the host feldspar; (3) the continued growth of the replacement albite into adjacent pores; (4) the delicate skeletal texture in partially dissolved areas of albitized feldspar; and (5) the occurrence of ankerite cement inclusions in authigenic albite. Backscattered electron imaging suggests that feldspar albitization occurs in irregular, vein-like and perthite elbite forms. Feldspar albitization is commonly associated with dissolution pores and twins. Backscattered electron imaging suggests that up to 50% of the mean total 4% detrital K-feldspars have been albitized. The volume percentage of feldspar albitization shows no trend with increasing burial depth or temperature. Most of the sandstones have 2–3% albite cement except in a high minus-cement porosity framework where it may exceed 30% of the sandstone.