A silica-deficient, shallow-marine zeolite assemblage in the Foveaux Formation, Bluff Peninsula, New Zealand

摘要

A gonnardite-thomsonite-chabazite-calcite assemblage forms a cement in the Foveaux Formation, a fossiliferous gabbroic boulder bed that accumulated at the base of a sea cliff cut in a Permian igneous complex during late Oligocene–early Miocene time. Gonnardite was the earliest zeolite to form, locally following minor calcite. It was followed epitaxially by thomsonite, co-precipitating with chabazite. Crystal habits indicate a low-temperature origin. The maximum temperature to which the deposit may have been subjected is estimated as not more than ~30°C. The chabazites are Ca-poor chabazite-K and chabazite-Na. Representative electron microprobe analyses are as follows, all + nH₂O: