Abstract

Laumontite and heulandite are extensively developed as metamorphic minerals in sandstones of the Late Cretaceous Nanaimo Group, Vancouver Island and Gulf Islands, British Columbia. Major post-depositional changes in the sandstones also include widespread carbonate cementation and replacement, alteration of plagioclase and biotite, and development of a phyllosilicate matrix. The sequence apparently is depth-zoned, with heulandite present only in the upper 1000 m of section, and laumontite developed in the upper 2500 m. The zeolite assemblages probably were developed during burial metamorphism, as subject to controls of permeability and suppression by a high chemical potential of CO2. Comparable assemblages should be expected in similar clastic sequences found in other portions of the Cordillera, particularly the thick Mesozoic successions of the Intermontane and Insular Fold Belts.

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