Zeolite Minerals from the North Shore of the Minas Basin, Nova Scotia‪.‬

ABSTRACT X-ray diffraction and electron microprobc analyses show Ihe following assemblages to be present in basalt flows and overlying siliciclastic sedimentary rocks along the Norlh Shore of the Minas Basin: Five Islands -- chabazite and stilbite are dominant, also "heulandite" and barrerite; Two Islands -- analcime is dominant, gmelinite, chabazite, stilbite, and natrolile; Wasson Bluff--chabazite, slilbite and "heulandite" are dominant, also herschelite, barrerite, stellerite, analcime, wairakite, natrolite, clinoptilolite, and thomsonite; Parlridge Island -- chabazite and stilbite are dominant, also analcime, epistilbite, natrolite, barrerite, and "heulandite"; Cape Sharp -- chabazite, stilbite, barrerite, stellerite, and "heulandite"; Horseshoe Cove -- "heulandite" and stilbite; Western Cape d'Or -- analcime, stilbite, natrolite, and mesolite are dominant, also stellerite, ?epistilbite, barrerite, scolecite, chabazite, "heulandite", wairakite, tetranatrolite and laumontite. Comparison is made with assemblages at Arlington Quarry on North Mountain, where the dominant zeolite minerals are heulandite (sensu stricto) and stilbite. Elsewhere on North Mountain, mordenite, natrolite, and laumontite have been confirmed. Chemical composition of hydrothermal fluids was likely different between North Mountain and the North Shore, wilh fluids in the latter area less sodic. The temperature ofzeo]ite crystallization appears to have been high at Arlington Quarry, where "heulandite" and stilbite crystallised with little Na in their crystal structure. With falling temperature the crystallizing solution became enriched in Na, and sodic zeolite minerals, such as natrolite, began to crystallize. At lower lemperatures on Ihe North Shore, Na was accommodated in the structure ofchabazite and other zeolites such as analcime, and final crystallisation was represented by only small amounls of Na-rich zeolites (natrolite group).