Chemical composition of zeolites in sandstones at DSDP Sites 445 and 446

Andesitic volcaniclastic sandstones of Middle Eocene age recovered from DSDP Sites 445 and 446, a back-arc basin, contain clinoptilolite, heulandite and analcite as a pore-filling cement. Clinoptilolite and heulandite at Sites 445 and 446 contain different chemical composition from other deep-sea clinoptilolites and heulandites. The dominant cation of both clinoptilolite and heulandite is Na+ ion activity in pore water was greater at the time of their formation. Volcanic glass has acted as a precursor for both clinoptilolite and heulandite at Sites 445 and 446. Biogenic silica is also suggested as a precursor. […]从位于弧后盆地（back-arc basin）的深海钻探计划（Deep Sea Drilling Project, DSDP）445与446站位获取的中始新世安山岩质火山碎屑砂岩中，赋存以孔隙充填胶结物形式产出的斜发沸石（clinoptilolite）、辉沸石（heulandite）与方沸石（analcite）。445和446站位的斜发沸石与辉沸石，其化学成分区别于其他深海产出的同类沸石。两类沸石的主要阳离子均为钠离子，且其形成时期孔隙水中的钠离子活度更高。445与446站位的斜发沸石和辉沸石均以火山玻璃作为形成前驱体，同时研究也表明生物成因二氧化硅可作为其另一形成前驱体。[…]