Diagenetic zeolite and clay minerals in Miocene Great Bahama Bank carbonate sediments (ODP Leg 166, Site 1007)

摘要

To study the fluid-flow processes and effects of sea-level fluctuations in the margin of a carbonate platform, seven sites were drilled during ODP Leg 166 on the western flank of the Great Bahama Bank, a prograding sequence active since late Oligocene. At the distal Site 1007, the early Miocene section is distinguished from the overlying units by a specific authigenic paragenesis made of Mg-smectite and abundant K-clinoptilolite filling foraminifer and pore spaces. The intense diagenetic transformation, recorded by sediment and interstitial fluid geochemical trends, implies by lack of any volcanic input the remobilization of Si-, Al- and Mg-rich fluids and appears promoted by in situ water-rock reactions. Thermodynamic modelling and isotopic data specify the diagenetic processes. The implications on the structure of the GBB platform is discussed.