Tholeiitic basalts in various stages of alteration were dredged from Late Cretaceous volcanic rocks (60-67 Ma) in the Hebrides Terrace seamount area in the Atlantic Ocean. These rocks are extrusive olivine basalts, in...Tholeiitic basalts in various stages of alteration were dredged from Late Cretaceous volcanic rocks (60-67 Ma) in the Hebrides Terrace seamount area in the Atlantic Ocean. These rocks are extrusive olivine basalts, including high- and low-Al basalts. High-Al basalts are depleted in MgO, CaO, Cr, Sc, V, Sr, Zr and enriched in TiO-2, Na-2O, Nb, Rb as compared with low-Al basalts. Petrography and bulk-rock composition (major, trace and rare-earth elements) data defined clear tholeiitic suites displaying possible liquid lines of descent related to different degrees of crystal fractionation and partial melting. Isotopic dating of dredged samples gave the guyot an age of 60-67 Ma, in support of the assumption that it was formed during the Late Cretaceous.展开更多
文摘Tholeiitic basalts in various stages of alteration were dredged from Late Cretaceous volcanic rocks (60-67 Ma) in the Hebrides Terrace seamount area in the Atlantic Ocean. These rocks are extrusive olivine basalts, including high- and low-Al basalts. High-Al basalts are depleted in MgO, CaO, Cr, Sc, V, Sr, Zr and enriched in TiO-2, Na-2O, Nb, Rb as compared with low-Al basalts. Petrography and bulk-rock composition (major, trace and rare-earth elements) data defined clear tholeiitic suites displaying possible liquid lines of descent related to different degrees of crystal fractionation and partial melting. Isotopic dating of dredged samples gave the guyot an age of 60-67 Ma, in support of the assumption that it was formed during the Late Cretaceous.
