Open AccessColor atlas of low‐temperature alteration features in basalts from the Southern East Pacific Rise
Author(s) -
Schramm Burkhard
Publication year - 2004
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2003gc000665
Subject(s) - geology , basalt , geochemistry , oceanic crust , mineralogy , paleontology , tectonics , subduction
Digital photomicrographs from thin sections of basalts dredged on the eastern flank of the Southern East Pacific Rise are used to illustrate the features of low‐temperature alteration in oceanic crust. The rocks have been altered under seawater‐dominated conditions and show typical precipitation sequences of secondary minerals covering crustal ages from 0 to 9 Ma. Fe‐oxyhydroxide and celadonite disseminated in the groundmass or as void and vein fillings are the first alteration products formed under oxidizing conditions. They are partly replaced by saponite under more reducing conditions. In older rocks phillipsite joints the alteration assemblage in fractures within the glassy rinds, sometimes occurring as a mixture with celadonite. Microprobe analyses of secondary minerals are given, and the location of all analyzed points are indicated in each photomicrograph. Additionally an overview of all thin sections with the location of each photomicrograph is presented in the appendix.