Geochemical evolution of a palaeolaterite: the Interbasaltic Formation, Northern Ireland

摘要: Abstract The Interbasaltic laterites of Northern Ireland were formed during a period relative volcanic inactivity by extensive chemical weathering Tertiary basalts. They reach maximum thickness 30 m and once provided major source iron aluminium ore. An database comprising major, minor, trace elements has been compiled for 240 samples in order to study the effects terms changes whole-rock chemistry mineralogy from basalt through iron-rich crust. Percolating waters caused degradation parent precipitation neoformed phases, principally incongruent dissolution processes. Primary olivine, plagioclase feldspar, augite successively broken down replaced mineral assemblage consisting hematite, gibbsite, goethite, anatase, meta-halloysite kaolinite. Changes facilitated concomitant element concentrations. Mass balance calculations indicate that all depleted Enrichment Al, LOI, Cr, Cu, V occurred laterite horizon, while enrichment Ba, Ce, Ni, Rb lithomarge. Notably, yttrium was found be mobile indicating weathered basalts should not used discrimination original tectonic environments. severe leaching conditions evidenced depletion, local redistribution, crust formation are indicative under humid sub-tropical monsoon climate.