Basalt-hosted massive sulfide deposits at the north Fiji Basin'NFB: results from the SO 134 cruise in August 1998

摘要

Following the second HYFIFLUX cruise SO 134 new sampling has substantially enlarged and improved the current database. Two areas (referred to as A and D in the text) were studied in tetail. Area D is located in the N-S segment of the NFB and is dominated by young basalitc volcanism, while area A lies immediately south of the triple junction and has formed in a period of extension with less volcanic activity. As a result, area A contains several sites with occurrences of diffeent types of massive sulfides and late-stage hydrothermal activity, two hydrothermal mound deposits wer discovered in the NW and W of the active graben structure. These mounds consist of chimney fragments of two stages of massive sulfide generation. Sometimes sulphide chimneys from the later event top the mound deposits. Five different types of sulfide mineralisation can be distinguished. Precious metals like Ag and Au are linked to a later-stage mesothermal sphalerite-silica mineral assemblage.