Abstract
The aim of this paper is the investigation of the role of diagenesis in the transformation of clastic sulfide sediments such as sulfide breccias from the Semenov-3 hydrothermal field (Mid-Atlantic Ridge). The breccias are composed of marcasite–pyrite clasts enclosed in a barite–sulfide–quartz matrix. Primary hydrothermal sulfides occur as colloform, fine-crystalline, porous and radial marcasite–pyrite clasts with inclusions or individual clasts of chalcopyrite, sphalerite, pyrrhotite, bornite, barite and rock-forming minerals. Diagenetic processes are responsible for the formation of more diverse authigenic mineralization including framboidal, ovoidal and nodular pyrite, coarse-crystalline pyrite and marcasite, anhedral and reniform chalcopyrite, inclusions of HgS phase and pyrrhotite–sphalerite–chalcopyrite aggregates in coarse-crystalline pyrite, zoned bornite–chalcopyrite grains, specular and globular hematite, tabular barite and quartz. The early diagenetic ovoid pyrite is enriched in most trace elements in contrast to late diagenetic varieties. Authigenic lower-temperature chalcopyrite is depleted in trace elements relative to high-temperature hydrothermal ones. Trace elements have different modes of occurrence: Se is hosted in pyrite and chalcopyrite; Tl is related to sphalerite and galena nanoinclusions; Au is associated with galena; As in pyrite is lattice-bound, whereas in chalcopyrite it is related to tetrahedrite–tennantite nanoinclusions; Cd in pyrite is hosted in sphalerite inclusions; Cd in chalcopyrite forms its own mineral; Co and Ni are hosted in chalcopyrite.
Highlights
Over the recent decades, great progress has been achieved in understanding trace element behavior in sulfide minerals from oceanic hydrothermal fields [1,2,3,4,5,6,7,8]
According to the morphological analysis of the massive sulfide bodies developed for the Uralian volcanic-hosted massive sulfide (VHMS) deposits [47,48], these features are characteristic of proximal sulfide breccias, which have been transported for some distance from the place of erosion
The textural–structural features of the Semenov-3 breccias are characteristic of proximal breccias, which have been transported for relatively small (≥25 m) distance from the place of erosion
Summary
Great progress has been achieved in understanding trace element behavior in sulfide minerals from oceanic hydrothermal fields [1,2,3,4,5,6,7,8]. Most studies of oceanic hydrothermal fields concern the geochemistry of sulfides from smoker chimneys, diffusers, and massive or colloform ores, which are the result of medium- to high-temperature hydrothermal processes. The lithified clastic sulfides mostly consist of fragments of hydrothermal sulfides from chimneys, diffusers, massive, colloform and stringer-disseminated sulfides, which underwent diagenetic alteration with formation of new (i.e., authigenic, cf [17]) mineral assemblages and redistribution (remobilization) of valuable components between primary hydrothermal and authigenic minerals. Of special interest are authigenic sulfide nodules, because they exhibit zonal morphological and geochemical structures related to the trace elements in the course of diagenesis [18,19]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
