Geochemical characterization of highly diverse hydrothermal fluids from volcanic vent systems of the Kermadec intraoceanic arc

• Verfasst von: Kleint, Charlotte [VerfasserIn]
• Verfasst von: Bach, Wolfgang [VerfasserIn]
• Verfasst von: Kleint, Jan F. [VerfasserIn]
• Titel: Geochemical characterization of highly diverse hydrothermal fluids from volcanic vent systems of the Kermadec intraoceanic arc
• Verf.angabe: Charlotte Kleint, Wolfgang Bach, Alexander Diehl, Nico Fröhberg, Dieter Garbe-Schönberg, Jan F. Hartmann, Cornel E. J. de Ronde, Sylvia G. Sander, Harald Strauss, Valerie K. Stucker, Janis Thal, Rebecca Zitoun, Andrea Koschinsky
• E-Jahr: 2019
• Jahr: 03 September 2019
• Umfang: 20 S.
• Fussnoten: Gesehen am 06.02.2020
• Titel Quelle: Enthalten in: Chemical geology
• Ort Quelle: New York, NY [u.a.] : Elsevier, 1966
• Jahr Quelle: 2019
• Band/Heft Quelle: 528(2019) Artikel-Nummer 119289, 20 Seiten
• ISSN Quelle: 1872-6836
• DOI: doi:10.1016/j.chemgeo.2019.119289
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: High Mg-fluids
• Sach-SW: High-chlorinity acid-sulfate fluids
• Sach-SW: Hydrothermalism at intraoceanic arcs
• Sach-SW: Kermadec arc
• Sach-SW: Trace metals
• K10plus-PPN: 1689525436

Abstract

During the R/V Sonne cruise SO253 in 2016/2017, hydrothermal vent sites along the Kermadec intraoceanic arc were sampled for hydrothermal fluids at four active volcanoes: Macauley, Haungaroa, Brothers and Rumble III, respectively. Water depths ranged between 290m and 1700m. A new vent field was discovered at Haungaroa. The samples were taken from diffuse-flow sites as well as from white and black smokers - rich in metals and gases - with discharge temperatures as high as 311°C. Their fluid composition is very variable but basically divides into two types: one that indicates distinct magmatic input and another that shows evidence for intense water-rock interaction under hot, acidic conditions. Fluid samples from Macauley, the shallowest sampling site (~300m), had Fe concentrations as high as 1.7mM, Al concentrations up to 122μM and H2S up to 10mM at a pH of only 1.2. At Brothers, the deepest sampling site (down to 1600m), we identified two different fluid types: 1) A magmatically-influenced type at the Upper and Lower Cone with highest temperatures of 115°C, up to 95.6mM Mg (the highest Mg concentration measured in fluids from intraoceanic arc systems so far), elevated SO42− (76.9mM), high H2S (5.0mM), but Fe concentrations of only 15μM and 2) A fluid with low Mg (5.4mM), low H2S (1.1mM), temperatures reaching 311°C and high Fe contents (12.4mM) at the Upper Caldera and NW Caldera Wall, typical of a black smoker fluid. Chloride concentrations in all fluids were similar, or highly enriched when compared to seawater (e.g. up to 787mM, brine fluids), with also one low-chlorinity vapor-phase fluid sample recovered, indicating that phase separation is occurring at Brothers. Unusual highly elevated Mg concentrations in fluids from the Brothers Lower Cone (95.6mM, compared to 53.2mM in ambient seawater) combined with highly elevated concentrations of SO42− (76.9mM, compared to 29.0mM in ambient seawater) indicate dissolution of Mg- and SO42−-bearing minerals in the subsurface, such as caminite. Our data show how highly diverse and variable island arc systems can be with respect to their fluid chemistry, both spatially and temporally. It adds to the still limited data set of arc systems compared to mid-ocean ridges and supplies an important contribution towards a better understanding of geochemical processes along arc volcanoes. The higher range in fluid chemistry together with shallower water depth implies that the fluids from intraoceanic arcs may contribute a significant fraction of dissolved metals not only to the global oceanic biogeochemical cycle but also into the photic zone, the area of highest bioproductivity.