ALBERT

Beschreibung: Deep-sea sediment samples were taken from the (wider) Kairei hydrothermal field area (25°S, 70°E) as well as a remote site (26°S, 71°E) in the Indian Ocean during the INDEX cruise 2016 with the N/O Pourquoi pas? (Ifremer, France). Push core samples from different areas of the Kairei vent field, as well as a sample from the remote site (~200 km south-east from the Kairei), were recovered with the help of the ROV VICTOR 6000 (Ifremer, France). All subsampling steps were carried out shipboard at 4 °C. With sterile syringes (nozzles removed) 3 ml of 2 cm layers of sediment were transferred into sterile falcon tubes for DNA extraction and stored at –80 °C. The remaining sediment was cut into 2 cm slices, freeze-dried, and partially milled to 〈75 mm for geochemical analyses. The sediment was analyzed for carbon chemistry, i.e. total organic carbon (TOC) and total inorganic carbon (TIC) with routine standard methods (IR-detection after combustion, ISO 10694, LECO CS 230 analyzer). Elemental composition of Kairei sediments was estimated by the accredited Actlab Laboratories, Canada (Multimethod mix called Ultratrace 3 program, using INAA, 4-Acid Digestion, ICP-OES, and ICP-MS). Sediments from the remote station were analyzed by routine WD-XRF after fusion with Li-Metaborate/Li-Bromide (XRF spectrometers Philips PW 2400 und Philips PW 1480).

Beschreibung: Most magmatic-hydrothermal Cu deposits are genetically linked to arc magmas. However, most continental or oceanic arc magmas are barren, and hence new methods have to be developed to distinguish between barren and mineralised arc systems. Source composition, melting conditions, the timing of S saturation and an initial chalcophile element-enrichment represent important parameters that control the potential of a subduction setting to host an economically valuable deposit. Brothers volcano in the Kermadec island arc is one of the best-studied examples of arc-related submarine magmatic-hydrothermal activity. This study, for the first time, compares the chemical and mineralogical composition of the Brothers seafloor massive sulphides and the associated dacitic to rhyolitic lavas that host the hydrothermal system. Incompatible trace element ratios, such as La/Sm and Ce/Pb, indicate that the basaltic melts from L'Esperance volcano may represent a parental analogue to the more evolved Brothers lavas. Copper-rich magmatic sulphides (Cu 〉 2 wt%) identified in fresh volcanic glass and phenocryst phases, such as clinopyroxene, plagioclase and Fe–Ti oxide suggest that the surrounding lavas that host the Brothers hydrothermal system represent a potential Cu source for the sulphide ores at the seafloor. Thermodynamic calculations reveal that the Brothers melts reached volatile saturation during their evolution. Melt inclusion data and the occurrence of sulphides along vesicle margins indicate that an exsolving volatile phase extracted Cu from the silicate melt and probably contributed it to the overlying hydrothermal system. Hence, the formation of the Cu-rich seafloor massive sulphides (up to 35.6 wt%) is probably due to the contribution of Cu from a bimodal source including wall rock leaching and magmatic degassing, in a mineralisation style that is hybrid between Cyprus-type volcanic-hosted massive sulphide and subaerial epithermal–porphyry deposits.

Beschreibung: The Universität Hamburg is part of the environmental studies in the INDEX (Indian Ocean Exploration) program, which was established by the BGR (Federal Institute for Geosciences and Natural Resources), Hanover. The INDEX license area is located in the oligotrophic subtropical gyre of the South Indian Ocean. Sinking particulate matter samples were collected by sediment trap mooring 05-01 to measure vertical particle flux quantitatively and qualitatively. Mooring 05-01 was deployed during cruise PE394 (RV Pelagia) and recovered during cruise PE405.

Beschreibung: Deep-sea sediment samples were taken from the (wider) Kairei hydrothermal field area (25°S, 70°E) as well as a remote site (26°S, 71°E) in the Indian Ocean during the INDEX cruise 2016 with the N/O Pourquoi pas? (Ifremer, France). Push core samples from different areas of the Kairei vent field, as well as a sample from the remote site (~200 km south-east from the Kairei), were recovered with the help of the ROV VICTOR 6000 (Ifremer, France). All subsampling steps were carried out shipboard at 4 °C. Porewater from push cores was extracted with rhizons (CSS, 5 cm Rhizosphere Research Products B.V., Netherlands) at a resolution of 2-3 cm, fixed with 1% HNO3 for trace element analyses and stored at 4 °C. With sterile syringes (nozzles removed) 3 ml of 2 cm layers of sediment were transferred into sterile falcon tubes for DNA extraction and stored at –80 °C. Concentrations of minor and trace elements Li, Al, Rb, Cs, Sr, Ba, V, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Tl, Pb, In, Sn, Sb, Bi, W, Mo, U, Au, As, and L were determined by highresolution ICP-SF-MS (Element XR, Thermo Scientific) after 25-fold dilution and spiking with Y and Re for internal standardization using appropriate mass resolution settings.

Beschreibung: Hydrothermal chimneys were collected by a ROV in 2016 from the Kairei and Pelagia vent fields along the Indian Ridge. Major element compositions of the chimney samples were determined by a combination of ICP emission and mass spectrometry. For semi-quantitative analysis of sulfide mineral distribution polished sections of the chimneys were investigated by optical and scanning electron microscopy and electron microprobe analyses. The abundance of bacterial and archaeal taxa was determined by sequencing of the 16S rRNA gene by Illumina MiSeq.