Trollveggen Vent Field: Mineralogy and geochemistry of chimneys and deposits, and evidence of hydrothermal activity in far‐field cores

The Jan Mayen vent fields were discovered in the Mohns Ridge during an expedition with the Norwegian research vessel "G.O. Sars" in July 2005. They comprise two main active areas: (1) Soria Moria and (2) Gallionella Garden & Trollveggen. The Trollveggen vent field is located at depths of 700-750 m. Venting takes place mainly through white smoker chimneys with fluid temperatures reaching up to 260-270°C. Here we present mineralogical and geochemical data from vent chimneys and near vent deposits collected at the Trollveggen vent field with an ROV. Cross-sections of chimneys present evident mineralogical zonation, showing acicular barite crystals in the outer parts and sulphide enrichments in the interior (Sph + Cpy +/- Py - Po). The near vent deposits are mainly formed by vent fragments, showing a mineral assemblage similar to that of chimneys. Total geochemical analyses both from vents and near vent deposits showed higher concentrations in Ba, Co, Zn, Fe, but also slight enrichments in Au and Ag. REE patterns from chimneys and near vent deposits suggest that REE have been deposited from hot (> 250ºC) hydrothermal fluids. Sediment cores collected in the vicinity of the Jan Mayen hydrothermal field suggests that hydrothermal activity is not restricted to the known vent areas. Two of the collected gravity cores registered geochemical signatures related with hydrothermal activity, showing metal enrichment and a slightly positive Eu anomaly

Geological mineral exploration tools in the Arctic near Loki's Castle, 74 degrees N (South Knipovich Ridge)

Discovery of the Loki’s Castle hydrothermal vent field (2008) was a great surprise, given its size and vigour of hydrothermal discharge. Several characteristics, including the fauna, separate it from either Atlantic or Pacific-type hydrothermal sites. Concerning size and grades, data are insufficient, but it appears so far that Loki’s Castle is a very large system, about 200 m in diameter. The metal contents (in discreet samples, this study) are quite interesting, with Zn up to 5.4wt% and Cu estimated at several percent in some samples. Ag attains 25 ppm and Au 1.3 ppm. The tonnage of Loki’s Castle may be, tentatively, in the range of 1-5 million tones. Loki’s Castle is certainly worthy of study from a mineral resource standpoint. Very active hydrothermal discharge sites such as Loki’s Castle raise the issue of the size gap between modern and ancient vms deposits (preserved in the geological record), with the latter often much larger than the former. For the land-based mining industry, a “large” vms deposit amounts to a least 25 Mt. The larger examples (supergiant deposits) exceed 150 Mt (Galley et al, 2007). We believe that this gap (by a factor of at least 20) is largely a consequence of incomplete knowledge of the present day systems. Too little attention has been given so far to deposits forming within the upper few metres of the oceanic crust, within sediments or other poorly consolidated rocks (e.g. volcaniclastics). We are studying sediments in detail to find clues of hydrothermal activity through them, and to test the possibility of some influence from within-crust microbial activity (deep biosphere)

Mineralogy and Geochemistry in the Arctic crust near Loki's Castle, 74 degrees N (South Knipovich Ridge).

The Loki’s Castle hydrothermal vent field is composed of several active, over 10 m tall chimneys, producing up to 320ºC fluid. The main sulfides in chimneys are sphalerite, pyrite and pyrrhothite, with generally lesser chalcopyrite. Alteration products collected adjacent to chimneys contain much anhydrite, gypsum and talc. Quartz, anhydrite, gypsum and barite are also present, and locally abundant. Rhythmically zoned sphalerites suggest pulsating hydrothermal activity. Here we report the preliminary results of a detailed study (in progress) of sequential extraction and analyses of metals from sediments in the vicinity of Loki’s Castle, in order to detect correlations with microbial populations and/or subseafloor mineralized intervals. The results expose numerous anomalies. Some consist of isolated high values of metals such as Cu or Zn, whereas others contain clusters of high values of several metals in the same interval. The former correspond to bedded fallout, from nearby hydrothermal activity (in a not too distant past), but the latter may correspond to intersections of hydrothermal plumes ascending through (variably) porous sediment. This may an effect on the microbial population (deep biosphere)

Loki’s Castle Arctic Vents and Host Sediments: Mineralogy and Geochemistry.

Loki’s Castle hydrothermal field is located in the Arctic Ocean, in the bend between the South Knipovich Ridge and the Mohns Ridge, at ≈74ºN. The results presented here are from samples collected with the ROV Bathysaurus XL and consist of chimney fragments and seafloor sediments from the vicinities. The studies consist of a petrographic description, X- ray diffraction analysis, chemical analyses under the electron microprobe and bulk chemical analyses of major and trace elements. The sulphide assemblage most commonly present in the samples consists of sphalerite, pyrite and pyrrhotite, with minor amounts of chalcopyrite. Sulphide-poor selected samples collected at the base of chimneys are mostly composed of anhydrite, gypsum and talc. Association of quartz, anhydrite, gypsum and barite were also found in some of the sediment samples. The observed sulphide assemblege is consistent with the temperature of 320ºC measured in Loki’s Castle vents. The interior of chimneys are enriched in Zn, Cu and Fe while the exterior are enriched in Ba and Sr. REE patterns for the recovered seafloor sediments show a perfect match with NASC. The sulphide-poor samples collected at the base of the chimneys denotes sea water interaction with the hydrothermal fluid and consequent decrease in the temperature, precipitating sulphates

Testing the preservation potential of early diagenetic dolomites as geochemical archives

Early marine diagenetic dolomite is a rather thermodynamically‐stable carbonate phase and has potential to act as an archive of marine porewater properties. However, the variety of early to late diagenetic dolomite phases that can coexist within a single sample can result in extensive complexity. Here, the archive potential of early marine dolomites exposed to extreme post‐depositional processes is tested using various types of analyses, including: petrography, fluid inclusion data, stable δ13C and δ18O isotopes, 87Sr/86Sr ratios, and U‐Pb age dating of various dolomite phases. In this example, a Triassic carbonate platform was dissected and overprinted (diagenetic temperatures of 50 to 430°C) in a strike‐slip zone in Southern Spain. Eight episodes of dolomitization, a dolostone cataclasite and late stage meteoric/vadose cementation were recognized. The following processes were found to be diagenetically relevant: (i) protolith deposition and fabric‐preservation, and marine dolomitization of precursor aragonite and calcite during the Middle–Late Triassic; (ii) intermediate burial and formation of zebra saddle dolomite and precipitation of various dolomite cements in a Proto‐Atlantic opening stress regime (T ca 250°C) during the Early–Middle Jurassic; (iii) dolomite cement precipitation during early Alpine tectonism, rapid burial to ca 15 km, and high‐grade anchizone overprint during Alpine tectonic evolution in the Early Eocene to Early Miocene; (iv) brecciation of dolostones to cataclasite during the onset of the Carboneras Fault Zone activity during the Middle Miocene; and (v) late‐stage regression and subsequent meteoric overprint. Data shown here document that, under favourable conditions, early diagenetic marine dolomites and their archive data may resist petrographic and geochemical resetting over time intervals of 108 or more years. Evidence for this preservation includes preserved Late Triassic seawater δ13CDIC values and primary fluid inclusion data. Data also indicate that oversimplified statements based on bulk data from other petrographically‐complex dolomite archives must be considered with caution

Smart On-board Processing for Next Generation SAR Payloads

Smart on-board processing for Earth observation systems (SOPHOS) is a 3-year Horizon Europe project. SOPHOS will design and implement enabling technology for high-end data products produced on board spacecraft via the implementation of more power efficient high-performance space processing chains for various Low-Earth Orbit (LEO) missions, with a focus on Synthetic Aperture Radar (SAR), which is one of the most data intensive space applications currently used. This paper describes the adopted technology and the selected SAR use cases