Description: The Aurora hydrothermal system, Arctic Ocean, hosts active submarine venting within an extensive field of relict mineral deposits. Here we show the site is associated with a neovolcanic mound located within the Gakkel Ridge rift-valley floor, but deep-tow camera and sidescan surveys reveal the site to be ≥100 m across—unusually large for a volcanically hosted vent on a slow-spreading ridge and more comparable to tectonically hosted systems that require large time-integrated heat-fluxes to form. The hydrothermal plume emanating from Aurora exhibits much higher dissolved CH〈jats:sub〉4〈/jats:sub〉/Mn values than typical basalt-hosted hydrothermal systems and, instead, closely resembles those of high-temperature ultramafic-influenced vents at slow-spreading ridges. We hypothesize that deep-penetrating fluid circulation may have sustained the prolonged venting evident at the Aurora hydrothermal field with a hydrothermal convection cell that can access ultramafic lithologies underlying anomalously thin ocean crust at this ultraslow spreading ridge setting. Our findings have implications for ultra-slow ridge cooling, global marine mineral distributions, and the diversity of geologic settings that can host abiotic organic synthesis - pertinent to the search for life beyond Earth.

Description: Microbial life can leave various traces (or biosignatures) in rocks, including biotic alteration textures, biominerals, enrichments of certain elements, organic molecules, or remnants of DNA. In basalt glass from the ocean floor, microbial alteration textures as well as chemical and isotopic biosignatures have been used to trace microbial activity. However, little is known about the relationship between the physical and chemical nature of the habitat and the prevalent types of biosignatures. Here, we report and compare strongly variable biosignatures from two different oceanic study sites. We analyzed rock samples for their textural biosignatures and associated organic molecules. The biosignatures from the 8 Ma North Pond Region, which represents young, well-oxygenated, and hydrologically active crust, are characterized by little textural diversity. The organic matter associated with those textures shows evidence for the occurrence of remnants of complex biomolecules like proteins. The biosignatures from the older Louisville Seamount Trail (~70 Ma), for which archaeal origin is suggested, are much more texturally diverse and the associated organic molecules are also more degraded. We hypothesize that microbial communities change significantly during crustal evolution and aging, and suggest that microbes that are associated with older and severely altered crust are not responsible for the biotic alteration textures commonly found in subseafloor basalt glass. We suggest that biotic alteration textures are related to microbially-catalyzed oxidation of Fe2+, Mn2+, and S compounds and form predominantly within the first ~10 Ma of crustal evolution. In older crust with less glass and decreased permeability, other metabolic pathways may dominate which only leave molecular biosignatures. We propose that diverse biosignatures in oceanic crust may form during different stages of crustal evolution.

Description: This expedition was conducted in the North Eastern Lau Basin, Southwest Pacific. The program aimed at improving our understanding of the igneous, hydrothermal, and tectonic processes that occur during island arc and back-arc formation. Cruise SO263 operated in June 2018. Raw data of physical oceanography was obtained during research cruise SO263 on RV SONNE. Data of vertical CTD casts was binned to 1 meter intervals and is reported with shortend header. Data of tow-yo CTD casts was binned to 1 second intervals and is reported with shortend header.

Description: This contribution comprises true-3D volume datasets ("Digital drill cores"), acquired by a X-ray Computed Microtomography (μ-CT) survey on reference drill core material recovered from Hole 5059-1-D (354 m length to a depth of 290 m, inclined 35° from vertical) on Surtsey volcano (Vestmannaeyjar archipelago, Iceland), drilled by the SUSTAIN drilling project (Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative Concretes, see Jackson et al. 2019 for details). Thirteen reference samples (see Weisenberger et al. 2019 for preparational details) (ranging from 220.35 to 344.47 inclined depth / 180.47 to 282.12 m vertical depth, sampling roughly every 10 m) were scanned as quarter cores. The X-ray μ-CT scans were performed using the ProCon CT-ALPHA system of the Petrology of the Ocean Crust research group at the University of Bremen, Germany. This μ-CT survey has been conducted as part of the DFG SPP 1006 grant "Rates and Processes of Tephra Alteration on Surtsey: Observations and Experiments". In order to avoid imaging of void space due to the quarter core shape, and to achieve a higher magnification, the scans were performed as "out-of-area"-scans (see, e. g. Kahl et al., 2016), restricting observations to the inner regions of the samples. The reconstructed image material is of cylindrical shape with a resolution of ca. 7.5 μm/voxel, and represents virtual drill cores of ca. 15 mm diameter and 15 mm height. The μ-CT-derived image volumes comprise the true 3-D spatial arrangement of fabric compounds in the rock. In the reconstructed 16-bit greyscale volume data, areas of highly attenuating phases (e.g. magnetite, olivine) are encoded in light grey values, whereas areas of low X-ray absorption are color-coded in dark grey (e.g. clays) or black (e.g. voids, cracks). In order to facilitate straightforward access to the digital drill core image material, the volume data is provided as a zipped stack of tif images. In addition, each digital drill core is characterized by three types of visualization: (i) shaded and classical texture-based volume rendering (volren), (ii) maximum intensity projection (volren-MIP): visualization of the highest or lowest intensity in a data volume along the current line of sight, and (iii) three perpendicular virtual cutting planes (3-slices). As an added value to the non-destructive visualization procedure, the reconstructed X-ray micro-CT scans of the studied reference drill core material provide volume reconstructions which can serve as digitypes that may be studied as digital facsimile without the necessity of consulting / modifying / destructive interactions of the actual type specimens (e. g. by physical permeability tests). These image data can be used for quantitative 3D image analysis, e. g. to derive empirical relations between porosity, the extent of replacement of primary phases, and the distribution of secondary phases (and many more).

Description: This expedition was conducted in the North Eastern Lau Basin, Southwest Pacific. The program aimed at improving our understanding of the igneous, hydrothermal, and tectonic processes that occur during island arc and back-arc formation. Cruise SO263 operated in June 2018. Raw data of physical oceanography was obtained during research cruise SO263 on RV SONNE. Data of vertical CTD casts was binned to 1 meter intervals and is reported with shortend header. Data of tow-yo CTD casts was binned to 1 second intervals and is reported with shortend header.