Low-chlorinity springs sampled from ten sites on nine serpentinite mud volcanoes show systematic chemical gradients across the outer Mariana forearc that result from progressive devolatilization of the subducting Pacific plate. Sites range from 50 to 90 km from the trench axis corresponding to depths to the top of the plate of similar to 15-29 km. Dissolved sulfate, Na/Cl, K, Rb, Cs, and B in the springs all increase regularly with distance from the trench, leached from subducting sediment and altered basalt in response to increasing temperature at depth from similar to 80 to 350 degrees C. Sites nearer the trench have high Ca (up to 76 mmol/ kg) and Sr, low alkalinity, and pH 10.7, whereas sites farther from the trench have almost no Ca and Sr, alkalinity (some carbonate but mostly hydroxyl) as high as 69 meq/kg, and pH 12.5. Springs with high alkalinity also have high methane (> 44 mmol/kg) that feeds sulfate-reducing archaeal communities in the shallow subsurface and macrofauna at the seafloor. These distal springs form chimneys and crusts of CaCO3, whereas the proximal springs form chimneys of brucite. High alkalinity at the distal sites apparently results from carbonate dissolution at the top of the subducting plate; because serpentinization during ascent generates both high pH and H-2, the resulting dissolved carbonate is reduced to methane such that carbonate alkalinity is replaced by hydroxyl alkalinity: 4H(2) + HCO3- -> CH4 + 2H(2)O + OH-. This reaction can account for the much higher pH of the distal springs. Chlorinity of the springs varies from 234 to 546 mmol/kg and is related to latitude N-S rather than distance from the trench. Distal springs have otherwise similar compositions over this entire range of chlorinity, implying that chloride derives from depth rather than from mixing with seawater within the seamounts themselves. The range in chlorinity can readily be explained by serpentinization at reasonable water/rock mass ratios of 0.2-1.0 if 30-40% of the spring water originates as residual pore water in subducted sediment and basalt rather than as H2O+ of dehydration. The pH, alkalinity, and methane content of the springs increase abruptly, while Ca and Sr decrease, because carbonate dissolution joins dehydration as a major process at the top of the subducting plate at similar to 70 km from the trench, where metabasites recovered from the serpentinite mud indicate the transition from lawsonite blueschist facies to epidote blueschist facies also occurs. Replacement of lawsonite by epidote drastically depletes the solution in Ca and shifts the equilibrium toward massive dissolution of subducted carbonate. Fluxes of sulfate, C, Na, K, Rb, Cs, B, Ca, and Sr in the forearc springs represent only a few percent of the amounts subducted, consistent with continued supply at greater depth. (c) 2022 Published by Elsevier Ltd.

Abstract The chemical composition of formation waters within the upper basaltic crust were calculated or measured at 24 sites on the northwest portion of the Juan de Fuca (JDF) Plate using data from sediment pore waters, scientific boreholes, and seafloor springs. Formation waters differ in composition across this ridge‐flank region because of variations in water‐rock reactions and residence times, exchange rates with overlying sediment pore waters, and microbial processes along flow paths. We interpret spatial variations in the solute composition of formation waters to resolve areas that are geochemically distinct or similar, lateral trends that result from water transport, areas where water‐rock reactions in the deeper crust are apparent, and sites of seawater recharge and formation water discharge. We provide evidence for large‐scale lateral flow associated with two (mostly) buried basement ridges on ∼1.4 and ∼3.5 Ma seafloor, which are subparallel to the JDF spreading axis to the west. Between these two ridges, where the seafloor and the sediment‐basement interface are relatively flat, formation waters have undergone extensive exchange with overlying sediment pore waters, consistent with a long residence time. Basaltic outcrops provide sites of seawater recharge and hydrothermal discharge, sometimes through the same feature, highlighting the heterogeneous nature of hydrogeologic conditions and processes. This work provides a blueprint for future plate‐scale studies to assess, for example, geologic controls of crustal age, spreading rate, and sedimentation on subsurface hydrologic patterns.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Shaking out water's dusty origin Where did Earth's water come from? Lavas erupting on Baffin Island, Canada, tap a part of Earth's mantle isolated from convective mixing. Hallis et al. studied hydrogen isotopes in the lavas that help to “fingerprint” the origin of water from what could be a primordial reservoir. The isotope ratios for the Baffin Island basalt lavas suggest a pre-solar origin of water in Earth, probably delivered by adsorption onto dust grains. Science , this issue p. 795

Interstitial water and sediment samples of Integrated Ocean Drilling Program (IODP) Expedition 313 (New Jersey Shallow Shelf) were analyzed for chemical composition and stable isotope ratios. The analyses indicate a previously unknown complex geometry of the underlying fresh-water lens with alternating fresh-water-salt-water intervals divided by sharp boundaries in the upper part of the cores. Three fluid sources were identified: (1) meteoric fresh water, (2) marine seawater, and (3) brine. The pore-fluid stable isotope values define a mixing line with end members that have delta O-18 and delta H-2 values of -7.0 parts per thousand and -41 parts per thousand for fresh water, and -0.8 parts per thousand and -6 parts per thousand for salt water, respectively. This is similar to the modern mean value of New Jersey precipitation and today's New Jersey shelf water. For fresh water, this either indicates modern meteoric recharge via aquifers that crop out on mainland New Jersey or emplacement at a time with climatic and hydrologic conditions similar to modern. An origin from Pleistocene glacial meltwaters with depleted isotope values is not confirmed by stable isotope data of this study. Salt water also represents modern isotope values suggesting an infiltration along permeable, coarse-grained sandy units. The lower core parts are characterized by mixing with brine fluids that originate from evaporites in the deep underground. Stable carbon isotope analyses of gas and fluids prove the existence of methane formation from degradation of marine organic matter and CO2 reduction in the lower core parts below similar to 350 m below seafloor. Methane concentrations above 10000 ppm and delta C-13(methane) values of similar to-80 parts per thousand were measured. Methane formation is also indicated by authigenic carbonates with low delta C-13(carbonate) values. Although not reaching the surface at present conditions, the venting out of variable fluxes of methane from passive continental margins due to sea-level fluctuations is significant for the long-term carbon cycle. Authigenic carbonates indicate the precipitation from pore fluids with marine oxygen stable isotope ratios at low temperatures. The geochemical data and interpretations presented in this study supply the missing link between existing onshore and offshore data and may provide the basis for an integrated approach to construct a geochemical transect across the New Jersey shallow shelf.

During the Integrated Ocean Drilling Program (IODP) Expedition 331 at the Iheya North hydrothermal system in the Mid-Okinawa Trough by the D/V Chikyu, we conducted microbiological contamination tests of the drilling and coring operations. The contamination from the drilling mud fluids was assessed using both perfluorocarbon tracers (PFT) and fluorescent microsphere beads. PFT infiltration was detected from the periphery of almost all whole round cores (WRCs). By contrast, fluorescent microspheres were not detected in hydrothermally active core samples, possibly due to thermal decomposition of the microspheres under high-temperature conditions. Microbial contamination from drilling mud fluids to the core interior subsamples was further characterized by molecular-based evaluation. The microbial 16S rRNA gene phylotype compositions in the drilling mud fluids were mainly composed of sequences of Beta- and Gammaproteobacteria, and Bacteroidetes and not archaeal sequences. The phylotypes that displayed more than 97% similarity to the sequences obtained from the drilling mud fluids were defined as possible contaminants in this study and were detected as minor components of the bacterial phylotype compositions in 13 of 37 core samples. The degree of microbiological contamination was consistent with that determined by the PFT and/or microsphere assessments. This study suggests a constructive approach for evaluation and eliminating microbial contamination during riser-less drilling and coring operations by the D/V Chikyu.

On the New Jersey shelf (offshore North America), the presence of pore water fresher than seawater is known from a series of bore-holes completed during the 1970s and 1980s. To account for this fresh water, a first hypothesis involves possible present-day active dynamic connections with onshore aquifers, while a second involves meteoritic and/or sub-ice-sheet waters during periods of lowered sea level. Expedition 313 drilled three bore-holes on the middle shelf, offering a unique opportunity for the internal structure of the siliciclastic system to be accessed, at scales ranging from the depositional matrix to the continental margin. This enables the stratigraphic architecture to be correlated with the spatial distribution and salinity of saturating fluids. Expedition 313 revealed both very low salinities (<3 g/L) at depths exceeding 400 m below the seafloor and evidence for a multilayered reservoir organization, with fresh- and/or brackish-water intervals alternating vertically with salty intervals. In this study we present a revised distribution of the salinity beneath the middle shelf. Our observations suggest that the processes controlling salinity are strongly influenced by lithology, porosity, and permeability. Saltier pore waters generally occur in coarse-grained intervals and fresher pore waters occur in fine-grained intervals. The transition from fresher to saltier intervals is often marked by cemented horizons that probably act as permeability barriers. In the lowermost parts of two holes, the salinity varies independently of lithology, suggesting different mechanisms and/or sources of salinity. We present an interpretation of the sedimentary facies distribution, derived from core, logs, and seismic profile analyses, that is used to discuss the margin-scale two-dimensional reservoir geometry and permeability distribution. These proposed geometries are of primary importance when considering the possible pathways and emplacement mechanisms for the fresh and salty water below the New Jersey shelf.

H.D. Holland was one of the great geochemists of modern times. As a Professor at Princeton University for 22years and at Harvard for 33, he mentored 24 graduate students and 24 postdoctoral researchers. He was a member of the U.S. National Academy of Sciences and a President of the Geochemical Society. He co-authored 179 publications in 64years from 1949 to 2012, including four books. He edited one other book and, with Karl Turekian, co-edited the ten-volume Treatise on Geochemistry. His contributions to geochemistry were mainly in economic geology, hydrothermal processes, and especially the chemistry and evolution of the Earth's atmosphere and oceans, a topic to which he devoted nearly half of his publications. His most significant contributions documented changes in the composition of seawater through geologic time and the rise of oxygen in Earth's atmosphere. He pioneered the use of mineral sequences in marine evaporite deposits and fluid inclusions in evaporite minerals to determine the composition of ancient seawater. He collected extensive data on paleosols and used them to calibrate the oxygen content of the ancient atmosphere, documenting its rise in the Great Oxidation Event that peaked between 2.41 and 2.32Ga, and writing extensively about the causes of this event, one of the most significant in Earth history.

Integrated Ocean Drilling Program (IODP) Expedition 331 drilled into the Iheya North hydrothermal system in the middle Okinawa Trough in order to investigate active subseafloor microbial ecosystems and their physical and chemical settings. We drilled five sites during Expedition 331 using special guide bases at three holes for reentry, casing, and capping, including installation of a steel mesh platform with valve controls for postcruise sampling of fluids. At Site C0016, drilling at the base of the North Big Chimney (NBC) mound yielded low recovery, but core included the first Kuroko-type black ore ever recovered from the modern subseafloor. The other four sites yielded interbedded hemipelagic and strongly pumiceous volcaniclastic sediment, along with volcanogenic breccias that are variably hydrothermally altered and mineralized. At most sites, analyses of interstitial water and headspace gas yielded complex patterns with depth and lateral distance of only a few meters. Documented processes included formation of brines and vapor-rich fluids by phase separation and segregation, uptake of Mg and Na by alteration minerals in exchange for Ca, leaching of K at high temperature and uptake at low temperature, anhydrite precipitation, potential microbial oxidation of organic matter and anaerobic oxidation of methane utilizing sulfate, and methanogenesis. Shipboard analyses have found evidence for microbial activity in sediments within the upper 10–30 m below seafloor (mbsf) where temperatures were relatively low, but little evidence in the deeper hydrothermally altered zones and hydrothermal fluid regime. doi:10.2204/iodp.sd.13.03.2011