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The recently discovered Fåvne vent field, located at 3,040 m depth on the slow‐spreading Mohns mid‐ocean ridge between Greenland and Norway, is a high‐temperature (≥250°C) vent field that is characterized by Fe oxyhydroxide‐rich and S‐poor chimneys and mounds. The vent field is located on both the hanging wall and footwall of a normal fault with a ∼1.5 km throw that forms the western edge of the ∼20 km wide ridge axial valley. Data collected during exploration of the site using a remotely operated vehicle as well as mineralogical and geochemical analyses of rock samples and sediments are used to characterize the geological setting of the vent field and composition of the hydrothermal deposits. The chimney walls are highly porous and lack defined chalcopyrite lined conduits, typical of high‐temperature chimneys. Overall, abundant Fe oxyhydroxide precipitation at high‐temperature vents at Fåvne reflects an excess of Fe over reduced S in the fluid, leading to precipitation of Fe oxide and oxyhydroxide minerals at high to moderate temperature vents (>100°C), and as microbially mediated and abiotic precipitation of Fe oxyhydroxide minerals at low‐temperature diffuse vents (<100°C). The mounds and chimneys exhibit low base metal and reduced S concentrations relative to globally averaged seafloor deposits and suggest subseafloor mixing of hydrothermal fluid with seawater, causing metal sulfide precipitation. Cobalt enrichment at Fåvne may reflect a subsurface influence of an ultramafic substrate on circulating fluids, although ultramafic rocks are absent on the seafloor and no other elements typical of ultramafic deposits are present. Plain Language Summary: Seafloor hydrothermal deposits are mineral deposits formed from seawater penetrating the oceanic crust and becoming enriched in metals by leaching the surrounding rocks as the temperature rises close to a heat source. Once heated, the fluid rises back to the seafloor where it comes into contact with cold seawater and the metals precipitate, forming chimneys and mounds. The minerals and metal concentrations record temperatures of formation and environments, and can help us understand the processes associated with plate tectonics and the formation of ore deposits. Using underwater vehicles, we collected rocks and sediments from the Fåvne vent field and measured the temperature of the chimneys, mounds, and surrounding seafloor to understand how these deposits form on the seafloor. The Fåvne vent field differs from other vent fields because it is enriched in iron‐rich‐minerals and depleted in sulfur‐rich‐minerals. The dominance of iron‐rich minerals and the abundance of fractures in the seafloor at the vent field suggest that the hydrothermal fluid is cooled by seawater percolating along the fractures, accumulating these metals in the subsurface instead of at the seafloor. This process is important for understanding the current land‐based mineral deposits being mined today and for the exploration of seafloor mineral deposits. Key Points: The Fåvne vent field consists of chimneys and mounds composed of Fe oxyhydroxide minerals with minor sulfide mineralsVenting of hot fluids with temperatures up to 267°C is dominantly diffuse, sustaining significant microbial communitiesLow base metal concentrations of the Fåvne deposits suggest subsurface seawater mixing and mineral precipitation [ABSTRACT FROM AUTHOR]

Introduction: Although, there is an increasing focus on inactive or extinct seafloor massive sulfide (SMS) deposits driven by the possibility of marine mining, only few studies have been devoted to them so far. The Trans-Atlantic Geotraverse (TAG) hydrothermal field is probably one of the best-studied hydrothermal systems even if the relict SMS deposits known since the mid-1980s have not been thoroughly explored. Objectives: The main objective of this study was to describe the characteristics of these so-called inactive sites. Methods: During four different expeditions, we acquired high-resolution acoustic data and performed numerous human occupied vehicle (HOV) dive operations including extensive rock sampling and in-situ temperature measurements. Results and Discussion: We discovered thirteen new hydrothermal mounds including six large (i.e. > 5,000 m2) deposits making the TAG hydrothermal field one of the largest accumulation of hydrothermal materials (21.1 Mt) known on the seafloor. However, copper and zinc grades of the largest SMS deposits remain low (i.e. < 1.4 wt%) even compared to on-land volcanogenic massive sulfide deposits. Additionally, eight areas of diffuse hydrothermal fluid flow were identified challenging the presumed inactivity of these SMS deposits and, for the first time, emphasizing the importance of low temperature (LT) hydrothermal activity in whole the TAG field. Inactive and weakly active SMS deposits exhibit a large diversity of surface mineralization (e.g. sulfides, Fe-Mn mineralization, jasper) illustrating complexity of hydrothermal activities but also different ageing history. Several mounds no longer have visible sulfide chimneys and are covered by a widespread layer of manganese and iron oxyhydroxides attesting the longevity of diffuse fluid flow at specific locations even long after last high-temperature (HT) hydrothermal activity has ceased. This contrasts with SMS deposits that are devoid of extensive LT precipitates but characterized by standing or topped sulfide chimney indicating a relatively abrupt cessation of HT hydrothermal activity. Conclusion: Together these results allow us to propose evolution models to explain the diversity of active, weakly active and inactive SMS deposits in the TAG hydrothermal field. [ABSTRACT FROM AUTHOR]

The blood-brain barrier (BBB) is located at the interface between the vascular system and the brain parenchyma, and is responsible for communication with systemic circulation and peripheral tissues. During life, the BBB can be subjected to a wide range of perturbations or stresses that may be endogenous or exogenous, pathological or therapeutic, or intended or unintended. The risk factors for many diseases of the brain are multifactorial and involve perturbations that may occur simultaneously (e.g., two-hit model for Alzheimer's disease) and result in different outcomes. Therefore, it is important to understand the influence of individual perturbations on BBB function in isolation. Here we review the effects of eight perturbations: mechanical forces, temperature, electromagnetic radiation, hypoxia, endogenous factors, exogenous factors, chemical factors, and pathogens. While some perturbations may result in acute or chronic BBB disruption, many are also exploited for diagnostic or therapeutic purposes. The resultant outcome on BBB function depends on the dose (or magnitude) and duration of the perturbation. Homeostasis may be restored by self-repair, for example, via processes such as proliferation of affected cells or angiogenesis to create new vasculature. Transient or sustained BBB dysfunction may result in acute or pathological symptoms, for example, microhemorrhages or hypoperfusion. In more extreme cases, perturbations may lead to cytotoxicity and cell death, for example, through exposure to cytotoxic plaques. [ABSTRACT FROM AUTHOR]

The blood-brain barrier (BBB) is located at the interface between the vascular system and the brain parenchyma, and is responsible for communication with systemic circulation and peripheral tissues. During life, the BBB can be subjected to a wide range of perturbations or stresses that may be endogenous or exogenous, pathological or therapeutic, or intended or unintended. The risk factors for many diseases of the brain are multifactorial and involve perturbations that may occur simultaneously (e.g., two-hit model for Alzheimer’s disease) and result in different outcomes. Therefore, it is important to understand the influence of individual perturbations on BBB function in isolation. Here we review the effects of eight perturbations: mechanical forces, temperature, electromagnetic radiation, hypoxia, endogenous factors, exogenous factors, chemical factors, and pathogens. While some perturbations may result in acute or chronic BBB disruption, many are also exploited for diagnostic or therapeutic purposes. The resultant outcome on BBB function depends on the dose (or magnitude) and duration of the perturbation. Homeostasis may be restored by self-repair, for example, via processes such as proliferation of affected cells or angiogenesis to create new vasculature. Transient or sustained BBB dysfunction may result in acute or pathological symptoms, for example, microhemorrhages or hypoperfusion. In more extreme cases, perturbations may lead to cytotoxicity and cell death, for example, through exposure to cytotoxic plaques. [ABSTRACT FROM AUTHOR]