The Effect of Arc Proximity on Hydrothermal Activity Along Spreading Centers: New Evidence From the Mariana Back Arc (12.7°N-18.3°N)

Back-arc spreading centers (BASCs) form a distinct class of ocean spreading ridges distinguished by steep along-axis gradients in spreading rate and by additional magma supplied through subduction. These characteristics can affect the population and distribution of hydrothermal activity on BASCs compared to mid-ocean ridges (MORs). To investigate this hypothesis, we comprehensively explored 600 km of the southern half of the Mariana BASC. We used water column mapping and seafloor imaging to identify 19 active vent sites, an increase of 13 over the current listing in the InterRidge Database (IRDB), on the bathymetric highs of 7 of the 11 segments. We identified both high and low (i.e., characterized by a weak or negligible particle plume) temperature discharge occurring on segment types spanning dominantly magmatic to dominantly tectonic. Active sites are concentrated on the two southernmost segments, where distance to the adjacent arc is shortest (48 mm/yr), and tectonic extension is pervasive. Re-examination of hydrothermal data from other BASCs supports the generalization that hydrothermal site density increases on segments <90 km from an adjacent arc. Although exploration quality varies greatly among BASCs, present data suggest that, for a given spreading rate, the mean spatial density of hydrothermal activity varies little between MORs and BASCs. The present global database, however, may be misleading. On both BASCs and MORs, the spatial density of hydrothermal sites mapped by high-quality water-column surveys is 2–7 times greater than predicted by the existing IRDB trend of site density versus spreading rate

Tectonic and magmatic controls on hydrothermal activity in the Woodlark Basin

The Woodlark Basin is one of the rare places on earth where the transition from continental breakup to seafloor spreading can be observed. The potential juxtaposition of continental rocks, a large magmatic heat source, crustal-scale faulting, and hydrothermal circulation has made the Woodlark Basin a prime target for seafloor mineral exploration. However, over the past 20 years, only two locations of active hydrothermalism had been found. In 2009 we surveyed 435 km of the spreading axis for the presence of hydrothermal plumes. Only one additional plume was found, bringing the total number of plumes known over 520 km of ridge axis to only 3, much less than at ridges with similar spreading rates globally. Particularly the western half of the basin (280 km of axis) is apparently devoid of high temperature plumes despite having thick crust and a presumably high magmatic budget. This paucity of hydrothermal activity may be related to the peculiar tectonic setting at Woodlark, where repeated ridge jumps and a re-location of the rotation pole both lead to axial magmatism being more widely distributed than at many other, more mature and stable mid-ocean ridges. These factors could inhibit the development of both a stable magmatic heat source and the deeply penetrating faults needed to create long-lived hydrothermal systems. We conclude that large seafloor massive sulfide deposits, potential targets for seafloor mineral exploration, will probably not be present along the spreading axis of the Woodlark Basin, especially in its younger, western portion

Oregon Subduction Zone: Venting, Fauna, and Carbonates

Transects of the submersible Alvin across rock outcrops in the Oregon subduction zone have furnished information on the structural and stratigraphic framework of this accretionary complex. Communities of clams and tube worms, and authigenic carbonate mineral precipitates, are associated with venting sites of cool fluids located on a fault-bend anticline at a water depth of 2036 meters. The distribution of animals and carbonates suggests up-dip migration of fluids from both shallow and deep sources along permeable strata or fault zones within these clastic deposits. Methane is enriched in the water column over one vent site, and carbonate minerals and animal tissues are highly enriched in carbon-12. The animals use methane as an energy and food source in symbiosis with microorganisms. Oxidized methane is also the carbon source for the authigenic carbonates that cement the sediments of the accretionary complex. The animal communities and carbonates observed in the Oregon subduction zone occur in strata as old as 2.0 million years and provide criteria for identifying other localities where modern and ancient accreted deposits have vented methane, hydrocarbons, and other nutrient-bearing fluids

Submarine Magmatic-Hydrothermal Systems at the Monowai Volcanic Centre, Kermadec Arc

Authors listed on this Accepted Manuscript vary slightly from those listed on the Version of Record. Harold L. Gibson is an additional author on the published version.The Monowai volcanic centre (MVC) is located at the mid-point along the ~2530 km long Tonga-Kermadec arc system, is probably the most hydrothermally active submarine volcanic system globally. The MVC is comprised of a large elongate caldera (Monowai caldera, 7.9 x 5.7 km; 35 km²; depth to caldera floor is 1590 m), which has formed within an older caldera some 84 km² in area. To the south of the nested caldera system is a large composite volcano, Monowai cone, which rises to within ~ 100 m of the sea surface and has been volcanically active for at least several decades. Despite the large size, mafic volcanic rocks dominate the MVC; basalts are the most common rock type recovered; less common are basaltic andesites and andesites. Hydrothermal plume mapping during the 2004 NZAPLUME III cruise showed at least three major hydrothermal systems associated with the caldera and cone. Monowai cone has hydrothermal venting from the summit. This summit plume is gas-rich and acidic; plume samples show a pH shift of -2.00 pH units, δ³He up to 358 ‰, H₂S concentrations up to 32 μM and CH₄ concentrations up to 900 nM. The summit plume is also metal-rich with elevated total dissolvable Fe (TDFe up to 4200 nM), TDMn (up to 412 nM), and TDFe/TDMn (up to 20.4). Monowai caldera has a major hydrothermal vent system with plumes extending from ~ 1000 to 1400 m depth. The caldera plume has lower values for TDFe, although ranges to higher TDMn concentrations than the summit plume, and is relatively gas-poor (no H₂S detected, pH shift of -0.06 pH units, CH₄ concentrations up to 26 nM). Hydrothermal vents have been observed associated with prominent basaltic andesite ridges (Mussel Ridge) proximal to the southwest wall of the caldera (1025 – 1171 m depth). However, the composition of the hydrothermal plumes in the caldera are different to the vents, indicating that the source of the caldera plumes is at greater depth and is more metal-rich and therefore likely higher temperature. Minor plumes detected as light scattering anomalies down the northern flank of Monowai caldera most likely represent resuspension of volcanic debris. Particulate samples from both the cone sites and the caldera site are enriched in Al, Ti, Ca, Mg, Si, and S, with the cone summit plume especially enriched in K, As, W and Cu, Pb, Zn. The elevated Ti and Al suggest acidic water-rock reactions and intense high-sulfidation alteration of the host volcanic rocks. Observations from submersible dives with Pisces V in 2005 and the remotely operated vehicle ROPOS in 2007 of Mussel Ridge indicate numerous low temperature vents (< 60°C), with a large biomass of vent-associated fauna, in particular large accumulations of the mussel Bathymodiolus sp. and the tubeworm Lamellibrachia sp. We interpret the Monowai volcanic centre as possessing a robust high-sulfidation magmatic-hydrothermal system, with significant differences in the style and composition of venting at the cone and caldera sites. At Monowai cone, the large shifts in pH, elevated TDFe and TDFe/TDMn, and H₂S-, CH₄- and ³He-rich nature of the plume fluids coupled with elevated Ti, P, V, S and Al in the particulates indicates significant magmatic volatile ± metal contributions to the hydrothermal system and aggressive acidic water-rock interaction. By contrast, Monowai caldera has low TDFe/TDMn in hydrothermal plumes; however, end-member vent fluid compositions, combined with presence of alunite, sulfide minerals and native sulfur in samples from Mussel Ridge suggest recent acid volatile-rich venting and active Fe-sulfide formation in the subsurface, and the potential for the presence of significant SMS mineralization

EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial

More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University Münster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369

ALK-positive histiocytosis: a new clinicopathologic spectrum highlighting neurologic involvement and responses to ALK inhibition

ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in three infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALKrearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (seven and twelve from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated-ERK, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, while CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, ten with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis, and provides guidance for the clinical management of this emerging histiocytic entity.Molecular tumour pathology - and tumour genetic