Textural evidence for recent co-seismic circulation of fluids in the Nojima fault zone, Awaji island, Japan

The Hirabayashi borehole (Awaji Island, Japan) was drilled by the Geological Survey of Japan (GSJ) 1 year after the Hyogo-ken Nanbu (Kobe) earthquake (1995, M_JMA=7.2). This has enabled scientists to study the complete sequence of deformation across the active Nojima fault, from undeformed granodiorite to the fault core. In the fault core, different types of gouge and fractures have been observed and can be interpreted in terms of a complex history of faulting and fluid circulation. Above the fault core and within the hanging wall, compacted cataclasites and gouge are cut by fractures which show high apparent porosity and are filled by 5–50 μm euhedral and zoned siderite and ankerite crystals. These carbonate-filled fractures have been observed within a 5.5-m-wide zone above the fault, but are especially abundant in the vicinity (1 m) of the fault. The log-normal crystal size distributions of the siderite and ankerite suggest that they originated by decaying-rate nucleation accompanied by surface-controlled growth in a fluid saturated with respect to these carbonates. These carbonate-filled fractures are interpreted as the result of co-seismic hydraulic fracturing and upward circulation of fluids in the hanging wall of the fault, with the fast nucleation of carbonates attributed to a sudden fluid or CO₂ partial pressure drop due to fracturing. The fractures cut almost all visible structures at a thin section scale, although in some places, the original idiomorphic shape of carbonates is modified by a pressure-solution mechanism or the carbonate-filled fractures are cut and brecciated by very thin gouge zones; these features are attributed to low and high strain-rate mechanisms, respectively. The composition of the present-day groundwater is at near equilibrium or slightly oversaturated with respect to the siderite, calcite, dolomite and rhodochrosite. Taken together, this suggests that these fractures formed very late in the evolution of the fault zone, and may be induced by co-seismic hydraulic fracturing and circulation of a fluid with a similar composition to the present-day groundwater. They are therefore potentially related to recent earthquake activity (<1.2 Ma) on the Nojima fault.     

The behavior of shape preferred orientations in metamorphic rocks: amphiboles and jadeites from the Monte Mucrone area (Sesia-Lanzo zone, Italian Western Alps)

In the eclogitic micaschists of the Monte Mucrone area (Sesia-Lanzo zone, Italian Western Alps), we have measured in detail the eclogitic lineation at several outcrops. We present observations at the markers scale, this scale allowing the whole range of progressive deformations to be described. Populations of glaucophanes and jadeites show different statistical features which must be, at least for a part, produced by the distinct mechanical behavior for these markers during the alpine history. The glaucophanes show a positive correlation between the intensity of preferred orientation and their aspect ratio, due to a mainly rigid behavior. The observed differences in shape and orientation of jadeites also show different behavior, related to different retromorphic overprints. We briefly discuss the implications of these observations on the significance of metamorphic lineations.     

Pyroxene-pyrolite and plagioclase-pyrolite in inclusions,with Norites,in an Alkali Basalt (Causses,France)

In three representative nodules contained in an alkali-olivine basalt, a succession of cumulate cycles has been noted: $$\begin{gathered} 1) olivine - orthopyroxene + \varepsilon (Cpx + Sp.); \hfill \\ 2) ortho - clinopyroxene + \varepsilon (Ol. + Sp. + Plag); \hfill \\ 3) ortho - clinopyroxene + Plag + \varepsilon (Ol. + Sp.). \hfill \\ \end{gathered} $$ The element distribution in the minerals enables us to say that these mafic and ultramafic nodules formed near the stability line of plagioclase at about 10 kb. These cumulates, which belong to a comagmatic series, from picrites to basalts, were formed in the upper mantle. They are associated with norites — Plag. + Opr. + Cpx. +≡ (Il. + Bi) — belonging to the same series, but crystallized in the deep part of the crust. On the other hand, these norites could be xenoliths taken away from an infragranitic basement of granulite facies.     

顽辉石陨石中A,B矿的微量元素化学意义

运用电子探针和中子活化分析方法测定了清镇和Ｂｕｓｔｅｅ顽辉石无球粒陨石中含铬硫化物相的组成和微量元素含量。正如早期的报告结果，电子探针分析结果不足１００％，表明有相当含量的轻元素（ｚ〈１０）存在。     

A novel method to infer historical DDT use on Cape Cod,Massachusetts (USA), based on ΣDDT degradation and <Superscript>210</Superscript>Pb dating in lake sediment cores

Glacier shrinkage and melting of snow patches caused by the current phase of warming is having a profound impact on lake ecosystems located in glacierized environments at high altitude and/or latitude because it alters the hydrology and the physico-chemistry of the river discharges and catchment runoff. These changes, in turn, have a major impact on the biota of these lakes. In this study, we combined geochemical and diatom analyses of a sediment core retrieved from Lake Kanas (N.W. China) to assess how climate change has affected this ecosystem over the past ~ 100 years. Our results show that the aquatic ecosystem of Lake Kanas was sensitive to changes in the regional climate over that period of time. The lake has been affected by change in hydrology (e.g. influx of glacier meltwater, variations in precipitation) and change in hydrodynamics (water column stability). The variations in abundance and composition of the diatom assemblages observed in the sedimentary record have been subtle and are complex to interpret. The principal changes in the diatom community were: (1) a rise in diatom accumulation rates starting in the AD 1970s that is coeval with changes observed in temperate lakes of the Northern Hemisphere and (2) an increase in species diversity and assemblage turnover and a faster rate-of-change since ~ AD 2000. The diatom community is expected to change further with the projected melting of the Kanas glacier throughout the twenty-first century.     

Improving hydrogeological understanding through well-test interpretation by diagnostic plot and modelling: a case study in an alluvial aquifer in France

Hydrogeology Journal - The study of groundwater resources using pumping test data is usually carried out with the Theis solution, which enables the hydraulic parameters of porous aquifers such as...     

Geochemical evaluation of mineralization potential of the Somie-Ntem area within the Tikar plain,Cameroon: implication on petrogenesis

Acta Geochimica - Somie-Ntem area of the Tikar plain belongs to the western Cameroon Domain. The lithology of the plain has been characterized, and the mineral potential is still unclear despite...     

The hesitant emergence of maximum sustainable yield (MSY) in fisheries policies in Europe

The dismal record of fisheries management worldwide is often blamed on managers' and scientists' bigoted pursuit of the flawed Maximum Sustainable Yield (MSY) objective. This paper aims at clarifying that MSY has never been a key element in the EU Common Fisheries Policy (CFP), and has not been for several decades the basis of scientific advice provided in support of that policy. The recent emergence of MSY in debates about the CFP might be a rhetoric response to international pressure rather than a willing change in policy. The major danger of assigning the notorious failure of the CFP to a wrong culprit, MSY, is to distract research efforts away from investigating the real causes that likely lay in the institutional set-up. Many objections against the reference points associated with MSY, as targets or limits, are well-founded but controversies among experts, when left unbridled, just provide the opportune climate for politicians to delay actions in the direction of reduced fishing impacts on fish stocks and marine ecosystems.     

Pre-1991 sulfur transfer between mafic injections and dacite magma in the Mt. Pinatubo reservoir

Before the 1991–1992 activity, a large andesite lava dome belonging to the penultimate Pinatubo eruptive period (Buag ∼ 500 BP) formed the volcano summit. Buag porphyritic andesite contains abundant amphibole-bearing microgranular enclaves of basaltic–andesite composition. Buag enclaves have lower K₂O and incompatible trace element (LREE, U, Th) contents than mafic pulses injected in the Pinatubo reservoir during the 1991–1992 eruptive cycle. This study shows that Buag andesite formed by mingling of a hot, water-poor and reduced mafic magma with cold, hydrous and oxidized dacite. Depending on their size, enclaves experienced variable re-equilibration during mixing/mingling. Re-equilibration resulted in hydration, oxidation and transfer of mobile elements (LILE, Cu) from the dacite to the mafic melts and prompted massive amphibole crystallization. In Buag enclaves, S-bearing phases (sulfides, apatite) and melt inclusions in amphibole and plagioclase record the evolution of sulfur partition among melt, crystal and fluid phases during magma cooling and oxidation. At high temperature, sulfur is partitioned between andesitic melt and sulfides (Ni-pyrrhotite). Magma cooling, oxidation and hydration resulted in exsolution of a S–Cl–H₂O vapor phase at the S-solubility minimum near the sulfide–sulfate redox boundary. Primary magmatic sulfide (pyrrhotite) and xenocrystic sulfide grains (pyrite), recycled together with olivines and pyroxenes from old mafic intrusives, were replaced by Cu-rich phases (chalcopyrite, cubanite) and, partially, by Ba–Sr sulfate. Sulfides degassed and transformed into residual spongy magnetite in response to fS₂ drop during final magma ascent and decompression. Our research suggests that a complete evaluation of the sulfur budget at Pinatubo must take into account the en route S assimilation from the country rocks. Moreover, this study shows that the efficiency of sulfur transfer between mafic recharges and injected magmas is controlled by the extent and rate of mingling, hydrous flushing and melt oxidation. Vigorous mixing/mingling and transformation of the magmatic recharge into a spray of small enclaves is required in order to efficiently strip their primary S-content that otherwise remains locked in the sulfides. Hydrous flushing increases the magma oxidation state of the recharges and modifies their primary volatile concentrations that cannot be recovered by the study of late-formed mineral phases and melt inclusions. Conversely, S stored in both late-formed Cu-rich sulfides and interstitial rhyolitic melt represents the pre-eruptive sulfur budget immediately available for release from mafic enclaves during their decompression.     

ERORUN-STAFOR: A collaborative observatory for the multidisciplinary study of the critical zone processes in a tropical volcanic watershed including a Tropical Montane Cloud Forest

Tropical volcanic islands are biodiversity hotspots where the Critical Zone (CZ) still remains poorly studied. In such steep topographic environments associated with extreme climatic events (cyclones), deployment and maintenance of monitoring equipment is highly challenging. While a few Critical Zone Observatories (CZOS) are located in tropical volcanic regions, none of them includes a Tropical Montane Cloud Forest (TMCF) at the watershed scale. We present here the dataset of the first observatory from the French network of critical zone observatories (OZCAR) located in an insular tropical and volcanic context, integrating a ‘Tropical Montane Cloud Forest’: The ERORUN-STAFOR observatory. This collaborative observatory is located in the northern part of La Réunion island (Indian Ocean) within the 45.0 km² watershed of Rivière des Pluies (i.e., Rainfall river) which hosts the TMCF of Plaines des Fougères, one of the best preserved natural habitats in La Réunion Island. Since 2014, the ERORUN-STAFOR monitoring in collaboration with local partners collected a multidisciplinary dataset with a constant improvement of the instrumentation over time. At the watershed scale and in its vicinity, the ERORUN-STAFOR observatory includes 10 measurement stations covering the upstream, midstream and downstream part of the watershed. The stations record a total of 48 different variables through continuous (sensors) or periodic (sampling) monitoring. The dataset consists of continuous time series variables related to (i) meteorology, including precipitation, air temperature, relative humidity, wind speed and direction, net radiation, atmospheric pressure, cloud water flux, irradiance, leaf wetness and soil temperature, (ii) hydrology, including water level and temperature, discharge and electrical conductivity (EC) of stream, (iii) hydrogeology, including (ground)water level, water temperature and EC in two piezometers and one horizontally drilled groundwater gallery completed by soil moisture measurements under the canopy. The dataset is completed by periodic time series variables related to (iv) hydrogeochemistry, including field parameters and water analysis results. The periodic sampling survey provides chemical and isotopic compositions of rainfall, groundwater, and stream water at different locations of this watershed. The ERORUN-STAFOR monitoring dataset extends from 2014 to 2022 with an acquisition frequency from 10 min to hourly for the sensor variables and from weekly to monthly frequency for the sampling. Despite the frequent maintenance of the monitoring sites, several data gaps exist due to the remote location of some sites and instrument destruction by cyclones. Preliminary results show that the Rivière des Pluies watershed is characterized by high annual precipitation (>3000 mm y⁻¹) and a fast hydrologic response to precipitation (≈2 h basin lag time). The long-term evolution of the deep groundwater recharge is mainly driven by the occurrence of cyclone events with a seasonal groundwater response. The water chemical results support existing hydrogeological conceptual models suggesting a deep infiltration of the upstream infiltrated rainfall. The TMCF of Plaine des Fougères shows a high water storage capacity (>2000% for the Bryophytes) that makes this one a significant input of water to groundwater recharge which still needs to be quantified. This observatory is a unique research site in an insular volcanic tropical environment offering three windows of observation for the study of critical zone processes through upstream-midstream-downstream measurements sites. This high-resolution dataset is valuable to assess the response of volcanic tropical watersheds and aquifers at both event and long-term scales (i.e., global change). It will also provide insights in the hydrogeological conceptual model of volcanic islands, including the significant role of the TMCFs in the recharge processes as well as the watershed hydrosedimentary responses to extreme climatic events and their respective evolution under changing climatic conditions. All data sets are available at https://doi.org/10.5281/zenodo.7983138 .