Geosciences and Geoengineering Research Department

Modern euxinic environments are useful proxies for early Earth. We investigated the morphological and chemical properties preserved in sediments impacted by a modern euxinic spring, an early Earth proxy, as compared to adjacent unimpacted sediments. We used X-ray diffraction (XRD) to analyze the mineralogy of bulk sediment and isolated clay fractions. We further examined the morphology and chemistry of smectite clay nanoparticles using scanning/transmission electron microscopy (S/TEM) and energy-dispersive X-ray spectroscopy (EDX). XRD results show that pyrite and barite are present in all of the impacted sediments but absent in the unimpacted sediments. Although grain size analysis shows the impacted samples have more clay-sized particles, the mineralogy of impacted and unimpacted clay fractions is composed of smectite, chlorite, kaolinite, and illite clays. We further focused on smectite clay nanoparticles, as they are known to be sensitive proxies for redox conditions. Smectites with a platy and cornflake texture were prevalent in all samples. However, EDX results reveal differences between the smectites in the impacted and unimpacted samples: impacted smectites additionally incorporate S, Ba, and Sr. Furthermore, STEM–EDX shows evidence of nanoscale barite and pyrite precipitation on the impacted smectites. Ultimately, this study demonstrates that (1) XRD-detectable sulfur bearing minerals in a soil profile exposed to euxinic groundwater are present outside the zone with visible sediment iron reduction and (2) Al-smectite nanoparticles primarily respond to euxinic conditions by immobilizing cations via adsorption or interlayer cation exchange rather than significantly changing their octahedral sheet cation composition.

Silicification in New Caledonian pseudo-karsts developed on peridotite was assessed using δ18O and δ30Si pairs on quartz cements. The objective was to document the chronology of pseudo-karst development and cementation relative to geomorphic evolution. The latter began at the end of the Eocene with the supergene alteration of peridotites and the subsequent formation of extended lateritic weathering profiles. Neogene uplift favoured the dismantling of these early lateritic profiles and valley deepening. The river incision resulted in (i) the stepping of a series of lateritic paleo-landforms and (ii) the development of a pseudo-karst system with subvertical dissolution pipes preferentially along pre-existing serpentine faults. The local collapse of the pipes formed breccias, which were then cemented by white quartz and Ni-rich talc-like (pimelite). The δ30Si of quartz, ranging between −5‰ and −7‰, are typical of silcretes and close to the minimum values recorded worldwide. The estimated δ18O of −6 to −12‰ for the fluids are lower than those of tropical rainfall typical of present-day and Eocene–Oligocene climates. Evaporation during drier climatic episodes is the main driving force for quartz and pimelite precipitation. The silicification presents similarities with silcretes from Australia, which are considered predominantly middle Miocene in age.

Abstract Moderate‐to‐large earthquakes in rifts may occur on leading boundary faults or inner antithetic faults. Here we show a rare case of the 2020–2021 seismic sequence in the Corinth rift, that culminated in the shallow rupture of the antithetic fault, neither preceded nor followed by the leading fault rupture. The hypocenter of the largest shock (Mw 5.3 of 17 February 2021) was located at ∼8 km depth. However, seismic waveform data, supported by satellite‐geodetic and tide gauge measurements, pointed to rupture at shallow depth (∼3 km), where no earthquakes were previously observed. We show that the earthquake most probably ruptured two orthogonal, conjugate fault segments: a weak nucleation phase occurred in the microseismically highly active sub‐horizontal detachment layer, followed – a few seconds later – by a larger, shallow moment release on a high‐angle, south‐dipping normal fault. The latter is the Mornos offshore fault, antithetic to the leading, north‐dipping Psathopyrgos fault. Our study presents the first instrumental/observational evidence of a very shallow Mw 5+ event in this rift – and one of the few reported worldwide. The depth limit of the main shallow slip patch coincides with the expected crossing of the Mornos fault with the Psathopyrgos fault, stressing the importance of fault segmentation and rooting inherited from the rift history. This unusual shallow slip in a depth range with little background seismicity and few aftershocks needs to be further investigated by dynamic modeling as a possible prototype of hazardous events in rift environments.

In the task of predicting spatio-temporal fields in environmental science using statistical methods, introducing statistical models inspired by the physics of the underlying phenomena that are numerically efficient is of growing interest. Large space-time datasets call for new numerical methods to efficiently process them. The Stochastic Partial Differential Equation (SPDE) approach has proven to be effective for the estimation and the prediction in a spatial context. We present here the advection-diffusion SPDE with first order derivative in time which defines a large class of nonseparable spatio-temporal models. A Gaussian Markov random field approximation of the solution to the SPDE is built by discretizing the temporal derivative with a finite difference method (implicit Euler) and by solving the spatial SPDE with a finite element method (continuous Galerkin) at each time step. The ''Streamline Diffusion'' stabilization technique is introduced when the advection term dominates the diffusion. Computationally efficient methods are proposed to estimate the parameters of the SPDE and to predict the spatio-temporal field by kriging, as well as to perform conditional simulations. The approach is applied to a solar radiation dataset. Its advantages and limitations are discussed.

The design of underground facilities in rock salt requires a correct characterization of the rock as a first step, which is usually performed at the laboratory scale using samples of a given size, constrained by the drilling equipment in the field and by the size of the experimental devices in the laboratory. Rock salt often contains impurities of different nature, which may rise representativity problems if the size of the tested samples is smaller than the representative volume element of the rock mass. An improper characterization of the rock in the laboratory may lead to an improper design of underground facilities. These two aspects are illustrated through an experimental campaign and subsequent computations at the cavern scale. In order to evaluate heterogeneity, different measurement techniques should be used in laboratory tests, covering different spatial scales within the samples. The use of two design criteria at the cavern scale is also discussed and proves that design criteria embedded at the constitutive level overcome the limitations of external criteria applied during post-processing of the cavern simulation results. Hence, the use of constitutive laws that reproduce laboratory data and yield pertinent long-term predictions is of utmost importance.

<p><strong>Abstract</strong></p><p>Climate change is a global concern, directly interfering with the local geology, causing changes, affecting the geomorphological structures and the stability of the rock masses.</p><p>The phenomena that occur due to changes in the geological materials, such as in coastal areas or abandoned quarries, significantly affect the behavior of the rock masses located in these areas, as they suffer the action of abrasion and erosion due to the dynamics of the sea or strong winds, which can provide an early instability of existing cliffs or slopes, endangering the surrounding environment, such as roads or buildings.</p><p>Knowing that storms are increasingly recurrent and stronger, the damages they can cause presents greater consequences, requiring a more objective analysis of the geological materials behavior when exposed to severe weather events, such as torrential rainfall or long lasting rainfall.</p><p>The geomechanical classifications e.g. Rock Mass Rating (RMR) and Slope Mass Rating (SMR), are crucial as the behavior of the rock masses can be foreseen when the values of the geotechnical parameters are suitably defined. Complementarily, it is useful to use geophysical methods allowing to obtaining more detailed information in a less invasive, but reliable way, including the degree of fracturing of the rock masses, provided that access and the characterization of the sites are feasible. Currently the geomechanical classifications are reliable at a small scale, failing to convey the geomechanical behavior of the rock masses as a whole, but rather in restricted locations. Realizing this difficulty, it is relevant to find a work methodology allowing the existing classifications to be used, so that the final results are a continuous evaluation of the rock mass behavior and not only in delimited sections or test sampling points.</p><p>Considering the goal of a continuous characterizing of the rock mass behavior through the results obtained, it is pertinent to present solutions, which should contribute, whenever possible, to greater sustainability.</p><p>Therefore, it is intended that geomorphology and geology, in association with the geotechnical studies should be used as a basis for the characterization of rock masses, allowing to identify the problems and instability causes and subsequently to present the solutions allowing to enhance profitability, sustainability and efficiency in the stabilization of the rock masses.</p>

Vietnam's mineral resources are very rich yet dispersed; the majority of ore mining are on a modest scale. One such mine is the Lang Vai antimony mine in Tuyen Quang province. The mine contains around 55,000 tons of main ore reserves with a concentration of 0.07 4.56 percent. The ore body is spread in the form of beds, veins, and steep slopes. With these sorts of mines, the issue for mining engineers is balancing technological indications, mining safety, and cheap production costs. If mechanized mining technology is used, capital recovery is not possible; if manual technology is used, productivity and safety are low, and the payback period is long. The building solution is simple, based on an examination of the features of such a mine, which is naturally placed of the ore body, the mechanical and physical qualities of the surrounding rock, and so on, with the objective of the shortest ore production time. simple. The article offers a strategy to approach the ore body through a vertical well combined with a through-seam furnace, an ore storage mining system, the building of a pipeline to prepare for production in the ore body, and a road drill construction technique. Breaking rock with 36 mm glass using a blasting technique. Simultaneously, compute some fundamental efficiency requirements based on the chosen plan.

One of the most important achievements of applying radioactive isotope in the geological study is to determine the age of mineralization. Based on the synthesis, comparison, and evaluation of the popular isotopic systems in dating mineralization, the Rb - Sr, Re - Os, and Ar - Ar dating methods are discussed in this study. The results show that the Rb - Sr dating method is likely to be successfully applied to sulfide mineralization. If the mineralization contains little or no sulfide minerals, then the method is applied to other minerals in an ore mineral association. The Re - Os dating method has shown great success when it is applied to hydrothermal deposits, especially for the molybdenite - bearing vein deposits. The limitation of the method is that when the concentration of the Os element in molybdenite is low, it is difficult to establish the Re/Os ratio in a single mineral. The Ar - Ar isotope system for dating mineralization often uses mica or feldspar minerals, which are minerals with blocking temperatures ranging from 150÷350 0C, and later metamorphic periods have higher than 350 0C often overprinted these minerals. Generally, tectonic, magmatic, and metamorphic events, which occur after mineralization, can cause difficulty in determining the age of mineralization and collecting analysis samples.

Manjula (one of our research assistants) said to Savita (a woman from a rich Jat family in Nangal) that girls in villages generally don’t wear the kind of clothes that Savita’s daughter Sumita was wearing — pant-shirt with denim jeans. Savita said, ‘Sumita’s father likes it. He doesn’t like shalwar suit. He himself brings these sorts of clothes for her. The mahaul [atmosphere] of our house is completely like that of a town. This one wears only frocks and pant-shirts. One shalwar suit has been sewn for her, but it is just lying unworn. When my nandot [husband’s sister’s daughter] was married, Sumita’s father himself went to Meerut and brought pant-shirt for Sumita. I said that everyone would be coming for the wedding and that he should not get her to wear such clothes, but he did not pay any heed’ . . . Patricia Jeffery asked whether people in the village object to this. Savita said, ‘We don’t go anywhere in the village. We remain just in the house. We don’t even step out of the gate. Though we sometimes have to go to neighbours’ homes to call on people, our muhalla [neighbourhood] is very good. No one says anything. Well, they all know who we are. There are two to four houses in the village that are very good, in whose homes there is a bilkul shahron-wala mahaul [completely urban atmosphere]. One is our house. One is the newish haveli [imposing house] near the bus stand — those people are also quite wealthy. One is the daroga-ji’s [ex-Police Inspector’s] house. These families are such that it does not feel like you are in a village when you are with them. All the luxuries and comforts are like in the town . . . When Sumita needs to go to the bazaar or to Bijnor, she goes with her father, sitting on the scooter or in the car. So then there is no question of anyone saying anything’. (Field notes: Savita and Sumita, 21 November 2001). 1