Composite Geoelectrical Investigation to Delineate Groundwater Feasibility in Hard Rock area of Raipur, Chhattisgarh, India.

In hard rock terrains, groundwater movement, migration, and storage occur through subsurface fractures. To assess the fractures and associated water, we carried integrated geophysical investigation with Wenner, (GRP), Schlumberger, and Pole-Dipole array in Indian State. The resistivity survey carried out using a CRM-500 resistivity meter. The analyzed results are also re-verified with the help of IPI2WIN software. Initially, lateral and surface variations of resistivity were plotted by using Wenner and Gradient Resistivity profiling array. Then the low resistivity points were investigated with Schlumberger and Pole-Dipole array. In interpretation, low resistive zones identified correspond to the possible fractured zones. The results allowed mapping of the weathering zone at depth 12 to 15 m, and deep fracture lies below depth 55.0 m depth. The present study validates that the integrated Geophysical survey is a powerful exploration technique to scrutinize and identify water-bearing fractures in the hard rock area.

Petrographic Record and Conditions of Expansive Hydration of Anhydrite in the Recent Weathering Zone at the Abandoned Dingwall Gypsum Quarry, Nova Scotia, Canada

In the Dingwall gypsum quarry in Nova Scotia, Canada, operating in 1933–1955, the bedrock anhydrite deposits of the Carboniferous Windsor Group have been uncovered from beneath the secondary gypsum beds of the extracted raw material. The anhydrite has been subjected to weathering undergoing hydration (gypsification), transforming into secondary gypsum due to contact with water of meteoric derivation. The ongoing gypsification is associated with a volume increase and deformation of the quarry bottom. The surface layer of the rocks is locally split from the substrate and raised, forming spectacular hydration relief. It shows numerous domes, ridges and tepee structures with empty internal chambers, some of which represent unique hydration caves (swelling caves, Quellungshöhlen). The petrographic structure of the weathering zone has been revealed by macro- and microscopic observations. It was recognized that gypsification commonly starts from a developing network of tiny fractures penetrating massive anhydrite. The gypsification advances from the fractures towards the interior of the anhydrite rocks, which are subdivided into blocks or nodules similar to corestones. Characteristic zones can be recognized at the contact of the anhydrite and the secondary gypsum: (1) massive and/or microporous anhydrite, (2) anhydrite penetrated by tiny gypsum veinlets separating the disturbed crystals and their fragments (commonly along cleavage planes), (3) gypsum with scattered anhydrite relics, and (4) secondary gypsum. The secondary gypsum crystals grow both by replacement and displacement, and also as cement. Displacive growth, evidenced by abundant deformation of the fragmented anhydrite crystals, is the direct cause of the volume increase. Crystallization pressure exerted by gypsum growth is thought to be the main factor generating volume increase and, consequently, also the formation of new fractures allowing water access to “fresh” massive anhydrite and thus accelerating its further hydration. The expansive hydration is taking place within temperature range from 0 to ~30 °C in which the solubility of gypsum is lower than that of anhydrite. In such conditions, dissolving anhydrite yields a solution supersaturated with gypsum and the dissolution of anhydrite is simultaneous with in situ replacive gypsum crystallization. Accompanying displacive growth leads to volume increase in the poorly confined environment of the weathering zone that is susceptible to upward expansion.

The Effect of Aspect and Elevation on Critical Zone Architecture in the Reynolds Creek Critical Zone Observatory: A Seismic Refraction Study

In the northern hemisphere within snow-dominated mountainous watersheds north-facing slopes are commonly more deeply weathered than south-facing slopes. This has been attributed to a more persistent snowpack on the north facing aspects. A persistent snowpack releases its water into the subsurface in a single large pulse, which propagates the water deeper into the subsurface than the series of small pulses characteristic of the intermittent snowpack on south-facing slopes. Johnston Draw is an east-draining catchment in the Reynolds Creek Critical Zone Observatory, Idaho that spans a 300 m elevation gradient. The north-facing slope hosts a persistent snowpack that increases in volume up drainage, while the south-facing slope has intermittent snowpack throughout the drainage. We hypothesize that the largest difference in weathering depth between the two aspects will occur where the difference in snow accumulation between the aspects is also greatest. To test this hypothesis, we conducted four seismic refraction tomography surveys within Johnston Draw from inlet to outlet and perpendicular to drainage direction. From these measurements, we calculate the weathering zone thickness from the P-wave velocity profiles. We conclude that the maximum difference in weathering between aspects occurs ¾ of the way up the drainage from the outlet, where the difference in snow accumulation is highest. Above and below this point, the subsurface is more equally weathered and the snow accumulations are more similar. We also observed that the thickness of the weathering zone increased with decreasing elevation and interpret this to be related to the observed increase soil moisture at lower elevations. Our observations support the hypothesis that deeper snow accumulation leads to deeper weathering when all other variables are held equal. One caveat is the possibility that the denser vegetation contributes to deeper weathering on north-facing slopes via soil retention or higher rates of biological weathering.

NEW DATA ON SEASONAL MINERALS OF MUD VOLCANOES IN AZERBAIJAN

The article discusses the morphology and material composition of seasonal minerals of mud volcanoes in Azerbaijan Mud volcanism is a complex and rather unexplored geological phenomenon. Mud volcanoes are known in Turkmenistan, Dagestan, Georgia, Sakhalin, Taman Peninsula, Crimea, Azerbaijan and many regions of the World. In the geological literature, this phenomenon has been widely reflected. The bibliography of scientific works on mud volcanism has hundreds of titles. One of the classic areas of mud volcano development is Azerbaijan. In the process of geological research in recent decades, a huge geological material has been accumulated on the mud volcanism of Azerbaijan. The described types of mud volcanoes eruptions and the material composition of the mound breccia, it was possible to discover new interesting facts of unusual mineralogical finds. Of particular interest are authigenic minerals formed directly from the water phase of mud volcanoes and are seasonal. Their formation indicates that mineral formation processes are active in these natural sites. The occurrence of seasonal minerals is controlled by several factors, including the climatic conditions of the region. Main part of such minerals crystallizes only in dry and warm weather, which makes their systematic research much more difficult. The sodium hydroxide described in the article, which is very unstable under natural conditions, is a confirmation of this. However, even for a short interval of the existence of seasonal minerals, studying the features of their composition, one can obtain important information for genetic constructions. In addition to exogenous minerals of the weathering zone, the article also describes molybdenite associated with hydrothermal processes. The study of the mineral component of both endogenous and exogenous processes makes it possible to assess their evolution, the direction of the geological development of mud volcanoes in the region.

Characterization of Weathered Soft Rock Mass by Index Tests

The understanding of geotechnical and geomechanical rock mass behavior is challenging, mainly regarding weathered parts, since they may trigger stability issues. Soft Rocks, as phyllite, are known to enhance these problems. In this case, a road cut on a highway between the cities of Ouro Preto and Mariana (MG – Brazil) was studied, showing a particular weathering zone with changing conditions. After morphological description and geological fragmentation (using geological hammer, the Schmidt hammer and a switchblade) of the weathering zone, tests were done on rock matrix and rock mass in order to identify the discontinuity features. Physical properties were determined by physical index, using the point load test and slake durability test. The results permit to define the weathering zone, showing some huge anisotropy and heterogeneity in the rock properties.

Q estimation and its application in the 3D shallow weathering zone

Attenuation in the shallow weathering zone is relatively strong, causing severe energy loss during wave propagation. It is difficult to estimate accurate [Formula: see text] values in the shallow weathering zone, and the influence of shallow weathering zone is seldom considered into attenuation estimation and compensation in the deep part. We achieved [Formula: see text] value estimation where there exist microlog data in the shallow weathering zone using the generalized S transform (GST); then, we establish an empirical formula using the velocity and [Formula: see text] value estimated with microlog data; finally, the [Formula: see text] value in the 3D shallow weathering zone can be obtained using the established formula and the velocity information. During the first procedure, the GST is used to provide reasonable time-frequency resolution, and linear regression is used in the obtained logarithmic spectral ratio to get the estimated [Formula: see text] value. An empirical formula is established using the estimated [Formula: see text] value and the velocity where there exists microlog data in the second procedure. In the third step, [Formula: see text] estimation in the whole shallow weathering zone can be obtained using the established formula and the velocity information, which can overcome the inaccuracy of spatial interpolation with the estimated [Formula: see text] factors where there exist different twin-well microlog data. Attenuation compensation to seismic data obtained from the deep part is carried out to prove the effectiveness of the estimated [Formula: see text] in the shallow weathering zone. After compensation, the resolution of seismic data is effectively increased, which demonstrates the validity of the estimated [Formula: see text] values in the shallow weathering zone. Synthetic data and field data examples demonstrate the validity of our method.

THREE-DIMENSIONAL GEOLOGICAL MAP OF THE ENVIRONS OF SHCHYRETS NEAR LVIV

The Badenian (Middle Miocene) gypsum occurring in the Carpathian Foredeep basin is exposed in a great number of locations in Ukraine, including the environs of Shchyrets, 25 km SSW of Lviv. In this area the potential stratotype of the Badenian gypsum is exposed, known as the Tyras Suite in Ukraine. The area is also of great scientific value because of the anhydrite rocks exposed at the Pisky quarry (near Shchyrets). Recently, unique forms of caves known as hydration caves or swelling caves have been formed in the weathering zone of this anhydrite. In the territory of Ukraine, both morfological and geological cartographic data are incomplete. Nowadays, available archival documents need updating. This paper describes the way of preparation of a new, updated version of the geological map of Shchyrets environs in three-dimensional space (3D). The topographic and archival geological maps were used, which were subjected to process of vectorization. The main part of the work was done in ArcGIS 10.1. Usefulness of the constructred 3D map for quantitative geomorphological and geological analysis is shown on selected examples.

Sulphate and arsenate minerals as environmental indicators in the weathering zones of selected ore deposits, Western Sudetes, Poland

The results of a complex investigation of the sulphate and arsenate assemblages forming in the weathering zone of selected ore deposits in the Sudetes are presented. The development of the weathering zone has been characterised in the polymetallic ore deposits at Miedzianka-Ciechanowice and Radzimowice, and the pyrite deposit at Wieściszowice, which differ in the chemical compositions of the ore and barren minerals and the hydrological conditions. Secondary sulphate and arsenate mineral assemblages vary significantly among the ore deposits under study. Their crystallization is discussed, taking into consideration the stability of particular minerals and the paths of their transformation. It is shown that these minerals have great potential as indicators of weathering processes. A significant role for microorganisms in the formation of the weathering zone of the ore deposits under study is also proven.