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26 pages, 12238 KiB

Open AccessFeature PaperArticle

Pseudo-Karst Silicification Related to Late Ni Reworking in New Caledonia

by Michel Cathelineau, Marie-Christine Boiron, Jean-Louis Grimaud, Sylvain Favier, Yoram Teitler and Fabrice Golfier

Minerals 2023, 13(4), 518; https://doi.org/10.3390/min13040518 - 6 Apr 2023

Cited by 4 | Viewed by 1833

Abstract

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. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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12 pages, 4967 KiB

Open AccessReview

The Effect of Mining Activities on the Paleokarstic Features, Recent Karstic Features, and Karst Water of the Bakony Region (Hungary)

by Márton Veress

Mining 2022, 2(4), 757-768; https://doi.org/10.3390/mining2040042 - 14 Nov 2022

Cited by 3 | Viewed by 2688

Abstract

This study describes the direct and indirect effects of mining on the karst of the Bakony Region. For this, the results of geological and mining research of the last century, the results of hydrological research of fifty years, as well as the investigations of several decades on the karst of the mountain region are used. Direct effects include the exploitation of filling materials (limonite, kaolinite, manganese ore, and bauxite) from paleokarst features, dolomite rubble, activities exploring or destroying cavities, and the pollution of cavity systems with mining waste (dirt). An indirect effect is karst water extraction. Mining activities (coal and quarrying) resulting in the development of pseudokarstic features are also mentioned here. It can be stated that the effects on the karst and karst features may be permanent and even renewing, but the original state may also have returned or can be expected in the near future. Damages may be local or regional. A regional effect is the decrease in karst water level, which has the most significant effect on the environment, but it has already reached its original state by now. Full article

(This article belongs to the Special Issue Application of Empirical, Analytical, and Numerical Approaches in Mining Geomechanics)

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12 pages, 2285 KiB

Open AccessArticle

Complexity and Geoheritage Importance of Granite Pseudokarst from the Belaya River Gorge (Western Caucasus)

by Dmitry A. Ruban

Geosciences 2022, 12(4), 175; https://doi.org/10.3390/geosciences12040175 - 15 Apr 2022

Viewed by 2721

Abstract

New investigations in the Western Caucasus contribute to the understanding of granite pseudokarst (sensu lato) and megaclasts linked to river erosion. A plot on the bank of the Belaya River (Mountainous Adygeya, Western Caucasus) was selected to examine diverse and abundant pseudokarst features (small rock basins, hollows, potholes, and channels) and large clasts. Morphological analysis of these features clarifies their general characteristics and genetic interpretations. Pseudokarst features can be classified into two major categories, namely the relatively small (<1 m) and large (>1 m) features. Potholes, which are usually 1–3 m in size, are the most characteristic features occurring on two levels, i.e., on steep walls of the gorge (half-filled with river water) and on slightly inclined surfaces of a terrace-like landform (subaerial exposure). In both cases, their walls from the side of the river are broken. Apparently, these potholes were formed on the river bottom. Subsequent incision of the gorge elevated potholes and the river has eroded them from one side. Apparently, some pseudokarst features are related to macroturbulent flood flows and granite weathering. Due to its scientific uniqueness and aesthetic attractiveness, this granite pseudokarst constitutes geoheritage, which can be exploited for the purposes of geoscience research and geotourism development. Full article

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26 pages, 22059 KiB

Open AccessArticle

Investigation of Critical Geotechnical, Petrological and Mineralogical Parameters for Landslides in Deeply Weathered Dunite Rock (Medellín, Colombia)

by Tamara Breuninger, Bettina Menschik, Agnes Demharter, Moritz Gamperl and Kurosch Thuro

Int. J. Environ. Res. Public Health 2021, 18(21), 11141; https://doi.org/10.3390/ijerph182111141 - 23 Oct 2021

Cited by 8 | Viewed by 2701

Abstract

The current study site of the project Inform@Risk is located at a landslide prone area at the eastern slopes of the city of Medellín, Colombia, which are composed of the deeply weathered Medellín Dunite, an ultramafic Triassic rock. The dunite rock mass can be characterized by small-scale changes, which influence the landslide exposition to a major extent. Due to the main aim of the project, to establish a low-cost landslide early warning system (EWS) in this area, detailed field studies, drillings, laboratory and mineralogical tests were conducted. The results suggest that the dunite rock mass shows a high degree of serpentinization and is heavily weathered up to 50 m depth. The rock is permeated by pseudokarst, which was already found in other regions of this unit. Within the actual project, a hypothesis has for the first time been established, explaining the generation of the pseudokarst features caused by weathering and dissolution processes. These parameters result in a highly inhomogeneous rock mass and nearly no direct correlation of weathering with depth. In addition, the theory of a secondary, weathering serpentinization was established, explaining the solution weathering creating the pseudokarst structures. This contribution aims to emphasize the role of detailed geological data evaluation in the context of hazard analysis as an indispensable data basis for landslide early warning systems. Full article

(This article belongs to the Special Issue Landslide Risk Assessment and Mitigation)

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8 pages, 637 KiB

Open AccessArticle

Karst as Important Resource for Geopark-Based Tourism: Current State and Biases

by Dmitry A. Ruban

Resources 2018, 7(4), 82; https://doi.org/10.3390/resources7040082 - 7 Dec 2018

Cited by 33 | Viewed by 6887

Abstract

The United Nations Educational, Scientific and Cultural Organization (UNESCO) Global Geoparks initiative balances the conservation of geological heritage with its use in purposes of tourism industry. However, the resources of geoparks and the current state of their use are yet to be fully understood. The phenomenon of karst (caves, sinkholes, etc.) appears to be a valuable geopark resource because it attracts numerous visitors interested in geo-, eco-, and speleotourism. Of 140 global geoparks, 37% exploit karst resources. These are located chiefly in Europe and Southeast Asia. Just a few geoparks are fully based on karst features and the others use this resource together with other geological heritage resources. Global geoparks tend to emphasize either particular karst elements or entire karst landscapes. Many interesting features (e.g., gypsum and salt karst) are underrepresented in global geoparks. The UNESCO Global Geoparks initiative should become more phenomenon-focused to offer full representation of karst resources. For some countries like Russia and the United States, where geoparks have not been created yet, the consideration of karst resources may provide significant advantages in the strategic development of geopark-based geotourism. Full article

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