pyroclastic rock
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In this paper, we discuss the hypothesis on the volcanic origin of the precursor sediments for a thick (0.6 m) clay bed, hosted by the sequence of lithothamnium limestones of the Pińczów Formation. Combined X-ray powder diffraction, imaging methods (optical and electron microscopy), and chemical analysis were used to document the volcanic markers, which were preserved in the rock studied. The results obtained show that the clay bed discussed is bentonite in origin. This bentonite, which can be called Drugnia Rządowa bentonite, is composed almost entirely of montmorillonite with little admixtures of quartz and biotite. A small amount of calcite is present, but only in the top of the bed. Despite that, the bentonite contains nothing but clay material—it is a model example of entirely altered pyroclastic rock, which retains texture originally developed in volcanic glass fragments and reveals the preserved original features of the precursor fallout pyroclastic deposits (rhyolitic in character). The thick bentonite beds, discovered for the first time within the Badenian lithothamnium limestones of the Pińczów Formation, can be considered as a record of a violent, explosive volcanic event related to the closure of the Outer Carpathian basin and the development of the Carpathian Foredeep.

Abstract Azores consists of nine islands and several islets, located in the North Atlantic to 1600 km from Continental Portugal and is distributed between latitudes 36° 55' to 39° 43' N and longitude 24° 46' to 31° 16' W. Azores archipelago is in a convergence zone of a series of dynamic tectonic structures, that are responsible for seismicity and volcanism, geological and petrological of these islands. The island of São Miguel, an eastern group, in addition to other petrology’s in its geology, has ignimbrite, which is a pyroclastic rock with a dacitic or rhyolitic composition, resulting from the deposition of materials in semi-melting at high temperatures from a pyroclastic flow. At the site of Água D’Alto, the residual soil sample resulting from the ignimbrite alteration was taken and was evaluated with the interest of studying its application or use as construction material. The soil was subjected to physical and chemical classification test, compressibility, and stress-strain behaviour. This material shows good mechanical characteristics, although its chemism is potentially corrosive.

<p>Tuff stone, a porous pyroclastic rock, is a light and soft material. Hence, tuff is easy to handle and to transport. It is used as construction material in numerous historical buildings. Due to its high water absorption and retention potential, heterogeneous pore structure, and clay mineral content, tuff is highly sensitive to weathering by moisture expansion and salt crystallization [1; 2]. The search for a protective agent for tuff stone has been subject to scientific studies for several decades. Yet, due to the high variability and heterogeneity of tuff stone, no generally applicable means to protect tuff against weathering has been found to date. Instead, case specific solutions are developed to preserve historical buildings. Often it is necessary to remove weathered parts of the stone or exchange whole tuff ashlars to ensure the stability of the construction. Since tuff is a limited resource, it is crucial to find suitable protective agents that prolong the life-cycle of tuff stone to preserve historical buildings</p><p>To favourably influence water absorption, effective porosity, and the pore structure of tuff stone, a thorough impregnation of the stone with the protective agent is desirable. This can be achieved by the application of silica sol products, which are dispersions of colloidal amorphous silicon dioxide particles. The small particle sizes (between 10 and 100 nm) facilitate a high penetration depth. Despite of the promising results of several studies, colloidal silicas are rarely used as protective agents for tuff stone in the restauration practice [3; 4]. This may be due to the lack of long-term experiences with these materials. Furthermore, the performance of protective agents is closely related to the pore structure and chemical and mineralogical composition of the rock [5; 6]. To understand these interactions, further research is needed.</p><p>The aim of a current research project is to study the application of colloidal silica as protective agent for Weiberner tuff. In first tests, penetration depth and changes in the pore structure are analyzed. Furthermore, the influence of the treatment on the hygric and mechanical properties and on the durability of the stone is studied. The new data will contribute to a better understanding of tuff stone deterioration and conservation.</p><p> </p><p>[1] Wedekind et al. (2013) Environ. Earth Sci. 69. [2] Pötzl et al. (2018) Environ. Earth Sci. 77. [3] Iucolano et al. (2019) Contr. Build. Mater. 202. [4] Zornoza-Indart & Lopez-Arce (2016) J. Cult. Herit. 18. [5] Török et al. (2007) Geol. Soc. London, Spec. Publ. 271. [6] Stück et al. (2008) Environ. Geol. 56.</p>

Lumpue Beach Subsurface Profile Analysis of Parepare City. This study aims to analyze the subsurface profile of Lumpue beach which is directly contaminated with activities around the coast. In this study, the Wenner Schlumberger method was used in the Lumpue beach area, Perepare City, South Sulawesi Province. The tool used is a multichannel geoelectric with a maximum length of 480 m in each trajectory, in this study there are 3 trajectories in which the first trajectory is 480 m with depth as deep as 91.2 m and the resistivity results obtained range from 0.207 -> 97.8 Ωm which identified as alluvium containing clay soil, silt soil, sandstone and pyroclastic rock bolder that has been contaminated by sea water. At lane 2 intersects the middle lane 1 with a length of 240 m and identified depths of 91.2 m, the recorded resistivity results range between 5.52 -> 623 Ωm where the resistivity value identifies the alluvium material, which contains clay, silt soil , sandstone that has been contaminated with water and the presence of some pyroclastic rock inserts that are contaminated by water. Whereas lane 3 intersects lane 1 at the end with a lenght of 240m and a depth of 91.2 m, while the recorded resistivity results range from 0.354 - 11776 Ωm where from the recorded resistivity results the material contained in lane 3 is the inserted alluvium material. by pyroclastic rocks. The area covered by the track is an area with alluvium material which is an alluvial unit and most of it is contaminated by water, either by sea water or fresh groundwater and is inserted by pyroclastic rocks.

Three different non-invasive techniques, namely Structure from Motion (SfM) photogrammetry, Terrestrial Laser Scanner (TLS) and ultrasonic tomography integrated with petrographic data, were applied to characterize two rock samples of a different nature: A pyroclastic rock and a carbonate rock. We started a computation of high-resolution 3D models of the two samples using the TLS technique supported by a digital SfM photogrammetry survey. The resulting radiometric information available, such as reflectivity maps, SfM photogrammetry textured models and patterns of geometrical residuals, were interpreted in order to detect and underline surface materials anomalies by a comparison of reflectance and natural colour anomalies. Starting from the 3D models from previous techniques, a 3D ultrasonic tomography on each rock sample was accurately planned and carried out in order to detect internal defects or sample heterogeneity. The integration of the above three geophysical non-invasive techniques with petrographical data—especially with the textural characteristics of such materials—represents a powerful method for the definition of the heterogeneity of the rocks at a different scale and for calibrating in situ measurements.

To explain the strong spatial heterogeneity of volcanic reservoirs porosity in the Songliao Basin and provide new ideas for predicting good volcanic reservoirs in other similar basins, the relationship between the pore evolution process and lithology of volcanic reservoirs has been described in this article. With the description and interpretation of core, thin section, scanning electron microscope, and the results of mercury injection experiment, this article clarifies the lithology, pore types, and pore structure features of the volcanic reservoirs in the Songliao Basin. The rocks of volcanic reservoirs in study area contain pyroclastic rock and volcanic lavas. The most common lithologies are rhyolite, volcanic breccia, and volcanic tuff. The pore size, morphology, and structure vary greatly between these three lithologies, the reason of which we think is the different volcanic eruption process as well as rock composition and its structure. The digenetic evolution of rhyolite includes gas dissipation of magmatic condensation; vesicles fulfilling by hydrothermal fluid; kaolinization and sericitization of feldspar phenocrysts; carbonation, devitrification, and recrystallization of felsic matrix; and finally, the dissolution of feldspar phenocrysts and felsic matrix. As for volcanic breccia, it usually go through the compaction, quartz and calcite filling the original pores between volcanic breccias, and dissolution of mineral debris together with tuff matrix. Similar with the rhyolite, volcanic tuff also undergoes the carbonation and kaolinization of felsic matrix, the dissolution of feldspar and felsic matrix, and compaction. Due to these comprehensive processes, a comprehensive analysis of volcanic rock lithology, which can indicate lithology distribution vertically and horizontally, is very necessary during volcanic reservoirs evaluation and prediction. These detailed analyses will help explorers to find potential reservoirs by distinguishing the diagenetic evolution and pore characteristic of volcanic reservoirs.