Comprehensive Geological Study Research Articles

Field and model investigations of clay layer permeability in the area of Paks II NPP construction

Background. The construction of a nuclear power plant inevitably requires excavation of a deep pit. This task may be impeded by high groundwater levels. The groundwater inflow into the pit can be limited by erecting a cut-off wall. As a rule, the cut-off wall is deepened to the aquitard elevation; however, the presence of hydrogeological windows therein may reduce the efficiency of such a solution.Aim. To determine the nature of clay layer deformation along the regional dislocation area of the Paks II NPP construction site.Materials and methods. A comprehensive geological and hydrogeological study was carried out to identify the continuity of the clay layer. This included an analysis of core samples from more than 1000 engineering and geological boreholes, surface and borehole geophysical surveys, a multi-level borehole network for groundwater level monitoring, as well as numerical hydrogeological modelling.Results. It was found that extensive borehole data does not always guarantee the sufficiency of information for mapping the hydrogeological settings. The continuity of the clay layer with a vertical displacement amplitude of 100 meters was established through a probabilistic analysis using a numerical model and a set of hydrogeological surveys aimed at confirming or refuting the modeling results.Conclusion. Assessment of hydrogeological conditions when implementing high-risk projects, such as nuclear power plants, underground excavations, and open-pit quarries, determines their safety and economic feasibility. In the absence or inconsistency of geological structure knowledge, hydrogeological surveys can serve as an independent source of missing information.

Geo-mechanical classification of the Ighrem Aousser rock mass mining site of the Touissit Mining Company

Purpose. The paper aims to classify the rock mass of the Ighrem Aousser (I/A) mine and analyze its fracturing to determine the appropriate excavation supports. Methods. The study begins with a geo-mechanical classification of the mass using widely used methods: Rock Quality Designation (RQD), Rock Mass Rating (RMR), Q-Barton, and Geological Strength Index (GSI). Fracturing surveys were then conducted to identify the main fracture families using DIPS software. Finally, UNWEDGE software was used to measure the support systems. Findings. The study provides a comprehensive geological study, including field observations, core drilling analysis, and structural analysis with DIPS software. Results indicate that the I/A mine rock mass is highly fractured and altered, as confirmed by mechanical tests at the Mohammadia School of Engineers' laboratory and empirical classifications. Based on these findings, appropriate support systems were identified using UNWEDGE software. Originality. This study provides a detailed classification and structural analysis of the I/A rock mass to propose and measure excavation supports. Integrated approach not only advances understanding of rock mass behavior, but also ensures optimized safety, stability, and productivity of mining operations, setting a new standard in sustainable mining development. Practical implications. In the mining industry, classifying rock masses and designing excavation supports enhances safety, increases site productivity by reducing contamination and lowering mining costs.

A giant porphyry-skarn-epithermal Mo-W-Cu-Zn-Pb-Ag metallogenic system in the Nannihu ore field, southern North China Craton: Constraints from new geochronological and pyrite geochemical data

The southern North China Craton owns substantial Mo, W, Zn, Pb, Cu, and Ag resources, and most of them are hosted in hydrothermal deposits that may co-exist in the same ore field. However, the relationship between the different types of deposits is not well-constrained. To better understand this, here we present a comprehensive geological, geochronological, and pyrite geochemical study on the Nannihu ore field in the Luanchuan district. The Nannihu ore field is largely represented by the Nannihu Mo-W deposit, Luotuoshan Zn-Cu-W deposit, and Lengshuibeigou Pb-Zn-Ag deposit. Mo-W mineralization at Nannihu occurs in the contact zone between the Nannihu intrusion and the wall rocks, showing typical characteristics of the porphyry-type deposit. Three paragenetic stages are recognized at Nannihu, including quartz-potassium feldspar stage, quartz-sulfide stage, and quartz-carbonate stage. The Zn-Cu-W orebodies at Luotuoshan are mainly layered or lens-like, occurring within the skarn zones in the Luanchuan Group. Skarn stage, polymetallic sulfide stage, and carbonate stage are revealed at Luotuoshan. Pb-Zn-Ag mineralization at Lengshuibeigou is characterized by banded sulfide veins that are hosted in the NNE-trending fault zone. Three paragenetic stages are developed at Lengshuibeigou: quartz-pyrite stage, quartz-polymetallic sulfide stage, and quartz-carbonate stage. New geochronological data confirm that the Nannihu intrusion was formed by at least two phases of magmatism including the granite porphyry (zircon U-Pb age of 145 ± 2 Ma) and the porphyritic monzogranite (zircon U-Pb ages of 142 ± 1 Ma and 140 ± 1 Ma), which accompanied by two episodes of Mo mineralization at the Nannihu deposit identified by molybdenite Re-Os dating (144.9 ± 0.7 Ma and 142.8 ± 0.6 Ma). The Luotuoshan deposit and Lengshuibeigou deposit formed at 141 ± 1 Ma to 140 ± 1 Ma and 140 ± 3 Ma to 139 ± 3 Ma revealed by U-Pb dating of garnet and monazite, respectively, which are contemporaneous with the late episode of the Nannihu intrusion and Mo mineralization. Pyrite grains of the three deposits have Co/Ni ratios higher than 1, suggesting a unified magmatic-hydrothermal origin for them. Pyrite from Nannihu and Luotuoshan is enriched in Co, Ni, Se, Mo, Mn, and Bi, whereas pyrite from Lengshuibeigou contains high Zn, Pb, As, Cu, Ag, and Au. The regular elemental distribution of pyrite in the Nannihu ore field is consistent with that of typical porphyry-related systems worldwide.Collectively, the Early Cretaceous magmatic rocks and diverse deposits in the Nannihu ore field make up a giant magmatic-hydrothermal Mo-W-Cu-Zn-Pb-Ag metallogenic system, with the porphyry, skarn, and epithermal types of mineralization displaying a zonation from inside to outside. The multi-episode magmatism and mineralization could result in the remarkable enrichment of mineral resources. The close spatial relationship among different types of mineralization in the Nannihu ore field has a significant implication for porphyry-related mineral prospecting in the southern NCC.

Gold mineralized diorite beneath the Linglong ore field, North China craton: New insights into the origin of decratonization-related gold deposits

Gold deposits in Precambrian cratons were mostly generated during the formation and stabilization of the cratons, but the North China craton is unusual in that its gold deposits were mainly formed ∼1.7 b.y. after its stabilization. A magmatic-hydrothermal origin or mantle-derived fluid source has been proposed for the giant gold deposits of the Jiaodong District in the eastern North China craton, but direct evidence is sparse, and the mineralization processes remain controversial. Here, we present the results of a comprehensive geological, geochronological, and geochemical study of the gold mineralized Xiejia diorite beneath the Linglong ore field at Jiaodong to link the gold mineralization to underlying magmatism. Magmatic zircon and titanite grains from the Xiejia diorite have laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) U-Pb ages of 121.3 ± 0.9 Ma to 120.8 ± 1.1 Ma and 121.7 ± 3.9 Ma, respectively, which are indistinguishable from the time of gold deposition throughout the Jiaodong District as constrained by previous studies. The diorite has a shoshonitic composition and is characterized by strong enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) along with significant depletion in high field strength elements (HFSEs) and heavy rare earth elements (HREEs). Samples of the diorite have high initial 87Sr/86Sr ratios, but low εNd(t) and ɛHf(t) values and low Pb isotope ratios. These geochemical characteristics are akin to those of contemporaneous mafic dikes in most gold mines at Jiaodong, indicating that the Xiejia diorite was most likely derived from an enriched lithospheric mantle source. The upper part of the diorite intrusion is pervasively altered and mineralized, containing an average of 0.32 g/t Au, but locally up to 7.59 g/t. Hydrothermal titanite from the mineralized diorite has a LA-ICP-MS U-Pb age of 122.3 ± 4.3 Ma, which is consistent with the gold-bearing pyrite Re-Os isochron age of 122.5 ± 6.7 Ma. Ore-related sericite aggregates from the Dongfeng gold deposit above the Xiejia diorite have a 40Ar/39Ar plateau age of 122.6 ± 1.3 Ma. Pyrite from the mineralized diorite yielded δ34SCDT values of 2.1‰−9.7‰, which are comparable with those of pyrite (δ34SCDT = 5.8‰−8.1‰, where CDT indicates the Canyon Diablo troilite standard) from gold ores of Dongfeng. Pyrite grains from both groups also have similar Pb isotope compositions. The S and Pb isotope data are consistent with values of mafic dikes that are spatially and temporally associated with gold veins in the Linglong ore field. The results presented here thus indicate a possible genetic link between gold mineralization in the Xiejia diorite and underlying magma presumably represented by the Xiejia diorite. The auriferous fluids exsolved from that magma and migrated upward along the Potouqing fault to form the Dongfeng gold deposit above the Xiejia diorite. The mineralized diorite thus links shallow gold mineralization to deep-seated mantle-derived magmatism generated during the extensive destruction of the North China craton induced by the rollback of the subducted paleo-Pacific plate.

ГЕОЛОГИЧЕСКАЯ ПОЗИЦИЯ И ЗОЛОТО-ВИСМУТОВАЯ МИНЕРАЛИЗАЦИЯ МЕСТОРОЖДЕНИЯ НАМОВСКОЕ (ЮЖНЫЙ СИХОТЭ-АЛИНЬ, ДВ РОССИИ)

Based on the results of a comprehensive geological and mineralogical-geochemical study of the ores of the Namovskoye deposit, new data have been obtained that reflect the specifics of mineralization. The ores of the deposit were formed in close connection with the manifestation of Early Cretaceous monzonitoid magmatism against the background of active left-hand movements along the Central Sikhote-Alin fault. U-Pb dating of the ore-bearing dike yielded an age of 103 Ma. The ores of the deposit, in addition to native gold, contain high concentrations of Ag, Bi, and Cu. A variety of bismuth minerals were found in the ores: sulfide (bismuthinite), telluride (hedleyite), sulfotellurides (tetradymite, joseite-А and joseite-В), Ag sulfobismuthite (matildite), Pb-Bi sulfosalts (aschamalmite, cannizzarite, cosalite, lillianite, nuffieldite, galenobismuthite), an intermetallic compound of gold (maldonite), and native bismuth. Silver minerals were also found: chloride (cerargyrite), sulfide (acanthite), and telluride (hessite). The typomorphic features of ore minerals and the geological structure of the Namovskoye deposit assign it to the gold deposits formed in a transform continental margin setting. A mantle source of ore mineralization is suggested.

Superimposed mineralization in the Tongbai composite orogen, central China: Revealed from geological and geochronological data of the Yindongpo gold deposit

Multi-period mineralizations commonly form superimposed deposits in the orogenic belt, resulting in some disputes about the ore geneses and metallogenic background. Here, we present a comprehensive geological and geochronological study on the Yindongpo super-large gold deposit in the Tongbai composite orogen, central China, to reveal the ages of multi-period gold mineralizations and their links to the complex tectonic evolution framework of the Tongbai orogen. The Yindongpo gold deposit is located in the Weishancheng ore field in the northern segment of the Tongbai orogen and is mainly hosted in the carbonaceous schist of the Waitoushan Formation. Zircon U-Pb dating of leptynite (445 ± 3 Ma) from the Waitoushan Formation shows that it was deposited in the Ordovician, in an island arc or back-arc basin setting during the accretionary orogeny. Orebodies at Yindongpo are strictly controlled by the Zhuzhuang anticline and related fault systems, and are mainly distributed in the turning end, the collapsed part of the dipping end, and the conjugate thrust shear zone of the limbs. Based on field and petrographic observations, two periods of mineralization and four paragenetic stages (stage I to IV) are recognized: the early period consists of the laminated quartz-molybdenite-pyrite stage (I) and laminated-disseminated pyrite stage (II), whereas the late period consists of the quartz-pyrite vein stage (III) and the quartz-polymetallic sulfide vein stage (IV). Molybdenite from stage I has a Re-Os model age of 409 ± 6 Ma, which broadly matches the U-Pb age of intergrown rutile grains (396 ± 4 Ma). These two ages, in combination with the mineralization characteristics, indicate that the early-period gold mineralization was generated by the metamorphism of the accreted terranes during the Early Devonian northward subduction of the oceanic plate. The timing of the late-period mineralization is constrained by the U-Pb age of monazite (127 ± 2 Ma) intergrown with gold-bearing pyrite from stage III and the 40Ar/39Ar ages of ore-related sericite (131 ± 1 Ma) from stage IV and altered sericite (133 ± 1 Ma) from the carbonaceous schist. Combined with the extensive development of coeval granitoids and porphyry Mo deposits in the region, the late-period gold mineralization at Yindongpo belongs to a unified large-scale metallogenic event related to the Early Cretaceous intensive granitic magmatism in an extensional tectonic setting. The results presented here thus reveal two discrete mineralization processes at Yindongpo related to the Tongbai composite orogeny: the early mineralization of Devonian accretionary orogeny and the later mineralization of Cretaceous intracontinental orogeny. Our study contributes to the knowledge of superimposed metallogenesis in composite orogen, and also highlights the decisive role of multi-mineral isotopic dating in revealing the metallogenic epoch of superimposed deposits.

Liquefied sites of the 2012 Emilia earthquake: a comprehensive database of the geological and geotechnical features (Quaternary alluvial Po plain, Italy)

This paper presents a comprehensive geological and geotechnical study of the whole area affected by liquefaction following the 2012 Emilia earthquakes, including all the available information from the field reconnaissance surveys, in situ tests, and laboratory analyses. The compilation was performed at 120 liquefied sites to verify and validate the reliability of liquefaction charts in alluvial sediments, and to assess liquefaction induced by the 2012 seismic sequence in the Emilia plain. The results reveal a wide range of grain sizes (from clean sands to sandy silts) and compositional characteristics (quartz-rich to litharenitic) in the 2012 ejecta, and show a strong relationship between the liquefaction and stratigraphic architecture of the subsurface. The availability of in situ tests at the liquefied sites makes it possible to verify and validate the reliability of the liquefaction charts in alluvial sediments with respect to the real observations. For the analyzed Emilia case studies, the use of non-liquefiable crust provides better estimations of the liquefaction manifestations when coupled with the thickness of the liquefiable layer rather than with the liquefaction potential index. Altogether, this work makes available to the international scientific community a consistent liquefaction database for in-depth earthquake studies.

Modern hydroacoustic methods for studying the bottom relief and bottom sediments of the Dnieper River: ways of using it in the exploration and development of river sand deposits

The difficult state of the economy of the state entailed a practical lack of funding for geological survey, prospecting work, a comprehensive geological study of the territory of Ukraine, natural and anthropogenic changes in the geological environment in the mode of its constant monitoring; the rates and volumes of reproduction of its own mineral resource base do not meet the needs of the country. Reforming the geological industry to ensure the effective functioning of institutions in the field of subsoil use and environmental protection is an extremely important task; proper provision of state control over subsoil use processes. The development of modern hydroacoustic methods for studying the bottom topography and bottom sediments of the Azov-Black Sea basin in order to search and assess the state of deposits of nonmetallic minerals, protect the environment will improve a specialized hydroacoustic complex (hydroacoustic tools, algorithms and software) for performing survey work, allowing the collection of ground maps and sections of bottom soil without taking samples, and to detect objects in the bottom layer of the water column.

Design peculiarities of pipeline support on landslide slopes

The pipeline construction in complex engineering-geological conditions requires a thorough initial data analysis, as well as complex slope modeling using modern software systems. The article discusses the features of the foundation construction for stand-alone supports for power lines and pipelines on landslide slopes composed of clay soils. Relevant Russian regulations documents administer above-ground pipelining, which significantly complicates the design process. However, above-ground pipelining allows monitoring the slope condition (formation road edge breakaway), foundations (deviation from the design location), as well as the pipeline (displacement of the route axis, the state of welds). Timely detected deviations allow avoiding an emergency situation. The author considers possible options for constructive solutions for support foundations, as well as protective structures exemplified by a real Krasnodar Krai object. The pipeline construction in active landslide displacements conditions, as well as the presence of seismic effects, requires not only ensuring the construction's economic feasibility, but also the work safety. In the developing process of optimal design solutions, slope computer modeling was executed both in two-dimensional and three-dimensional formulations based on the finite element method using the Plaxis 2D and Plaxis 3D programs. The considered design situations made it possible to take into account the worst load combinations possible during pipeline operation. According to the calculation results and a comprehensive engineering and geological conditions study at the site, as well as the construction organization peculiarities, a block diagram has been developed that makes it possible to determine the optimal design solutions for protective structures in relation to any landslide construction site.

Hominin homelands of East Java: Revised stratigraphy and landscape reconstructions for Plio-Pleistocene Trinil

Trinil (Java, Indonesia) yielded the type fossils of Homo erectus and the world’s oldest hominin-made engraving. As such, the site is of iconic relevance for paleoanthropology. However, our understanding of its larger geological context is unsatisfactory. Previous sedimentological studies are around 100 years old and their interpretations sometimes contradictory. Moreover, the existing stratigraphic framework is based on regional correlations, which obscure differences in local depositional dynamics. Therefore, a new and more local framework is urgently needed. We carried out a comprehensive geological study of the Trinil area. Using a Digital Elevation Model, we identified seven fluvial terraces. Terrace deposits were described and OSL-dated and fluvial behaviour was reconstructed. The terraces were correlated with terraces of the Kendeng Hills (e.g. the hominin-bearing Ngandong terrace) and date back to the past ∼350 ka. Thus far, most of the Trinil terraces and their deposits had remained unidentified, confounding sedimentological and stratigraphic interpretations. The exposed pre-terrace series has a thickness of ∼230 m. Together with the terraces, it forms a ∼3 Ma record of tectonism, volcanism, climate change and sea-level fluctuations. We subdivided the series into five new and/or revised stratigraphic units, representing different depositional environments: Kalibeng Formation, Padas Malang Formation, Batu Gajah Formation, Trinil Formation and Solo Formation. Special attention was paid to erosional contacts and weathering profiles, forming hiatuses in the depositional series, and offering insight into paleoclimate and base-level change. The Trinil Formation provides a new landscape context of Homo erectus. Between ∼550 and 350 ka, the area was part of a lake basin (Ngawi Lake Basin), separated from the marine base level by a volcanic barrier, under dry, seasonal conditions and a regular supply of volcanic ash. An expanding and retreating lake provided favourable living conditions for hominin populations. After 350 ka, this role was taken over by the perennial Solo River. Landscape reconstructions suggest that the Solo formed by headward erosion and stream piracy, re-connecting the Ngawi Lake Basin to the plains in the west. Our study offers a local framework, but its Pleistocene landscape record has regional significance. Most of all, it forms a much-needed basis for future, detailed studies on the build-up of the hominin site of Trinil, its fossil assemblages and numerical ages.

“Exploring petroleum inside source kitchen”: Shale oil and gas in Sichuan Basin

The Sichuan Basin is rich in shale oil and gas resources, with favorable geological conditions that the other shale reservoirs in China cannot match. Thus, the basin is an ideal option for fully “exploring petroleum inside source kitchen” with respect to onshore shale oil and gas in China. This paper analyzes the characteristics of shale oil and gas resources in the United States and China, and points out that maturity plays an important role in controlling shale oil and gas composition. US shale oil and gas exhibit high proportions of light hydrocarbon and wet gas, whereas Chinese marine and transitional shale gas is mainly dry gas and continental shale oil is generally heavy. A comprehensive geological study of shale oil and gas in the Sichuan Basin reveals findings with respect to the following three aspects. First, there are multiple sets of organic-rich shale reservoirs of three types in the basin, such as the Cambrian Qiongzhusi Formation and Ordovician Wufeng Formation-Silurian Longmaxi Formation marine shale, Permian Longtan Formation transitional shale, Triassic Xujiahe Formation lake-swamp shale, and Jurassic lacustrine shale. Marine shale gas enrichment is mainly controlled by four elements: Deep-water shelf facies, moderate thermal evolution, calcium-rich and silicon-rich rock association, and closed roof/floor. Second, the “sweet section” is generally characterized by high total organic carbon, high gas content, large porosity, high brittle minerals content, high formation pressure, and the presence of lamellation/bedding and natural microfractures. Moreover, the “sweet area” is generally characterized by very thick organic-rich shale, moderate thermal evolution, good preservation conditions, and shallow burial depth, which are exemplified by the shale oil and gas in the Wufeng-Longmaxi Formation, Longtan Formation, and Daanzhai Member of the Ziliujing Formation. Third, the marine, transitional, and continental shale oil and gas resources in the Sichuan Basin account for 50%, 25%, and 30% of the respective types of shale oil and gas geological resources in China, with great potential to become the cradle of the shale oil and gas industrial revolution in China. Following the “Conventional Daqing-Oil” (i.e., the Daqing oilfield in the Songliao Basin) and the “Western Daqing-Oil & Gas” (i.e., the Changqing oilfield in the Ordos Basin), the Southwest oil and gas field in the Sichuan Basin is expected to be built into a “Sichuan-Chongqing Daqing-Gas” in China.

Origin of a multi-stage epithermal Ag-Zn-Pb-Sn deposit: the Miocene Cortaderas breccia body, Pirquitas mine, NW Argentina

The Miocene aged polymetallic (Ag-Zn-Sn-Pb) Pirquitas deposit of NW Argentina, hosted in an uplifted horst of Ordovician metaturbiditic rocks, defines the southern extent of the Andean Tin Belt. The nearby and recently discovered Cortaderas breccia-hosted Ag-Zn deposit contrasts markedly with the main Pirquitas deposit. To address these differences, a comprehensive geological, mineralogical, and geochemical study was undertaken and here reported. Ore formation commenced with brecciation and clay alteration of host rocks followed by six polymetallic ore stages and a waning stage. The complex mineralization (Ag, Sb, As, Sn, Fe, Zn, Cu, Pb, and Bi) consists of pyrite, marcasite, sphalerite, arsenopyrite, galena, cassiterite, quartz, dickite, siderite, hydrous phosphate minerals, and various sulfosalts and sulfides; metal assays indicate a telescoped system. Sphalerite-rich domains are characterized by massive, colloform, dendritic, and cockade textures. Silver and Sn principally occur in various sulfosalts (tetrahedrite, pyrargyrite, miargyrite, pirquitasite-hocartite, and canfieldite). Fluid inclusions reflect mixing of a ca. 5 wt% eq. NaCl fluid having a maximum Th value of 340 °C with heated meteoric water; in addition, fluid unmixing and flashing are documented to have accompanied ore formation. The δ34S values for pyrite and sphalerite constrain δ34SH2S to ≈ 5‰ which suggests a magmatic reservoir. Collectively the data support a model, whereby the Cortaderas breccia reflects focusing of magmatic-sourced mineralizing fluids along an episodically dilating fault zone. Fluids ascended and depressurized following brecciation of the host rocks which initiated fast and slow boiling. The latter processes accounts for the intimate association of colloform- and dendritic-textured sphalerite. Subsequent sealing of the system allowed temperature gradients to rise which resulted in telescoping of the system and generation of this polymetallic ore zone.

Discontinuity Mapping using Terrestrial Laser Scanner and Kinematic Method

This study presents the results of discontinuity mapping using terrestrial laser scanning (TLS) survey and the kinematic method. The results provide the current site and slope condition of comprehensive geological study using terrestrial laser scanning and discontinuity survey at Simpang Pulai, Perak. From the results obtained, it can be concluded that the major potential failures in this area are wedge and plane failures, but there are some area had the potential of toppling failure. This study, however, constitutes a preliminary design consideration and not intended for use in final design or construction. The final design shall be made by the engineer based on the further detail site investigation (S.I.) and other design factors to be used in the actual design of the project.

Facies architecture and sediment infilling processes in intrabasinal slope belts of lacustrine rift basins, Zhanhua Depression, Bohai Bay Basin

Abstract Intrabasinal slope belts, which were previously thought to lack sandy sediments, have been largely understudied due to their distance from their sediment provenance. Thus, our study sought to conduct a comprehensive geological study of the facies architecture and sediment infilling processes in the intrabasinal slope belts of the Zhanhua Depression during the Paleogene using seismic data, drill cores and well logs. Three distinctive depositional systems were identified: near-shore subaqueous fan, shallow/deep lakes, and braided-river delta. The facies architecture and sediment infilling processes were primarily characterized by different stages of diversiform tectonic geomorphologies in cyclothem motifs of rift lacustrine basins. The geomorphological characteristics of the Shahejie Formation exhibited multiple alternating uplifts and sags, resulting in multiple intra- and extra-basinal sediment provenances, while those of the Dongying Formation displayed a single depocenter with a wide and gentle geomorphology derived from several extra-basinal sediment provenances. Coarse-grained sediments formed near-shore subaqueous fans, primarily accumulated on the slopes around the Kenli Uplift during the member 3 of the Shehejie Formation interval; medium- and fine-grained sediments deposited in the proximal and distal environment of the delta front and sandy sediments formed thick-bedded sandy beach bars on subaqueous uplifts during member 2 of the Shehejie Formation interval; ultrafine-grained, fine-grained, and carbonate sediments deposited as thin-bedded carbonate banks and sandy beach bars in a shallow/deep lake during member 1 of the Shehejie Formation interval; and fine-to medium-grained sediments abundantly accumulated in the proximal environment of the delta front by passing the uplifts and infilling the slopes during the Dongying Formation interval. This integrated study demonstrates the effectiveness of a process-based analytical approach and depositional models in predicting facies architecture and sediment infilling processes. Furthermore, it provides guidelines for oil and gas exploration in intrabasinal slope belts of rift basins.

Sources of Sediment Clasts and Depositional Environment of the Upper Paleozoic Shazagaitui and Zhipkhoshi Formations of the Chiron Basin, Eastern Transbaikalia

The article presents the results of comprehensive geological and geochemical study of the sedimentary rocks of the Upper Paleozoic Shazagaitui and Zhipkhoshi formations filling the upper part of the Chiron Basin, as well as U–Pb geochronological and Lu–Hf isotopic studies of zircons from these formations. The geochemical features of the terrigenous rocks of the Shazagaitui and Zhipkhoshi formations indicate that they were formed in a subduction zone environment. The presence of conglomerates and gravelstones and the predominance of unrounded and subrounded fragments in the rocks of the Shazagaitui and Zhipkhoshi formations also indicate their sedimentation in tectonically active zones. The abundant detrital zircons of Paleoproterozoic age, as well as the Paleoproterozoic and Archean Hf model ages of most of the zircons in the sandstones of the Shazagaitui and Zhipkhoshi formations, suggest that the main source of sediment clasts for these formations are the magmatic and metamorphic rocks of the southern surrounding of the North Asian Craton. However, the presence of Devonian–Carboniferous zircons with relatively young (mostly Neoproterozoic) Hf model ages is evidence that these zircons in the sedimentation basin were derived through erosion of mature (?) island arcs, but the contribution of this source is minor. The obtained results in combination with our regional geological data from previous studies suggest that the sediments of the Shazagaitui and Zhipkhoshi formations were accumulated in a basin setting on the southern framing of the North Asian Craton facing the Paleozoic Ocean.

Structural analysis of the 1997 Mw 7.5 Manyi earthquake and the kinematics of the Manyi fault, central Tibetan Plateau

On 8th November 1997, the Mw 7.5 Manyi earthquake ruptured the left-lateral strike-slip Manyi fault in the central Tibetan Plateau. Despite its large magnitude, a comprehensive geological study on the co-seismic surface rupture has not yet been reported so far. Here we reported on our new results of the co-seismic surface ruptures and left-lateral offsets caused by the earthquake based on detailed interpretation of recently acquired high-resolution WorldView and SPOT-5 images. We recognized a primary ∼185-km-long surface rupture that trends N80°E, in consistence with previous results. Along the poorly developed segment at the eastern end of the Manyi fault, a new rupture is also identified, which trends N57°E and extends ∼17 km. The co-seismic surface rupture zone exhibits many distinct features such as stepovers, extensional cracks, ponds, restraining and releasing bends in relation to fault geometrical complexities. By visual analysis of the displaced geomorphic features using satellite imagery, we measured 198 co-seismic offsets along the ∼200 km fault trace. The results show a ∼3.7 m average offset and a maximum offset of up to ∼7.5 m near the epicenter area. The newly found ∼17-km-long rupture is interpreted to be linked to the main fault during the event. If the Manyi fault continues this northeastward propagation for additional 100 km, it will separate the BayanHar Block into two sub-blocks. Such a new hypothetical block model will influence assessment of seismic potential near the block boundaries and estimate of deformation of the BayanHar Block and the central Tibetan Plateau.

A structure and composition of sediment waves in the Middle Caspian Sea

A comprehensive geological and geophysical study of wave-like accumulative bodies on the continental slope of the Caspian Sea was carried out to determine their genesis. As a result, a regular change in the geometry of the layers and the composition of sediments on different morphological elements of waves were revealed, expressed in their textural and structural features, similar to the examples described in the literature for the regions of development of sedimentary waves.

Volcano stratigraphy and physical characterization of the San Mateo Pomez Unit, Cerritos Member: Temascalcingo Volcano, Central Mexico

The Temascalcingo volcano is a dacitic stratovolcano located at the eastern part of the Acambay graben, a tectonic basin in the central sector of the Trans-Mexican Volcanic Belt (TMVB), which is an active, mostly calc-alkaline volcanic arc that crosses Mexico from the Pacific Ocean to the Gulf of Mexico. This study characterises the explosive activity of the San Mateo Pumice eruption that is the most recent and largest paroxysmal episode of this volcano and the last unit of the Cerritos Member. Indeed, this eruption is associated with an undated debris avalanche event consisting of a major sector collapse developed on the western flank of the volcano.Stratigraphic data suggest a highly explosive eruption that generated a relatively thick (up to 10 m) and widespread pumice fallout deposit, trending to the NE, and an aerial distribution of at least 100 km2. This subplinian type eruption of VEI 4 lasted about 9 h and produced a plume height up to 12 km above the vent (i.e., ~14 km above sea level). This type of explosive eruption is relatively common in the TMVB, so a comprehensive geological study, with the corresponding numerical simulations like the one that was carried out, contributes to the understanding of the explosive volcanism of modest size stratovolcanoes that are common in the TMVB.

Sedimentology and mechanism of a lacustrine syn-rift fan delta system: A case study of the Paleogene Gaobei Slope Belt, Bohai Bay Basin, China

Abstract Fan delta systems have long been studied as a kind of good hydrocarbon reservoirs. Although many models have been raised according to their local conditions, there still exists some controversies regarding the formations of the ones developed in continental syn-rift settings. Taking Paleogene Es32+3 of Gaobei Slope Belt as an example, this paper conducted a comprehensive geological study and a forward depositional modeling. The results show that the sediment within the study area came mainly from the northeastern Baigezhuang uplift and the northwestern Xinanzhuang uplift over a short distance. The sedimentary system is characterized by subaerial debris flow, subaerial braided channels, subaqueous distributary channels, front sand bars and front sand sheets. Furthermore, the study area is a balance-filled basin that experienced a 3rd order normal regression followed by a transgression during the development of the study interval. The results also show that, a stable subsidence rate with small-magnitude climate changes would be a plausible explain for the entire sequence of the fan delta system in the study area. The tectonic subsidence was indeed the dominant driving force to a continental syn-rift fan delta system, although the climate, sediment supply or lake level might bring some lower order (e.g., 4th and 5th order) superimpositions. This paper proposed a likely model for fan deltas developed in continental syn-rift settings, which is expected to gain some insights into the forming mechanism and provide some supports for the reservoir characterization of similar and correlative sedimentary systems.

Систематизація та характеристика геотуристичних об’єктів регіонального ландшафтного парку «Знесіння» (м. Львів)

Регіональний ландшафтний парк «Знесіння» розміщений майже в центрі Львова, - надзвичайно цікаве місце як у геотуристичному аспекті, так і для геологічних досліджень. Парк має унікальну геологічну і геоморфологічну позицію. Він розташований на збігу двох геоморфологічних областей - Подільської, представленої Лисогірською височиною Львівського Опілля, та Волино-Малополіської у складі Пасмового Побужжя Малого Полісся. В тектонічному відношенні цим одиницям відповідають тектонічні блоки: Львівський (Лисогірська височина) (ймовірно, Західноєвропейської платформи) і Буський (Пасмове Побужжя) Східноєвропейської платформи, які відділені один від одного різким і крутим уступом. Парк «Знесіння» - це єдиний парк м. Львів, у якому є численні геологічні об’єкти – відслонення відкладів різних геологічних періодів, джерела, техногенні форми рельєфу, доступні для спостережень. Розроблено класифікацію геологічних об’єктів парку. Вони поділені на дві групи (політипна, монотипна), чотири типи (стратиграфічний – до нього віднесено п’ять об’єктів, палеонтологічний – один, гідрогеологічніий – три, гірничо-промисловий – три). Наведено їх узагальнену стандартизовану характеристику за такими ознаками: категорія, геоморфологічне і географічне положення, стратиграфічна, літологічна, палеонтологічна характеристика, науково-пізнавальне, освітнє і геоатракційне значення тощо; і розроблено паспорти. Описані геологічні об’єкти - важлива ланка для відновлення історії Землі. Вони мають наукову, пізнавальну, культурно-естетичну цінність, розміщені недалеко від центру Львова, легкодоступні, важливі для навчального процесу і в разі їх популяризації стануть привабливими геотуристичними атракціями.