Carbonates and Evaporites最新文献

The Rouana formation consists of Turonian interbedding dolostones, breccias and marls that developed in Sidi Bouzid area in middle central Tunisia. The study of a geological section in the Jebel Rouana, complemented by the microscopic observations of thin sections allowed distinguishing different types of breccias and non-breccias deposits. The Rouana formation includes five different types of breccias arranged into eight levels generally interbedded by laminated tidalitic dolomites. The succession of breccias occurred in a marginal paleogeographic environment between continental and marine domains; it consists of a shallow-water uplift on which developed alternating shallow-marine and continental deposits. The sedimentation was controlled by third-order sea level variation. Indeed, during the sea level rise, the Sidi Bouzid uplift was covered with shallow-marine waters where tidalitic dolomites occurred, simultaneously the shoreline extended southward beyond this uplift and reaches the supratidal evaporitic domain in Gafsa area. During the sea level fall, the shoreline retreats toward the North and the uplift became exposed and continental conditions occurred materialized especially by the development of polygenic, alluvial, palustrine, collapse and desiccation breccias. The Rouana formation records third-order eustatic fluctuation during the Turonian interval, materialized by the development of depositional sequences bounded by subaerial exposure surfaces. The studied depositional sequences may be correlated, respectively, with the coeval open-marine sequences (Annaba and Bireno formations) in North central Tunisia as well as with the coeval supratidal evaporitic sequences (Beida formation) in south central Tunisia.

Abstract

This research addresses the severe water shortage in Iran, focusing on the Hashtgerd watershed, through the innovative use of remote sensing and sophisticated modeling techniques. Given the alarming depletion of surface and groundwater in the region, the study explores unconventional water sources for consumption and agricultural purposes. It employs a methodical fusion of the Fuzzy Analytical Hierarchy Process and Analytical Hierarchy Process to assess the viability of karst aquifers. Central to the analysis is eight critical criteria: geology, precipitation, temperature, slope, fault density, altitude, slope direction, and waterway density, all pivotal for understanding the environmental factors influencing water resources. The FAHP model reveals a considerable potential for karst aquifer development in the northern and northeastern segments of the watershed, constituting about 19% of the analyzed area. In contrast, the AHP model identifies a somewhat smaller area with potential, approximately 6%, in the same regions. This discrepancy underscores the differing predictive strengths of these models. Field observations play a crucial role in the study, confirming the FAHP model’s enhanced precision compared to the AHP model. This finding is essential for the effective management of water resources, offering a dependable method for locating potential water sources in dry regions. This study provides valuable insights into sustainable water management strategies in semi-arid areas, demonstrating the successful integration of remote sensing with analytical models. It offers an innovative solution to water scarcity challenges, with potential applications in similar global settings. This research also signifies the effectiveness of specific techniques in evaluating karst and carbonate rock aquifers.

In recent years, the rapid development of new energy vehicles and energy storage technology, driven by the new energy industry, has led to rapid growth in lithium consumption. China has abundant lithium resources, especially in salt lake brine. Zabuye salt lake is the only salt lake in Tibet that has achieved the industrial development of lithium carbonate by using the lithium extraction technique with salinity-gradient solar pond (SGSP) so far. In this paper, the stereo-crystallization process is innovated and optimized based on an enhanced SGSP with nucleation matrix. The optimal processing parameters such as the structure design of the nucleation matrix, the spatial range of underutilized heterogeneous nucleation zone (UHNZ), and the appropriate area ratio of crystallization units have been obtained by experiments. The results show that the UHNZ should be about 0.80–2.00 m from the bottom of the pond, when the total depth of water body in the solar pond is controlled within 2.80–3.30 m and the thickness of the freshwater layer is between 0.30 and 0.60 m. For the best precipitation effect of lithium carbonate, it is suggested that the height of lower nucleation matrix (LNM) in the crystallization unit should be controlled above the height of about 0.80 m from the bottom of the pond, and the area ratio of crystallization units should be about 10%, when implementing the stereo-crystallization process. In 2022, the stereo-crystallization process with the enhanced SGSP has been fully promoted and implemented in Zabuye mining area of Tibet, increasing the output and grade of lithium concentrates significantly.

Abstract

The lithofacies, microfacies, and depositional environments of the Dhruma Formation were studied at the type locality at Khashm adh Dhibi to better understand the sedimentology and depositional history on the Arabian Platform. Twelve lithofacies were identified that can be grouped into four lithofacies associations corresponding to depositional paleoenvironments ranging from peritidal to open marine. The vertical distribution of the lithofacies and their corresponding depositional settings allow for the division of the Dhruma Formation into six 3rd-order sequences (DS1–DS6), each bounded by sharp vertical facies changes, and/or hiatuses. Abrupt negative shifts in both δ¹³C_carb and δ¹⁸O_carb values coincide closely with the placement of sequence boundaries on the Arabian Platform. This suggests that the carbonates in these zones underwent meteoric diagenesis during episodes of subaerial exposure. Comparison of the sequence stratigraphy interpreted from the vertical distribution of facies with published eustatic sea-level curves improves our understanding of the eustatic sea-level variation and/or local tectonics in forming both local hiatuses and regional unconformities.

Oil and gas production from carbonate reservoirs heavily depends on the extent of fracture propagation in the producing formations. Detecting fractures in subsurface rock formations is challenging due to their potential impact on oil production, fluid movement, reservoir connectivity to wells, and hydrocarbon production methods. Therefore, detecting fractures and quantifying their characteristics in carbonate reservoirs is of utmost importance. Detecting fractures in subsurface rock formations is challenging due to their potential impact on oil production, fluid movement, reservoir connectivity to wells, and hydrocarbon production methods. This study identifies natural fractures in the Asmari reservoir (with Eligo-Miocene age and Cenozoic era) of an oil field in Southern Iran. The Asmari carbonate reservoir owes most of its hydrocarbon production to natural fractures. This study uses image logs, drilling cores, maximum flow rate, and mud loss data to analyze fractures in reservoirs due to their complexities and limitations, including high cost, non-directionality, and low recovery coefficient in fractured zones. Data from cores and full-bore Formation MicroImager (FMI) logs acquired from five wells drilled into this reservoir identify fractures and enhance our understanding of their effect on hydrocarbon production. In addition, by analyzing the image logs and creating rose diagrams of fractures, a better interpretation of the dip and direction of the fractures on the fault map is obtained. As a result, it was found that the density of the fractures and faults calculated from image logs corresponds closely with the bubble map of mud loss and maximum flow rate in the production sections of the reservoir. According to the extent of the Asmari reservoir anticline, in three sectors, including northwest, southwest, and central areas, where the highest fracture density is detected, bubble maps of mud loss and flow rate index also show the highest values.

The Oligocene of the eastern area of the Arabian Plate is worthwhile studying due to it being both poorly exposed and understood. This first bed-by-bed lithostratigraphic/microfacies study of the Oligocene coral-bearing Ma’ahm Beds elucidates their depositional environments by analyzing their standard microfacies (SMF). The Ma’ahm Beds are >112 m thick. The basal Unit 1 is ≧22 m thick, dominated by thick-bedded foraminferal wackestones, packstones, and grainstones. Unit 1 evolves from restricted lagoonal conditions (SMF 16) to a transition toward open marine lagoonal conditions. Coarsening-up and thickening-up trends in Unit 1 last into Unit 2, which is 65 m thick, mainly characterized by very thick-bedded floatstones and float- to rudstones. This unit is more coarsely grained and thicker bedded than Unit 1, with prevailing corals and red algae. Unit 2 represents open marine lagoonal conditions (SMF 8). Unit 3 is 25 m thick and defined by alternating of boundstones (SMF 7) and floatstones (SMF 8), the dominant bioclasts being corals. Unit 3 represents an open marine lagoon, and its top contains a coral patch reef complex. The limestones are typically pure as the influx of siliciclastic material was negligible. The corals indicate clean water, lacking high amounts of suspended fines, which is compatible with (1) the slow regional doming of the southerly located Jabal Akhdar and Saih Hatat domes after 30 Ma (low/moderate relief), (2) the absence of the South Asian Monsoon (limited fluvial discharge of fines) and (3) the long-term rise of the eustatic sea level during much of the Oligocene shifting the depocenter landward. The lagoon was likely protected by coral barrier reefs, separated by reef gaps, allowing for an efficient water exchange with the open ocean. The coral patch reefs formed within the lagoon. Based on the scattered outcrop pattern of the Ma’ahm Beds, we suggest that future facies maps of the easternmost part of the Arabian Plate should consider marly deposits as the most widespread Oligocene sediment, while pure limestones (patch reefs and their debris) should represent only small speckles on such maps.

The aim of this study is to determine the potential toxic element (PTE) content linked to the geochemical features of Berriasian–Aptian carbonate rocks commonly outcropping in Gümüşhane, along with the degree of pollution and possible sources of these toxic elements, and to compare dolomite with limestone in terms of toxic metal abundance. In the field, dolomite and limestone samples were collected by measuring stratigraphic sections around Yuvacık, Ünlüpınar, Çukutbaşı, Bağlarbaşı, Mescitli and Gülaçar (Gümüşhane). The samples were analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). The mean values for Mo, Cu, Pb, Zn, Ni, As, and Co were 3.1, 23.8, 7.1, 14.5, 13.5, 30.9, and 8 mg/kg in Yuvacık; 6, 2.3, 1.1, 3.5, 8.1, 12.3 and 2.5 mg/kg in Ünlüpınar; 17.9, 1.8, 1.5, 8.6, 7.9, 13.9 and 1.7 mg/kg in Çukutbaşı; 3.7, 6.5, 31.7, 82.7, 9.5, 32.0 and 1.9 mg/kg in Bağlarbaşı; 0.7, 0.7, 7.1, 21.3, 2.6, 11.8 and 0.7 mg/kg in Mescitli; and 1.2, 1.1, 2.4, 5.2, 1.3, 4.0 and 0.2 mg/kg in Gülaçar, respectively. According to geochemical pollution parameters [geo-accumulation (Igeo), pollution index (Pi), and pollution load index (P_ln)], the rocks were generally significantly polluted by Mo and As, without notable pollution by the other elements. Limestone samples from the Yuvacık, Ünlüpınar, and Çukutbaşı areas were more polluted in terms of Mo and As compared to dolomites. This pollution in Yuvacık and Ünlüpınar was identified to have geogenic sources (Pb–Zn–Cu mineralization) and in Çukutbaşı was identified to have lithogenic sources. Dolomites from the Bağlarbaşı area were more polluted in terms of As and less polluted in terms of Mo compared to limestones. In the Mescitli location, both dolomites and limestones were occasionally polluted in terms of As, while limestones were polluted in terms of Mo. In these two areas, the sources of As and Mo are geogenic (Pb–Zn mineralization), In Gülaçar, dolomites were more polluted in terms of Mo and less polluted in terms of As compared to limestones. In this locality, As and Mo are thought to have a geogenic source (Pb–Zn–Cu mineralization).

Abstract

Studying the lacustrine microbialites in the Western Qaidam Basin in the northeastern margin of the Qinghai–Tibetan Plateau may provide clues to the sedimentary record, the depositional model, and the hydrocarbon potential. Based on geological, geochemical, and seismic data, the sedimentary characteristics and hydrocarbon potential of Eocene lacustrine microbialites in Western Qaidam Basin are estimated. Three microbialites are identified In the Eocene lacustrine system of the Qaidam Basin, including the thick thrombolites in relatively high-energy near-shore settings, the small-scale stromatolites and thrombolites in extremely shallow water environment, and the laminates in relatively deep water of intrabasinal environments. Three sedimentary models have been established, including the marginal steep slope zone, the marginal gentle slope zone, and the intrabasinal deep-water zone, respectively. The framework pores, intergranular pores, dolomite intercrystalline pores, dissolved pores and interlayered fractures commonly composed the pore spaces of microbialites. The Fossil Group of Botryococcus (a lipid-rich algae) contributed the main source of hydrocarbons particularly in saline water in Western Qaidam Basin. The development of Eocene lacustrine microbialites on the northeastern Qinghai–Tibetan Plateau provides a new perspective to explore the complex mineralization processes and hydrocarbon potential of microbialites.

Stylolites are intergranular dissolution structures commonly found in carbonate petroleum reservoirs and have a complex geometry characterized by multiple wavelengths. A classical and natural approach to simplifying the morphology of a stylolite is to focus on its dominant wavelength (DWL), but the advantages and disadvantages of this simplification are poorly understood. We propose a new analysis procedure for testing the dominant wavelengths as a tool for the morphological simplification of stylolites. Hundreds of stylolite samples from carbonate rocks of the Água Clara Formation at the Rio Bonito Quarry (RBQ), Brazil, had their dominant wavelengths extracted and selected through the Fast Fourier Transform and Bandpass Filters. Two types of DWL results were obtained: (i) numerical DWL, a quantitative result that shows a strong correlation with stylolite amplitude and length, with R values between 0.47 and 0.84; (ii) graphic DWL, a qualitative result showing the simplification of the main stylolites features, which is more easily applied to stylolites with wavy teeth. Based on the DWL results, it is possible to state that there is a directly proportional relationship between the scale of a stylolite and its dominant wavelength, corroborating the self-affine nature of the analyzed stylolites. In addition to standard geometric analysis, the DWL method emerges as a novel tool for characterizing and visualizing the undulatory components of stylolites, simplifying their morphology, and contributing to the modeling of oil and gas reservoirs.

Abstract

In this study, the chemical composition of calcite crystals and pore-filling sediments in a stalagmite from Küpeli Cave was investigated for the first time using the electron probe microanalysis (EPMA). It was supplemented by petrographic, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analyses to improve understanding of EPMA findings. The EPMA results show that the stalagmite consists mainly of pure calcite crystals with a CaO composition of 56 ± 1 wt%. These crystals are the primary components of both sparite calcite mosaic and dendritic microfabrics. Calcite crystals in the dendritic microfabric appear as long fiber-like crystals surrounding calcite needles extending in two directions and cement filling the pores between these crystals. Internal sediments are also abundant in the pores of the dendritic microfabric and contain components such as Al₂O₃, SiO₂, K₂O, FeO, and CaO. The XRD analyses show that the pore-filling sediments consist mainly of calcite, smectite, quartz, chlorite, and feldspar. The abundance of siliceous constituents in the internal sediment, together with the stalagmite position within the conduit, indicate that the clastic sediments in the pores were deposited primarily by floods. However, it is thought that some clastic carbonates in the pores may have been transported by water dripping from the epikarst region.