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This landmark volume, edited by Bruce H. Purser, represents one of the most significant contributions to modern carbonate sedimentology. It provides a comprehensive analysis of the Persian Gulf as a premier contemporary model for a shallow-water epicontinental sea. Through a series of technical papers, the work explores the complex interplay between biological, chemical, and physical processes that govern the formation and alteration of carbonate sediments in a high-salinity, subtropical environment.

Karst regions offer a variety of natural resources such as freshwater and biodiversity, and many cultural resources. The World Karst Aquifer Map (WOKAM) is the first detailed and complete global geodatabase concerning the distribution of karstifiable rocks (carbonates and evaporites) representing potential karst aquifers. This study presents a statistical evaluation of WOKAM, focusing entirely on karst in carbonate rocks and addressing four main aspects: (1) global occurrence and geographic distribution of karst; (2) karst in various topographic settings and coastal areas; (3) karst in different climatic zones; and (4) populations living on karst. According to the analysis, 15.2% of the global ice-free continental surface is characterized by the presence of karstifiable carbonate rock. The largest percentage is in Europe (21.8%); the largest absolute area occurs in Asia (8.35 million km2). Globally, 31.1% of all surface exposures of carbonate rocks occur in plains, 28.1% in hills and 40.8% in mountains, and 151,400 km or 15.7% of marine coastlines are characterized by carbonate rocks. About 34.2% of all carbonate rocks occur in arid climates, followed by 28.2% in cold and 15.9% in temperate climates, whereas only 13.1 and 8.6% occur in tropical and polar climates, respectively. Globally, 1.18 billion people (16.5% of the global population) live on karst. The highest absolute number occurs in Asia (661.7 million), whereas the highest percentages are in Europe (25.3%) and North America (23.5%). These results demonstrate the global importance of karst and serve as a basis for further research and international water management strategies.

An accessible resource, covering the fundamentals of carbonate reservoir engineering Includes discussions on how, where and why carbonate are formed, plus reviews of basic sedimentological and stratigraphic principles to explain carbonate platform characteristics and stratigraphic relationships Offers a new, genetic classification of carbonate porosity that is especially useful in predicting spatial distribution of pore networks. Includes a solution manual

Karst aquifers contribute substantially to freshwater supplies in many regions of the world, but are vulnerable to contamination and difficult to manage because of their unique hydrogeological characteristics. Many karst systems are hydraulically connected over wide areas and require transboundary exploration, protection and management. In order to obtain a better global overview of karst aquifers, to create a basis for sustainable international water-resources management, and to increase the awareness in the public and among decision makers, the World Karst Aquifer Mapping (WOKAM) project was established. The goal is to create a world map and database of karst aquifers, as a further development of earlier maps. This paper presents the basic concepts and the detailed mapping procedure, using France as an example to illustrate the step-by-step workflow, which includes generalization, differentiation of continuous and discontinuous carbonate and evaporite rock areas, and the identification of non-exposed karst aquifers. The map also shows selected caves and karst springs, which are collected in an associated global database. The draft karst aquifer map of Europe shows that 21.6% of the European land surface is characterized by the presence of (continuous or discontinuous) carbonate rocks; about 13.8% of the land surface is carbonate rock outcrop.

Using X-ray computed microtomography, we have visualized and quantified the in situ structure of a trapped nonwetting phase (oil) in a highly heterogeneous carbonate rock after injecting a wetting phase (brine) at low and high capillary numbers. We imaged the process of capillary desaturation in 3D and demonstrated its impacts on the trapped nonwetting phase cluster size distribution. We have identified a previously unidentified pore-scale event during capillary desaturation. This pore-scale event, described as droplet fragmentation of the nonwetting phase, occurs in larger pores. It increases volumetric production of the nonwetting phase after capillary trapping and enlarges the fluid−fluid interface, which can enhance mass transfer between the phases. Droplet fragmentation therefore has implications for a range of multiphase flow processes in natural and engineered porous media with complex heterogeneous pore spaces. Significance Fluid displacement processes in carbonate rocks are important because they host over 50% of the world's hydrocarbon reserves and are aquifers supplying water to one quarter of the global population. A previously unidentified pore-scale fluid displacement event, droplet fragmentation, is described that occurs during the flow of two immiscible fluids specifically in carbonate rocks. The complex, heterogeneous pore structure of carbonate rocks induces this droplet fragmentation process, which explains the increased recovery of the nonwetting phase from porous carbonates as the wetting phase injection rate is increased. The previously unidentified displacement mechanism has implications for ( i ) enhanced oil recovery, ( ii ) remediation of nonaqueous liquid contaminants in aquifers, and ( iii ) subsurface CO ₂ storage.

The deep carbonate reservoirs in the Tarim Basin, Xinjiang, China, are widely developed with multi-scale complex reservoir spaces such as fractures, pores, and karst caves under the coupling of abnormal high pressure, diagenesis, karst, and tectonics and have strong heterogeneity. Among them, fracture–cavity carbonate reservoirs are one of the main reservoir types. Revealing the petrophysical characteristics of fracture–cavity carbonate reservoirs can provide a theoretical basis for the log interpretation and geophysical prediction of deep reservoirs, which holds significant implications for deep hydrocarbon exploration and production. In this study, based on the mineral composition and complex pore structure of carbonate rocks in the Tarim Basin, we comprehensively applied classical petrophysical models, including Voigt–Reuss–Hill, DEM (Differential Effective Medium), Hudson, Wood, and Gassmann, to establish a fracture–cavity petrophysical model tailored to the target block. This model effectively characterizes the complex pore structure of deep carbonate rocks and addresses the applicability limitations of conventional models in heterogeneous reservoirs. The discrepancies between the model-predicted elastic moduli, longitudinal and shear wave velocities (Vp and Vs), and laboratory measurements are within 4%, validating the model’s reliability. Petrophysical template analysis demonstrates that P-wave impedance (Ip) and the Vp/Vs ratio increase with water saturation but decrease with fracture density. A higher fracture density amplifies the fluid effect on the elastic properties of reservoir samples. The Vp/Vs ratio is more sensitive to pore fluids than to fractures, whereas Ip is more sensitive to fracture density. Regions with higher fracture and pore development exhibit greater hydrocarbon storage potential. Therefore, this petrophysical model and its quantitative templates can provide theoretical and technical support for predicting geological sweet spots in deep carbonate reservoirs.

Pegmatitic dyke-like carbonate rocks mainly composed of very coarse-grained calcite, are a rare type of carbonate rocks found in some of orogenic belts in the world. These specific carbonate rocks generally occur intimately with high-temperature granulites and marbles. In the Proterozoic Highland Complex of Sri Lanka which is a segment of the Mozambique suture, they are associated with marbles and granitic pegmatites, and intercalated with high-grade calc-silicate gneisses and highly folded ortho- and para-gneisses. These pegmatitic carbonate rocks do not show any signs of metamorphic or deformed overprint, but instead well preserve igneous textures and contain various silicate crustal xenoliths. The calcite crystals occur as euhedral to subhedral grains and are large in size from 1 to 15 cm. The diverse colors of calcite from white to yellow and blue derive from mineral inclusions and their own compositions. Non-carbonate minerals, commonly present in typical carbonatites such as phlogopite, apatite, clinopyroxene, olivine, plagioclase, iron oxides and spinel, are all found in the rocks. Meanwhile, a skarn-type assemblage of wollastonite, garnet, clinopyroxene and sulfide occurs in contact between the carbonate rocks and gneiss xenoliths, which probably resulted from antiskarn reactions. Chemical compositions of major constituent minerals (calcite, dolomite and apatite) of the carbonate rocks are intermediate between typical marbles and mantle-derived carbonatites and akin to crustal-origin carbonatites worldwide. We thus classify the studied rocks as ‘anatectic carbonatite pegmatite’, and suggest that they originated from the melting of a mixture of marbles and surrounding silicate rocks at crustal levels during high-temperature metamorphism.

Microdamage in a rock induces a change in the rock’s internal structure, affecting the stability and strength of the rock mass. To determine the influence of dissolution on the pore structure of rocks, the latest continuous flow microreaction technology was used, and a rock hydrodynamic pressure dissolution test device simulating multifactor coupling conditions was independently developed. The micromorphology characteristics of carbonate rock samples before and after dissolution were explored using computed tomography (CT) scanning. To conduct the dissolution test on 64 rock samples under 16 groups of working conditions, 4 rock samples under 4 groups were scanned by CT under working conditions, twice before and after corrosion. Subsequently, the changes in the dissolution effect and pore structure before and after dissolution were quantitatively compared and analyzed. The results show that the dissolution results were directly proportional to the flow rate, temperature, dissolution time, and hydrodynamic pressure. However, the dissolution results were inversely proportional to the pH value. The characterization of the pore structure changes before and after sample erosion is challenging. After erosion, the porosity, pore volume, and aperture of rock samples increased; however, the number of pores decreased. Under acidic conditions near the surface, carbonate rock microstructure changes can directly reflect structural failure characteristics. Consequently, heterogeneity, the presence of unstable minerals, and a large initial pore size result in the formation of large pores and a new pore system. This research provides the foundation and assistance for predicting the dissolution effect and evolution law of dissolved pores in carbonate rocks under multifactor coupling, offering a crucial guide for engineering design and construction in karst areas.

This research discusses the digital core to understand better the petrophysics parameters, especially the relative permeability of carbonate rocks. The method used in this research is descriptive-analytic by using primary data. The primary data is sample core data (digital data) collected and processed directly to compare results from digital data to laboratory data. This research indicates a relationship between the results from digital data with the results from laboratory data such as porosity, permeability, and trendline of a curve from relative permeability. Analysis from the research results shows that the relative permeability value was caused by several factors, i.e., wettability, cementation, clay, and bound water constant.

Fluid infiltration into (meta-)carbonate rocks is an important petrologic process that induces metamorphic decarbonation and potential mineralization of metals or nonmetals. The determination of the infiltration time and the compositional features of reactive fluids is essential to understand the mechanism and process of fluid–rock interactions. Zirconolite (ideal formula: CaZrTi2O7) is an important U-bearing accessory mineral that can develop in metasomatized metacarbonate rocks. In this study, we investigate the occurrence, texture, composition, and chronology of various types of zirconolite from fluid-infiltrated reaction zones in dolomite marbles from the Mogok metamorphic belt, Myanmar. Three types of zirconolite are recognized: (1) the first type (Zrl-I) coexists with metasomatic silicate and oxide minerals (forsterite, spinel, phlogopite) and has a homogeneous composition with high contents of UO2 (21.37 wt %–22.82 wt %) and ThO2 (0.84 wt %–1.99 wt %). (2) The second type (Zrl-II) has textural characteristics similar to those of Zrl-I. However, Zrl-II shows a core–rim zonation with a slightly higher UO2 content in the rims (average of 23.5 ± 0.4 wt % (n=8)) than the cores (average of 22.1 ± 0.3 wt % (n=8)). (3) The third type (Zrl-III) typically occurs as coronas around baddeleyite and coexists with polycrystalline quartz. Zrl-III has obviously lower contents of UO2 (0.88 wt %–5.3 wt %) than those of Zrl-I and Zrl-II. All types of zirconolite have relatively low rare earth element (REE) contents (< 480 µg g−1 for ΣREE). Microtextures and compositions of the three zirconolite types, in combination with in situ zirconolite U–Pb dating using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), reveal episodic fluid infiltration and element mobilization in the dolomite marbles. The first-stage infiltration occurred at ∼ 35 Ma, leading to the formation of Mg-rich silicates and oxides and accessory minerals (Zrl-I, baddeleyite, and geikielite). The reactive fluid was characterized by high contents of Zr, Ti, U, and Th. After that, some Zrl-I grains underwent a local fluid-assisted dissolution–precipitation process, which produced a core–rim zonation (i.e., the Zrl-II type). The final stage of fluid infiltration, recorded by the growth of Zrl-III after baddeleyite, took place at ∼ 19 Ma. The infiltrating fluid of this stage had relatively lower U contents and higher SiO2 activities than the first-stage infiltrating fluid. This study illustrates that zirconolite is a powerful mineral that can record repeated episodes (ranging from 35 to 19 Ma) of fluid influx, metasomatic reactions, and Zr–Ti–U mineralization in (meta-)carbonates. This mineral not only provides key information about the timing of fluid flow but also documents the chemical variation in reactive fluids. Thus, zirconolite is expected to play a more important role in characterizing the fluid–carbonate interaction, orogenic CO2 release, and the transfer and deposition of rare metals.