Characteristics Of Deposits Research Articles

Mineral and Geochemical Features of Zeolite-Silica Deposits of the Pauzhetka Geothermal Field (Southern Kamchatka)

On the Pauzhetka geothermal field the mineral deposits which are formed, when dumping thermal water of separators of wells, are allocated. Compositions, structure and geochemical properties of this precipitation on pro-deleting and in vertical slits of “raincoats” are studied. It is established that they are put X-ray amorphous mordenite – opal mixes (in the beginning dumping of thermal waters), further precipitation becomes completely siliceous. The zeolitic component of mineral deposits defines their high sorption properties in the relation of Au, Ag, Hg, As, Rb, Sr, Ba, Cs, etc. elements; in a mordenitovy matrix sulfides of iron, silver, copper are formed. It is shown that the mineral deposits which are formed on the day surface of the Pauzhetka geothermal field are the indicator of alkaline mineral- and the ore-forming processes on the lower horizons of the Pauzhetka hydrothermal system.

Petrological Characteristics of Lateritic Bauxite Deposits of India and Their Significance in Mineral Processing

India is endowed with 3896 million tons of bauxite resources and ranking it fifth globally. The bauxite comprises various minerals such as gibbsite, boehmite, diaspore, hematite, goethite, kaolinite, quartz, anatase and rutile. India possesses abundant lateritic bauxite resources originating from parent rocks like Khondalite, Deccan trap basalt, Granite Gneiss, Sandstone, etc., each exhibiting its specific characteristics. The geotechnological evaluation of India's lateritic bauxite deposits, conducted by Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARDDC), revealed the presence of two types of deposits: high-level and low-level (coastal). In this study, bauxite and laterite samples were collected from different regions in India and subjected to comprehensive technological evaluation. Mineral processing techniques are optimized based on the mineralogical and petrological characteristics of the bauxite deposits. The mineral liberation, association, and alteration information obtained through petrological analysis guide the selection and optimization of various methods. The understanding of the mineralogy and petrological characteristics also assists in predicting the behaviour of bauxite during the processing stages, facilitating process control and minimizing losses. This paper aims to highlight the petrological, chemico-mineralogical characteristics of Indian lateritic bauxite deposits and emphasize the significance of petrology and mineralogy in their evaluation and mineral processing. Microscopic examination plays a vital role in mineral characterization and the beneficiation process by enabling mineral identification, texture analysis, grain size, mineral liberation, association, alteration, and process optimization. Such comprehensive analysis contributes to maximizing the economic value of mineral resources, aiding informed decision-making in exploration, mining, and mineral processing industries. Keywords: Bauxite, Lateritic Deposits, Petrological Characteristics, Mineralogy, Mineral Processing

The contribution and impact of shallow water platform as a potential source area on siliceous submarine fans

AbstractThe shelf‐margin deltas are the primary ‘sources’ of interest in siliceous submarine fan source‐to‐sink systems. However, less has yet to be discovered about the roles and effects of the shallow water platform situated on continental slopes. Using the Miocene sediments of the Ledong‐Lingshui Sag in the western part of the Qiongdongnan Basin (QDNB), this paper studies the YC35 coarse‐grained submarine fan that developed in the Meishan Formation (Fm.). The material sources, depositional characteristics, and developmental mechanisms of this fan were investigated. The restored palaeogeomorphology, based on high‐resolution 3D seismic data, shows that a shallow water platform exists. According to geochemical palaeoenvironmental data, the shallow water platform was ideal for forming carbonate deposits in the Meishan Fm., owing to the warm and humid palaeoclimate and the shifting trend in palaeowater depth. Based on the combined source tracing of heavy minerals, coherence slices, and seismic profiles, the shallow water platform and the Ningyuan River source on Hainan Island contributed to the YC35 coarse‐grained submarine fan. Compared to submarine fans formed during different periods, coarse‐grained fan stands out due to its distinct sedimentary structure, rock composition, and microlithological characteristics. Aside from not following the usual Bowmar sequence, there is an excess of gravel and no clear bedding or lamination. A large number of rock fragments, mostly granite and sedimentary rock (carbonatite), make up the rock composition. According to these results, the shallow water platform significantly affects submarine fan material composition. In addition, the attribute slice based on the root mean square reveals that shallow water platforms moderate peripheral deposition. We attribute the development and proximal supply of the shallow water platform to diapirism and forced regression. Our research provides novel insights and comprehension into the investigation of submarine fan sedimentary systems.

Mixing, Burning and Deposit Characteristics of a Mixture of Karanja Oil Biodiesel and Tyre Pyrolysis Oil Along with Graphene Nanoparticles

Mixing, Burning and Deposit Characteristics of a Mixture of Karanja Oil Biodiesel and Tyre Pyrolysis Oil Along with Graphene Nanoparticles

Sedimentological depositional features of Imam Hatip, Çiftlik Basin Central Anatolia, Turkey

Sedimentological depositional features of Imam Hatip, Çiftlik Basin Central Anatolia, Turkey

Gold mineralization in the diaphthorites of the Verkhne-Timptonskiy ore district (Aldan-Stanovoy shield)

In the Verkhne-Timptonskiy gold ore district, located where the Stanovoy and Aldan blocks intersect (Aldan-Stanovoy shield), substantial placer gold deposits have been found in the Gonam, Timpton, and Iengra rivers. The exploration of certain deposits in this area began at the end of the 19th century. Despite exploration efforts conducted in the second half of the 20th century, only minor gold ore findings were made, with uncertain links to greenstones and igneous formations from various periods. After conducting a thorough analysis of both existing and new data on the geology and metallogeny of the Verkhne-Timptonskiy gold ore district, we have concluded that gold occurrences in diaphthorites of the Kholodnikan belt display characteristic features of orogenic-type gold deposits. These features include disseminated pyrite and veinlet mineralization containing iron (Fe), lead (Pb), zinc (Zn), copper (Cu) sulfides, and sulfosalts. The near-ore alterations are represented by silicification, sericitization, carbonatization, and beresitization, characteristic of mesothermal fluid systems. Moreover, we identified common features of the geological structure and metallogeny of the Verkhne-Timptonskiy gold ore district and the Jiaodong province of the North China Craton. Thus, gold mineralization in the Verkhne-Timptonskiy gold ore district and the Jiaodong province is spatially associated with suture zones. In the Verkhne-Timptonskiy gold ore district, the Amga zone of tectonic melange in the Paleoproterozoic era was one of the regions where cratonization of blocks of the Earth’s crust occurred. Later, it became a zone of permeability and concentration of tectonothermal and metallogenic events of various ages. The results obtained will help assess the metallogenic potential of the Verkhne-Timptonskiy district and the Aldan-Stanovoy shield as a whole. They make it possible to increase the efficiency of search operations and focus on localizing research objects.

Experimental study on the scaling law of the heat exchange tube surface in the process of low-temperature single-effect distillation of high-mineralized mine water

High-mineralized mine water, due to its characteristics such as high mineralization degree, will have scaling phenomena on the surface of the heat exchange tube during the desalination treatment process, resulting in a reduction in the water production efficiency of the equipment and affecting the normal operation. To reduce the cost of water production and improve the service life of distillation equipment, this paper independently designs and builds a low-temperature single-effect distillation high-mineralized mine water experimental system to study the influence of operating parameters (temperature, spray density, concentration ratio, and system pressure) on the scaling law on the surface of the heat exchange tube. The distribution and characteristics of scale deposits on the surface of the heat exchange tube are analyzed through the growth rate and microscopic morphology of the scale deposit. The results indicate that the scaling on the surface of the titanium plate is mainly in the needle-like and rod-like morphology of CaCO3 aragonite, and a small amount of CaSO4 and calcite are generated with the increase of temperature. It was found that within the range of spray density from 0.0509 kg/(m·s) to 0.0625 kg/(m·s), concentration ratio from 2.3 to 2.7, and system pressure at 36.3 kPa, it is beneficial to the evaporation heat transfer of the heat exchange tube and the reduction of scaling generation. At the same time, it is found that the scaling of the first row of heat exchange tubes is mainly within the range of circumferential angle from 0 to 100 degrees, and the scaling of the second row and the third row of heat exchange tubes is mainly within the range of circumferential angle from 110 to 170 degrees. The research results of this paper provide support for the design and operation of the low-temperature multi-effect treatment system for mine water in engineering, promote the process of zero discharge of high-mineralized mine water in Xinjiang, China, and improve the resource utilization rate of high-mineralized mine water.

АНАЛИЗ МИНЕРАЛЬНО-СЫРЬЕВОЙ БАЗЫ И ДИНАМИКИ ДОБЫЧИ ДРАГОЦЕННЫХ МЕТАЛЛОВ В МАГАДАНСКИЙ ОБЛАСТИ

The authors of the article provides data on the balance reserves of mineral resources of the Magadan region, gives characteristics of the main deposits of precious metals that form the mineral resource base of the Magadan region, analyzes the dynamics of the production of precious metals (gold, silver) in the Magadan region for the period 2021-2023, highlights shares of precious metals extraction from ore and placer deposits.

Constraints of alkaline magmatic evolution on the enrichment and mineralisation of rare-earth elements in the eastern part of the northern margin of the North China Craton: a case study of the Baerzhe and Saima deposits

The eastern part of the northern margin of the North China Craton is a key metal metallogenic province in China, hosting many important rare metal and rare earth element (REE) deposits and having great resource potential. This study investigated the Saima deposit, a niobium (Nb) and tantalum (Ta) deposit and the Baerzhe deposit hosting zirconium (Zr), Nb and REEs. Based on previous LA-ICP-MS zircon U–Pb dating results obtained by the authors’ team, this study compared the whole-rock geochemistry and whole-rock Sr–Nd–Pb isotopes of an orebody with its surrounding rocks. The geochemical characteristics of both deposits are used to systematically review the evolution of the alkaline magma and the differences in the physical and chemical conditions for enrichment and mineralisation of late-stage rare elements and REEs such as Nb, Ta and Zr. Comparing the mineralisation of the Saima and Baerzhe deposits, the alkaline magmatic evolution plays a crucial role in the enrichment of rare-earth elements, which are generally formed in the late stage of alkaline magmatic evolution.

The interplay of detrital modes and depositional facies on diagenesis and petrophysics of deep-marine Miocene sandstones (Cilento Group), Southern Apennines, Italy

The Cilento Group (Langhian-to-Tortonian) is a thick turbiditic succession of the Southern Apennines foreland region that unconformably overlain the Lucanian oceanic terranes. The San Mauro Formation (SMF) form the uppermost portions of the Cilento Group, and consists of 1400–1600 m thick turbiditic succession including quartzolithic, volcanolithic, and quartzofeldspathic sandstones with several carbonatoclastic layers interbedded, passing upward from distal-to proximal-facies associations. Here, based on the vertical changes of texture and petrology in the succession, the SMF was divided in two main sections. The key depositional features and the main post-depositional processes, of lower- and upper-part of SMF, are compared with the most significant petrophysical properties with the purpose to elucidate the major controls on the porosity and permeability evolution during burial. With this aim, fifty-four thin sections were petrographically investigated, while mercury intrusion analysis was performed on twenty-four samples. Compaction, cementation, dissolution and fracturing occurred in the SMF, altering porosity and permeability. The main authigenic minerals are: 1) carbonates, mainly calcite and less dolomite, dominantly occurring as replacement of framework grains; 2) Phyllosilicates, mainly developing in the upper part of SMF as pore-filling cement or as small and incomplete grain coatings; 3) Fe-oxides occurring as coatings or localized crystals. The relationship between the compactional porosity loss (COPL) and the cementational porosity loss (CEPL) testifies the primary role of compaction in decreasing porosity, reducing the intergranular volume (IGV) to 11.1% in the lower SMF and to 16.7 % in the upper SMF. The coarse upper SMF samples exhibit lower mean porosity and permeability (6 % and 215 mD, respectively) than the fine lower SMF samples (9.2 % and 774.2 mD, respectively). In the upper section of SMF, a comparatively more widespread pore-filling cementation and the abundant detrital matrix affect depositional intergranular porosity, reducing the pore size and interconnectivity. Moreover, the higher amount of rigid grains (petrofacies dependent) and their brittle deformation produce an intricate fragmentation and micro-fracturing system, altering pores geometry and affecting permeability. On the contrary in the lower SMF, ductile components suffer compaction more than rigid ones, leading the lowest IGV. In addition, a higher volume of authigenic carbonates occur as replacement on framework components, hence playing a minor occluding role and less affecting the pore system. Composition and tectonics rule the effects of diagenetic processes in the San Mauro turbiditic succession, following the vertical evolution of depositional facies association and petrology.

Effect of different HVOF coatings on the tribological behavior of PVD/HVOF duplex coatings

CrN film shows obvious differences in hardness, elastic modulus, and thermal expansion coefficient between film and substrate, suffering from poor adhesion and wear resistance. Here we combined PVD and HVOF technologies to produce CrN/WC-12Co and CrN/WC-10Co-4Cr coatings, and then compare their mechanical and tribological behavior with that of CrN film. We show that the PVD/HVOF coatings exhibit higher hardness, load carrying capability, and adhesion; the wear resistance also be improved greatly, especially for CrN/WC-10Co-4Cr. We discuss the wear mechanism of such duplex coatings and analyze the influence of different HVOF coatings on the deposition characteristic of CrN film.

Experimental and mechanism study on wax deposit dissolution characteristics by light crude oil

During the sequential transportation of waxy crude oil and light oil, the previous formed wax deposits on the pipe wall will dissolve by light oil, which brings risks to the flow safety of the pipeline. This paper adopted a Couette wax deposit dissolution experimental device to systematically study the effects of dissolution duration, oil temperature, rotation speed and wax deposit properties on the dissolution characteristics of wax deposits. It is found that the dissolution of wax deposits is a process that starts quickly and then slows down. Moreover, the wax content of wax deposit also decreased during the dissolution process. The wax deposit dissolution process is mainly divided into five stages such as diffusion of wax molecules from wax deposit to the light oil and from bottom layer deposit to the wax deposit-oil interface, dissolution of wax crystal particles, weakening of wax deposit structural strength, and shear stripping of wax deposits. Finally, an empirical model of wax deposit dissolution was established and the undetermined parameters were fitted based on experimental data. The prediction results have good prediction accuracy with the experimental values.

Interpreting environments of deposition from facies analysis of outcrop versus seismic reflection data: A cautionary tale from the Mount Messenger Formation, Taranaki Basin (New Zealand)

The lower part of the Mount Messenger Formation, which crops out along the North Taranaki coast (North Island, New Zealand), is widely regarded to display classic examples of exhumed basin floor fan strata. This interpretation is supported by numerous publications on the sedimentary facies and depositional environments inferred for these strata, which are exposed in coastal cliff exposures about 20 m high with limited lateral extent. Consequently, for almost three decades, this succession has served as an analogue and training ground for geoscientists investigating the features of basin floor fan deposits and their reservoir characteristics. Here, we bring together seismic stratigraphy and seismic geomorphology of 2D and 3D seismic reflection datasets, as well as photogrammetric models based on images collected using uncrewed aerial vehicle (UAV) drones from selected locations along the outcrop belt to challenge this paradigm. We analyzed seismic reflection data in an area immediately offshore and down-dip of the strata exposed in the coastal outcrop and found no objective criteria for submarine fan depositional elements based on accepted seismic stratigraphic criteria. Furthermore, mapping of seismic reflectors revealed large submarine channel systems (up to 3 km wide and up to 200 m deep) within the lower part of the Mount Messenger Formation. Submarine channel depositional elements (less than 250 m wide and 25 m thick) are also observed to incise through the outcrops, but they are generally below seismic resolution. In the context of the regional geology, we conclude that the lower Mount Messenger Formation accumulated as continental slope sediments cross-cut by channels rather than as basin floor fans. This study issues a cautionary tale about applying facies analysis to outcrop with limited 3D exposure to interpret sedimentary environments. The spatial distribution of facies and architectural elements viewed in seismic data are invaluable for testing the veracity of facies interpretations.

Ex Vivo Histological Analysis of Corneas with Manually Implanted Intracorneal Stromal Ring Segments.

Backgrond: Intracorneal ring segments (ICRSs) are utilized to correct refractive changes impacting visual acuity, commonly implanted via femtosecond laser but can also inserted manually. Corneal deposits alongside the ICRS channels are seen commonly. Methods: This study explores the histological characteristics of corneal deposits following manual ICRS implantation, comparing them to previously published articles describing femtosecond laser-assisted cases. Results: This is a retrospective analysis of three cases involving manual ICRS implantation, accumulation of whitish deposits and later explanation of the corneas due to penetrating keratoplasty (PKP). Patient demographics, ocular history, and surgical details were collected. Histological analysis employed Hematoxylin and Eosin (H&E) and Masson's trichrome staining. Whitish deposits along ICRS tracts were observed in all cases, with minimal fibroblastic transformation of keratocytes adjacent to the segments. Comparing these cases of manual to femtosecond laser-assisted ICRS implantation, in most cases, similar deposits were identified, indicating the deposits' association with the stromal tissue reaction to the ring segment and not to the surgical technique. Conclusions: This study contributes insights into the histopathology of manually implanted ICRS, emphasizing the shared nature of deposits in both insertion methods. The findings highlight the link between deposits and the stromal tissue reaction to the ring segment, irrespective of the insertion technique.

Coupling relationship and genetic mechanisms of shelf-edge delta and deep-water fan source-to-sink: A case study in Paleogene Zhuhai Formation in south subsag of Baiyun Sag, Pearl River Mouth Basin, China

The coupling relationship between shelf-edge deltas and deep-water fan sand bodies is a hot and cutting-edge field of international sedimentology and deep-water oil and gas exploration. Based on the newly acquired high-resolution 3D seismic, logging and core data of Pearl River Mouth Basin (PRMB), this paper dissected the shelf-edge delta to deep-water fan (SEDDF) depositional system in the Oligocene Zhuhai Formation of Paleogene in south subsag of Baiyun Sag, and revealed the complex coupling relationship from the continental shelf edge to deep-water fan sedimentation and its genetic mechanisms. The results show that during the deposition of the fourth to first members of the Zhuhai Formation, the scale of the SEDDF depositional system in the study area showed a pattern of first increasing and then decreasing, with deep-water fan developed in the third to first members and the largest plane distribution scale developed in the late stage of the second member. Based on the development of SEDDF depositional system along the source direction, three types of coupling relationships are divided, namely, deltas that are linked downdip to fans, deltas that lack downdip fans and fans that lack updip coeval deltas, with different depositional characteristics and genetic mechanisms. (1) Deltas that are linked downdip to fans: with the development of shelf-edge deltas in the shelf area and deep-water fans in the downdip slope area, and the strong source supply and relative sea level decline are the two key factors which control the development of this type of source-to-sink (S2S). The development of channels on the continental shelf edge is conducive to the formation of this type of S2S system even with weak source supply and high sea level. (2) Deltas that lack downdip fans: with the development of shelf edge deltas in shelf area, while deep water fans are not developed in the downdip slope area. The lack of “sources” and “channels”, and fluid transformation are the three main reasons for the formation of this type of S2S system. (3) Fans that lack updip coeval deltas: with the development of deep-water fans in continental slope area and the absence of updip coeval shelf edge deltas, which is jointly controlled by the coupling of fluid transformation at the shelf edge and the “channels” in the continental slope area.

Correlation Analysis Between Tumor Deposit and Clinicopathologic Characteristics and Prognosis of Gastric Cancer: A Multicenter Retrospective Study.

The mechanism underlying the formation of gastric tumor deposits (TDs) is unclear. We aimed to explore the risk factors for the formation and prognostic value of TDs. This retrospective analysis included 781 locally advanced gastric cancer (LAGC) patients from four medical institutions in China, from June 2014 to June 2018. The risk factors for TD formation and prognostic value were determined through univariate and multivariate analyses. Univariate analysis revealed that TD positivity was closely related to tumor diameter, Borrmann classification, differentiation degree, pT stage, pN stage, pTNM stage, and nerve and vascular invasion (p < 0.05). Multivariate logistic regression revealed that tumor diameter ≥ 5cm (odds ratio [OR] 1.836, 95% confidence interval [CI] 1.165-2.894, p = 0.009) and vascular invasion (OR 2.152, 95% CI 1.349-3.433, p = 0.001) were independent risk factors for TD positivity. Multivariate Cox analysis revealed that TD positivity (OR 1.533, 95% CI 1.101-2.134, p = 0.011), tumor diameter ≥ 5 cm (OR 1.831, 95% CI 1.319-2.541, p<0.001), pT4a stage (OR 1.652, 95% CI 1.144-2.386, p = 0.007), and vascular invasion (OR 1.458, 95% CI 1.059-2.008, p = 0.021) were independent risk factors for GC prognosis. The 5-year overall and disease-free survival of the TD-positive group showed significant effects among patients in the pT4a and pN3b stages (p < 0.05). TDs are closely related to tumor diameter and vascular invasion in LAGC patients, and TD positivity is an independent prognostic factor for LAGC patients, especially those at pT4a and pN3b stages.

Correlation between flood couplet-based sediment yield and rainfall patterns in a small watershed on the Chinese Loess Plateau

Understanding how rainfall patterns impact sediment yields during rainfall events is important to explore soil erosion changes and to prevent watershed flood disasters. However, few studies identified sediment yields variation affected by rainfall patterns at continuous deposited flood couplet scale. This study analyzed sediment yields under different rainfall patterns and correlated particle depositional features on the condition that the erosive environment was obviously changed by anthropogenic activities in a check dam-controlled small watershed on the Chinese Loess Plateau. Results showed that erosive rainfall events, having formed 40 flood couplets behind the check dam between 1978 and 2010, can be grouped into three rainfall patterns (i.e., rainfall patterns I, II, and III) according to changes in rainfall amount, erosivity, and duration. Rainfall pattern III, characterized by high rainfall amount and erosivity within a short duration (i.e., rainstorm) accounted for only 15.0 % of erosive rainfall events while yielding 44.7 % of the total sediment. Conversely, rainfall pattern I (the most common, 55.0 %), characterized by its long duration and relatively low rainfall amount and erosivity, only contributed 25.3 % of the total sediment. Both sediment yields and thickness proportions of coarse particle layer in flood couplets exhibited a decreasing trend under all three rainfall patterns. Meanwhile, the main factor that impacted sediment yields changed from rainfall in the 1980s and 1990s to the “Grain for Green” program dominated anthropogenic activities since 1999. For a small watershed with a few terraces and only one check dam at the outlet, artificial vegetation restoration significantly reduced coarse soil particle loss and sediment yield. Findings showed that sediment yield and deposition feature variations in flood couplets under different rainfall patterns are helpful in improving watershed soil and water conservation measures against flood disasters, particularly under rainstorms.

Effects of dissolved oxygen on the corrosion-related unidentified deposit formed of 304 SS in the flow accelerated zone under the simulated secondary water chemistry

Effects of dissolved oxygen (DO) on the deposition characteristics of corrosion-related unidentified deposit (CRUD) were investigated by using 304 stainless steel micro-orifices. The main results indicate that the change of DO concentration resulted in a change of the composition of the outermost deposition layer. The DO concentration amplifies/diminishes the porosity in CRUD effect by changing the rate of ion transport. Meanwhile, the electrokinetic effect is weakened by the decrease of the thickness of the electric double layer, which is caused by the dissolution of Cr ions increased by increasing the DO concentration. Meanwhile, the chromium ion concentration increases with the dissolved oxygen concentration, which leads to a decrease in the thickness of the electric double layer, weakening the electrodynamic effect. The above results in the thickness and width of CRUD in the flow acceleration zone vary in varying degrees. This suggests that the deposition process of CRUD occurs under the mechanism of mass transfer and electrokinetic mechanism.

Correlation between geomechanical and sedimentary facies and their implications for flow unit definition in the pre-salt carbonate reservoir, Brazil

Carbonate reservoirs are of great economic importance due to their frequent association with high permeability and hydrocarbon storage capacity. One of the most significant discoveries of this type of reservoir in recent decades has been the Brazilian Pre-salt. This deep reservoir has unusual depositional features, consisting of a wide variety of textures with different compositions, influenced by diagenetic overprinting that modify most of its mechanical, elastic and petrophysical properties. Despite the marked heterogeneity, these carbonates are characterized by excellent reservoir quality. The objective of this study is to establish a correlation between geomechanical behavior and sedimentary facies and its implications for the definition of flow units in the Barra Velha Formation, the main reservoir of the Brazilian Pre-salt. Thus, using a database from the Buzios field composed of well logs (conventional and advanced), well tests, thin sections, and laboratory petrophysics, geomechanical facies (GMFs) were defined using dynamic geomechanical modeling and an unsupervised algorithm (K-mean clutering), followed by textural classification of sedimentary facies and definition of flow units (FUs) on the decametric scale. These classifications were compared using frequency histograms. The geomechanical model revealed that the in-situ stress state exhibits a dual regime, between normal and strike slip. In addition, it was found that the direction of the maximum horizontal stress is in the NE-SW azimuth. In this context, four geomechanical facies were defined, which showed a notorious variation in mechanical strength. The strongest GMFs consisted mainly of well-cemented Grainstones and Packstones with no apparent porosity or microcrystalline porosity and correlated with the FU with the worst production rates. On the other hand, the weaker GMFs were mainly composed of Grainstones and Spherulistones with high intergranular porosity generated by dissolution processes, with higher risk of pore collapse and correlated with the FUs with the best production rates. However, this classification also identified laminated mudstones with microporosities associated with FUs that act as flow barriers. Geomechanical facies have also been incorporated into reservoir development by evaluating wellbore stability, fault reactivation risk, and brittleness index for future CO2 injection projects.

Epithermal Ag–Au mineralization at Galim-Legalgorou, Cameroon Volcanic Line: insights from alteration mineralogy and mineral chemistry of electrum and sphalerite

The Galim-Legalgorou area, located along the north-western branch of the Cameroon Volcanic Line (CVL), is known for artisanal gold mining and primary gold exploration, but the style and origin of the mineralization has not been fully described in the scientific literature. The close spatial association of the mineralization with Tertiary volcanic rocks raises the question of whether or not this is an epithermal system in a region where all previously studied gold occurrences have been classified as orogenic. In this contribution, we use ore mineral and alteration assemblage and mineral microchemistry to constrain the origin and evolution of the mineralization. Gold is alloyed mainly with Ag (max. 53.1 wt%) and show fineness values that vary 379 and 721 with an average of 455. A cumulative percentile plot of Ag concentrations in the cores of all electrum particles, and the observed step-change from Au-rich cores to more Ag-rich mantles in zoned electrum particles, suggest that the mineralization was deposited by two distinct hydrothermal fluid influxes. The observed ore mineral association-electrum, Se/Tl-acanthite, pyrite, Fe-rich sphalerite, ± galena; the measured FeS contents of sphalerite (average 23.1 mol%), and the presence of colloform banded chalcedony and hydrothermal breccia are all consistent with features of low sulfidation epithermal deposits. This study, therefore, demonstrates for the first time, the presence of significant low sulfidation epithermal Ag–Au mineralization on the CVL, an intracontinental rift region only previously known for orogenic gold mineralization.Graphical