Development Of Deposits Research Articles

Insights into the synergistic effects of tectonics and climate from the formation and evolution of the Hongwen allochthonous deposit, southwestern China

Abstract The formation and evolution of large-scale deposits generated by mass movement are often closely related to tectonic and climatic conditions. Investigating deposits under the influence of complex geological conditions can aid in reconstructing paleoenvironmental characteristics and fluvial geomorphic evolution. The First Bend of the Yangtze River (FBYR), located in the Jinsha River basin in southwest China, represents a significant section characterized by abundant allochthonous deposits. We conducted a detailed investigation of the Hongwen allochthonous deposit (HAD) and the river sediments in the First Bend. Through terrain interpretation, dating, and paleoenvironmental analysis, the HAD was determined to be a complex deposit with multiple sources and stages (46.4–33.5 ka), formed under the combined influence of tectonic activity and climate. Three mass-movement events occurred during the interglacial stage of the last glacial period or its transitional period, coinciding with the rapid uplift stage of the Tibetan Plateau since the late Pleistocene. Prominent features of this period include significant rainfall and tectonic activities. By dating fluvial sediments and examining the evolution of the HAD, we revealed a river incision rate of 2.30 mm/yr for the Jinsha River, providing a basis for analyzing periodic river cutting and the development pattern of surface processes.

Sea-level changes and human economic development in the northern flank of the Yangtze River Delta during the Middle to Late Holocene

The environmental dynamics in coastal regions are inevitably influenced by fluctuations in sea levels and human interventions. Evidence derived from archeological site remains and sediment cores indicates that sea-level change has been the primary driving force behind the continuous relocation of human settlements since the Holocene epoch. However, the understanding of the Holocene land formation process and its relationship with human activities in the northern flank of the Yangtze River Delta remains limited. The Guoqing Temple, located in southwest Juegang and serving as a hub for sea salt production during the Sui and Tang Dynasties, was established in the Tang Dynasty and served as one of the pivotal points along the Maritime Silk Road. A sedimentary core was obtained in close to the Guoqing Temple, and the sedimentological and micropalaeontological data were analyzed to investigate the process of sedimentary evolution from marine to terrestrial environments, as well as the environmental factors facilitating the development of the salt industry. Analysis results explained that: Between 6360 and 1750 cal yr BP, the study area was situated in a shallow sea on the outermost periphery of the sandbank, with a maximum water depth of 20 m. After 1750 cal yr BP, it underwent a transition to a supratidal low-salinity shallow marsh environment that continued to be influenced by marine conditions. The climate in the study area is primarily influenced by the Asian monsoon: Before 3000 cal yr BP, the overall climatic conditions were characterized by warm and humid conditions; After 3000 cal yr BP, climate stability prevailed in the region. Meanwhile, due to the newly formed wetlands that facilitated extensive salt production, economic shifts toward southern regions, and reforms in salt laws during the Tang Dynasty, Juegang emerged as a flourishing commercial trade hub and a prosperous center for Buddhist culture.

Deeply buried clastic rock diagenesis evolution mechanism of Dongdaohaizi sag in the center of Junggar fault basin, Northwest China

Abstract To reveal the diagenetic sequence of reservoir rocks in the central part of the deep depression basin, the Wuerhe Formation in Junggar Basin was taken as an example to conduct the detailed studies on its sedimentary facies, diagenetic sequence, and the micropore structure evolution rules based on the comprehensive data from a super deep exploration well C-6 (approximately 7,000 m in depth). First, an arid environment fan delta sedimentary model of the Wuerhe Formation was established, and its sedimentary evolution law was clarified as a gradual transition from a fan delta front to a fan delta plain during the water-regression process until the lake dried up. Then, the diagenesis types and evolution sequence of the Wuerhe Formation, and the influence degrees of the compaction, cementation, and dissolution on the rock formation process were clarified. Finally, the diagenesis and pore evolution model was established, and the greatest impact factors of the late reservoir densification were clarified. Based on this research, the diagenesis and pore evolution processes of the deep rocks in the studied deep central sag were ultimately revealed to provide useful guidance for the deeply buried oil and gas reservoir exploration.

Hydrothermal mineral replacement of bastnäsite by rhabdophane and monazite: effects of temperature on mineralogy, REE immobilisation, and fractionation

The rare-earth elements (REEs, La–Lu, Y) are essential for the development of renewable technologies. Bastnäsite (REECO3F) is a common REE ore mineral that is often subject to hydrothermal alteration at all crustal levels. Mechanisms of hydrothermal bastnäsite alteration therefore govern the evolution of REE deposits, though these mechanisms remain poorly understood. This experimental work investigates the hydrothermal replacement of bastnäsite by rhabdophane (REEPO4∙xH2O, x = 0–1) and monazite (REEPO4) in phosphatic fluids. Two temperature-dependent alteration pathways were identified; both follow the coupled dissolution-reprecipitation (CDR) mechanism. At 90 °C, bastnäsite was replaced by highly-porous metastable rhabdophane which was then replaced by monazite, forming an inner layer of rhabdophane and an outer layer of monazite. At 220 °C, bastnäsite was replaced directly by monazite. Although replacement initiated more quickly at 220 °C, greater overall replacement occurred at 90 °C (~ 61 wt.% after 500 h, compared to ~ 13 wt.% at 220 °C) due to surface passivation by monazite at 220 °C. Geochemical analyses showed REE fractionation during bastnäsite alteration. At 90 °C, rhabdophane was enriched in heavy REEs (Eu–Lu, Y), likely due to the evolving fluid chemistry, while at 220 °C secondary monazite was enriched in Sm and Ho compared to bastnäsite. These results indicate that: 1) the hydrothermal alteration of bastnäsite by rhabdophane and monazite in ore deposits leads to REE immobilisation, with little net loss of REEs to solution; 2) rhabdophane is metastable relative to monazite at 90 °C, and; 3) variable temperatures can cause different mineral textures and REE fractionation trends during hydrothermal alteration and mineral replacement.

Holocene environmental evolution and its relationship with human culture in the Luoyang area, Central China

As a key region for the origin and development of Chinese civilization, the relationship between the Holocene environment and human culture in the Luoyang area has garnered significant attention. However, the lack of long-term and multi-factor studies impedes our understanding of the overall characteristics of environmental systems and their interactions with human cultures. Based on extensive field investigations, we conducted a comprehensive study of the BZ profile, which exhibits continuous sedimentation and abundant paleoenvironmental information. The Holocene evolution of climate, deposition, hydrology, and landforms was analyzed, and the human-environment interaction was also examined. The findings demonstrate that the regional Holocene climate also exhibits fluctuations, albeit within a relatively narrow range. The regional sediment was predominantly composed of aeolian loess-paleosols during the early to middle Holocene, while the process of alluviation gradually intensified in the late Holocene. The moderate climatic fluctuations have facilitated the sustainable development of ancient cultures. The intensification of anthropogenic activities may contribute to the increased alluviation during the late Holocene. Ancient humans effectively adapted to this adverse condition by constructing city walls with flood control functions. Our study is significant for enhancing the comprehension of the operational characteristics inherent in human ecological systems.

Along-strike variation in volcanic addition controlling post-breakup sedimentary infill: Pelotas margin, austral South Atlantic

Abstract. We investigate, using observations from seismic reflection data, the lateral variability in breakup extrusive magmatic addition along the strike of the Pelotas segment of the austral South Atlantic rifted margin and its control on post-rift accommodation space and sediment deposition. Our analysis of regional seismic reflection profiles shows that magmatic addition on the Pelotas margin varies substantially along strike from extremely magma-rich to magma-normal within a distance of ∼300 km. Using 2D flexural back-stripping, we determine the post-rift accommodation space above top volcanics. In the north, where volcanic seaward-dipping reflectors (SDRs) are thickest, the Torres High shows SDRs up to ∼20 km thick, and post-breakup water-loaded accommodation space is much less than in the south, where magmatic addition is normal and SDRs are thinner. We show that post-breakup accommodation space correlates inversely with SDR thickness, being less for magma-rich margins and more for magma-normal/intermediate margins. The Rio Grande Cone, with large sediment thickness, is underlain by small SDR thicknesses allowing large post-breakup accommodation space. A relationship is observed between the amount of volcanic material and the two-way travel time (TWTT) of first volcanics: first volcanics are observed between 1.2 and 2.2 s TWTT for the highly magmatic Torres High profile, while, in contrast, for the normally magmatic profiles in the south, first volcanics are observed between 4.2 and 6.5 s TWTT. The observed inverse relationship between post-breakup accommodation space and SDR thickness is consistent with predictions by a simple isostatic model of continental lithosphere thinning and magmatic addition melting during breakup. The methodology that we use in this paper provides a new approach for investigating the complex magmatic and sedimentary evolution of rifted continental margins.

Metamodeling the deposition process in oil preprocessing to optimize heat exchanger cleaning: a deep neural network approach

The accumulation of deposits in heat exchangers during oil preprocessing, known as fouling, compromises thermal efficiency and increases maintenance and energy costs. This study aimed to develop effective strategies for managing these deposits to optimize heat exchanger operations. Metamodeling combined with Artificial Intelligence was employed, using machine learning models to process sequential data, which is crucial for understanding the evolution of deposits over time. Two machine learning models, Deep Neural Networks (DNN) and Long Short-Term Memory (LSTM), were trained and evaluated. The DNN achieved a Mean Squared Error (MSE) of 0.05345, outperforming the LSTM, which had an MSE of 0.8763. The results suggest that the DNN was more effective in predicting fouling, although both models showed signs of overfitting. Advanced monitoring technologies, such as IoT and remote sensing, as well as predictive maintenance, were found to be essential for improving operational efficiency and reducing costs, highlighting the importance of digitalization and automation in oil preprocessing.

Eolian-fluvial succession in the Early Cretaceous from the Ordos Basin

Cretaceous eolian deposits are widely developed in North China, among which the Lower Cretaceous eolian (erg) sedimentary strata in the Ordos Basin are the most representative. Many studies have been conducted on eolian deposits in the Ordos Basin, especially the Luohe Formation; however, there is a lack of systematic sedimentology research and the corresponding research on the evolution of sedimentary facies. Therefore, to explore the Mesozoic drought events and the systematic evolution of the sub-tropical erg zone, this study reports the fluvial–eolian sedimentary sequences of the Early Cretaceous Luohe and Yijinhuoluo Formations in the Ordos Basin. Spatially, through detailed sedimentary lithofacies and structural analysis of different outcrops, the combination law of sedimentary facies can be determined. Based on this, a three-dimensional sedimentary model of erg is reconstructed. The erg environment is divided into three sub-environments: erg margin, erg margin–centre transition and erg centre. According to the evolution of the sedimentary facies, the sedimentary evolution from the Latef Jurassic to the Early Cretaceous in the Ordos Basin is divided into five stages. The Ordos Basin has experienced the delta, erg formation, erg deposition, erg shrinkage and evaporating salt-lake stages. The vertical sedimentary evolution indicates climatic oscillation in North China from the Late Jurassic to the Early Cretaceous. Under the control of the sub-tropical high belt, the Ordos Basin experienced a hot and arid climate during the Cretaceous, forming a widely distributed erg belt in the region. During this period, a small-scale climate shock occurred under the hot and arid background, changing the sedimentary environment.

Pollen morphology and fruit anatomy of the enigmatic monotypic genus Dicranocarpus (Coreopsideae, Asteraceae)

Dicranocarpus is a monotypic genus endemic to the Chihuahuan Desert with atypical attributes among species of tribe Coreopsideae. Phylogenetic position of Dicranocarpus parviflorus has been controversial. A molecular phylogeny showed that the taxon was closely related to Dahlia; however, further analyses with a wider sampling of Dahlia, also including Hidalgoa, identified the genus in a more distant clade. The objective of this study is to gather anatomical attributes from the cypselae as well as palynological characters along with macromorphology to determine whether Dicranocarpus shares characters with these genera in Coreopsideae. Our results show that although the pollen of D. parviflorus does not possess attributes that distinguish it from the rest of the tribe Coreopsideae, they were useful to confirm its membership in the tribe. The cypselae anatomy identified that D. parviflorus has characters of taxonomic value that differentiate this species from the rest of the Coreopsideae. The three most significant novel characters in Dicranocarpus were in the outer mesocarp, consisting of tracheoidal-like cells forming irregular rows up to 250 μm in length, an aerenchyma in the middle mesocarp, and the lack of phytomelanin and calcium oxalate crystals. Furthermore, the results of the phytomelanin patterns in the studied taxa highlight the need for further anatomical studies of the cypselae to fully understand the evolution of phytomelanin deposition in the tribe Coreopsideae and even in the Heliantheae Alliance. Macromorphological, palynological and anatomical attributes of the cypsela in Dicranocarpus were not shared with Dahlia. Moreover, the sexual condition of the disc and ray florets shared with Hidalgoa has evolved independently in lineages of Asteraceae.

Evolution and hydro-stratigraphy of the coastal aquifer in Garopaba/SC: Interpretation from georadar and tubular wells

This work analyzes the geological evolution of sedimentary deposits in the coastal aquifer of Garopaba, south Brazil, using ground penetrating radar (GPR) and data from tubular wells. The aquifer is localized in the coastal plain, where Quaternary lagoon-barrier environments are set between the Precambrian crystalline mountains and the sea. Over ten tubular wells are scattered in urbanized areas, which highlights the vulnerability of the unconfined, granular shallow aquifer. The results show that the aquifer has lithologic units of local scale. Tubular well data show the basal limit of the aquifer overlying clayey layers between 30 and 40 m deep and intercalation of sand layers up to the surface, mostly fine to very fine sand, with metric thickness, secondary lenses of clay and minor occurrence of gravel. The radarfacies interpretation shows fluvial-estuarine deposits as a local hydrostratigraphic unit, with lateral accretion bars filling a NE-axis paleochannel. The basal surface of the channel is interpreted as the sequence boundary surface of the lagoon-barrier systems III (upper Pleistocene) and IV (Holocene). The geological evolution of the aquifer is related to the upper Pleistocene marine regression (120–18 ka), that caused the aerial exposure of the continental shelf, and the development of complex drainage channels, which were superimposed during the Holocene transgression by lagoon-barrier IV deposits. After the post-glacial transgression, the lowering of the RSL to the current level promoted the silting of part of the lagoon system by continental sedimentation and aeolian deposits composing the surface.

Fluid evolution and genesis of the Shipenggou gold deposit in Central Jilin Province, China: Constraints from C–H–O and in–situ sulphur isotopes of pyrite and fluid inclusions

The origin and evolution of the Shipenggou gold deposit in the Shipenggou–Jiapigou–Jinchengdong (SJJ) gold belt in Jilin Province, Northeast China, remain poorly understood. In this study, fluid inclusion and C–H–O–S isotopes from the Shipenggou deposit were investigated to clarify the fluid evolution and mineralisation process. The gold mineralisation is hosted in the biotite plagiogneiss of the Archaean Sandaogou Formation and is dominated by gold–bearing quartz veins. The orebodies are controlled by NNE– and NEE–striking brittle–ductile structures. Four stages of mineralisation have been identified: (I) milky quartz–minor pyrite, (II) quartz–pyrite–minor gold, (III) gold–quartz–polymetallic sulphide, and (IV) quartz–carbonate. Fluid inclusions were identified as four types: aqueous (VL–type), CO2–bearing (CL–type), CO2–rich (LC–type), and carbonic (PC–type). VL–, CL–, LC–, and PC–type FIs were developed within quartz from Stages I–II. Stage III quartz contains both CL– and VL–type FIs. Only VL–type FIs were observed in calcite from Stage IV. The total homogenisation temperatures (Tht) of FIs in Stages I, II, III, and IV are of 281.5–324.8, 215.5–269.1, 151.2–198.3, and 125.4–149.5 °C with salinities of 2.8–13.2, 2.8–9.6, 3.2–8.4, and 3.0–5.9 wt% NaCl eqv. Laser Raman spectroscopy analysis indicated the CL– and PC–type FIs from Stages I and II contain CO2 and minor quantities of CH4. The ore–forming fluids have developed from a medium temperature, low–medium salinity immiscible NaCl–H2O–CO2 ± CH4 system to a low temperature, low salinity homogeneous NaCl–H2O system. The HO isotopic compositions indicate that the initial ore–forming fluids were mantle–derived magmatic water. Subsequently, the ore–forming fluids were gradually joined by meteoric water. δ13C values indicate C in the fluids have originated from organic matter. Organic matter may have originated from the mantle, which mixed crust materials influenced by the subduction of the Palaeo–Pacific slab. In–situ, S isotope data of pyrite indicate that the origin of sulphur at the Shipenggou deposit is the mantle containing a crust component. Based on the above analysis results, the Shipenggou gold deposit is a mesothermal magma-hydrothermal vein–type gold deposit.

Anatomy of the late Pennsylvanian to early Triassic failed rift system of the Cooper Basin, eastern Australia

The onshore intracratonic Cooper Basin of central Australia developed during the Late Pennsylvanian to Middle Triassic periods at paleolatitudes of approximately 50°S within the Gondwanan sector of the Pangea. Despite the wealth of data available, including the drilling of over 4,800 boreholes, there is limited knowledge about the Cooper Basin’s origins and evolution. To better understand the basin’s geological history, legacy data sets, including composite 2D seismic sections, well logs, measured sections, and 1D burial history models from the west of the basin, are integrated to reinterpret the basin’s tectonic and sedimentary evolution. Interpretation of the seismic sections and calculated subsidence rates indicates an earlier active rift phase with grabens and half-grabens that transitioned, in the latest Permian, into a regional sag phase. The evolution of tectonic styles heavily influenced the paleogeographic evolution of the basin fill and resulting depositional architecture. The basin sediments are entirely terrestrial in nature and facies reflect a transition from glacial environments in the late Pennsylvanian to warmer and drier conditions in the early Triassic. During much of the Permian the basin was underfilled and the relative low influx of fluvial sediment did not keep pace with creation of accommodation, allowing the development of extensive mire and lake systems. Coal beds are up to 30 m thick. By contrast, the basin appears to have been overfilled during the latest Permian to Triassic with rivers flowing along the central axis of the basin. The synchroneity of commencement of rifting, termination of rifting, and commencement of a sag phase within the failed rift systems of the Cooper Basin, the East Gondwana Interior Rift, and the East Australian Rift strongly suggests a continent-wide period of extension related to significant changes in plate motions during the Late Pennsylvanian to Middle Triassic.

Ultrafast Laser Manipulation of In-Lattice Plasmonic Nanoparticles.

Plasmonic nanoparticles enable manipulation and enhancement of light fields at deep subwavelength scales, leading to structures and devices for diverse applications in optics. Despite hybrid plasmonic materials display remarkable optical properties due to interactions between components in nanoproximity, scalable production of plasmonic nanostructures within a single-crystalline matrix to achieve an ideal plasmon-crystal interface remains challenging. Here, a novel approach is presented to realize efficient manipulation of in-lattice plasmonic nanoparticles. Employing ultrafast-laser-driven plasmonic nanolithography, metallic nanoparticles with controllable morphology are precisely defined in the crystalline lattice of yttrium aluminum garnet (YAG) crystal. Through direct ion implantation, hybrid plasmonic material composed of nanoparticles embedded in a sub-surface amorphous YAG layer is created. Subsequently, femtosecond laser pulses guide formation and reshaping of plasmonic nanoparticles from the amorphous layer into the single-crystalline matrix along direction of light propagation, facilitated by a plasmon-mediated evolution of laser energy deposition. By tailoring resonance modes and optimizing the coupling between structured particle assemblies, a range of applications including polarization-dependent absorption and nonlinearity, controllable photoluminescence, and structural color generation is demonstrated. This research introduces a new approach for fabricating advanced optical materials featuring in-lattice plasmonic nanostructures, paving the way for the development of diverse functional photonic devices.

Paleogeographic reconstruction and sedimentary evolution of tidal-dominated estuarine depositional systems: Insights from the campanian M1 sandstone formation, Oriente Basin, Ecuador

The Oriente Basin is a back-arc basin located east of the Ecuadorian Andes in South America. Evidence suggests that during the Cretaceous period, the basin's margins received a terrigenous shallow marine sedimentation. Due to regional variations in accommodation and depositional controlling factors near a shoreline, the sedimentary environments in the fluvial-marine transitional zones exhibit considerable variability. In this study, we analyzed the sedimentological characteristics of the M1 Sandstone Formation unit (∼83 Ma-72 Ma), which comprises a set of ancient estuarine deposits preserved in the northern part of the basin. We quantified the impact of mixed hydrodynamic processes on the distribution of tidal-dominated estuarine facies and discussed the development conditions and evolutionary processes of an estuarine formation under the background of persistent transgression. Core, well log, and seismic data provide evidence for reconstructing the tidal-dominated estuarine environment. In the core section, we identified 14 lithofacies and 7 major facies association types. The frequent occurrence of sedimentary structures associated with tidal currents indicates that tidal processes extensively reworked the deposits. The spatial distribution trends of facies associations reveal the evolution of mixed hydrodynamic conditions dominated by tidal processes in the estuary and allow us to divide the M1 Sandstone Formation into four depositional periods: the initial development, rapid development, decline, and the post-infilling open coast tidal flat development periods. Furthermore, through a systematic analysis of hydrodynamic conditions and sediment distributions, we identified multiple depositional centers in the tidal-dominated estuary influenced by different hydrodynamic processes. These correspond to the upstream fluvial-dominated tidal point bar depositional region, the middle mixed-energy depositional interaction zone, and the downstream tidal-dominated tidal sand bar depositional region. In these regions, the substantial accumulation of sandy deposits, represented by tidal sand bars, reflects the high accommodation space characteristic of tidal-dominated estuaries. Our findings indicate that the slow subsidence of a broad and gently sloping coastal topography, stable material transport, and sea level change dominated by marine transgression ensured the necessary accommodation for the development of the estuary in the M1 Sandstone Formation. The sedimentological study of the M1 Sandstone Formation provides a case for understanding the sedimentary evolution in fluvial-marine transitional zones.

Hydrogeological Regions of Kolubarska Posavina (Central Serbia)

The groundwater catchments of the Kolubarska Posavina are of significant importance because if some contamination affects the groundwater system, it is necessary to find a quality groundwater source for the water supply of Obrenovac Municipality. Reconstruction of sedimentary evolution plays a significant role in the investigation of groundwater catchment. In this study, the variation in sedimentary characteristics and sedimentary evolution/paleogeography were studied for Quaternary catchment identification in Kolubarska Posavina. The groundwater catchment of the Kolubarska Posavina can distinguished into two main parts. The western part of Kolubarska Posavina is identified as the Sava groundwater catchment, where the Sava alluvial plain and the (paleo) meanders of the Sava are located. The east part belongs to the Kolubara groundwater catchment, characterized by the remnants of the (macro) alluvial fan of Kolubara and the Kolubara floodplain. The Kolubara catchment is located eastwards from the older meander of the Sava River.

Sequence stratigraphic architecture and depositional evolution of the early Eocene-early Miocene Al Jabal Al Akhdar carbonate successions, N Cyrenaica Promontory, NE Libya – Interplay of tectonics and eustasy

The interactions of tectonics and eustasy on the stratigraphic architectural evolution of the early Eocene-early Miocene Al Jabal Al Akhdar carbonate sedimentary successions were evaluated. This evaluation was achieved through detailed analyses of microfacies, depositional interpretation, and sequence stratigraphic framework of five measured sections located within the Al Jabal Al Akhdar Uplift, northeast Libya. The study interval was subdivided into distinct microfacies based on lithological changes, grain size and components, sedimentary texture and structures, fossil contents, color, and vertical stacking pattern. Six major depositional settings were delineated: restricted lagoon, open marine lagoon, platform margin and shoals, platform-margin reefs, foreslope, and middle to lower slope. Four third-order unconformity-bounded depositional sequences were identified based on vertical and lateral facies distribution, variations in fossil contents, and diagenetic features. Each sequence is composed of a transgressive-regressive interval, except for the younger sequence, which only contains a transgressive unit. Four evolutionary stages are recognized: initiation, growth, high-relief platform, and subaerial exposure. Subsidence resulting from tectonism and sediment loading, coupled with rising sea-level, created the accommodation space for the sedimentation of the studied carbonates. Repeated eustatic sea-level fluctuations controlled the internal stratigraphic heterogeneity and sequence development. Tectonic uplift caused a major sea-level retreat, resulting in the emersion of the carbonate sequences. The pre-existing Mesozoic and Paleocene sequences that underwent major uplift during the Late Cretaceous-early Eocene formed a shallow-water positive-antecedent topography for the formation of the carbonate sediments. This study establishes a carbonate sequence stratigraphic hierarchy of different cyclic sedimentation orders and improves our knowledge of sedimentary and stratigraphic architectural evolution and depositional mechanisms of carbonate platforms in an inverted basin setting. This knowledge can aid in predicting the distribution of lithofacies and depositional systems of economic importance.

Effect of heat input on ultrahard Fe-Cr-B-C-W-Mo-Nb hardfacing

Multicomponent alloys (Cr, Mo, W, Nb, C, B) nanostructured iron base with complex carboborides have been developed to provide great protection against abrasive wear to elements of agricultural and mining machines. These overlays are subject to severe material losses due to impact and abrasion of hard particles and therefore optimizing their wear resistance is critical when it comes to their lifespan, increasing it as a result. The objective of this work was to study the influence of heat input on the wear resistance through of the analysis of the solidification rate. In this sense, the increase of welding speed was produced a decrease of heat input and refined of microstructure. In order to explain these effects, an analysis was made of of the influence of welding speed on the geometry of the deposited metal, dilution with the base metal, microstructural evolution and hardness of iron-based nanostructured deposits with complex carbides. For this, four samples were welded with different speeds; these being 1, 2.5, 5 and 12 mm/s. A semi-automatic welding process was used with a 1.6 mm wire rope used to provide gas protection. The chemical composition was analyzed on a dilution free welded sample. For the each welded sample the dilution percentage was determined, the dimensional survey of the beads was carried out and the microstructure was characterized by X-ray diffraction and optical and scanning electron microscopy. In addition, Vickers microhardness tests were measured in the central area of the beads and the microhardness of phases were measured. The dilution of the deposited metals ranged from 17% to a maximum of 28%. A microstructure formed by a matrix with complex metal carbides and carboborides was observed. The hardness of the beads varied between 960 and 1350 HV2. The highest wear resistance was found in the sample with highest speed welding.

Genesis and fluid evolution of the Hatu orogenic gold deposit in the West Junggar, Western China

The West Junggar in Xinjiang, western China, represents a significant gold mineralization belt hosting over 200 gold deposits, with the Hatu gold deposit being the largest among them. In this study, ore geology and fluid inclusion assemblages of quartz samples from the Hatu gold deposit were investigated in an effort to clarify the mineralization process and its relationship with the geodynamic settings. The mineralization process is delineated into early (pyrite-albite-quartz veins), middle-a (quartz-ankerite veins), middle-b (quartz-ankerite-sulfide-native gold veins), and late (quartz-calcite veins) stages. The early stage veins suggest a compressional setting while the middle-a and middle-b stage veins suggest a tensional shear setting. The late stage veins are typically filled fissures cutting through earlier veins. Scanning electron microscope-cathodoluminescence (SEM-CL) reveals that early stage quartz (Q1) exhibits concentric CL-oscillatory growth zoning, while middle-a stage quartz (Q2a) displays unidirectional zoning and ranges from CL-bright to CL-dark, middle-b stage quartz (Q2b) is CL-bright and weakly zoned, and late-stage euhedral quartz (Q3) shows sector zoning transitioning from CL-gray to CL-dark. Quartz that formed in these stages developed three types of fluid inclusions: pure CO2 (PC-type), CO2–H2O (C-type), and H2O–NaCl (W-type). The early stage quartz contains C- and W-type fluid inclusions homogenizing at 309–345 °C, while the late stage quartz contains only W-type fluid inclusions with homogenization temperatures of 164–229 °C. Microthermometry of fluid inclusion indicated the evolutionary of the metallogenic fluid from a high-temperature, CO2-rich, and minor CH4 metamorphic fluid to a low-temperature, CO2-poor meteoric fluid. From the early to middle-a stages, fluid boiling caused the unloading of ore-forming elements whereas fluid mixing led to the precipitation of polymetallic sulfides and gold in the middle-b stage. Trapping pressures in the middle-b stage were estimated using C-type inclusions, illustrating that gold mineralization took placed at depth of 8.0 km. We propose classifying the Hatu gold deposit as an orogenic deposit, originating from the collisional orogenesis between the Yili-Kazakhstan and Siberian continents in the Late Carboniferous.

Reconstructing early sedimentation patterns of the lower Codó Formation (Early Cretaceous, NE Brazil): Evidence of marine influence and the onset of an alkaline hypersaline lake

The upper Aptian lower Codó Formation is an attractive stratigraphic unit within the Parnaíba and São Luís basins, northeastern Brazil, formed during the break-up of Western Gondwana. Located in a large sag basin, the formation records a dynamic depositional history of deltaic, lacustrine, and sabkha environments. This sedimentary evolution is reflected in a diverse lithological succession characterized by intermittent terrestrial input, episodic marine incursions, and restricted lacustrine phases culminating in sulfate evaporite precipitation. While the later stages of the formation have been extensively studied, the initial sedimentary processes and environmental conditions remain poorly understood. This research aims to reconstruct the depositional paleoenvironments during the initial stages of Codó sedimentation, elucidating the onset of the alkaline hypersaline lake environment and the earlier marine incursions in the study region. To achieve this, it was conducted a high-resolution facies analysis using core descriptions, trace fossil analysis, petrography, various types of X-ray fluorescence, scanning electron microscopy, X-ray diffractometry, and isotope analyses (δ1³C, δ1⁸O, and ⁸⁷Sr/⁸⁶Sr) on a ∼63-m-thick succession from borehole 2-TV-1-MA. Thirteen facies were recognized and grouped into brackish lake, prodelta, delta front, and alkaline hypersaline lake facies successions. The lower Codó Formation exhibits cyclic sedimentation, indicating fluctuating water dynamics associated with shifts between open and closed drainage systems controlled by paleoclimate. Tectonic subsidence drove the basin's evolution from a brackish lacustrine-deltaic environment with an incipient marine influence (balanced-fill basin stage) to a restricted system with the establishment of an alkaline hypersaline lake (underfilled basin stage).

The Psematismenos-Maroni Basin (South Cyprus): Cenozoic tectonic and sedimentary evolution

The Tertiary regressive sedimentary succession, which forms the sedimentary cover of the Troodos Ophiolitic Massif, was studied in the Psematismenos-Maroni Basin in Southern Cyprus. A series of unconformity surfaces were identified based on key surfaces, morphologies, and sedimentary facies. These observations are reinforced by numerous new biostratigraphic datings mainly based on calcareous nannofossil analysis. Unsuspected biostratigraphic hiatuses ranging from million to dozens of millions of years are illustrated. Some unconformity surfaces are tectonically enhanced leading to the emersion of this basin. In addition, our work highlights the importance of the Messinian Salinity Crisis in the shaping of an onshore erosion surface in Cyprus as it is the case in the Sorbas basin in the western Mediterranean. Constrained by new datings, this work finally proposes a tectono-stratigraphic calendar for the Psematismenos-Maroni Basin, starting from the Paleogene Lefkara Formation up to the first alluvial deposits at the end of the Neogene.