Exploration Targets Research Articles

Geological evidence for extensive basin ejecta as plains terrains in the Moon’s South Polar Region

Water ice and other volatiles that accumulated in the Moon’s polar regions are among the top priority targets for lunar exploration, due to their significances in both lunar geology and extraterrestrial resource utilization. Locating suitable landing sites and determining the provenance of sampled/measured surface materials are critical for future landed missions. Here, we map over 800 sites of plains terrains in the Moon’s south polar region, with a total surface area of ~46,000 km2. Orbital measurements and analog studies show that most of these plains have apparently higher albedo and lower iron content than volcanic mare plains, suggesting an origin of ejecta-induced debris flows from distant impact craters, especially from the Schrödinger basin. Our findings suggest that the entire lunar south polar region probably have experienced contributions from distant basin materials. We recommend these plains as priority landing sites for future exploration of lunar polar volatiles and early bombardment history.

Palaeozoic Amotape Group in the Colán District:

The Amotape Gr. Consists of metasedimentites with varying degrees of metamorphism and Paleozoic intrusions, exposed as isolated blocks that form an NNE-SSW belt, separating the Meso-Cenozoic depocenters of the Talara (west) and Sechura and Tumbes basins (east) along the Pacific margin of NW Perú. We describe three metamorphic/tectonic episodes that produced sub-planar structures (cleavages, fractures) affecting the rocks of the Amotape Gr, allowing this unit to be classified as a fractured reservoir. Field survey and multi-scale subsurface data from the Colán region, evidence a secondary porosity system associated with fracture networks that affect both the basin fill and the basement units. This configures a complementary unconventional exploration target. Sandstone levels in lateral contact with leptometamorphic rocks of the Amotape Gr. define good reservoir potential due to the preferentially brittle mechanical behavior of the basement, which develops abundant fractures. The porosity values of the Amotape Gr range between 4.62% and 1.23%, while permeabilities are on the order of 0.519-0.016 mD. Elevated trapping positions seem to be successfully sealed by Cretaceous units. The reservoir properties define a complementary play concept that could be extended to other positions of the technical basement in the Talara Basin and analogous regions.

Lithological Control to the Gold Mineralization in the Main Ridge Complex of the Bakan Gold District, Northern Sulawesi, Indonesia

Abstract Main Ridge complex is characterized by prominent high sulfidation epithermal-style mineralization with windows of porphyry style mineralization in the deeper zone. Several lithologic features play important controlling role in the occurrences of those mineralization. The oldest rock observed in the Main Ridge complex is unmineralized hornblende diorite (IDO-1) which encompasses the whole Bakan district. Several late intrusive stocks were concealed below the current topographic as mentioned as the microdiorite (IDO-2) and quartz diorite (IDO-3) in which the latter exhibits windows of porphyry-style mineralization. Those intrusive units were then covered by two unconformable volcanic tuff sequences which are andesitic tuff and dacitic tuff in compositions. Dacitic tuff is more favourable unit for gold mineralization compared to andesitic tuff which shown by near-surface ‘mushroom-like’ deposit form. In more peripheral area, the mineralization is also controlled by the bedding features of dacitic tuff which underlain by the less-mineralized andesitic tuff. In the latest stage, diatreme breccia cut all the lithologic units and becomes the most favourable host rock in sub-vertical deposit form. The comprehensive understanding of the lithological features is important to understand the mineralization control for further exploration target.

Distribution of Radiation-Induced Defects in Quartz at the ACKIO Uranium Prospect, Athabasca Basin, Saskatchewan: Tracing Uranium-Bearing Fluids

Abstract Quartz grains from the ACKIO uranium prospect, located near the eastern margin of the Athabasca Basin, Saskatchewan, have been investigated using powder X-band electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra of quartz separates from samples systematically collected from the Athabasca Supergroup sandstones and the underlying metamorphosed basement reveal a suite of silicon-vacancy hole centers, which were formed by the bombardment of alpha particles emitted from the radioactive decay of uranium, thorium, and their unstable progeny. The differences in EPR signal intensities of these hole centers indicate that quartz grains received different accumulative doses of alpha particle irradiation in different locations within the ACKIO prospect. For example, quartz extracted from a mineralized sample has the highest EPR signal intensity due to the presence of disseminated uraninite. For quartz sampled at distance from uranium mineralization, the elevated intensities of the silicon-vacancy hole centers most likely indicate a temporary source of radiation, such as ancient uranium-bearing fluids. The median EPR intensities of quartz from the basement rocks at ACKIO are an order of magnitude higher than those of its counterpart from the Athabasca sandstones. Also, the EPR intensities of quartz along the sandstone–basement contact at ACKIO differ by more than two orders of magnitude, suggesting limited migration of uranium-bearing fluids along this contact in the study area. Instead, anomalously high EPR intensities in quartz close to the sandstone–basement contact and elsewhere are restricted to fault gouges and brecciated areas, suggesting that they are the structural pathways for channelized migration of ancient uranium-bearing fluids. A three-dimensional distribution model of the EPR signal intensities has been constructed to define conduits for the migration of ancient uranium-bearing fluids at ACKIO and suggest favorable targets for further exploration. These findings demonstrate the power of EPR spectroscopy in delineating pathways of uranium-bearing fluids and predicting potential mineralization targets.

Integrated geophysical Investigation for gold mineralization potential over southern parts of Kebbi state and its Environs, northwestern Nigeria

The potential zones of gold mineralization were identified in this study using aeromagnetic and aero-radiometric methods. The Nigerian Geological Survey Agency (NGSA) provided half-degree airborne magnetic and radiometric datasets covering the southern part of Kebbi State. Magnetic data were subjected to first vertical derivative (1VD), total gradient amplitude (TGA), total horizontal derivative (THD), source edge detection (SED), center for exploration targeting (CET), Euler deconvolution (ED) and source parameter imaging (SPI) to identify favourable structures to gold mineralization. Aero-radiometric data delineation of the region of hydrothermal alteration zones through the K/eTh ratio, K_deviation, F_parameters, and Ternary image analyses were successful. The results of the magnetic data techniques revealed the regions of major structures/or lineaments with gold mineralization attributes, trending in the NE to SW directions and the SE to NE parts of the study area. The depth to the structures of the magnetic source hosting gold mineralization was less than 5 m using algorithm ED and SPI techniques. Normalized radiometric data showed the area of anomalously high and moderate hydrothermal altered zones. The region's designation as a gold field is supported by major fault lines observed on the 1VD, a sequence of bristle fractures from the CET analysis, and high values of K_deviation and F_parameter, all of which are were visible on the Ternary images. The integrated results revealed zones of major structures and hydrothermal regions of gold fields at Agwara, Western Magama, Rijau, Fakai, Bukkuyum, and Borgu in the SE of the study area.

Integrated Geophysical Investigation for Potential Gold Mineralised Zone within Lower Part of Zuru Schist Belts, NW Nigeria

The study began with a reconnaissance survey that used high-resolution aeromagnetic data of the study area to identify suitable structure zones with the potential to trap mineral resources within the context of the gold exploration target. The findings of magnetic studies were followed up with detailed investigations using 2D electrical resistivity tomography (ERT) and induced polorisation (IP) techniques to reveal further details about gold mineral zones and other lithological boundaries. The airborne magnetic data of sheet 118_Yelwa was obtained from the NGSA; these datasets were processed and analyzed using Oasis Montaj's first vertical derivative (FVD) and center for exploration targeting (CET) techniques. Results of FVD and CET grid anomalies show that regions of major magnetic structures (lineaments) are associated with granite gneiss, migmatitic augen gneiss, and medium to coarse-grained biotite when compared to the geological settings of the area. The zones of major structures obtained in this study coincided with previous magnetic studies of the area, located in the eastern parts of Ngaski, Yauri (Yelwa), Shanga, Agwara, as well as Magama's northwest region. Some of the regions for lineament (in the eastern part of Ngaski/Yauri) were investigated further with 2D ERT and IP detailed geophysical methods in a dipole-dipole configuration. The results of geoelectric techniques along profiles 1, 2, and 3 identified the major gold mineralisation potential zones, which were labeled A1, A2, and A3. These regions have low/high resistivity (1.6 to 459 Ωm/1889 to 7773 Ωm) and chargeability signatures (≥ 20 msec), and could thus be interpreted as potential target zones for metallic mineral exploration, particularly gold mineralisation. The regions are located in the northern Mararraba and southwest of the Jinsani areas of Kebbi State. The results of integrated geophysical methods have produced updated structural features of the regions, as well as a database containing precise locations, lateral lengths,...

Integrated Geophysical Investigation for Potential Gold Mineralised Zone within Lower Part of Zuru Schist Belts, NW Nigeria

The study began with a reconnaissance survey that used high-resolution aeromagnetic data of the study area to identify suitable structure zones with the potential to trap mineral resources within the context of the gold exploration target. The findings of magnetic studies were followed up with detailed investigations using 2D electrical resistivity tomography (ERT) and induced polorisation (IP) techniques to reveal further details about gold mineral zones and other lithological boundaries. The airborne magnetic data of sheet 118_Yelwa was obtained from the NGSA; these datasets were processed and analyzed using Oasis Montaj's first vertical derivative (FVD) and center for exploration targeting (CET) techniques. Results of FVD and CET grid anomalies show that regions of major magnetic structures (lineaments) are associated with granite gneiss, migmatitic augen gneiss, and medium to coarse-grained biotite when compared to the geological settings of the area. The zones of major structures obtained in this study coincided with previous magnetic studies of the area, located in the eastern parts of Ngaski, Yauri (Yelwa), Shanga, Agwara, as well as Magama's northwest region. Some of the regions for lineament (in the eastern part of Ngaski/Yauri) were investigated further with 2D ERT and IP detailed geophysical methods in a dipole-dipole configuration. The results of geoelectric techniques along profiles 1, 2, and 3 identified the major gold mineralisation potential zones, which were labeled A1, A2, and A3. These regions have low/high resistivity (1.6 to 459 Ωm/1889 to 7773 Ωm) and chargeability signatures (≥ 20 msec), and could thus be interpreted as potential target zones for metallic mineral exploration, particularly gold mineralisation. The regions are located in the northern Mararraba and southwest of the Jinsani areas of Kebbi State. The results of integrated geophysical methods have produced updated structural features of the regions, as well as a database containing precise locations, lateral lengths,...

Oil-and-gas potential of the northeast Predpatom trough

This article discusses the geological structure and prospects of the oil and gas potential in the northeastern part of the Predpatom trough. The materials of the study included geological findings from deep drilling and data from direct geochemical studies conducted in recent years. It describes the specific features of the structural plans of the upper versus the lower part of the geological cross-section. It is assumed that deep drilling in the area of the Ulugur structure has not reached the target productive horizons in the autochthonous part of the section. After acquiring more recent seismic data, there is a proposal to drill a deeper exploratory well in the area. As another priority target for oil and gas exploration, a potential zone of Vendian clastic deposits wedging on the southwestern slope of the Suntar uplift has been identified. A forecast has been made for the distribution of lithological traps stacked with well-sorted granular Vendian reservoirs in the northern parts of the Ergedzheysky and Ulugursky license areas. In the allochthonous part of the section, the potential for oil and gas content in carbonate deposits from the Vendian and Lower Cambrian periods is highlighted in reservoirs formed by secondary processes. It is assumed that thrust deformations could lead to the circulation of aggressive solutions, resulting in the formation of secondary fractured cavernous reservoirs. Subsequently, hydrocarbon accumulations may migrate and accumulate within these reservoirs. Good gas prospects were also noted in the upper part of the section, where gas deposits were confirmed in newly discovered fields. The results of direct geochemical testing of the Ulugur and Ergedzheysky license areas are presented, enabling the preliminary delineation of promising zones and areas in the studied territory. At the same time, narrow elongated geochemical anomalies are associated with the prospects of the allochthonous part of the section, while isometric anomalies are linked to the autochthonous part of the section. The need to consolidate all available geological and geophysical information on the Pre-Atomic deflection within the framework of case studies is noted.

From the mantle source to the crustal sink: magmatic differentiation and sulfide saturation of the Paleoproterozoic komatiites of the Central Lapland Greenstone Belt, Finland

Paleoproterozoic (2.05 Ga) komatiites are widespread in the Central Lapland Greenstone Belt (CLGB), northern Finland. Close association with sulfur (S)-rich country rocks and spatiotemporal connection with the Cu-Ni(-PGE) deposits of Kevitsa and Sakatti make these komatiites interesting targets for sulfide deposit exploration. We provide whole-rock geochemical data from Sattasvaara komatiites and combine it with literature data to form a geochemical database for the CLGB komatiites. We construct a model for the komatiites from adiabatic melting of the mantle source to fractional crystallization at crustal conditions. Using MELTS, we calculate three parental melts (MgO = 20.6–25.7 wt%) in equilibrium with Fo92, Fo93, and Fo94 olivine for the CLGB komatiites. Based on REEBOX PRO simulations, these parental melts can form from a single mantle source by different pressures and degrees of melting when the potential temperature is 1575–1700 °C. We calculate ranges of S contents for the parental melts based on the different mantle melting conditions and degrees of melting. We use Magma Chamber Simulator to fractionally crystallize the parental melt at crustal conditions. These simulations reproduce the major element oxide, Ni, Cu, and S contents from our komatiite database. Simulated Ni contents in olivine are compatible with literature data from Kevitsa and Sakatti, hence providing a baseline to identify Ni-depleted olivine in CLGB komatiites and related intrusive rocks. We show that fractional crystallization of the komatiitic parental melt can form either Ni-rich or Cu-rich sulfide melt, depending on the initial Ni and S content of the parental melt.

Natural hydrogen extracted from ophiolitic rocks: A first dataset

Serpentinization is an important geochemical process producing natural hydrogen (H2), and mafic and ultramafic serpentinized rocks, typically occurring in ophiolites and peridotite massifs, are major targets for H2 exploration. Understanding the volumes of H2 stored in these rocks is a key step towards establishing the potential of sepentinized systems to host H2 sources and reservoirs. Nonetheless, published data on the concentration of H2 directly extracted from serpentinized rocks are extremely scarce. This work provides a first dataset of H2 extracted by planetary ball mill from 58 rock samples from different ophiolites in Greece, peridotites of the Tekirova ophiolite in Turkey, and chromitites and surrounding talc schist from an Archean-Paleoproterozoic greenstone belt in Brazil. The highest H2 concentrations, from 0.1 mL/kg (considered as a threshold above which artificial H2 by milling is negligible) to 16.2 mL/kg, were found in serpentinized harzburgites or dunites, and in chromitites hosted within serpentinized peridotites. The H2 content of other mafic rocks that are not in contact or influenced by a serpentinized system, mostly basalts, is below 0.1 mL/kg. Serpentinized peridotites represent the logical source rocks of H2 (i.e., hydrogen in peridotites is generally autochtonous) and chromitites, lacking significant olivine and serpentinized minerals, may host H2 derived by the surrounding serpentinized rocks (hydrogen in chromitites is mostly allochtonous). The H2 dataset of this work can be used as a reference for further studies on the capacity of ophiolitic rocks to produce and host natural hydrogen.

Early‐Precambrian crystalline basement beneath the Upper Yangtze Block from regional aeromagnetic anomalies: Depth from extreme points approach

AbstractAlthough the early‐Precambrian crystalline basement is now only sporadically exposed in the northern and south‐western parts of the Yangtze Block, it is supposed to have a widespread distribution beneath its Neoproterozoic and Phanerozoic covers. Here we present results of regional aeromagnetic data processing in consideration of remanent magnetization to investigate the spatial distribution of the early‐Precambrian basement buried deep under the Upper Yangtze Block and surrounding areas. The direct analytic signal amplitude of the aeromagnetic anomalies, which is less affected by the magnetization direction, reveals a broader basement below the Sichuan Basin, extending far north to the Micang Mountain. A comparison between the direct analytic signal amplitude with the reduction to the pole aeromagnetic anomalies indicates that possible remanent magnetization exists beneath the Micang Mountain near the boundary between the Qinling Orogen and Sichuan Basin. The automatic depth from extreme points transform is then performed on the direct analytic signal amplitude to estimate the depth to the early‐Precambrian crystalline basement. A synthetic model of a magnetic interface with remanent magnetization and random noise shows that the depth from extreme points method is able to resolve variable basement depths. Application of the depth from extreme points method to the direct analytic signal amplitude of the Upper Yangtze Block presents meaningful results about the early‐Precambrian crystalline basement undulations. It is shallow and uplifted beneath the Sichuan Basin, extending north to the Qinling‐Dabie Orogen, probably corresponding to the ancient Chuanzhong palaeo‐uplift. Although it gradually deepens to the east, the deepest basement is buried under the Jiangnan Orogen, which is likely associated with the collision‐induced crustal thickening between the Yangtze and Cathaysia blocks during the assembly of the Columbia supercontinent. Large gas fields around the Sichuan Basin are found at the slopes or depressions between basement uplifts, indicating that the deep marine carbonate rocks in the south and east of Sichuan Basin, particularly those located at the slopes or depressions between ancient basement uplifts, are favourable targets for further petroleum exploration.

Paleo-Sedimentary Environment and Formation Mechanism of the Organic-Rich Shale of the Permian Lucaogou Formation, Jimsar Sag, Junggar Basin, China

The Jimsar Sag is an important shale oil exploration target area in the Junggar Basin, northwestern China. The Permian Lucaogou Formation, with a thickness of 200–300 m, is the primary exploration target. High-frequency variation in lithology is a typical feature of the Lucaogou Formation, reflecting the fluctuation of the depositional environment and organic matter enrichment. The evolution of the depositional environment and accumulation mechanism of organic matter still need to be elucidated for the Lucaogou Formation. High-resolution sampling of the entire Lucaogou Formation was applied to a 248 m long core from Well JX in the Jimsar Sag to examine the depositional environment and organic matter enrichment. The findings unveiled that the Lucaogou Formation was deposited under a hot and arid climate, within the confines of a closed saline paleo-lake, where sediments endured an extended period of anoxic conditions, displayed periodic oscillations in paleo-temperature and paleo-salinity values over time, alongside a continuous rise in paleo-water depth. The predominant source lithology of the Lucaogou Formation is felsic igneous rock. Small-scale transgression and hydrothermal sedimentation occurred during the deposition of the Lucaogou Formation. The prevailing hot climate and enduring reducing environment fostered ideal circumstances for the enrichment of organic matter in the Lucaogou Formation. Due to different sedimentary environments and enrichment mechanisms, organic matter is enriched in two modes in the Lucaogou Formation.

A Comprehensive Network Pharmacology Study on the Diabetes-Fighting Capabilities of Yacon Leaf Extract

Indonesia ranks fourth in the world for the number of diabetes mellitus (DM) sufferers. DM is a group of metabolic disorders characterized by hyperglycemia due to insulin abnormalities. This research employs Network Pharmacology analysis to examine the target proteins and pharmacological network profiles predicted to be influenced by compounds in the leaves of Smallanthus sonchifolius (yacon) for their anti-diabetic effects. Gas chromatography-mass spectrometry (GC-MS) identified 41 secondary metabolite compounds in yacon leaves, seven of which have a Pa value > 0.5. Compound C28 has the highest Pa value as an insulin promoter, at 0.662. A total of 129 target proteins were found for the secondary metabolite compounds in yacon leaves, and 5,112 target proteins were identified for Type 2 Diabetes Mellitus (T2DM). The intersection analysis between yacon leaves and T2DM revealed 32 common proteins. Network analysis highlighted 10 top proteins: ESR1, PPAR-α, HMGCR, CYP19A1, PPARD, PTP1N, GRIN2B, FYN, AR, and SHBG. Among these, PPAR-α shows great potential and promising prospects as a target for further exploration. Considering several parameters, it can be concluded that PPAR-α is a promising protein and a potential target for new drug candidates for T2DM.

Genesis of the sediment-hosted Qukuleke Au deposit in the East Kunlun Orogenic Belt, NW China: Constraints from geology, apatite U–Pb age, and C–O–S–Pb isotopes

Genetic classification of sediment-hosted Au deposits is often disputed in many orogenic belts around the world. The marine sediment-hosted Qukuleke Au deposit (>5 t Au) is an example of this, which has been attributed to orogenic or intrusion-related type. This paper addresses its metallogeny through detailed geologic and petrographic studies, together with apatite U–Pb dating and C–O–S–Pb isotopes.The hydrothermal paragenesis at Qukuleke is divided into three stages (I to III): Stage I (pre-ore) sheeted quartz veins; Stage II (main ore) pervasive sericite ± carbonate ± apatite ± pyrite ± arsenopyrite alteration associated with quartz–calcite ± stibnite veins; Stage III (post-ore) barren calcite veins. LA-ICP–MS hydrothermal apatite U–Pb dating on Stage II disseminated Au ore yielded 208.1 ± 6.5 Ma, coeval with the Late Triassic post-collisional intrusions from the periphery of Qukuleke deposit. Carbon–oxygen isotopes of Au–Sb ore-related hydrothermal calcite show that the hydrothermal fluids were derived from the marine carbonate ore host with considerable magmatic input. Lead–sulfur isotopes of the Au–Sb ore-related are consistent with those of coeval intrusions around the deposit, but different from those of the local sedimentary strata. Our age and geochemical data suggest the presence of a magma source that supplied the hydrothermal fluids, sulfur and metals for the mineralization. Combining the low sulfide content and the Au–As–W–Sb–Mo assemblage characteristics, the Qukuleke is best classified as a sediment-hosted intrusion-related Au deposit. Considering also the discovery of the large coeval Qukukekedong Au deposit nearby, we propose that Late Triassic intrusion-related Au system is a high-potential exploration target in the western EKOB.

Paleosedimentary environmental reconstruction and mechanisms of the response to the Toarcian OAE in a lacustrine shale system

The Lower Jurassic Ziliujing Formation in China’s Sichuan Basin is a significant shale target for exploration; however, the strong heterogeneity of the properties of organic matter (OM) in shale makes it challenging to identify the target area for exploration, and the mechanism of OM enrichment is still unclear. Furthermore, the mechanisms of the response of the Da’anzhai member to the Toarcian Oceanic Anoxic Event (T-OAE) are controversial. Previous studies have focused on sedimentary facies analysis based on mineralogy and elemental abundances and have provided minimal information about organic geochemistry, which adds to the challenge of deeply understanding the influence of the T-OAE on the molecular geochemical characteristics of the Da’anzhai member. In this study, the Da’anzhai member of the Lower Jurassic Ziliujing Formation in the Langzhong area, Sichuan Basin, is studied via X-ray diffraction, total organic carbon, gas chromatography–mass spectrometry, organic carbon isotope, organic petrographical and pyrolysis analyses. To accurately identify the trend of the paleosedimentary environmental proxies, the Mann‒Kendall test is utilized to identify the trend of the data. Our results show that the Da’anzhai shale was deposited in a dysoxic transitional environment to an intermittent reducing environment with freshwater to brackish conditions. The response to the T-OAE can be identified in the middle and upper parts of the middle submember and the bottom of the upper submember of the Da’anzhai member. The T-OAE influenced the redox conditions, salinity, and OM origins during deposition in the middle of the Da’anzhai member, which resulted in the enrichment of OM. The abnormally high C30 diahopane/C30 hopane (C30D/C30H) ratio can be considered a potential proxy for locating the section of strata that responded to the T-OAE in the Da’anzhai member. In the study area, the mechanism of the response of the Da’anzhai shale to the T-OAE manifested as an improvement in hydrological cycling rather than a marine incursion. Our study provides new information that deepens the understanding of the mechanisms of the response of lacustrine shales to oceanic anoxic events from the perspective of molecular organic geochemistry.

Compositional differences of near-critical petroleum from closed pores to wellhead in Gulong shale oil play, Songliao Basin, NE China

The Gulong shale oil play located in northern Songliao Basin is a promising exploration target in China. Member 1 of Qingshankou Formation (Well H) with high thermal maturity was preferred to obtain pressure-retained cores, long-time exposed cores, and produced petroleum (crude oil and gas). The selected samples were subjected to sequential extraction, GC, GC-MS, thermal desorption–gas chromatography (TD-GC) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. The compositional differences of in-situ fluids, residual bitumen trapped in open, confined, and closed pores, as well as wellstream, were systematically investigated. (1) In-situ fluid compositions, with a 30.8% proportion of nC1−5 in n-alkanes, were studied by TD-GC analysis on pressure-retained cores. Interestingly, limited amounts of C8- compounds were detected in long-time exposed bulk cores but were almost absent in exposed powder. Primally poor pore connectivity and partially adsorption or absorption of organic matter contribute to the retention of gaseous hydrocarbons. (2) Sequential extraction is a best method for obtaining compositions of fluid in pores with variable sizes. Aliphatic compounds of residual bitumen trapped in open pores are similar to those in confined pores, while polar compounds are more enriched in confined and closed pores. Originally connected pores in early oil window, has turned into confined or closed pores by compaction and cementation with increasing depth. (3) Wellstream compositions are significantly different from in-situ fluid compositions, especially in shale oil extraction. The proportion of gaseous hydrocarbons in the wellstream (76.2%) is considerably higher than that of in-situ fluids (34.1%). Comparison of aromatic hydrocarbons indicated that the wellstream is sourced from free fluids and partially adsorbed hydrocarbons in open pores. (4) Nitrogen and oxide compounds with a higher degree of condensation (higher DBE value) have poor movability, leading to extremely low content or even absence in crude oil. The compositional differences from in-situ fluids to the wellbore through the stimulated fractures are caused by selective adsorption of pore walls, confinement effect of nanopores and fluid phase changing. This study provides a window to the compositional differences of fluids released from different occurrence spaces and confirms compounds heterogeneity.

A deep autoencoder network connected to geographical random forest for spatially aware geochemical anomaly detection

Machine learning (ML) and deep learning (DL) techniques have recently shown encouraging performance in recognizing metal-vectoring geochemical anomalies within complex Earth systems. However, the generalization of these techniques to detect subtle anomalies may be precluded due to overlooking non-stationary spatial structures and intra-pattern local dependencies contained in geochemical exploration data. Motivated by this, we conceptualize in this paper an innovative algorithm connecting a DL architecture to a spatial ML processor to account for local neighborhood information and spatial non-stationarities in support of spatially aware anomaly detection. A deep autoencoder network (DAN) is trained to abstract deep feature codings (DFCs) of multi-element input data. The encoded DFCs represent the typical performance of a nonlinear Earth system, i.e., multi-element signatures of geochemical background populations developed by different geo-processes. A local version of the random forest algorithm, geographical random forest (GRF), is then connected to the input and code layers of the DAN processor to establish nonlinear and spatially aware regressions between original geochemical signals (dependent variables) and DFCs (independent variables). After contributions of the latter on the former are determined, residuals of GRF regressions are quantified and interpreted as spatially aware anomaly scores related to mineralization. The proposed algorithm (i.e., DAN‒GRF) is implemented in the R language environment and examined in a case study with stream sediment geochemical data pertaining to the Takht-e-Soleyman district, Iran. The high-scored anomalies mapped by DAN‒GRF, compared to those by the stand-alone DAN technique, indicated a stronger spatial correlation with locations of known metal occurrences, which was statistically confirmed by success-rate curves, Student's t‒statistic method, and prediction-area plots. The findings suggested that the proposed algorithm has an enhanced capability to recognize subtle multi-element geochemical anomalies and extract reliable insights into metal exploration targeting.

Predictive Modeling of Canadian Carbonatite-Hosted REE +/− Nb Deposits

Carbonatites are the primary geological sources for rare earth elements (REEs) and niobium (Nb). This study applies machine learning techniques to generate national-scale prospectivity models and support mineral exploration targeting of Canadian carbonatite-hosted REE +/− Nb deposits. Extreme target feature label imbalance, diverse geological settings hosting these deposits throughout Canada, selecting negative labels, and issues regarding the interpretability of some machine learning models are major challenges impeding data-driven prospectivity modeling of carbonatite-hosted REE +/− Nb deposits. A multi-stage framework, exploiting global hierarchical tessellation model systems, data-space similarity measures, ensemble modeling, and Shapley additive explanations was coupled with convolutional neural networks (CNN) and random forest to meet the objectives of this work. A risk–return analysis was further implemented to assist with model interpretation and visualization. Multiple models were compared in terms of their predictive ability and their capability of reducing the search space for mineral exploration. The best-performing model, derived using a CNN that incorporates public geoscience datasets, exhibits an area under the curve for receiver operating characteristics plot of 0.96 for the testing labels, reducing the search area by 80%, while predicting all known carbonatite-hosted REE +/− Nb occurrences. The framework used in our study allows for an explicit definition of input vectors and provides a clear interpretation of outcomes generated by prospectivity models.

Recognition of Neogene tin mineralization in the Southeast Asian tin belt

The Southeast (SE) Asian tin belt is a major tin producer globally, with a prolonged mineralization history from the Permian to Paleogene (ca. 285−45 Ma). Tin deposits in this region are typically associated with tectonic settings that involve subduction and collision of the Paleo-, Meso-, and Neo-Tethys slabs. Ca. 40 Ma, a notable transition occurred in the tectonic regime of SE Tibet, with the Neo-Tethys subduction giving way to lateral extrusion of the Indochina block along major strike-slip faults. Previously, it was believed that this shift had brought tin mineralization to a halt. In this study, we present in situ laser ablation−inductively coupled plasma−mass spectrometry U-Pb cassiterite ages of 21−19 Ma from the Yunling tin deposit located in western Yunnan, China. Yunling produces gem-quality cassiterite that is transparent but contains low U contents, which renders usual U-Pb dating techniques unusable. To address this, a customized dating protocol involving cathodoluminescence (CL) imaging and testing of U distribution on crystallographically well-defined cassiterite crystals was applied. The study revealed two types of primary microstructures in cassiterite: volumetrically dominant concentric oscillatory growth zones and subordinate CL-dark sector zones. The U content shows a preferential enrichment in the CL-dark sector zones, typically tens of parts per million (ppm), which is two orders of magnitude greater than the U content in the concentric zone. This is significant, as the dating results (21−19 Ma) obtained through the targeted selection of CL-dark sector zones represent the youngest tin mineralization event in the SE Asian tin belt. Additionally, these results challenge the established belief that the ore-hosting Indosinian granite, dated to ca. 215 Ma, was related to Sn mineralization in the Yunling area. We suggest that emplacement of the early Neogene Sn mineralization at Yunling may be genetically connected to extensive delamination of the lithosphere in southeastern Tibet. The lithospheric delamination led to the upwelling and decompression partial melting of the asthenosphere, which provides a plausible explanation for the high temperature required for the release of Sn from biotite-dehydration melting of sedimentary protolith. The study also highlights the potential of Oligocene−Miocene-aged granites situated in the Sanjiang Tethys and adjacent areas of western Yunnan as prospective exploration targets for tin mineralization.

Three-Dimensional Geologic Modeling of the Kiruna Mining District, Sweden: Insights into the Crustal Architecture and Structural Controls on Iron Oxide-Apatite Mineralization

Abstract To support economic decisions and exploration targeting, as well as to understand processes controlling the mineralization, three-dimensional structural and lithological boundary models of the Kiruna mining district have been built using surface (outcrop observations and measurements) and subsurface (drill hole data and mine wall mapping) data. Rule-based hybrid implicit-explicit modeling techniques were used to create district-scale models of areas with high disproportion in data resolution characterized by dense, clustered, and distant data spacing. Densely sampled areas were integrated with established conceptual studies using geologic conditions and the addition of synthetic data, leading to variably constrained surfaces that facilitate the visualization, interpretation, and further integration of the geologic models. This modeling approach proved to be efficient in integrating local, frequently sampled areas with district-scale, sparsely sampled regions. Dominantly S-plunging lineation on N-S–trending fracture planes, characteristic fracture mineral-fill, and weak rock mass at the ore contact indicated by poor core orientation quality and rock quality description suggest that ore-parallel fractures in the Kiirunavaara area were more commonly reactivated. Slight variation in the angular relationship of fracture sets situated in different fault-bound blocks suggests that strain accommodation across the orebodies was uneven. The location of brittle faults identified in drill core, deposit-scale structural analysis, and aeromagnetic geophysical maps indicate a close relationship between fault locations and the iron oxide-apatite mineralization, suggesting that uneven stress accommodation and proximity of conjugate fault sets played an important role in juxtaposing blocks from different crustal depths and controls the location of the iron oxide-apatite orebodies.