Geology Field Methods

WA just found a better way to hunt for gold. Geologists at the Geological Survey of Western Australia (GSWA) have cracked a chemical fingerprint that points to hidden gold deposits. This could be a massive shift for gold exploration, not just in WA, but globally. It gives explorers a way to zero in on high-potential ground without relying only on old drill data or luck. They’ve already used it to identify new targets in the Yilgarn Craton, which is one of the oldest and richest gold regions on the planet. If this works like they say, we could see more discoveries in areas people thought were tapped out. This kind of breakthrough doesn't come out of nowhere. It’s backed by public investment, WA’s Exploration Incentive Scheme, advanced lab tools like the TESCAN analyser, and huge data sets the state is making public. Over 10 TB of exploration data is already online, with 30 TB more coming next year. Exploration is expensive and slow. If this fingerprinting cuts time and cost, it could reshape where and how gold is found. The big question is, how fast will the industry move to put it to work? #GoldExploration #WesternAustralia #MiningInnovation #Geoscience #YilgarnCraton https://lnkd.in/gHaA-N2R https://lnkd.in/gDnc2P_Q https://lnkd.in/gfTQnbdW

ECONOMIC GEOLOGY: OROGENIC GOLD DEPOSITS INTRODUCTION Orogenic gold deposits are one of the most significant sources of gold in the world, accounting for a large proportion of global production. These deposits are formed in regions of mountain-building, known as orogenic belts, and are closely associated with metamorphic rocks and major fault systems. Orogenic gold deposits are particularly important because they provide high-grade gold resources and are economically viable to mine in many regions. GEOLOGICAL SETTING Orogenic gold deposits typically occur in metamorphic terranes ranging from low-grade greenschist to high-grade amphibolite facies. They are commonly found along major crustal-scale faults or shear zones, which act as conduits for hydrothermal fluids that transport and deposit gold. FORMATION AND GENESIS The formation of orogenic gold deposits involves several interrelated processes, including fluid generation, fluid migration, and mineral precipitation. Metamorphic dehydration reactions in rocks at depth produce hot, aqueous fluids rich in dissolved gold and other metals. These fluids migrate along faults, fractures, and shear zones toward the surface. As they ascend, changes in pressure, temperature, and chemistry cause gold and associated minerals, such as quartz, pyrite, arsenopyrite, and sulfides, to precipitate. The fluids in orogenic gold systems are typically low in salinity and contain significant amounts of carbon dioxide and methane, which help in the transport and deposition of gold. Structural traps, such as bends in faults, dilation zones, and intersections of shear zones, provide the physical space for ore deposition. MINERALOGY AND PETROGRAPHY Quartz is the dominant gangue mineral in orogenic gold deposits, often forming veins, veinlets, and stockworks. Gold occurs both as free metal and in association with sulfide minerals, including pyrite, arsenopyrite, chalcopyrite, and galena. Minor amounts of other trace metals such as bismuth, tellurium, and antimony may also be present. Orogenic gold deposits frequently show multiple stages of mineralization, with early sulfide-rich veins overprinted by later quartz-rich veins containing gold. STRUCTURAL AND GEOCHEMICAL CHARACTERISTICS Structurally, orogenic gold deposits are intimately associated with shear zones and faults. These zones provide the permeability necessary for hydrothermal fluids to circulate and deposit gold. Geochemically, the host rocks often display anomalous concentrations of gold, arsenic, antimony, and other pathfinder elements, which are crucial for exploration. Modern geochemical techniques, including multi-element soil and rock sampling, help identify prospective areas. #EconomicGeology #OrogenicGold #GoldMining #HydrothermalDeposits #Geoscience #MineralExploration #SustainableMining

Revolutionizing Mineral Exploration with Remote Sensing (RS) &GIS 🌍⛏️ RS and GIS are essential tools in mineral exploration. RS utilizes satellite capture spectral and spatial data, identifying mineralogical features and geological structures. GIS integrates this data with spatial analysis, enabling the creation of detailed geological models, enhancing target identification, and optimizing exploration workflows. RS Workflow 1. Image Acquisition: Utilizing advanced satellite platforms (e.g., Landsat, Sentinel-2, ASTER) and hyperspectral imagery to meet specific spatial, spectral, and radiometric resolution requirements. 2. Pre-processing: Applying radiometric calibration, geometric corrections, and atmospheric removal techniques to eliminate noise and enhance data fidelity. 3. Image Enhancement: Leveraging advanced methods like band rationing, decorrelation stretching, and principal component analysis (PCA) to emphasize key geological features. 4. Spectral Analysis: Extracting diagnostic absorption features from reflectance spectra to characterize mineralogical compositions and identify alteration zones. 5. Feature Extraction: Employing algorithms such as edge detection, thresholding, and object-based image analysis to delineate structural controls, lithologies, and mineralization patterns 6. Spatial Analysis: Quantifying spatial relationships between features and integrating remote sensing-derived anomalies with ground-truth data to validate exploration models 7. GIS Integration: Combining multisource datasets (RS , geophysical, geochemical, and field data) within GIS for spatial modeling, 3D visualization, and predictive analysis Applications in Mineral Exploration Regional Exploration Lithological Mapping: Discriminating and classifying rock units based on spectral properties and reflectance curves. Structural Mapping: Accurately identifying faults, lineaments, folds, and fracture systems critical for ore deposition using high-resolution imagery and LiDAR data Alteration Mapping: Detecting hydrothermal alteration minerals (e.g., clays, iron oxides, carbonates) indicative of mineralization processes Target Generation Anomaly Detection: Recognizing spectral and geophysical anomalies associated with buried ore bodies or surface mineralization signatures Data Integration: Fusing remote sensing data with magnetometry, radiometry, and gravity surveys to refine geological interpretations Target Prioritization: Applying multi-criteria decision analysis and machine learning algorithms to rank prospective targets based on integrated datasets Benefits of RS and GIS Efficiency: Rapid acquisition of regional-scale data, enabling large-area exploration in diverse terrains Precision: High-resolution and multispectral imaging improve the accuracy of mineralogical mapping and resource estimation Cost-effectiveness: Reduction in fieldwork expenditures through preliminary remote investigations #RemoteSensing #GIS #GeospatialAnalysis

“𝑯𝒐𝒘 𝒎𝒖𝒄𝒉 𝒊𝒔 𝒓𝒆𝒂𝒍𝒍𝒚 𝒊𝒏 𝒕𝒉𝒆 𝒈𝒓𝒐𝒖𝒏𝒅?” This is the single most important question in mining. To answer this, mining engineers and geologists use different resource estimation methods. Each method has its own accuracy, data requirements, and ideal use case. 1. Polygonal / Triangular Methods (Classical) Draw polygons (or triangles) around sample points (e.g., drill holes). Assign the grade of the sample to the whole polygon or use the average of three samples for a triangle. Used in : Early exploration, very sparse data, quick first-look estimates. 2. Inverse Distance Weighting (IDW) Estimate the grade at an unsampled point by averaging nearby samples. Closer samples have more weight (weight decreases with distance, often by distance²). Used in : Moderate drill density, mid-stage projects needing a straightforward interpolator. 3. Ordinary Kriging (OK) Use a semivariogram to model how grades correlate with distance and direction. Calculate optimized weights from that model to produce an unbiased estimate and error measure. Used in: Advanced exploration, feasibility studies, and formal resource reporting (JORC/NI 43-101). 4. Indicator Kriging (IK) Convert grades into indicators (e.g., above/below a cutoff). Krige those indicators to estimate probabilities that blocks exceed cutoffs; combine probabilities to infer grade classes. Used in : Highly variable deposits, modelling cutoffs for ore/waste, probabilistic resource classification. 5. Sequential Gaussian Simulation (SGS) / Multiple Simulations Generate multiple equally-probable realizations of the grade distribution that honour data and spatial continuity. Use the ensemble of realizations to assess uncertainty and preserve local variability. Used in : Uncertainty / risk analysis, complex or highly heterogeneous ore bodies, mine planning with scenario testing. 6. Machine Learning (ML)–Based Estimation Use supervised learning algorithms (e.g., random forests, gradient boosting, neural networks) to predict grades or classes from many inputs: drill data, geology logs, geophysics, remote sensing, structural interpretations, and derived features. ML models learn non-linear relationships and can incorporate large multi-source datasets. Often used together with spatial methods (e.g., ML predictions as inputs to kriging or as features in simulations). Used in : Complex datasets with many predictors, integrating geophysics/chemistry/structural data, rapid scenario testing, and when non-linear patterns are suspected. Increasingly used for feature engineering, anomaly detection, and to augment traditional geostatistics. #mining #geology #resources #resourceestimation #geostatistics #Kriging #IDW

EPITHERMAL AND PORPHYRY GOLD-SILVER-COPPER MINERALIZATION INTRODUCTION Epithermal and porphyry deposits represent some of the most important sources of gold (Au), silver (Ag), and copper (Cu) in the world. These deposits are closely associated with magmatic-hydrothermal systems, where mineralized fluids migrate through the Earth’s crust, depositing metals in favorable geological environments. The diagram below illustrates the genetic relationship between high sulphidation epithermal, low sulphidation epithermal, sediment-hosted, and porphyry systems. ✓ HIGH SULPHIDATION EPITHERMAL SYSTEMS (Au) These deposits form from hot, acidic fluids rich in magmatic volatiles. They are characterized by: • Steam-heated alteration zones. • Silica caps and advanced argillic alteration. • Breccia pipes and structural controls. Mineralization styles such as banded veins, fissure veins, and breccia fills. These systems typically occur at shallow crustal levels above porphyry intrusions. ✓ LOW SULPHIDATION EPITHERMAL SYSTEMS (Au-Ag) These deposits form when metal-rich fluids interact with meteoric waters under neutral to slightly alkaline conditions. Its features include: • Banded chalcedony and ginguro veins. • Quartz-adularia vein systems. • Deposits controlled by rifts, faults, and permeable horizons. • Polymetallic veins with Au-Ag mineralization. PORPHYRY CU-AU SYSTEMS Porphyry deposits are large, low-grade but high-tonnage systems that form from magmatic fluids exsolved from cooling intrusions. They are characterized by: ~ Stockwork quartz-sulphide veins. ~ Alteration zones (potassic, phyllic, propylitic, and argillic). ~ Central porphyry intrusions hosting disseminated mineralization. These deposits represent the root zones of epithermal systems. SKARN AND REPLACEMENT DEPOSITS At the contact between intrusions and carbonate host rocks, mineralized fluids produce exoskarns and endoskarns with gold, copper, and base metals. Sediment-hosted replacement deposits also form when fluids infiltrate carbonate-rich rocks, producing localized ore zones. FLUID PROCESSES ° The genesis of these deposits depends on different fluid processes, including: ° Rising magmatic mineralized fluids (high temperature, metal-rich). ° Circulation of meteoric-dominant waters (cooler, near-surface). ° Mixing and collapse of evolved fluids, producing zones of mineral deposition. ° Variations in pH, bicarbonate concentration, and oxygenation that control ore precipitation. CONCLUSION The figure below demonstrates the continuum between porphyry and epithermal mineralization, showing how different fluid-rock interactions and structural controls produce diverse ore deposit types. Understanding these systems is critical for mineral exploration and economic geology. Geology forum 1 #geologyknowledge #GeologyLovers #geologyforum1 #porphyry #porphyrymineralization #epithermalmineralization #geology #epithermal

✅ Structural Geology — The Hidden GPS of Mineral Exploration In exploration, many still rely on geochemistry and geophysics alone… but ore deposits don’t form randomly. They follow structural controls — and those who can read rocks like a deformation map will always have an advantage in discovery. 🔎 Why Structural Geology Matters : Critical minerals, gold or base metals — whether in shear-hosted lodes, VMS reactivations, IOCG systems or REE veins — their localization is rarely chemical… it is structural. If you understand where the rocks opened, where fluids focused, or where permeability changed, you can predict mineralization even before drilling. 🧭 Field Checklist — What to Look For in Outcrop : 🪨 Planar Structures ● Foliation / Schistosity → Mineral alignment = pathway for gold & sulfide fluids ● Bedding (S0) → Reference layer to define folding direction ● Cleavage → Often at an angle to bedding — intersection lines = fold axes 🌀 Folds & Flexures ● S/Z drag folds, hinge thickening, repetition of layers ● Fold hinges often serve as fluid traps → mineral concentration zones ⚡ Faults & Shear Zones ● Gouge, breccia, quartz-carbonate veins ● Primary fluid pathways — follow them relentlessly 🪟 Joints & Tension Gashes ● Vein-filled cracks → can indicate stress directions & mineralized veins 🛠️ Quick Recognition Tricks : ✅ Bedding vs Foliation? → Bedding shows grain-size changes, foliation shows aligned micas ✅ Shear Sense? → Look for sigma clasts or S-C fabrics ✅ Fold Geometry? → Plot bedding vs cleavage intersection to determine plunge ✅ Fault Activity? → Gouge = long-term slip, angular breccia = sudden movement 📐 Never Leave an Outcrop Without Measuring: ✔ Strike & dip of all planar surfaces ✔ Lineations or slickensides on shear planes ✔ Fracture density & spacing ✔ Mineralization aligned with deformation fabrics 🎯 Bottom Line Structural geology is not academic theory — it’s the cheapest and most powerful targeting tool in mineral exploration. #StructuralGeology #MineralExploration #FieldMapping #CriticalMinerals #Mining #Tectonics #OreDeposits #Geoscience

📌 Optimizing Drilling and Core Logging for Accurate 3D Ore Body Modeling In mineral exploration, the precision of your 3D geological model is fundamentally linked to the quality of drilling and core logging practices. To accurately capture lithology, alteration, and structural features at depth, it's crucial to align your drilling strategy with the ore body's geometry. 💡 Why Drill Perpendicular to the Ore Body? Drilling perpendicular to the ore body maximizes the intersection angle, providing a true representation of its thickness and structure. Vertical holes may not always suffice, especially in deposits with significant dip angles. Aligning drill holes perpendicular to the strike of the ore body ensures maximum exposure and contributes to constructing an accurate structural and grade model. 💡 Determining Ore Body Orientation Surface mapping of geological structures—such as bedding planes, faults, and foliation—offers initial insights into the ore body's orientation. Combining this with data from early drill holes enhances the drilling plan to intersect the ore body at optimal angles. 💡 Importance of Structural Features in Core Logging Logging the structural features of drill cores is a critical component in mining exploration and development. Detailed documentation of features such as faults, folds, fractures, and vein orientations provides essential insights into the geological framework of a deposit. This information is indispensable for constructing accurate three-dimensional models, which are vital for effective resource estimation, mine design, and geotechnical planning. Moreover, understanding the structural characteristics of the rock mass aids in assessing ground stability, thereby enhancing safety and efficiency in mining operations. In essence, meticulous structural core logging underpins informed decision-making throughout the mining lifecycle, from exploration to production. #Mining #Geology #CoreLogging #Drilling #StructuralGeology #MineralExploration #OreBodyModeling

Exploration of hydrothermal Gold Deposit: Exploration of hydrothermal gold deposits involves systematic geological, geochemical, and geophysical investigations to locate economically viable mineralization formed by hot, mineral-rich fluids. These deposits typically occur in structurally controlled settings such as faults or shear zones and can be classified into epithermal, mesothermal (orogenic), and porphyry-related systems. The process begins with regional geological mapping and remote sensing to identify favorable tectonic settings and alteration zones. Geochemical surveys, including stream sediment, soil, and rock chip sampling, help identify gold and associated pathfinder elements like arsenic, antimony, and mercury. Alteration mapping is crucial, as hydrothermal fluids often alter host rocks, resulting in zones of silicification, argillic, or sericitic alteration. Portable spectrometers or satellite data can aid in detecting these zones. Geophysical methods such as Induced Polarization (IP), resistivity, and magnetics help identify subsurface structures and sulfide-rich zones potentially hosting gold mineralization. Drilling is the definitive stage of exploration, providing subsurface data and samples for assay to determine gold grade and continuity. Integration of geological, geochemical, and geophysical data into 3D models helps in resource estimation and planning further exploration or development. Effective exploration of hydrothermal gold requires a multidisciplinary approach and careful interpretation of subtle geological indicators to reduce risk and improve discovery success. #ExploExplorationofhydrothermalGoldDeposit #mining #geology #goldexploration