Study guide
6.1 Geochemical & Remote Sensing Exploration Techniques
PRC Mining Engineer Licensure Examination Philippines
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1 Chapter 1: Surface Mining Methods & Pit Optimization
1.1 Surface Mining Unit Operations & Method Selection 1.2 Bench Geometry, Slope Stability & Geotechnical Pit Design 1.3 Cut-Off Grade Optimization & Lerchs-Grossmann Pit Limits
2 Chapter 2: Underground Mining Methods & Strata Control
2.1 Underground Mining Method Classification & Selection 2.2 Rock Mechanics, Stress Analysis & Strata Control 2.3 Underground Ground Support Systems & Excavation Design
3 Chapter 3: Materials Handling, Equipment & Mine Economics
3.1 Drilling, Blasting & Explosives Engineering 3.2 Mine Loading, Haulage & Materials Handling Systems 3.3 Mine Capital (CAPEX), Operating Costs (OPEX) & Financial Evaluation
4 Chapter 4: Mine Safety, Ventilation & Philippine Mining Laws
4.1 Mine Ventilation Network Analysis & Environmental Quality 4.2 Philippine Mine Safety Rules, Health & Disaster Prevention 4.3 Philippine Mining Act of 1995 (RA 7942), DAO 2010-21 & Mining Ethics
5 Chapter 5: Physical Geology, Mineralogy & Philippine Deposit Types
5.1 Structural Geology, Tectonics & Ore Controls 5.2 Igneous, Metamorphic & Sedimentary Ore Mineralogy 5.3 Major Philippine Ore Deposit Models
6 Chapter 6: Mineral Exploration, Geophysics & Core Logging
6.1 Geochemical & Remote Sensing Exploration Techniques 6.2 Geophysical Exploration Methods in Mining Geology 6.3 Diamond Drilling, Core Logging & QA/QC Protocols
7 Chapter 7: Geostatistics, Resource Estimation & PMRC Code
7.1 Ore Body Block Modeling & Spatial Variography 7.2 Inverse Distance & Ordinary Kriging Grade Estimation 7.3 Philippine Mineral Reporting Code (PMRC 2020) & Resource Classification
8 Chapter 8: Comminution, Sizing & Physical Mineral Separation
8.1 Crushing, Grinding & Bond Work Index Calculations 8.2 Particle Screening, Hydrocyclone Classification & Sizing 8.3 Gravity Concentration & Magnetic/Electrostatic Separation
9 Chapter 9: Froth Flotation & Extractive Hydrometallurgy
9.1 Froth Flotation Chemistry, Reagents & Cell Kinetics 9.2 Leaching Technologies (Heap, Agitation & Tank) 9.3 Precious Metal Recovery: CIP, CIL, Merrill-Crowe & Electrowinning
10 Chapter 10: Process Plant Flowsheets & Environmental Tailings Management
10.1 Metallurgical Plant Flowsheets & Pulp Mass Balances 10.2 Tailings Storage Facility (TSF) Design & Dam Safety 10.3 Acid Mine Drainage (AMD) Mitigation & Environmental Protection (EPEP/FMR/DP)
11 Chapter 11: 2025 PRC Blueprint, Prospecting Tools & Exploration Decisions
11.1 Official 2025 TOS, Three-Paper Structure & Exam Strategy 11.2 Prospecting Instruments, Base Maps & Surface Geological Mapping 11.3 Integrating Direct and Indirect Evidence for Exploration Decisions
12 Chapter 12: Mine Infrastructure, Sustainable Development & Climate
12.1 Power, Water, Drainage & Support-Facility Selection 12.2 Sustainable Development, Progressive Rehabilitation & Community Impact 12.3 Mining, Climate, Reforestation, Coal & Energy-Transition Minerals
13 Chapter 13: Mine Valuation, Financial Analysis & Due Diligence
13.1 Time Value of Money, Future Value & Present Value 13.2 Financial Statements, Mine Economics & External Price Drivers 13.3 Exploration Provenance, Technical Review & Legal Due Diligence
14 Chapter 14: Mine Organization, Communication & Accountable Leadership
14.1 Line and Staff Functions in a Mining Organization 14.2 Communication With Superiors, Peers & Subordinates 14.3 Authority, Responsibility, Delegation & Safety Accountability
15 Chapter 15: Philippine Mining Law, Indigenous Rights & Professional Ethics
15.1 Legal Hierarchy, Mineral Tenure & Compliance Analysis 15.2 Constitutional Participation, IPRA, FPIC & Ancestral Domains 15.3 RA 4274, Professional Scope, Ethics & Document Integrity
16 Chapter 16: Applied Mathematics & Mine Surveying
16.1 Engineering Mathematics for Safe, Efficient Mine Decisions 16.2 Survey Control, Instruments, Traverses & Error Adjustment 16.3 Topographic Maps, Underground Set-Out & Survey Timeliness
17 Chapter 17: Feasibility Studies, Data Quality & Project Decisions
17.1 Scoping, Pre-Feasibility & Final Feasibility Study Maturity 17.2 Data Accuracy, Assumption Control & Go/No-Go Decisions 17.3 Multidisciplinary Integration, Interfaces & Independent Review
18 Chapter 18: Mining Computer Applications, Digital Control & Global Developments
18.1 Computer Functions, Office Applications & Data Governance 18.2 Geological Modeling, Mine Planning, Scheduling & Valuation Software 18.3 Real-Time Control, Critical Minerals & Regional Mining Developments
19 Chapter 19: Earth Systems, Geologic Time & Philippine Hazards
19.1 Solar-System Origin, Earth Interior & Atmospheric Layers 19.2 Rock Cycle, Landforms & the Geologic Time Scale 19.3 Philippine Tectonics, Geologic Hazards & Mitigation
20 Chapter 20: Metallurgy, Foundry Practice & Assaying
20.1 Extractive, Physical & Adaptive Metallurgy Principles 20.2 Foundry Materials, Casting, Solidification & Defects 20.3 Sampling, Fire Assay, Cupellation, Parting & Assay Calculations
21 Chapter 21: Solid–Liquid Separation, Environmental Law & Mine Ecology
21.1 Thickening, Filtration & Solid–Liquid Separation 21.2 Philippine Air, Water, Waste & Hazardous-Substance Controls 21.3 Mine Ecology, Closure, Tailings, Waste & Community Livelihood
6.1 Geochemical & Remote Sensing Exploration Techniques
Key Takeaways Explain This Topic AI
Mineral exploration progresses systematically through staged workflows: regional reconnaissance, target generation, detailed prospect evaluation, and deposit delineation to mitigate technical and economic risk.
Stream sediment sampling, including Bulk Leach Extractable Gold (BLEG), captures catchment-wide geochemical anomalies, while grid-based soil sampling and rock chip/trenching delineate localized drill targets.
Pathfinder elements exploit primary and secondary dispersion halos; for example, As, Sb, Hg, and Te serve as volatile pathfinders for epithermal gold, whereas Cu, Mo, Au, and Zn halo porphyry systems.
Remote sensing can screen exposed alteration using spectral and spatial evidence: archival ASTER SWIR data remain useful, while Sentinel-2, Landsat-8/9, airborne data, and field spectra have different band, resolution, vegetation, and calibration limits.
In tropical, deeply weathered terrains such as the Philippines, geochemical interpretations must account for soil horizon development (pedogenesis), lateritization, and hydraulic dispersion along active drainage networks.
Last updated: August 2026
Mineral exploration is a high-risk, capital-intensive endeavor that aims to discover economically viable mineral deposits beneath the Earth's surface. To systematically reduce technical and financial uncertainty, exploration programs follow a staged workflow ranging from broad regional reconnaissance to site-specific deposit evaluation. Geochemical surveying and spectral remote sensing represent the primary front-line methodologies deployed during early-stage exploration to identify hydrothermally altered rock packages and surface geochemical anomalies.
Staged Mineral Exploration Framework
Modern mineral exploration programs progress through four sequential stages, with each stage serving as a decision gate to commit or divest capital:
Regional Reconnaissance (Grassroots Exploration) : Covers large areas ( 1 , 000 to 10 , 000 km 2 1,000\text{ to } 10,000\text{ km}^2 1 , 000 to 10 , 000 km 2 ) to establish regional metallogenic potential. Activities focus on satellite imagery interpretation, airborne geophysics, and wide-spaced stream sediment sampling.
Target Generation (Prospecting) : Reduces exploration area to 10 to 100 km 2 10\text{ to } 100\text{ km}^2 10 to 100 km 2 . High-resolution remote sensing, grid-based soil sampling, and ground geophysical surveys delineate anomalous zones for follow-up.
Detailed Prospect Evaluation : Encompasses 1 to 10 km 2 1\text{ to } 10\text{ km}^2 1 to 10 km 2 . Outcrop mapping, structural analysis, trenching, rock chip sampling, and initial scout drilling test mineralized structures at depth.
Deposit Delineation & Pre-Feasibility : May involve progressively closer-spaced diamond drilling, detailed core logging, 3D geological and grade modeling, QA/QC verification, and metallurgical testing to estimate mineral resources under recognized reporting codes (e.g., PMRC, JORC, NI 43-101).
The stage areas above are order-of-magnitude illustrations. Deposit footprint, access, terrain, data maturity, decision, and budget determine program scale; stages can overlap and targets can be abandoned or recycled.
Geochemical Exploration Protocols & Media Selection
Geochemical exploration measures the abundance and distribution of chemical elements in natural surface materials to detect primary and secondary dispersion halos.
1. Stream Sediment Sampling & BLEG
Stream sediment sampling evaluates active drainage catchments by collecting fine sediment deposited by running water. In mountainous tropical catchments, stream sediment surveys provide rapid coverage of entire river basins.
Conventional Stream Sediment Surveys : Sediment is sieved in the field to fine fractions (typically − 80 mesh -80\text{ mesh} − 80 mesh or 177 μ m 177\text{ }\mu\text{m} 177 μ m ) and analyzed for multi-element suites using Inductively Coupled Plasma Mass Spectrometry (ICP-MS).
Bulk Leach Extractable Gold (BLEG) : BLEG leaches a comparatively large stream-sediment sample to reduce nugget-effect variability and improve sensitivity to low-level catchment anomalies. Sample mass, preparation, leach chemistry, reporting limit, and downstream dispersion distance must be established by the program and laboratory rather than assumed from one generic value.
2. Soil Geochemistry & Sampling Grids
Soil sampling maps secondary dispersion halos in residual soil profiles overlying bedrock mineralization.
Horizon Selection : Select and document a consistent sampling medium only after an orientation survey relates horizons, regolith processes, and target response. A B-horizon may concentrate metals on clays or iron-manganese oxides, while organic A-horizon material is often avoided and saprolite may be appropriate for another program; no horizon is universally discarded or preferred.
Grid Patterns : Grid orientation and spacing follow expected target geometry, dispersion, topography, access, and orientation results. Values such as 200 m by 100 m for reconnaissance or 25 m by 25 m for follow-up are illustrations, not prescriptions.
3. Rock Chip & Trench Sampling
Rock sampling provides direct geochemical evidence of bedrock mineralization.
Grab and Characterization Sampling : Grab or characterization samples provide selective reconnaissance evidence from outcrop, float, or veins but are not grade-representative unless a defensible sampling design establishes representativity.
Continuous Channel Sampling & Trenching : Excavated trenches cut across structural strike. Continuous channel samples are cut with controlled width, depth, orientation, and interval across the exposure. Dimensions such as a 5–10 cm channel and 1 m interval are illustrative; geology, grain size, expected grade variability, safety, and the required support determine the actual protocol.
Pathfinder Elements & Dispersion Halos
Hydrothermal ore-forming processes create primary zoning (in host rocks surrounding the orebody) and secondary zoning (in weathered regolith). Pathfinder elements are mobile, easily detectable trace elements associated with specific ore deposits that form wider dispersion halos than the target ore metals.
1. Epithermal Gold-Silver Systems
Epithermal deposits form at shallow depths ( < 1 km < 1\text{ km} < 1 km ) and low temperatures ( 100 – 300 ∘ C 100\text{--}300^\circ\text{C} 100 – 30 0 ∘ C ). High volatile element mobilities produce broad trace-element halos:
Primary Pathfinders : Arsenic ( A s As A s ), Antimony ( S b Sb S b ), Mercury ( H g Hg H g ), Tellurium ( T e Te T e ), Bismuth ( B i Bi B i ), Thallium ( T l Tl Tl ).
Zoning Vectoring : In high-sulfidation epithermal systems (e.g., Lepanto, Benguet), elevated H g Hg H g and S b Sb S b occupy shallow steam-heated clay caps, while A s As A s and T e Te T e envelope the underlying high-grade A u – C u – A g Au\text{--}Cu\text{--}Ag A u – C u – A g silica-enargite ore zone.
2. Porphyry Copper-Gold-Molybdenum Systems
Porphyry systems represent large-volume, low-grade magmatic-hydrothermal systems with distinct concentric alteration and geochemical halos:
Core Metal Suite : Copper ( C u Cu C u ), Molybdenum ( M o Mo M o ), Gold ( A u Au A u ).
Peripheral Pathfinder Halo : Zinc ( Z n Zn Z n ), Lead ( P b Pb P b ), Manganese ( M n Mn M n ), Selenium ( S e Se S e ). Zinc, lead, manganese, and related element ratios can form broad peripheral patterns, sometimes at kilometre scale, but lithology, weathering, analytical support, and local deposit orientation must be established before using them as vectors.
3. Philippine Tropical Weathering Considerations
In tropical, high-rainfall environments like the Philippines, intense chemical weathering (lateritization) leaches mobile alkali and alkaline earth cations ( M g 2 + , C a 2 + , N a + , K + Mg^{2+}, Ca^{2+}, Na^+, K^+ M g 2 + , C a 2 + , N a + , K + ), concentrating immobile elements ( F e 3 + , A l 3 + , N i 2 + , C r 3 + Fe^{3+}, Al^{3+}, Ni^{2+}, Cr^{3+} F e 3 + , A l 3 + , N i 2 + , C r 3 + ) in residual ferruginous limonite and saprolite horizons. Geochemical interpretations must differentiate hydromorphic dispersion (groundwater transport) from mechanical residual accumulation.
Remote Sensing & Spectral Geology
Remote sensing exploits optical satellite imagery and hyperspectral sensors to map lithology, structural lineaments, and hydrothermal alteration zones over inaccessible terrain.
1. Multispectral Platforms & Spectral Regions
Satellites measure reflected solar radiation across distinct wavelength regions:
Visible and Near-Infrared (VNIR, 0.4 – 1.0 μ m 0.4\text{--}1.0\text{ }\mu\text{m} 0.4 – 1.0 μ m ) : Detects electronic absorption transitions in transition metals, notably ferric ( F e 3 + Fe^{3+} F e 3 + ) and ferrous ( F e 2 + Fe^{2+} F e 2 + ) iron oxides.
Shortwave Infrared (SWIR, 1.0 – 2.5 μ m 1.0\text{--}2.5\text{ }\mu\text{m} 1.0 – 2.5 μ m ) : Measures vibrational absorption of hydroxyl ( O H − OH^- O H − ), carbonate ( C O 3 2 − CO_3^{2-} C O 3 2 − ), and sulfate ( S O 4 2 − SO_4^{2-} S O 4 2 − ) molecular bonds. SWIR is critical for identifying clay minerals, micas, and sulfates.
Key spaceborne sources : archival ASTER, Sentinel-2, and Landsat-8/9. ASTER SWIR stopped acquiring usable new data in 2008, so its pre-failure archive can support alteration mapping but is not current imagery.
2. Band Ratios & Alteration Mineral Mapping
Band ratioing divides digital number (DN) values of one spectral band by another to highlight specific mineral absorption and reflectance features while reducing some illumination and albedo effects when ratios are validated:
Iron Oxides (Gossans / Cappings) : Ferric oxides and hydroxides produce diagnostic color and VNIR absorption contrasts. Validated ratios such as ASTER Band 2/Band 1 or Landsat-8/9 Band 4/Band 2 can enhance iron-rich surfaces, but vegetation, soil, illumination, atmospheric correction, sensor scaling, and non-ore ferric material make the result non-unique.
Phyllic & Argillic Alteration : Clay minerals (kaolinite, alunite, illite, montmorillonite, white mica/sericite) display intense absorption features around 2.17 – 2.20 μ m 2.17\text{--}2.20\text{ }\mu\text{m} 2.17 – 2.20 μ m (ASTER Band 6). The ratio ( Band 4 + Band 7 ) / Band 6 (\text{Band } 4 + \text{Band } 7) / \text{Band } 6 ( Band 4 + Band 7 ) / Band 6 highlights phyllic (sericitic) and advanced argillic zones characteristic of porphyry and epithermal deposit cores.
Propylitic Alteration : Chlorite, epidote, and calcite absorb at 2.30 – 2.35 μ m 2.30\text{--}2.35\text{ }\mu\text{m} 2.30 – 2.35 μ m (ASTER Band 8), mapped via ( Band 5 + Band 9 ) / Band 8 (\text{Band } 5 + \text{Band } 9) / \text{Band } 8 ( Band 5 + Band 9 ) / Band 8 .
Exploration Geochemistry & Remote Sensing Method Summary
Technique Operating Principle Target Material / Signal Primary Exploration Application
BLEG Sampling Large-sample leach under a validated laboratory protocol Low-level catchment gold signal with method-specific reporting limit Catchment-wide gold reconnaissance
Soil Geochemistry Orientation-selected horizon and spacing Secondary metal dispersion halos Delineating sub-cropping drill targets
Pathfinder Halos Multi-element ICP-MS analysis A s , S b , H g , T e , B i , T l As, Sb, Hg, Te, Bi, Tl A s , S b , H g , T e , B i , Tl Epithermal Au-Ag vectoring
VNIR Remote Sensing 0.4 – 1.0 μ m 0.4\text{--}1.0\text{ }\mu\text{m} 0.4 – 1.0 μ m spectral band reflectance F e 3 + Fe^{3+} F e 3 + hematite, goethite, jarosite Gossan & iron-hat capping mapping
SWIR Remote Sensing 1.0 – 2.5 μ m 1.0\text{--}2.5\text{ }\mu\text{m} 1.0 – 2.5 μ m spectral absorption O H − OH^- O H − alunite, kaolinite, illite, sericite Phyllic & argillic alteration mapping