Sustainable Natural Resources Development on a Small Planet. Mineral Exploration

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Caren Hill
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principles used for exploring, discovering, and evaluating mineral resources Better

1 Sustainable Natural Resources Development on a Small Planet Mineral Exploration Exploration the mining industry s principal activity in research and development Scientific and engineering principles used for exploring, discovering, and evaluating mineral resources Better understanding of subsurface processes and geologic features greatly aids in mineral exploration and evaluation 1

$refractory resources$ deposits at depth

2 Energy (coal, oil, gas, and uranium), Industrial minerals, especially for infrastructure and urban usage, Metallic minerals for manufacturing: lower grade resources refractory resources deposits at depth deposits in countries with open door policies 2

Supergene enriched mineral deposits Small footprints, but can occur in clusters Complexgeology with alteration, mineralization, and geochemical haloes; but can be subtle Difficult to

3 A Genetic Model formation of ore deposits: Ancient pre concentration (e.g. sedimentation) Capturing metals by a magma Transporting and further concentration Crystallization Magmatic mineral deposits Precipitation Hydrothermal mineral deposits Oxidation Supergene enriched mineral deposits Small footprints, but can occur in clusters Complexgeology with alteration, mineralization, and geochemical haloes; but can be subtle Difficult to find if deposit not exposed Exposure of even a small part of a deposit s haloes provides exploration clues Geophysical anomalies provide more clues Metals respond to electrical, magnetic, and electromagnetic geophysical methods Drilling tests and defines subsurface geology Often complex 3 dimensional shapes 3

Exploration (ore deposit) modeling interpretation Geology basis for all exploration Geophysics measure of rocks physical properties Geochemistry rocks chemical properties Drilling methods for

Geologic mapping and drill hole sample logging Lithology rock types and inter relationships Hydrothermal alteration Mineralization Structures Weathering and oxidation Microscopic rock and mineral

4 Exploration (ore deposit) modeling interpretation Geology basis for all exploration Geophysics measure of rocks physical properties Geochemistry rocks chemical properties Drilling methods for subsurface testing Resource (reserve) modeling grade, size, shape, and mineralization continuity Geographic Information Systems Remote sensing / satellite imagery Assaying and sample preparation 1. Geologic mapping and drill hole sample logging Lithology rock types and inter relationships Hydrothermal alteration Mineralization Structures Weathering and oxidation Microscopic rock and mineral examination including Qemscan and computer assisted analysis of minerals & textures Geometallurgy 2. Airborne geophysics: gravity, magnetic, radiometric, and electromagnetic surveys (identify geology & structures) 3. Ground geophysics: electrical methods, magnetic, gravity, radiometric, electromagnetic, VLF, and seismic surveys 4 Geochemical surveys 5. Remote sensing / satellite imagery 4

5 1. Exploration geology relies on analogies to known deposits in guiding most activities empirical model of geology, geophysics, & geochemistry of a deposit 2. Conceptual modeling of types of mineral deposits and the range of their variable features and halos 3. Also genetic modeling of processes within earth (e.g. magmas release of hydrothermal fluids, alteration of the wall rocks, and precipitation of metallic minerals) 4. Difficulties in modeling processes and the resulting features that occur at depth within the crust 5. Models becoming much more sophisticated with GIS & computer assisted three dimensional analysis 1. Geologic mapping and drill hole sample logging Lithology rock types and inter relationships, lti brecciation Hydrothermal alteration zoning& patterns Mineralization zoning& patterns Structures pre mineral controlling, syn mineral, post mineral Weathering and oxidation supergene enrichment 2. Microscopic rock and mineral examination Qemscan and computer assisted analysis of minerals & textures Geometallurgy beyond process mineralogy 5

1. Airborne methods: gravity, magnetic, radiometric, and electromagnetic surveys (each of these identifies large geologic g features and possibly major structures in the region.) 2.

6 1. Airborne methods: gravity, magnetic, radiometric, and electromagnetic surveys (each of these identifies large geologic g features and possibly major structures in the region.) 2. Ground methods: electrical, magnetic, gravity, radiometric, and electromagnetic, VLF, seismic (more detailed info) 3. Down hole methods: electrical, radiometric, magnetic Geochemical Surveys zoning & patterns All Data Entered into a GIS System REE an unusual group of 15 metallic elements with unique properties: chemical, catalytic, magnetic, metallurgical and phosphorescent Applications: high strength magnets largest andfastest growing market requires neodymium, praseodymium, dysprosium and terbium; used in hybrid and electric autos, and wind turbines; compact fluorescent lighting europium plus others; many green technology and high technology uses China accounts for ~96% of the world s current REE production; believed to be operating at near capacity; reducing exports year by year; potentially will import rare earths in 3 4 years Critical need for non Chinese production for world s manufacturing industries; two mines going into production in 2011 and 2012 Total demand for REE expected to grow from 125,000 tonnes in 2010, to 205,000 tonnes by 2015, and over 280,000 tonnes in 2020; a growth rate of nearly 10% per year; prices of most rare earths increased over 1000% during past year (ranges from 200% to 3000% per element) 6

7 1. Small deposits, subtle geologic halo features, limited geophysical response, limited geochemical clues 2. Geologic rock types and features: Carbonatites (carbonate rich intrusive rocks) host light rare earth element (REE) deposits (largest and highest grade deposits, 3 10% REO) Alkaline igneous rocks host heavy REE deposits (unproven, 0.5 2%) Lateritic clays host heavy REE deposits (production in China) Hydrothermal alteration fenitization common (Na Fe metasomatism) Mineralization a large variety of rare earth minerals, many as carbonates, minor to abundant iron sulfide minerals, Th bearing minerals Sometimes modified by weathering and oxidation 3. Geophysical features: Radiometric anomalies due to consistent thorium occurences with REEs Electrical methods CSAMT, magnetic low anomalies mm 3.46% REO, extensive soil and colluvial cover, radiometric (Th) anomaly, CSAMT for structures, limited geochemical clues 2. History rare earths found by USGS in1949as a result of uranium exploration; drilled in 1970 s first by Duval and Molycorp; Hecla Mining in 1980 s; most work done by Rare Element since Carbonatite dike system at least 1500 feet long, hosts light rare earthelement (REE) deposit with some HREE; may be 5000 feet in length Hydrothermal alteration fenitization common Mineralization predominantly rare earth strontium carbonate (ancylite) at depth with abundant (10 15%) pyrite minerals Weathering andoxidationplayedmajor role inremoving waste mineralsandand converting REE to bastnasite group minerals 4. Geophysical features Radiometric anomalies due to minor thorium occurring with REEs; electrical methods CSAMT, magnetic lows 5. Geochemical features surface anomalies of Sr, Ba, and other elements, halo of gold deposits 7

8 Extensive soil cover challenging exploration High-grade REE found through detailed step-off drilling Carbon Diatreme Whitetail Ridge Diatreme All alkaline igneous rocks REE dike trend Bull Hill Diatreme 8

9 Bear Lodge Geology Central Area 9

10 1. Tonnage and grade 2. Distribution of most valuable rare earths 3. Metallurgy good recovery & concentrate grade, low acid consumption in digestion process; Infrastructure Rare-Earth Element Wt-% Oxide Distribution % Relative Value Lanthanum 29.3% 20.4% Cerium 45.9% 15.5% Neodymium 14.4% 25.4% Praseodymium 4.4% 7.7% Samarium 2.4% 1.1% Europium 0.6% 17.5% Gadolinium 1.2% 0.8% Terbium 0.2% 5.6% Dysprosium 0.5% 5.3% Yttrium 0.9% 0.6% Total 99.8% 99.9% 1. Research should focus on improving exploration models, genetic models, and tools for understanding geology, geochemistry, and geophysics (electrical, magnetic, etc.). 2.. Continuous enhancement of technologies is occurring including better drilling methods, miniaturization of analytical equipment, computer assisted modeling, and more is needed. 3. No new breakthrough technologies are evident in recent years, probably due to erratic exploration funding and fewer major companies investing in exploration research. 4. More effort is needed to adapt technologies developed in other industries to mineral exploration (past examples include GPS, GIS, X ray fluorescence, remote sensing) 5. Improvement and greater efficiency in mining methods and in metallurgical processing of ores can make economic deposits out of mineral occurrences 10

Mineral Resources Supply & Information with a Focus on Rare Earth Elements

Mineral Resources Supply & Information with a Focus on Rare Earth Elements Larry Meinert Mineral Resources Program, USGS September 12-13th, 13th, 2012, US-EU Workshop on: "Informed policy-making through