Introduction to mineral exploration - Charles J Moon

This was one of the first books about mineral exploration that I had read. Its content is slightly dated, but because the mineral exploration industry moves in decades, the content is still extremely relevant. It has a decent degree of technical sophistication for a beginner to get into and best serves as a starting point for more advanced topics. I mainly read chapters about the economics of mineral deposits, reconnaissance, geochemical, and geophysical exploration. The book contains a few case studies that are interesting, but I overlooked them. I have revisited some of the case studies at later dates, but I would approach this book with the intention of a broad overview and finding a book for each chapter to further expand and deepen your knowledge.

Spatial data models

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There are two main ways of representing spatial data:

• Raster
• Vector

Vector is based on Euclidean geometry, where a map is composed down into x, y, z coordinates.

Raster is where a map is composed down into blocks - think Minecraft.

Some more complex models can be established where the details of the map are mapped with polygons.

As things become more complex, you need to have some way of establishing the relationship of the polygons in a model. This is known as topology.map.**

This can be used to make triangular irregular networks and digital terrain models.

Storage methods

In a very basic way, data can be stored in CSV files in Excel. Data points are known as tuples in this form.

However, relational databases are a far superior way to store data in exploration.

There are ways to convert flat files to relational databases, called normalization.

Relational databases break the data down into smaller tables with some relations to another table.

Relational databases were/are very good for 2D models of exploration data.

However, 3D models were (at the time of writing) very complex to create.

Object oriented databases were used instead.

Using databases as a store of truth is very important for statistics and legal reasons.

Each company will usually have its own data collection procedure.

There are then usually some internal tools to make sure that the data fits within some range that the geologist is aware of (all holes are between 0-100, etc.).

Documentation is often very important as it provides information about who collected the data, where it was collected, and anything noteworthy.

Paper can, however, remain the most common long-term source of data recording, which is then translated into digital format.

Data capture

Around the turn of the century, most of the data was being recorded on paper.

Nowadays, most modern companies are going to be taking their data digitally.

However, older records that may provide useful information may still need to be digitized.

Spatial data was once being copied over by tracing with a pencil. Then, some software started to improve the process. (Not sure what it's like now.)

Attribute data had either been typed out or, if clean and clear enough, could have been scanned.

Data sources

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• Digital topographical data:
  • ESRI 2004
  • GLOBE 2004
  • LANDSAT

Most of the geospatial data was charged for physically or was free over the internet. I imagine that is still the same.

Data integration and Geographical info systems

GIS systems have and still continue to be general-purpose and produced by some companies with large market shares.

ARCView and ARCGIS were dominant players.

At the time of writing, there were some trade-offs between the more powerful mass-produced GIS systems and the more specialized systems for mining. It's possible that this has remained the same.

It would be important to find out what companies are using for this.

3D data and 2D differences were still stark in 2005.

Arrangement of data using layers

In the past, different 2D layers were stacked up on top of each other to get a more complete picture.

This was usually done in the past with actual paper.

Later, older maps were compared with satellite data.

Exploration economics

1. Mineral exploration

   1. Study phase (1-2 years $250k)
   2. reconnaissance phase(2 years $500k - 1.5M
   3. Target testing (2-3 years $2.5M - 50M)
   4. pre-feasibility (2-3 years $2.5M - 50M)
   5. feasibility (2-3 years $2.5M - 50M)

   Further information on costs of mineral exploration - Tilton et Al (1988) & Crowson (2003)

2. Feasibility

3. Mine development

4. Mining

5. Mineral processing

6. Smelting

7. Refining

8. Marketing

9. Closure

Exploration locations - considering factors - for normal mines

• Electric power
• water supply
• roads
• railways
• houses
• schools
• hospitals

Sustainable development

• Political and local environmental concerns are just as big a factor as economic considerations in the mining industry.
• The Mining Minerals and Sustainable Development (MMSD) project addressed issues of sustainable development in the mining industry.
• Overcoming political and environmental hurdles can take several years even after a mineral deposit has been deemed profitable.
• In the 1960s, Ireland implemented positive tax laws for mining.
• Junior mining companies use "farming out" to give bigger companies access to their finds.
• Major mining companies often sell finds that they consider too small to operate on.
• The general success rate of exploration is around 0.1%, with the best success rate at 1%.
• Data on exploration success is rare and scattered.
• Gold and nickel are considered profitable, but base metals have generally only been a source of break-even profitability in the past.
• The location and conditions of an exploration site have a significant effect on the viability of a deposit. If the location is very remote or lacks infrastructure, the deposit must be of high grade and large in order to be economically viable.

Exploration planning

Exploration planning:

• Market planning: figuring out if there is a market to sell the minerals you are planning to mine.
• Metal pricing: determining where you think the price of metal is going to be during the lifetime of the mine. (Will there be a demand for a certain mineral? Will this make a new venture more profitable than another?)

Basis for a successful exploration team

1. A high-quality team of geologists, with plenty of in-house training.
2. A supportive environment that fosters innovation.
3. A "can-do" attitude among the workers.
4. A sound basis of operations (guidelines).

For a small team, 7-10 geologists have traditionally been the best number.

Exploration groups have traditionally been split into location or deposit type groups.

Exploration can account for 1 to 20% of the annual corporate cash flow.

Exploration efforts are more difficult to come by for smaller companies as bigger companies have the option of selling shares in their company.

Companies often lease vehicles and tools for exploration efforts. However they are often only given certain budgets to work with.

• The cost of mine closure and reclamation of the site is now a cause for a decrease in overall profits, and this affects the exploration process.
• There is now a concept of environmentally friendly deposits.
• The Kennecott mine in Alaska was a good example of an environmentally friendly mine. It had a very small ore vein, but it was very high in percentage of copper. So, the economic advantages of it are becoming more attractive as the environmental effects of big mining operations are being factored into the cost of mine exploration.
• Analytical equipment is being miniaturized, which is making it much easier to test the minerals and obtain the necessary data for exploration.

Topics of possible innovation

• More robust thermodynamic and kinetic geochemical data
• New ore-deposit models, particularly for deposits with less environmental impact when mined
• Better geohydrological models
• Geological maps of more mineralized areas
• Databases for mineralized areas using geochemical/geophysical methods
• Hand-held and down-hole analytical instruments
• Cross-borehole characterization
• Better understanding of element mobility in soils
• Drones for airborne geophysics
• Low-cost, shallow seismic methods
• Better interpretation of hyperspectral data
• Application of existing petroleum and geothermal drilling technologies to the minerals sector
• Novel drilling techniques (e.g., improvements in slimhole drilling and in-situ measurements)

Drilling

Drilling techniques

• When an anomaly seems to have been found, then you can invest in a drilling investigation.
• There are two types of drilling: diamond drilling and reverse circulation drilling. RC drilling can create chip samples, while diamond drilling allows you to get one long sample of the rock.
• Diamond drilling is the most accurate.
• Interval core from diamond drilling can be assayed and then you can create a boundary of cut-off grade. For example, you only have an area that has 0.5% copper, and you exclude an area that does not have that.

"No significant changes in mineral drilling technology or techniques have been made for more than three decades" (NRC, 1994b)

"The need for miniaturization of existing drilling equipment is growing not only in the mineral industry but also for NASA to investigate drilling on Mars."

• drilling is the most expensive process in the whole mining lifecycle. Hundreds of holes may have to be drilled in order to understand the boundaries of an orebody
• Ways to reduce the cost of drilling
  • increasing drill rate
  • decreasing the amount of holes needed
  • reducing the energy requirements for drilling
• Novel drilling technologies could all contribute to the reduction of drilling these include
  • down hole drilling( a jack hammer turns the rock to dust and the dust is blown out)
• Down hole drilling, is a method for oil exploration. They use a gamma ray process to look at the radioactivity of the rocks that they are drilling.

"The development of down-hole analytical devices, such as spectrometers, would make it possible to conduct in-situ, real-time analyses of trace elements in the rock mass that could dramatically shorten the time required to determine if a drill hole had 'hit' or not."

The conclusion is that drilling technologies remain an area with significant challenges, indicating that there is room for improvement and innovation in this field.

Geophysical methods of exploration

• Magnetism - used to find the amount of magnetite/pyrrhotite in a sample, useful for Volcanogenic massive sulfide ore deposits (VMS) and Kimberlites (minerals containing diamonds) VMS is a primary source of copper, zinc, lead, and sulfur
• Electromagnetic - used for sulphide minerals like copper and nickel
• Induced polarization - charges the sample with electrical charge to see how it responds, used for things like copper, precious metals, and VMS
• Radioactivity - used for samples that emit subatomic radiation, such as uranium, iron oxide copper gold (IOCG)
• Conductivity - used to determine the extent to which current passes through a material
• Density
• Geophysical methods are useful when there is a great amount of overburden (rock above a deposit) that makes other methods impossible. Geophysical methods can detect anomalies up to 500m away.
• Methods such as laser and X-ray fluorescence are used to determine the concentrations of different materials.
• Differential leaching techniques compare the solubility of certain minerals in a solution to see how much they will fall to the bottom of a liquid.
• Gravity measurements are also a non-invasive method of finding anomalies
• Magnetic surveys are traditionally done by aircraft (helicopters) that fly at a fixed distance from the ground, known as a magnetic survey system.
• Near-surface seismic surveys look at differences in seismic activity to suggest where there may be an anomaly. These can be very expensive, especially due to data collection and processing. However, this may have changed now.
• Landsat thematic mapper looks at visible, infrared, and ultraviolet light to provide imaging of the Earth's surface.
• Several different types of satellites look at topographic details of the Earth, providing imaging for exploration efforts. This was first military data but is now in the public domain.
• The airborne visible/infrared imaging spectrometer (AVRIS) has allowed for mine exploration and closure.
• Multispectral analysis is used to map areas of the globe to give insights into what is below the surface.
• Can the same techniques used for imaging of galaxies be applied to the Earth for mineral exploration, combining many small, close satellites to make a greater image?
• Hyperspectral data is often expensive.
• Tomographic methods are like an MRI, beaming the area with electromagnetic waves and seeing the differences in composition on a screen.

Geochemical methods of exploration

Geochemical analysis

• The data for geochemical and geophysical is obtained from soil, rock, water, vegetation, and vapor.
• Trace elements may indicate the possibility of deposits and ore veins.
• Concerns in the exploration process include:
  • Groundwater and surface water quality
  • Trace elements in existing soils
  • Trace elements in ores, particularly elements of concern such as mercury and arsenic
  • The presence of asbestiform minerals associated with industrial-minerals operations
  • The potential for acid-rock drainage (amounts of sulfide minerals and buffering minerals, climate, and hydrology)
  • Location of aquifers in relation to ore bodies
  • Existence and location of sensitive biological communities
  • Climatological impacts on mining operations, including precipitation and prevailing winds
  • Socioeconomic and cultural issues
• Third-party labs usually do the testing of the sediments found.
• Labs perform something called assaying.
• Rocks are dried, milled, and crushed to create a fine material that can be analyzed.
• This can give you the chemical concentration of the rocks.
• An example of assaying is to dissolve the sediment in an acid. Then an inductively coupled plasma (ICP) device will conduct mass spectrometry on the sediment. This will ascertain the type of materials that the sediment contains. ICP can detect up to 40 different elements.

Rock sampling

When geologists collect rock samples, they can obtain three different types:

• Grab samples, which involve randomly selecting samples or taking samples that appear to be most common. This method may not provide representative data, but it can indicate where to go next in the exploration process.
• Chip samples, which involve taking chips of rock along the length of exposed rock and combining them into one sample the size of a regular rock. This method provides grade and width information, which refer to the quality and thickness of the mineral deposit, respectively.
• Channel samples, which involve digging a channel into the rock and collecting multiple samples to compose a rock sample. This method is usually the most accurate form of analysis.

Geological methods of exploration

• Geologists will create high-quality maps of an area over time by examining rocks in the area.
• A topographical map is made first, then an area is surveyed and a geological map is constructed of the area.
• The rocks must be surveyed, usually by a process involving stripping and trenching the top surface of the area being surveyed.
• Stripping involves removing topsoil and dirt, while trenching usually involves blasting the area to expose a vertical area to sample.
• Besides proprietary data held by companies, there doesn't seem to be any way for geologists to obtain large stores of data to study how rock formations form. The idea here is that if geologists could access large amounts of data across large areas, they could better understand how certain minerals get to the surface of some areas and then better predict where to look for future exploration efforts.
• Understanding how fluids move around the earth is important in understanding how minerals are deposited. This is an important factor in the exploration of minerals.
• Cox and Singer's 1992 paper is about models for ore deposits. This is beneficial because having the right amount of data reduces the environmental impact of mining in the wrong areas.
• Much of the data in certain areas is in physical format, and the cost to digitize it is very expensive. Large companies have these databases, but they are generally not available to research institutes.