16 Energy and Mineral Resources

Learning Objectives

By the end of this chapter, students should be able to:

  • Describe how a  resource is different from a  resource.
  • Compare the pros and cons of extracting and using and conventional and unconventional sources.
  • Describe how   are formed and extracted.
  • Understand how society uses   resources.
A brown smooth rock that has chips flaked off of it on one side, sharpening it.
Figure 16.1: A Mode 1 Oldowan tool used for chopping.

This text has previously discussed geology’s pioneers, such as scientists James Hutton and Charles Lyell, but the first real “geologists” were the hominids who picked up stones and began the stone age. Maybe stones were first used as curiosity pieces, maybe as weapons, but ultimately, they were used as tools. This was the Paleolithic , the beginning of geologic study, and it dates back 2.6 million years to east Africa.

In modern times, geologic knowledge is important for locating economically valuable materials for society’s use. In fact, all things we use come from only three sources: they are farmed, hunted or fished, or . At the turn of the twentieth century, speculation was rampant that food supplies would not keep pace with world demand, suggesting the need to develop artificial fertilizers. Sources of fertilizer ingredients are: nitrogen is processed from the , using the Haber process for the manufacture of ammonia from atmospheric nitrogen and hydrogen; potassium comes from the , such as lakes or ocean evaporation; and phosphorus is from the , such as minerals like apatite from phosphorite rock, which is found in Florida, North Carolina, Idaho, Utah, and around the world. Thus, without and processing of natural materials, modern civilization would not exist. Indeed, geologists are essential in this process.

16.1 Mining

A world map showing the locations of certain ores in the world. A specific focus has been put on metals and construction materials. The various resources are unevenly distributed across the globe.
Figure 16.2: Map of world mining areas.

is defined as extracting valuable materials from the Earth for society’s use. Usually, these include solid materials such as gold, iron, , diamond, sand, and gravel, but materials can also include fluid resources such as and . Modern has a long relationship with modern society. The oldest dates back 40,000 years to the Lion Cavern in Swaziland where there is evidence of concentrated digging into the Earth for hematite, an important iron used as red dye. Resources extracted by are generally considered to be .

16.1.1 Renewable versus Nonrenewable Resources

Resources generally come in two major categories:  and . resources can be reused over and over or their availability replicated over a short human life span; resources cannot.

Aerial view of a large dam. The water level is much higher behind the dam than in front of it, and a road bridge runs across the canyon in front of the dam.
Figure 16.3: Hoover Dam provides hydroelectric energy and stores water for southern Nevada.

 resources are materials present in our environment that can be exploited and replenished. Some common energy sources are linked with green energy sources because they are associated with relatively small or easily remediated environmental impact. For example, solar energy comes from within the Sun, which radiates electromagnetic energy. This energy reaches the Earth constantly and consistently and should continue to do so for about five billion more years. Wind energy, also related to solar energy, is maybe the oldest energy and is used to sail ships and power windmills. Both solar and wind-generated energy are variable on Earth’s surface. These limitations are because we can use energy storing devices, such as batteries or electricity exchanges between producing sites. The Earth’s heat, known as geothermal energy, can be viable anywhere that geologists drill deeply enough. In practice, geothermal energy is more useful where heat flow is great, such as zones or regions with a thinner . Hydroelectric dams provide energy by allowing water to fall through the dam under gravity, which activates turbines that produce the energy. Ocean tides are also a reliable energy source. All of these resources provide energy that powers society. Other resources are plant and animal matter, which are used for food, clothing, and other necessities, but are being researched as possible energy sources.

Clear, glassy diamond with an octahedral shape embedded in a black chunk of rock.
Figure 16.4: Natural, octahedral shape of diamond.

 resources cannot be replenished at a sustainable rate. They are finite within human time frames. Many resources come from planetary, , or long-term biologic processes and include materials such as gold, lead, copper, diamonds, , sand, , , and . Most resources include specific concentrated listed on the periodic table; some are compounds of those . For example, if society needs iron (Fe) sources, then an exploration geologist will search for iron-rich deposits that can be economically extracted. resources may be abandoned when other materials become cheaper or serve a better purpose. For example, is abundantly available in England and other nations, but because and are available at a lower cost and lower environmental impact, use has decreased. Economic competition among resources is shifting use away from in many developed countries.

16.1.2 Ore

Zoomed-in photo of a slice of rock, showing red and brown layers with glittering dots throughout; a scale bar at the lower left says 5.0 mm.
Figure 16.5: Banded-iron formations are an important ore of iron (Fe).

Earth’s materials include the periodic table . However, it is rare that these are concentrated to the point where it is profitable to extract and process the material into usable products. Any place where a valuable material is concentrated is a geologic and geochemical . A body of material from which one or more valuable substances can be mined at a profit, is called an  deposit. Typically, the term  is used for only metal-bearing , but it can be applied to valuable  resource concentrations such as , building stones, and other nonmetal deposits, even . If a metal-bearing resource is not profitable to , it is referred to as a deposit. The term is more common than the term  for non-metal-bearing materials.

Diagram shows the small box of "reserves" within a larger box of "resources". There is also an "inferred resources" box that is slightly larger than "proven reserves" box and an "undiscovered resources" box slightly larger than the resources box.
Figure 16.6: Diagram illustrating the relative abundance of proven reserves, inferred reserves, resources, and undiscovered resources.

It is implicit that the technology to is available, economic conditions are suitable, and political, social and environmental considerations are satisfied in order to classify a deposit as . Depending on the substance, it can be concentrated in a narrow vein or distributed over a large area as a low-concentration . Some materials are directly from bodies of water (e.g. sylvite for potassium; water through desalination) and the (e.g. nitrogen for fertilizers). These differences lead to various methods of , and differences in terminology depending on the certainty. mineral resource is used for an indication of that is potentially extractable, and the term   reserve is used for a well defined (proven), profitable amount of extractable .

Graphical representation of mineral resource classification with respect to economics and geologic certainty. Three rows are labeled economic, marginally economic, and sub-economic. Two columns are labeled identified resources and undiscovered resources. The identified resources column is split into demonstrated and inferred columns, and the demonstrated column is further divided into measured and indicated columns. At the intersection of the demonstrated column and economic row, the box is labeled reserves; at the intersection of the demonstrated column and marginally economic row, the box is labeled marginal reserves; at the intersection of the demonstrated column and sub-economic row, the box is labeled demonstrated subeconomic resources. At the intersection of the inferred column and economic row, the box is labeled inferred reserves; at the intersection of the inferred column and marginally economic row, the box is labeled inferred marginal reserves; at the intersection of the inferred column and sub-economic row, the box is labeled inferred subeconomic resources. The boxes are blank under the column labeled undiscovered resources.
Figure 16.7: McKelvey diagram showing different definitions for different degrees of concentration and understanding of mineral deposits.

16.1.3 Mining Techniques

The style is determined by technology, social license, and economics. It is in the best interest of the company extracting the resources to do so in a cost-effective way. Fluid resources, such as  and gas, are extracted by drilling wells and pumping. Over the years, drilling has evolved into a complex discipline in which directional drilling can produce multiple bifurcations and curves originating from a single drill collar at the surface. Using geophysical tools like  imaging, geologists can pinpoint resources and extract efficiently.

Solid resources are extracted by two principal methods of which there are many variants.  is used to remove material from the outermost part of the Earth.  is used to target shallow, broadly disseminated resources.

Immense terraced dirt-lined open pit with snow-covered mountains visible around the back of the mine.
Figure 16.8: Bingham Canyon Mine, Utah. This open pit mine is the largest man-made removal of rock in the world.

requires careful study of the body through surface mapping and drilling exploratory cores. The pit is progressively deepened through additional cuts to extract the . Typically, the pit’s walls are as steep as can be safely managed. Once the pit is deepened, widening the top is very expensive. A steep wall is thus an engineering balance between efficient and profitable (from the company’s point of view) and ( from a safety p0int of view) so that there is less waste to remove. The waste is called non-valuable rock or overburden and moving it is costly. Occasionally, do occur, such as the very large in the Kennecott Bingham Canyon , Utah, in 2013. These events are costly and dangerous. The job of engineering geologists is to carefully monitor the mine; when company management heeds their warnings, there is ample time and action to avoid or prepare for any slide.

A large yellow machine is removing black coal from a terraced slope.
Figure 16.9: A surface coal mine in Wyoming.

 and  are  techniques that are used to resources that cover large areas, especially layered resources, such as . In this method, an entire mountaintop or rock layer is removed to access the  below. ’s environmental impacts are usually much greater due to the large surface footprint that’s disturbed.

A photo in an underground mine with horizontal layering visible in the mine walls; there is also a large yellow truck with a bucket attached to its front containing brown rocky material.
Figure 16.10: Underground mining in Estonia of oil shale.

is a method often used to higher-, more localized, or very concentrated resources. For one example, geologists some underground by introducing chemical agents, which the target . Then, they bring the to the surface where extracts the material. But more often, a shaft tunnel or a large network of these shafts and tunnels is dug to access the material. The decision to underground or from Earth’s surface is dictated by the deposit’s concentration, depth, geometry, land-use policies, economics, surrounding rock strength, and physical access to the . For example, to use techniques for deeper deposits might require removing too much material, or the necessary method may be too dangerous or impractical, or removing the entire overburden may be too expensive, or the footprint would be too large. These factors may prevent geologists from materials and cause a project to be underground. The method and its feasibility depends on the commodity’s price and the cost of the technology needed to remove it and deliver it to market. Thus, and the towns that support them come and go as the commodity price varies. And, conversely, technological advances and market demands may reopen and revive ghost towns.

16.1.4 Concentrating and Refining

A man is operating a large machine that looks like a blast furnace.
Figure 16.11: A phosphate smelting operation in Alabama, 1942.

All   occur mixed with less desirable components called . The process of physically separating   from ore bearing  is called . Separating a desired  from a host  by chemical means, including heating, is called . Finally, taking a metal such as copper and removing other trace metals such as gold or silver is done through the process. Typically, is done one of three ways: 1. Materials can either be mechanically separated and processed based on the  ’s unique physical properties, such as recovering  gold based on its high density. 2. Materials can be heated to chemically separate desired components, such as  crude  into . 3. Materials can be smelted, in which controlled chemical reactions unbind metals from the  they are contained in, such as when copper is taken out of chalcopyrite (CuFeS2). , , , and processes require enormous energy. Continual advances in metallurgy- and mining-practice strive to develop ever more energy efficient and environmentally benign processes and practices.

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16.2 Fossil Fuels

A power plant with steam coming out, surrounded by rocky hills on either side.
Figure 16.12: Coal power plant in Helper, Utah.

are extractable sources of stored energy that were created by ancient ecosystems. The that typically fall under this category are , , , and . These resources were originally formed via photosynthesis by living organisms such as plants, phytoplankton, algae, and cyanobacteria. This energy is actually solar energy, since the sun’s ancient energy was converted by ancient organisms into tissues that preserved the chemical energy within the . Of course, as the energy is used, just like photosynthetic respiration that occurs today, carbon enters the as CO2, causing consequences (see chapter 15). Today humanity uses  for most of the world’s energy.

Colorful coral reef underwater in light blue, shallow water.
Figure 16.13: Modern coral reefs and other highly-productive shallow marine environments are thought to be the sources of most petroleum resources.

Converting solar energy by living organisms into hydrocarbon is a complex process. As organisms die, they decompose slowly, usually due to being buried rapidly, and the chemical energy stored within the organisms’ tissues is buried within surrounding geologic materials. All contain carbon that was produced in an ancient environment. In environments rich with organic matter such as swamps, coral , and planktonic blooms, there is a higher potential for to accumulate. Indeed, there is some evidence that over geologic time, organic hydrocarbon material was highly produced globally. Lack of oxygen and moderate temperatures in the environment seem to help preserve these organic substances. Also, the heat and pressure applied to organic material after it is buried contribute to transforming it into higher quality materials, such as brown to anthracite and to gas. Heat and pressure can also cause mobile materials to migrate to conditions suitable for extraction.

16.2.1 Oil and Gas

World map showing oil reserves by nation in various shades of blue: darker blue nations richest in oil include Canada, Venezuela, and Saudi Arabia. Oil reserves vary geographically.
Figure 16.14: World oil reserves in 2013. Scale in billions of barrels.

Petroleum is principally derived from organic-rich shallow  sedimentary deposits where the remains of micro-organisms like plankton accumulated in fine grained . ’s liquid component is called , and its gas component is called , which is mostly made up of methane (CH4). As rocks such as , , or lithify, increasing pressure and cause the and gas to be squeezed out and migrate from the to a different rock unit higher in the rock column. Similar to the discussion of good in chapter 11, if that rock is a , , or other porous and permeable rock, and involved in a suitable or structural trapping process, then that rock can act as an  and gas .

Block diagram showing upward-arching layers with petroleum pooling toward the top of the fold beneath the surface; natural gas forms above the petroleum; there is a well at the surface drilled down into the oil deposit.
Figure 16.15: Examples of different forms of hydrocarbon traps: in the core region of anticlines.

is a combination of a subsurface geologic structure, a porous and permeable rock, and an impervious layer that helps block and gas from moving further, which concentrates it for humans to extract later. A develops due to many different geologic situations. Examples include an or domal structure, an impermeable salt , or a bounded block, which is porous rock next to nonporous rock. The different have one thing in common: they pool fluid into a configuration in which extracting it is more likely to be profitable. or gas in outside of a renders it less viable to extract.

Two cross sectional diagrams; the top diagram shows onlap with layers of sediments being deposited on top of each other, with each successive upper layer being deposited toward inland; there is an arrow pointing toward the right-hand side labeled transgression; the bottom diagram shows offlap with layers of sediments being deposited on top of each other, with each successive upper layer being deposited toward the ocean; there is an arrow pointing toward the left-hand side labeled regression.
Figure 16.16: The rising sea levels of transgressions create onlapping sediments, regressions create offlapping.

is a branch of geology that studies sedimentary both horizontally and vertically and is devoted to understanding how sea level changes create organic-rich shallow muds, , and sands in areas that are close to each other. For example, environments may have beaches, , , and deposits, all next to each other. Beach sand, lagoonal and muds, and coral reef layers accumulate into that include —good rocks— next to , next to , both of which are potential . As sea level either rises or falls, the shoreline’s location changes, and the sand, mud, and reef locations shift with it (see the figure). This places oil and gas producing rocks, such as mudstones and limestones next to oil and gas reservoirs, such as sandstones and some limestones. Understanding how the lithology and the facies/stratigraphic relationships interplay is very important in finding new petroleum resources. Using sequence stratigraphy as a model allows geologists to predict favorable locations of the source rock and .

16.2.2 Tar Sands

Blocky chunk of sandstone that is black in color due to being filled with tar.
Figure 16.17: Tar sandstone from the Miocene Monterey Formation of California.

Conventional  and gas, which is pumped from a , is not the only way to obtain hydrocarbons. There are a few fuel sources known as unconventional  sources. However, they are becoming more important as conventional sources become scarce. Tar sands, or , are that contain products that are highly , like tar, and thus cannot be drilled and pumped out of the ground readily like conventional . This unconventional is bitumen, which can be pumped as a fluid only at very low recovery rates and only when heated or mixed with solvents. So, using steam and solvent injections or directly tar sands to process later are ways to extract the tar from the sands. Alberta, Canada is known to have the largest reserves in the world. Note: as with , an energy resource becomes uneconomic if the total extraction and processing costs exceed the extracted material’s sales revenue. Environmental costs may also contribute to a resource becoming uneconomic.

16.2.3 Oil Shale

Graph of global production of oil shale: the horizontal axis is labeled Year and goes from 1880 to 2010; the vertical axis is labeled Mined shale, million tonnes and goes from 0 to 50. Eight countries' oil production is graphed and stacked to show world production: Estonia, Russia, Brazil, China, Scotland, Germany, Sweden, and United States. Total oil production remains low until around the year 1940, when it increases and peaks at 46 million tonnes around the year 1980; past 1980, the production decreases to 15 million tonnes around the year 2000. From 2000 to 2010, production increases again.
Figure 16.18: Global production of oil shale, 1880-2010.

, or , is a fine-grained  that has significant  or  quantities locked tightly in the  has high  but very low and is a common . To extract the  directly from the , the material has to be  and heated, which, like with tar sands, is expensive and typically has a negative environmental impact.

16.2.4 Fracking

Block diagram showing fracking: a vertical well is drilled through numerous sedimentary layers until it reaches a layer labeled Gas-bearing Formation. Then, the well turns horizontal where it extends throughout the gas-bearing formation. Fracking fluid is pumped from the surface into the well and cracks are formed along the horizontal portion of the well, labeled hydraulic fractures; methane flows from the cracks into the horizontal well segment and flows toward the surface. A preexisting fault is seen to the right of the end of the horizontal well, and an earthquake is shown labeled Induced seismicity.
Figure 16.19: Schematic diagram of fracking.

Another process used to extract the  and gas from  and other unconventional tight resources is called , better known as . In this method, high-pressure water, sand grains, and added chemicals are injected and pumped underground. Under high pressure, this creates and holds open  in the rocks, which help release the hard-to-access mostly  fluids. is more useful in tighter sediments, especially shale, which has a high porosity to store the hydrocarbons but low to allow transmission of the hydrocarbons. Fracking has become controversial because its methods contaminate  and induce activity. This has created much controversy between public concerns, political concerns, and energy value.

16.2.5 Coal

Chart showing the coal rankings: the vertical axis is labeled percentage of fixed carbon and goes from 40 to 100; the horizontal axis is labeled gross calorific value (BTU/LB) and goes from 16,000 on the left to 5,000 on the right. Lignite is colored yellow and fills the chart from 40 to 60 percent carbon and 8,3000 to 5,000 calorific value; subbituminous is colored green and fills the chart from 40 to 60 percent carbon and around 12,000 to 8,3000 calorific value; high-volatile bituminous is colored lavender and fills the chart from 40 to 69 percent carbon and 16,000 to around 12,000 calorific value; medium-volatile bituminous is also colored lavender and fills the chart from 69 to 78 percent carbon and 16,000 to around 13,500 calorific value; low-volatile bituminous is colored red and fills the chart from 78 to 86 percent carbon and 16,000 to around 14,000 calorific value; semi-anthracite is colored orange and fills the chart from 86 to 92 percent carbon and 16,000 to around 13,500 calorific value; anthracite is also colored orange and fills the chart from 92 to 98 percent carbon and around 15,800 to around 12,500 calorific value; and meta-anthracite is also colored orange and fills the chart from 98 to 100 percent carbon and around 12,500 to around 12,000 calorific value.
Figure 16.20: USGS diagram of different coal rankings.

 comes from fossilized swamps, though some older  deposits that predate  plants are presumed to come from algal buildups. is chiefly carbon, hydrogen, nitrogen, sulfur, and oxygen, with minor amounts of other . As plant material is incorporated into , heat and pressure cause several changes that concentrate the fixed carbon, which is the ’s combustible portion. So, the more heat and pressure that  undergoes, the greater is its carbon concentration and fuel value and the more desirable is the .

This is the general sequence of a swamp progressing through the various stages of and becoming more concentrated in carbon: Swamp => Peat => Lignite => Sub-bituminous => Bituminous => Anthracite => Graphite. As swamp materials collect on the swamp floor and are buried under accumulating materials, they first turn to peat.

A hand holding an elongated chunk of dull black peat, with a dirt-like texture and visible plant bits grown into it.
Figure 16.21: Peat (also known as turf) consists of partially decayed organic matter. The Irish have long mined peat to be burned as fuel though this practice is now discouraged for environmental reasons.

Peat itself is an economic fuel in some locations like the British Isles and Scandinavia. As occurs, peat turns to lignite. With increasing heat and pressure, lignite turns to sub-bituminous , bituminous , and then, in a process like , anthracite. Anthracite is the highest and most desirable since it provides the highest energy output. With even more heat and pressure driving out all the and leaving pure carbon, anthracite can become graphite.

Chunk of black, very shiny rock.
Figure 16.22: Anthracite coal, the highest grade of coal.

Humans have used for at least 6,000 years, mainly as a fuel source. resources in Wales are often cited as a primary reason for Britain’s rise, and later, for the United States’ rise during the Industrial Revolution. According to the US Energy Information Administration, US production has decreased due to competing energy sources’ cheaper prices and due to society recognizing its negative environmental impacts, including increased very fine-grained particulate matter as an air pollutant, greenhouse gases, acid rain, and heavy metal pollution. Seen from this perspective, the industry as a source of energy is unlikely to revive.

As the world transitions away from including , and manufacturing seeks strong, flexible, and lighter materials than steel including carbon fiber for many applications, current research is exploring as a source of this carbon.

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16.3 Mineral Resources

Chunk of glassy white mineral with thin gold veins running through the sample.
Figure 16.23: Gold-bearing quartz vein from California.

 resources, while principally , are generally placed in two main categories: , which contain metals, and , which contain other useful materials. Most  has been traditionally focused on extracting  . Human society has advanced significantly because we’ve developed the knowledge and technologies to yield metal from the Earth. This knowledge has allowed humans to build the machines, buildings, and monetary systems that dominate our world today. Locating and recovering these metals has been a key facet of geologic study since its inception. Every  across the periodic table has specific applications in human civilization.    is the source of many of these .

16.3.1 Types of Metallic Mineral Deposits

The various ways in which  and their associated  concentrate to form  deposits are too complex and numerous to fully review in this text. However, entire careers are built around them. In the following section, we describe some of the more common deposit types along with their associated elemental concentrations and world class occurrences.

Magmatic Processes

Vertical outcrop of alternating tan and black horizontal layers.
Figure 16.24: Layered intrusion of dark chromium-bearing minerals, Bushveld Complex, South Africa.

When a magmatic body crystallizes and differentiates (see chapter 4), it can cause certain and to concentrate. Layered intrusions, typically to , can host deposits that contain copper, nickel, platinum, palladium, rhodium, and chromium. The Stillwater Complex in Montana is an example of economic quantities of layered intrusion. Associated deposit types can contain chromium or titanium-vanadium. The largest magmatic deposits in the world are the chromite deposits in the Bushveld Igneous Complex in South Africa. These rocks have an areal extent larger than the state of Utah. The chromite occurs in layers, which resemble sedimentary layers, except these layers occur within a crystallizing .

Closeup view of rock with elongated glassy green crystals intergrown with light purple glassy grains.
Figure 16.25: This pegmatite contains lithium-rich green elbaite (a tourmaline) and purple lepidolite (a mica).

Water and other that are not incorporated into crystals when a crystallizes can become concentrated around the crystallizing ’s margins. Ions in these hot fluids are very mobile and can form exceptionally large crystals. Once crystallized, these large crystal masses are then called . They form from fluids that are expelled from the solidifying when nearly the entire body has crystallized. In addition to that are predominant in the main mass, such as , , and , bodies may also contain very large crystals of unusual that contain rare like beryllium, lithium, tantalum, niobium, and tin, as well as like gold. Such are of these metals.

Cross section of a kimberlite pipe: at depth of 0 (the surface) is a bowl-shaped crater filled with washed-back ejecta; surrounding the crater is a raised deposit labeled tuff ring. Deeper into the ground is a thin pipe of orange material that contains smaller grains labeled xenoliths; a bracket labels this section diatreme from 0.5 to 1.5 km depth. at the deepest part of the pipe, a horizontal intrusion of magma labeled dike feeds the vertical pipe; a bracket labels this section root from 2.0 to 2.6 km depth.
Figure 16.26: Schematic diagram of a kimberlite pipe.

An unusual magmatic process is a  pipe, which is a that transports from within the to the surface. Diamonds, which are formed at great temperatures and pressures of depth, are transported by a pipe to locations where they can be . The process that created these rocks is no longer common on Earth. Most known deposits are from the .

Hydrothermal Processes

Cross section of a deep-sea vent; a bulbous pool of magma is beneath the vent, heating the crust and seawater entering through cracks on either side of the vent; the seawater entering from the sides becomes heated above the pool of magma and leaves the vent, releasing oxyanions, REE, and trace metals. There are complex chemical reactions occurring beneath and above the vent.
Figure 16.27: The complex chemistry around mid-ocean ridges.

Fluids rising from crystallizing magmatic bodies or that are heated by the  cause many geochemical reactions that form various  deposits. The most active  process today produces  (VMS) deposits, which form from chimney activity near all over the world. They commonly contain copper, zinc, lead, gold, and silver when found at the surface. Evidence from around 7000 BC in a known as the Chalcolithic shows copper was among the earliest metals smelted by humans as means of obtaining higher temperatures were developed. The largest of these VMS deposits occur in rocks. The Jerome deposit in central Arizona is a good example.

Another deposit type that draws on -heated water is a  deposit. This is not to be confused with the texture, although the name is derived from the that is nearly always present in the rocks associated with a deposit. Several types of deposits exist, such as copper, molybdenum, and tin. These deposits contain low- disseminated closely associated with and rocks that are present over a very large area. deposits are typically the largest on Earth. One of the largest, richest, and possibly best studied in the world is Utah’s Kennecott Bingham Canyon Mine. It’s an , which, for over 100 years, has produced several including copper, gold, molybdenum, and silver. Underground replacement deposits produce lead, zinc, gold, silver, and copper. In the ’s past, the open pit predominately produced copper and gold from chalcopyrite and bornite. Gold only occurs in minor quantities in the copper-bearing , but because the Kennecott Bingham Canyon Mine produces on such a large scale, it is one of the largest gold in the US. In the future, this may produce more copper and molybdenum (molybdenite) from deeper .

A large terraced open pit mine that contains both gray and red rocks; a haul truck is seen driving in the foreground.
Figure 16.28: The Morenci porphyry is oxidized toward its top (as seen as red rocks in the wall of the mine), creating supergene enrichment.

Most  copper deposits owe their high metal content, and hence, their economic value to  processes called which occurs when the deposit is uplifted, eroded, and exposed to . This process occurred millions of years after the initial intrusion and expulsion ends. When the deposit’s upper pyrite-rich portion is exposed to rain, the pyrite in the oxidizing zone creates an extremely acid condition that dissolves copper out of copper , such as chalcopyrite, and converts the chalcopyrite to iron , such as hematite or goethite. The copper are carried downward in water until they arrive at the  table and an environment where the primary copper  are converted into secondary higher-copper content . Chalcopyrite (35% Cu) is converted to bornite (63% Cu), and ultimately, chalcocite (80% Cu). Without this enriched zone, which is two to five times higher in copper content than the main deposit, most  copper deposits would not be economic to .

A closeup photo of a chunk of rock made up of glassy amber-colored grains, olive green glassy grains, and a light blue glassy grains.
Figure 16.29: Garnet-augite skarn from Italy.

If  or other calcareous sedimentary rocks are near the magmatic body, then another type of  deposit called a  deposit forms. These  rocks form as -derived, highly saline metalliferous fluids react with  rocks to create calcium-magnesium-  like , and garnet, as well as high- iron, copper, zinc , and gold. Intrusions that are genetically related to the intrusion that made the Kennecott Bingham Canyon deposit have also produced copper-gold skarns, which were  by the early European settlers in Utah. When iron and/or  deposits undergo , the  commonly increases, which makes separating the  from the desired  or   much easier.

Chunk of brick red rock with flecks of gold left behind in a void. A 5 cm scale bar spans the width of the rock sample.
Figure 16.30: In this rock, a pyrite cube has dissolved (as seen with the negative “corner” impression in the rock), leaving behind small specks of gold.

deposits consist of low concentrations of microscopic gold as and disseminated atoms in pyrite crystals. These are formed via low- reactions, generally in the realm of , that occur in certain rock types, namely muddy and limey . This alteration is generally far removed from a source, but can be found in rocks situated with a high . The Mercur deposit in Utah’s Oquirrh Mountains was this type’s earliest locally deposit. There, almost a million ounces of gold was recovered between 1890 and 1917. In the 1960s, a metallurgical process using cyanide was developed for these low- types. These deposits are also called  deposits because the disseminated deposit near Carlin, Nevada, is where the new technology was first applied and where the first definitive scientific studies were conducted. Gold was introduced into these deposits by fluids that reacted with silty calcareous rocks, removing , creating additional , and adding silica and gold-bearing pyrite in the space between grains. The Betze-Post mine and the Gold Quarry mine on the Carlin Trend are two of the largest disseminated gold deposits in Nevada. Similar deposits, but not as large, have been found in China, Iran, and Macedonia.

Non-magmatic Geochemical Processes

Dark mining shaft with rusted cart tracks leading into it. The shaft is carved into a cliffside composed of alternating red and whitish green sandstone and mudstone.
Figure 16.31: Underground uranium mine near Moab, Utah.

Geochemical processes that occur at or near the surface without ’s aid also concentrate metals, but to a lesser degree than  processes. One of the main reactions is , short for reduction/ chemistry, which has to do with the amount of available oxygen in a . Places where oxygen is plentiful, as in the today, are considered oxidizing environments, while oxygen-poor places are considered reducing environments. Uranium deposits are an example of where the metal. Uranium is soluble in oxidizing environments and precipitates as uraninite when encountering reducing conditions. Many of the deposits across the Colorado Plateau, such as in Moab, Utah, were formed by this method.

 reactions are also responsible for creating  (BIFs), which are interbedded layers of iron —hematite and magnetite, , and  . These deposits formed early in the Earth’s history as the  was becoming oxygenated. Cycles of oxygenating iron-rich waters initiated of the iron . Because BIFs are generally  in age, happening at the event of atmospheric oxygenation, they are only found in some of the older exposed rocks in the United States, such as in Michigan’s upper peninsula and northeast Minnesota.

World map showing location of Mississippi Valley-Type and clastic-dominated sediment-hosted lead-zinc deposits. Mississippi Valley-Type locations are marked by red diamonds and are scattered across western Canada, the United States, eastern and western Greenland, western and eastern South America, Europe, southern and northeastern Africa, southern and eastern Asia, and Australia. Clastic-dominated deposits are marked by green squares and are located in western Canada, the United States, northern Greenland, the Caribbean, eastern South America, southwestern Africa, Europe, southern and eastern Asia, and Australia.
Figure 16.32: Map of Mississippi-Valley type ore deposits.

Deep, saline, (trapped in spaces) within  may be highly metalliferous. When expelled outward and upward as compacted, these fluids formed lead and zinc deposits in by replacing or filling open spaces, such as caves and , and in by filling spaces. The most famous are called  deposits. Also known as deposits, they are large deposits of galena and sphalerite lead and zinc that form from hot fluids ranging from 100°C to 200°C (212°F to 392°F). Although they are named for occurring along the Mississippi River Valley in the US, they are found worldwide.

 deposits occurring in , and marls are enormous, and their contained resources are comparable to  copper deposits. These deposits were most likely formed diagenetically by  fluids in highly permeable rocks. Well-known examples are the Kupferschiefer in Europe, which has an areal coverage of >500,000 Km2, (310,685.596mi) and the Zambian Copper Belt in Africa.

Chunk of heavily weathered tan and porous rock that has unweathered elongated gray and black crystals in the center.
Figure 16.33: A sample of bauxite. Note the unweathered igneous rock in the center.

 and  deposits that are exposed at the surface experience deep and intense , which can form surficial deposits. , an aluminum , is preserved in topography and laterites, which are formed in wet tropical environments. containing aluminum concentrate , such as , and ferromagnesian in and rocks, undergo processes that concentrate the metals. rocks that undergo form nickel-rich , and when the magnetite and hematite in undergo , it forms goethite, a friable that is easily for its iron content.

Surficial Physical Processes

Side view of a sand deposit that has layers of tan sand interbedded with layers of gray and black sand; a penny is stuck into the sand for scale.
Figure 16.34: Lithified heavy mineral sand (dark layers) from a beach deposit in India.

At the Earth’s surface, and moving water can cause hydraulic , which forces high-density to concentrate. When these minerals are concentrated in , , and beaches, they are called  deposits, and occur in modern sands and ancient lithified rocks.  gold,  platinum, , ilmenite, rutile, magnetite, diamonds, and other gemstones can be found in . Humans have mimicked this natural process to recover gold manually by gold panning and by mechanized means such as dredging.

16.3.2 Environmental Impacts of Metallic Mineral Mining

Bright orange river flowing toward the viewer. The land on either side of the river is rocky and barren.
Figure 16.35: Acid mine drainage in the Rio Tinto, Spain.

  ’s primary impact comes from the  itself, including disturbing the land surface, covering landscapes with tailings impoundments, and increasing  by accelerating . In addition, many metal deposits contain pyrite, an uneconomic  , that when placed on waste dumps, generates  (ARD) during . In oxygenated water, such as pyrite react and undergo complex reactions to release metal ions and hydrogen ions, which lowers pH to highly acidic levels. and processing of materials typically increase the surface area to volume ratio in the material, causing chemical reactions to occur even faster than would occur naturally. If not managed properly, these reactions lead to acidic and plumes that carry toxic metals. In where is a waste rock or where like or dolomite are present, their acid neutralizing potential helps reduce . Although this is a natural process too, it is very important to isolate dumps and tailings from oxygenated water, both to prevent the from dissolving and subsequently percolating the -rich water into waterways. Industry has taken great strides to prevent contamination in recent decades, but earlier projects are still causing problems with local ecosystems.

16.3.3 Nonmetallic Mineral Deposits

A quarry carved into a hillside with large blocks of gray and white marble removed.
Figure 16.36: Carrara marble quarry in Italy, source to famous sculptures like Michelangelo’s David.

While receiving much less attention, resources, also known as industrial , are just as vital to ancient and modern society as . The most basic is building stone. , , , , and are common building stones and have been quarried for centuries. Even today, building stones from roof tiles to countertops are very popular. Especially pure is ground up, processed, and reformed as plaster, cement, and concrete. Some resources are not specific; nearly any rock or can be used. This is generally called aggregate, which is used in concrete, roads, and foundations. Gravel is one of the more common aggregates.

Evaporites

A flat white expanse with a mountain range in the distant background.
Figure 16.37: Salt-covered plain known as the Bonneville Salt Flats, Utah.

deposits form in restricted basins where water evaporates faster than it , such as the Great Salt Lake in Utah, or the Dead Sea, which borders Israel and Jordan. As the waters evaporate, soluble are concentrated and become supersaturated, at which point they from the now highly-saline waters. If these conditions persist for long stretches, thick rock salt, rock , and other deposits accumulate (see chapter 5).

Cream-colored translucent crystal with 6 sides. A marker sits next to the sample for scale.
Figure 16.38: Hanksite, Na22K(SO4)9(CO3)2Cl, one of the few minerals that is considered a carbonate and a sulfate.

, such as , are used in our food as common table salt. Salt was a vitally important food preservative and economic resource before refrigeration was developed. While still used in food, is now mainly as a chemical agent, water softener, or road de-icer. is a common used as a building material; it is the main component in dry wall. It is also used as a fertilizer. Other include sylvite—potassium chloride, and bischofite—magnesium chloride, both of which are used in agriculture, medicine, food processing, and other applications. Potash, a group of highly soluble potassium-bearing , is used as a fertilizer. In hyper-arid locations, even more rare and complex , like borax, trona, ulexite, and hanksite are . They can be found in places such as Searles Dry Lake and Death Valley, California, and in the Green River Formation’s ancient deposits in Utah and Wyoming.

Phosphorus

An elongated prismatic crystal of light green apatite with a glassy luster.
Figure 16.39: Apatite from Mexico.

Phosphorus is an essential that occurs in the apatite, which is found in trace amounts in common rocks. Phosphorite rock, which is formed in sedimentary environments in the ocean, contains abundant apatite and is to make fertilizer. Without phosphorus, life as we know it is not possible. Phosphorous is an important component of bone and DNA. Bone and guano are natural sources of phosphorus.

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Summary

Energy and resources are vital to modern society, and it is the role of the geologist to locate these resources for human benefit. As environmental concerns have become more prominent, the value of the geologist has not decreased, as they are still vital in locating the deposits and identifying the least methods of extraction.

Energy resources are general grouped as being or . Geologists can aid in locating the best places to exploit resources (e.g. locating a dam), but are commonly tasked with finding . resources are also grouped in two categories: and . have a wide variety of processes that concentrate them to economic levels, and are usually via surface or underground methods.

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Figure References

Figure 16.1: A Mode 1 Oldowan tool used for chopping. José-Manuel Benito Álvarez. 2007. Public domain. https://commons.wikimedia.org/wiki/File:Canto_tallado_2-Guelmim-Es_Semara.jpg

Figure 16.2: Map of world mining areas. KVDP. 2009. Public domain. https://commons.wikimedia.org/wiki/File:Simplified_world_mining_map_1.png

Figure 16.3: Hoover Dam provides hydroelectric energy and stores water for southern Nevada. Ubergirl. 2012. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Hoover_Dam,_Colorado_River.JPG

Figure 16.4: Natural, octahedral shape of diamond. USGS. 2003. Public domain. https://commons.wikimedia.org/wiki/File:Rough_diamond.jpg

Figure 16.5: Banded-iron formations are an important ore of iron (Fe). Wilson44691. 2008. Public domain. https://commons.wikimedia.org/wiki/File:MichiganBIF.jpg

Figure 16.6: Diagram illustrating the relative abundance of proven reserves, inferred reserves, resources, and undiscovered resources. Kindred Grey. 2022. CC BY 4.0.

Figure 16.7: McKelvey diagram showing different definitions for different degrees of concentration and understanding of mineral deposits. USGS. 1980. Public domain. https://commons.wikimedia.org/wiki/File:McKelveyDiagram.jpg

Figure 16.8: Bingham Canyon Mine, Utah. Doc Searls. 2016. CC BY 2.0. https://commons.wikimedia.org/wiki/File:Bingham_Canyon_mine_2016.jpg

Figure 16.9: A surface coal mine in Wyoming. Bureau of Land Management. Unknown date. Public domain. https://www.usgs.gov/news/science-snippet/earthword-thermal-maturity

Figure 16.10: Underground mining in Estonia of oil shale. Kaupo Kikkas. 2011. CC BY-SA 4.0. https://commons.wikimedia.org/wiki/File:VKG_Ojamaa_kaevandus.jpg

Figure 16.11: A phosphate smelting operation in Alabama, 1942. Alfred T. Palmer. 1942. Public domain. https://commons.wikimedia.org/wiki/File:TVA_phosphate_smelting_furnace.jpg

Figure 16.12: Coal power plant in Helper, Utah. David Jolley. 2007. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Castle_Gate_Power_Plant,_Utah_2007.jpg

Figure 16.13: Modern coral reefs and other highly-productive shallow marine environments are thought to be the sources of most petroleum resources. Toby Hudson. 2010. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Coral_Outcrop_Flynn_Reef.jpg

Figure 16.14: World oil reserves in 2013. GunnMap; generated with settings from Emilfaro and A5b. 2014. CC BY-SA 1.0. https://commons.wikimedia.org/wiki/File:Oil_Reserves.png

Figure 16.15: Examples of different forms of hydrocarbon traps: in the core region of anticlines. MagentaGreen. 2014. CC BY-SA 4.0. https://commons.wikimedia.org/wiki/File:Anticlinal_Oil_trap.png

Figure 16.16: The rising sea levels of transgressions create onlapping sediments, regressions create offlapping. Woudloper. 2009. CC BY-SA 1.0. https://commons.wikimedia.org/wiki/File:Offlap_%26_onlap_EN.svg

Figure 16.17: Tar sandstone from the Miocene Monterey Formation of California. James St. John. 2015. CC BY 2.0. https://flic.kr/p/rECMTD

Figure 16.18: Global production of oil shale, 1880-2010. USGS. 2011. Public domain. https://commons.wikimedia.org/wiki/File:Production_of_oil_shale.png

Figure 16.19: Schematic diagram of fracking. Mikenorton. 2012. CC BY-SA 3.0. https://en.wikipedia.org/wiki/File:HydroFrac.png

Figure 16.20: USGS diagram of different coal rankings. USGS. 2009. Public domain. https://commons.wikimedia.org/wiki/File:Coal_Rank_USGS.png

Figure 16.21: Peat (also known as turf) consists of partially decayed organic matter. David Stanley. 2019. CC BY 2.0. https://commons.m.wikimedia.org/wiki/File:Peat_(49302157252).jpg

Figure 16.22: Anthracite coal, the highest grade of coal. USGS. 2007. Public domain. https://commons.wikimedia.org/wiki/File:Coal_anthracite.jpg

Figure 16.23: Gold-bearing quartz vein from California. James St. John. 2014. CC BY 2.0. https://commons.wikimedia.org/wiki/File:Mother_Lode_Gold_OreHarvard_mine_quartz-gold_vein.jpg

Figure 16.24: Layered intrusion of dark chromium-bearing minerals, Bushveld Complex, South Africa. kevinzim / Kevin Walsh. 2006. CC BY 2.0. https://commons.wikimedia.org/wiki/File:Chromitite_Bushveld_South_Africa.jpg

Figure 16.25: This pegmatite contains lithium-rich green elbaite (a tourmaline) and purple lepidolite (a mica). Parent Géry. 2011. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Elba%C3%AFte_et_mica_(Br%C3%A9sil)_1.JPG

Figure 16.26: Schematic diagram of a kimberlite pipe. Asbestos. 2005. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:VolcanicPipe.jpg

Figure 16.27: The complex chemistry around mid-ocean ridges. NOAA. 2011. Public domain. https://commons.wikimedia.org/wiki/File:Deep_Sea_Vent_Chemistry_Diagram.svg

Figure 16.28: The Morenci porphyry is oxidized toward its top (as seen as red rocks in the wall of the mine), creating supergene enrichment. Stephanie Salisbury. 2012. CC BY 2.0. https://commons.wikimedia.org/wiki/File:Morenci_Mine_2012.jpg

Figure 16.29: Garnet-augite skarn from Italy. Siim Sepp. 2012. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:00031_6_cm_grossular_calcite_augite_skarn.jpg

Figure 16.30: In this rock, a pyrite cube has dissolved (as seen with the negative “corner” impression in the rock), leaving behind small specks of gold. Matt Affolter (QFL247). 2009. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:GoldinPyriteDrainage_acide.JPG

Figure 16.31: Underground uranium mine near Moab, Utah. Matt Affolter. 2010. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:UraniumMineUtah.JPG

Figure 16.32: Map of Mississippi-Valley type ore deposits. Kbh3rd. 2010. CC BY 3.0. https://commons.wikimedia.org/wiki/File:MV-Type_and_clastic_sediment-hosted_lead-zinc_deposits.svg

Figure 16.33: A sample of bauxite. Werner Schellmann. 1965. CC BY-SA 2.5. https://commons.wikimedia.org/wiki/File:Bauxite_with_unweathered_rock_core._C_021.jpg

Figure 16.34: Lithified heavy mineral sand (dark layers) from a beach deposit in India. Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster). 2008. Public domain. https://commons.wikimedia.org/wiki/File:HeavyMineralsBeachSand.jpg

Figure 16.35: Acid mine drainage in the Rio Tinto, Spain. Carol Stoker, NASA. 2002. Public domain. https://commons.wikimedia.org/wiki/File:Rio_tinto_river_CarolStoker_NASA_Ames_Research_Center.jpg

Figure 16.36: Carrara marble quarry in Italy, source to famous sculptures like Michelangelo’s David. Michele~commonswiki. 2006. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Carrara_Marble_quarry.jpg

Figure 16.37: Salt-covered plain known as the Bonneville Salt Flats, Utah. Michael Pätzold. 2008. CC BY-SA 4.0. https://commons.wikimedia.org/wiki/File:Bonneville_salt_flats_pilot_peak.jpg

Figure 16.38: Hanksite, Na22K(SO4)9(CO3)2Cl, one of the few minerals that is considered a carbonate and a sulfate. Matt Affolter(QFL247). 2009. CC BY-SA 3.0.

Figure 16.39: Apatite from Mexico. Robert M. Lavinsky. Before March 2010. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Apatite-(CaF)-280343.jpg

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