The Future of Economic Geology - Metals and Society: An Introduction to Economic Geology - page 142

technology involves horizontal drilling to provide better access to flat-lying sedi-
mentary strata combined with a process, called “fracting” or hydraulic fracturing, in
which mixtures of water, sand, and chemical additives are injected at high pressure
into the shale to increase its permeability and extract the products - mainly gas and
also some oil.
The prices of oil and gas had both dropped drastically during the 2008 financial
crisis yet unlike the oil price (and that of most metals), which have since risen
dramatically, the gas price has remained at a low level - due to the sudden
availability of shale gas. The USA is now expected to satisfy most of its domestic
consumption for the next decades, and the potential development of shale gas in
Europe, mainly in Poland, Germany, Hungary, Romania and perhaps Great Britain,
has loosened the dependence on Russian supplies. There are, to be sure, environ-
mental issues, and ecologists have manifested their concern about the high con-
sumption of water and potential leaks of the chemicals used in the process. But
more generally, the global availability of new supplies of natural gas - a clean, low-
CO 2 energy source - must be considered a positive development. China, for
example, may also possess significant resources of shale gas, and its substitution
for the other major domestic energy source - coal - can only be beneficial.
Future decline in the production and consumption of petroleum will probably be
driven more by the need to reduce emissions of greenhouse gases than a real
exhaustion of resources. The accelerating drive to reduce overall energy consump-
tion will be accompanied by substitution of petroleum by other sources of energy.
Nuclear power will play an important role, and a whole array of wind turbines,
hydro- or geothermal stations, and solar panels will tap renewable resources. To
fuel the nuclear reactors requires uranium; to build the turbines and solar panels,
and to improve the performance of cars, electric devices or home heating systems
will require a spectrum of hitherto obscure metals. In the following sections we
discuss two groups of minerals that have suddenly received global attention and
aptly illustrate the challenges of mining in the twenty-first century.
6.2 Rare Earth Elements (REE)
This group of elements, well known to geochemists who use them as tracers of
geological processes in the mantle, crust and oceans, is becoming increasingly
important in modern industry. They are used in a wide variety of applications,
mostly in electronic components, but also in a range of industrial processes. Some
typical examples are listed in Table 6.1 and Fig. 6.1 shows where these elements are
used in a modern hybrid vehicle.
In geochemical terms, the rare earths are classed as incompatible elements,
which means that they become concentrated in the water-rich silicate liquids that
remain after a magma has almost completely crystallized or in very low degree
partial melts of the mantle. They are present in high abundances in some pegmatites
(the products of crystallization of aqueous melts expelled from granitic magmas)