Mining

Geologist wielding pick axe, other standing nearby
Geologist wielding pick axe, other standing nearby (Photo: D. McVeigh)

Antarctica, like all large land masses, contains minerals, oil and gas from the times when it was a temperate continent.

The Protocol on Environmental Protection to the Antarctic Treaty (The Madrid Protocol) bans all mineral resource activities in Antarctica (other than scientific research). Economically, there are problems associated with mining; the cold, the ice covering land and sea, drifting icebergs which could collide with platforms and mining infrastructure, its remoteness from inhabited places and the sheer cost of operations. Mining also poses a real threat to the ecological integrity of the continent.

The current status of mining in the Antarctic is the result of a complex history involving a variety of disciplines – science (geology), economics and the politics of international agreements.

In the 1980s the question of possible mineral exploitation (including the hydrocarbons oil and gas) was addressed by the nations of the Antarctic Treaty. They negotiated an agreement called the Convention on the Regulation of Antarctic Mineral Resource Activities (CRAMRA) which would have regulated mining should it have ever been contemplated. CRAMRA did not come into force. Instead, the Madrid Protocol was negotiated and it includes a ban on Antarctic mining.

Minerals

Minerals have been discovered in Antarctica as a result of general geological studies. Primarily, the known minerals are iron oxides and coal. 

Antarctica, like all other continents, has at its core an ancient shield. East Antarctica is composed of rocks almost 4 billion years old; some of the oldest rocks known on Earth. The age of the Earth is estimated to be 4.6 billion years and thus ancient Antarctic rocks can be studied to gain insight into processes active in the early days of the Earth's history. These most ancient rocks are very well-exposed in Enderby Land at the western extremity of the Australian Antarctic Territory.

Many other rock groups formed as sequences of volcanic rocks and sediments at 2.5 to 2.8 billion years ago, and others at 1.4 billion years. Many other ages also are known.

The ancient shield is not homogeneous but can be subdivided into clearly separable units (cratons). These cratons and the boundaries between them have been the locations of much activity as the cratons have moved against one another. In other continents, the same structure and similar age relationships are known. Most of the world's mineral resources come from these cratonic units and thus it is reasonable to expect that the Antarctic shield has the same mineral resource potential as other parts of the globe. However there are some features of Antarctica that dramatically reduce the chance of mineral availability.

Firstly, 98 per cent of the continent is overlain by ice up to 4 kilometres thick and thus very little area is accessible for exploration. In the Australian Antarctic Territory, the exposure is even lower; about 0.2 per cent is exposed (20 per cent of the area of Tasmania).

Secondly, many types of minerals which are important elsewhere on Earth cannot be expected in Antarctica.

A common way of commencing mineral exploration elsewhere is to pan for gold or heavy metals or minerals in rivers. More detailed exploration includes river water sampling to locate likely ore bodies. Antarctica does not have many rivers and those that do exist are very small, seasonal and drain limited areas. Thus heavy mineral 'placer' deposits are very unlikely. Similarly, because of the different oceanographic conditions and lack of beaches, the heavy mineral beach sands so important in Australia are unavailable.

Thirdly, certain mineral occurrences such as bauxite (the ore of aluminium), some iron ores or even some nickel-bearing laterites are formed by long term leaching of a parent rock and virtually all of the parent is altered and dissolved away to leave an insoluble residue, commonly soft. Antarctica does not have the weathering conditions (it is too cold), nor the dissolving power (water is almost absent), and glacial activity removes anything soft or that formed in ages past.

Another related occurrence missing from Antarctica is supergene enrichment to produce a porous iron-rich surface material known as gossan. Gossans form over some ore bodies (and very often even where no valuable ore exists at depth) particularly where the ore body may be made of sulphides of iron with inclusions of copper, gold and others minerals such as at the original site of the Mt Lyell mine in Tasmania. The gossan is often a guide to an ore body at depth and covers a larger area than the ore body. A feature of such supergene enrichments is that, as the parent rocks weather through water and other action the residual gossan is enriched (hence the name) in gold and some forms of copper, including native copper. Such supergene enrichments are absent from Antarctica because of unfavourable weathering conditions and removal by moving ice.

Thus many kinds of ores mined elsewhere cannot be expected in Antarctica. Any mineral search in Antarctica would need to find the parent ore body directly; a search for small areas in an already very small area of outcrop.

Of course, it may be that, due to the unique oceanic conditions around Antarctica, as yet unknown mechanisms may be concentrating minerals. There is no evidence of this so far.

An argument often asserted to suggest that East Antarctica is mineral-rich is based on the fact that if continents are placed in their original places in the ancient supercontinent of Gondwana, parts lie against mineral rich ancient rocks of Western Australia. Unfortunately for those who use it, this is not a valid argument. Along the south coast of Western Australia is the Albany-Fraser block which has almost totally defied concerted efforts to find mineral wealth.

The geological story of West Antarctica is very different but the mineral resource potential is also low. West Antarctica is much smaller than East Antarctica but has a higher proportion as outcrop. The history is much more recent, encompassing the last 200 million years, less than 10 per cent of the age of East Antarctica. The story relates to the evolution of the Southern Pacific Ocean margin, including New Zealand and South America.

The Antarctic Peninsula, the main exposed part of West Antarctica, was formed by complex processes nearly 200 million years ago as the Pacific (and possibly Atlantic) Ocean seafloor has been subducted (lead under) the Peninsula. This process has also occurred in New Zealand and along the west coast of South America. In the process, it formed the rich copper ores of Chile, hence the Peninsula has been put forward as a potential copper province. Again, the facts do not support it. Copper in Chile only occurs north of the capital Santiago, not along the entire west coast.

Coal

Coal has been found in two regions in East Antarctica—the Transantarctic Mountains and Prince Charles Mountains. The two occurrences are quite different. Those in the Transantarctic Mountains are Triassic (200 million years which is roughly the same age as the sandstones in the spectacular cliffs around Sydney), and those in the Prince Charles Mountains are 250 million years (roughly the same age as the Collie or Hunter Valley coals).

Iron Ore

Boulders of Banded Iron Formation (BIF) are widespread in glacial debris of East Antarctica and it is clear that BIFs are common but mainly under the ice. At Mt Ruker in the Prince Charles Mountains, BIF is known in outcrops. Most BIFs formed about 2 billion years ago when oxygen first started to accumulate in the atmosphere. The BIF at Mt Ruker is quite extensive and has been traced under the ice for over 100 kilometres using magnetic methods. It contains about 35 per cent iron.

Chromium

One region in East Antarctica – the Dufek Massif – has been identified as a possible source of chromium, but the case is very weak. The Dufek Massif is a large area where, 170 million years ago, there was an intrusion of magma (molten rock below ground level) which cooled and crystallised where it now is. The intrusive event had very widespread effects, extending from South Africa, through the Transantarctic Mountains to Tasmania and Kangaroo Island (but not the Australian mainland) to form the rocks of the Tasmanian Central Highlands and such areas as the Organ Pipes on Mt Wellington. In most areas the rocks are 350 meters thick and lay flat with a vertical columnar structure (hence Organ Pipes).

In the Dufek Massif, while part of the same intrusion, the rock differs in being several kilometres thick, thus requiring a much longer time to cool and crystallise. It has been proposed that the long crystallisation allowed chromium oxide to crystallise and sink, forming a layer of chromite at the base of the magma chamber. No such chromite layer has been seen: its existence is purely hypothetical.

Seafloor Manganese Nodules

In many areas of the world oceans there is a dense layer (sometimes a pavement) of black, manganese and iron oxides, usually made of nodules about golf-ball size or a little larger. They also contain more valuable elements such as copper, nickel and cobalt. Such nodules or pavements occur near Antarctica.

Hydrocarbons

Hydrocarbons – oil and gas – are dominantly the product of maturation of organic material incorporated in sediments that accumulate in the ocean, lakes and river systems. Approximately one per cent of sediments is organic matter, i.e., the remains of animal and (dominantly) plant material.

Land plants have strengthening fibres (wood) and waxy covering (cuticle) to prevent them from drying out. Aqueous plants (algae and unicellular plants of the phytoplankton) do not need this strengthening or coating and, as a result, land and aqueous plants have a different chemistry, leading to different products of maturation.

As a gross generalisation (with many exceptions) sediments deposited in lakes and the sea (in an aqueous environment) give rise to oil (perhaps with a little gas) whereas those deposited in major river systems (similar to the sediments forming in the channel country of central Australia) give rise to gas.

For maturation to occur and useful hydrocarbons to be generated, the organic matter needs to be buried and subjected to raised temperatures for geological time. Normally, burial to 3 kilometres or so is needed and a temperature of 80-200°C. If temperatures get higher than 120°C, oil breaks down to gas and even aqueous sediments then produce gas. If the temperature exceeds 200°C for any significant time, even the gas changes and methane (the dominant part of natural gas) reacts with steam to produce carbon dioxide. At this point the gas is of little commercial value and geologists would recommend that drilling stop if evidence of these temperatures is found.

Most oil and gas occurs in geologically young rocks, 160 million years or younger. This is relevant when considering onshore Antarctica, where so little outcrop is known, and what is known is older, highly deformed rocks that have been subject to high temperatures. We should then look at the situation offshore where we require enough sediment thickness to have been deposited in a basin form. We know little of the geometry of Antarctic sediments. There has been reconnaissance offshore geophysical study and we have a very rough idea of basin configuration for much of the Antarctic margin, but there are large areas for which almost nothing is known.

The potential for offshore oil or gas is closely linked to sediments formed as the supercontinent Gondwana broke up millions of years ago. It is clear that in many areas, sedimentary basins formed and that sediment thickness is enough that oil and gas may be predicted in some areas. Very little is known of the geometry, composition or structure of these sediments.

The only drilling that has been done has been for scientific purposes by the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) and by specific projects in the Ross Sea. These all have avoided any circumstance where oil or gas would be predicted, for safety and environmental reasons. Deep Sea Drilling Project activity in the early 1970s did encounter traces of gas in the Ross Sea and drilling ceased. No other drilling-based oil or gas shows are known from the Antarctic.

In Bransfield Strait, on the western side of the Antarctic Peninsula, German surface sediment sampling recovered thermogenic hydrocarbons (generated by heat), probably modern organic material modified by high heat flow over a modern seafloor spreading centre where heat flow from below is high.

Onshore Antarctica has sedimentary basins but they are under thick ice and they have not been delineated adequately nor is much known of the rocks that fill them.

This page was last modified on 19 November 2012.