Category: Economic and applied geology

The longest and most devastating wars in history have centred rather more on economic interests than nationalism or chivalrous defence of principles, and in some case a specific commodity created an issue that annexation served to resolve.  For instance, the 1914-18 war was not unconnected with the vast iron ore reserves of Alsace-Lorraine.  Similarly, the Nigerian civil war of the late 1960s was bound up with the oil reserves of the Niger delta, and that of Congo centred on base-metal resources of the Copper Belt, particularly the fact that vast strategic reserves of cobalt occur in its Congolese sector.  The running sores of present conflicts in Africa – Angola, Congo, Sierra Leone, Liberia – are about and financed by gems that adorn the rich, the self-regarding and the lazy.  These diamond wars are a direct concern of geologists, for who else finds the elusive kimberlites and traces the natural dispersion of the diamonds that they contain?

More than 30 years on from the start of gem-related carnage in Africa, in which dealers and giant mining corporations have been implicated up to their collective eyebrows, local people have been drawn into “illicit” diamond mining when their livelihoods have been destroyed by perpetual danger and insecurity.  Preyed on by many so-called “rebel” groups, even kids as young as 8 or 9 have been armed and set upon one another and the inhabitants of regions blighted by the presence of what is no more than an allotrope of carbon.  Eugenie Samuel writes on a possible means of defining the source of diamonds “fenced” by the gem trade from on-going conflict zones (Samuel, E. 2002.  Diamond wars.  New Scientist, 25 May 2002, p. 6-7).  It seems that ultra-thin coatings on rough diamonds carry a geochemical signature from the chemically diverse kimberlites and other unusual mafic rocks that carry them from the mantle.  Given research on rough stones from every kimberlite province it should be possible for this forensic approach to help stamp out what is the world’s largest blood trade. 

The problems are many.  For a start, trade in “conflict diamonds” is now illegal, so it is unlikely that rough stones used to calibrate the technique would be given a bona fide provenance by dealers. It would be a courageous geochemist who went sampling in interior Congo, Angola, Liberia or Sierra Leone.  The method clearly requires funds, yet the obvious source, diamond mining and trading companies, are engaged in their own tagging schemes that use using ion beams to bar-code their products on a minute scale.  In fact this tagging method was developed under great secrecy to distinguish from the “real” thing perfect artificial diamond gems synthesized by Russian geochemists.  Finding diamonds requires considerable exploration, which involves systematic sampling of sediments along streams that drain likely kimberlite-bearing ground.  Although high-quality rough found by geologists would be sold, there must be small diamonds archived from such sampling by mining companies and geological surveys.  They could be supplied to forensic geochemists to calibrate the method.  In Sierra Leone, for instance, the diamond fields were located in the early 1950s by geologists of the then Overseas Geological Survey – part of what became the modern British Geological Survey.  Belgian and Portuguese equivalents may well have archival material from Congo and Angola.

In waters that are anaerobic, metabolism of dead organic matter requires a means of accepting electrons transferred away from the necessary oxidation, other than that which involves oxygen as an electron acceptor.  Some heterotrophic bacteria achieve this by the simple chemical trick of reducing sulphate ions (SO₄^2-) to sulphide ions (S^2-).  This form of heterotrophy does not oxidise carbohydrate back to carbon dioxide plus water, but produces methane.  In the context of economic geology, it is the generation of sulphide ions that is more interesting, for any dissolved metal ions will swiftly combine with sulphide to form highly insoluble sulphides – the general form taken by many ore minerals.  This is the process observed to occur around deep-ocean hydrothermal vents, where biogenic sulphide ions cause metals dissolved in the hot water to precipitate and form the dark clouds from which such vents get their name – “black smokers”.  Many metal deposits are now known to have formed in such an environment, notably the volcanogenic massive sulphide or VMS ores.

However, there are many sulphide ores that have no obvious relationship to hydrothermal vents, such as sediment hosted deposits like the massive lead and zinc sulphide deposits of the Mississippi type.  Moreover, most sulphate-reducing bacteria are intolerant of oxygen whereas sediment-hosted deposits often bear isotopic witness to the presence of oxygen.  But, deposits of that kind often show intricate fine banding, suggesting slow deposition of fine-grained sulphides.  Some light is thrown on the problem by a daring piece of research involving sampling from flooded caves in a flooded Pb-Zn mine in Wisconsin (Labrenz, M.  et al. 2000.  Formation of sphalerite (ZnS) deposits in natural biofilms of sulfate-reducing bacteria.  Science, v. 290, p. 1744-1747).  SCUBA divers recovered scum formed by bacterial filaments or biofilm, and analyses showed the clear association of the bacterial cells with nanometre-scale spheres of zinc sulphide.  The species of sulphate-reducing bacteria involved is not exactly oxygen-loving, but will tolerate moderate levels dissolved in water.  Here clearly is a means for the formation of low-temperature massive Pb-Zn sulphide deposits.

The astonishing feature of the results of Lanbrenz and co-workers is that the zinc sulphide forms from water with very low levels of the metal (less than one part per million).  The bacteria, or at least their metabolic products, scavenge the metal, and quite probably dangerous cadmium, extremely efficiently.  Chances are that similar bacteria could also pick out lead and arsenic.  That opens up a new means of  bio-remediation – clean-up of both mine waste and contaminated drinking water.

The activity of sulphate reducers leaves its signature on the sulphur isotopes of ancient sediments, revealing periods when the burgeoned, as in Phanerozoic black-shale strata.  They were most active in this respect before about 2 billion years ago, when atmospheric oxygen levels were so low as to diminish oxidation by that highly active gas.  It seems that sulphate reducers also promote the precipitation of dolomite – (Ca,Mg)CO₃ – over that of calcite in sea water.  This tallies with the common association of dolomitization of calcite in many sedimentary sulphide deposits, and also with the predominance of dolomites over limestones in the early Precambrian. [see also:  Vasconcelos, C. and McKenzie, J.A. 2000.  Sulphate reducers – dominant players in a low-oxygen world.  Science, v.  290, p. 1711-1712].

Satellites demand durable components, and for some applications the metal rhenium is irreplaceable.  But it is hard to smelt, as well as being rare.  Its current price of US$1.45 per gram reflects its conventional extraction from gases emitted by roasting molybdenum ore, a by-product of copper mining.  At around one sixth the value of gold and with work beginning in earnest on the US-Russian International Space Station, a sizeable chunk of rhenium promises a quick profit.  For geologists in the economic black hole that was the Soviet Union, rhenium has become a magnet and they are developing possibly the most extraordinary mining venture ever attempted.

Volcanologists of the Russian Institute of Experimental Mineralogy discovered, in 1992, that fumaroles of the volcano Kudriavy in the Kuril Archepelago exhale and precipitate pure rhenium sulphide – the hitherto unknown mineral rheniite.  The vents’ build-ups contain at least ten tonnes of rhenium, and fumarole gases replenish it at a rate of several grammes each day.  As well as mining the vents, even condensing rheniite is an economically attractive proposition.  Even now, scientists of the Moscow-based Institute of Mineralogy, Geochemistry and Crustal Chemistry are building a wooden pyramid to cap one of the vents.  This will funnel fumarole gases into a chemical trap for rhenium, that uses zeolites as an ion extractor.  Future plans, sensibly, focus on concrete or ceramic caps to tap all the fumaroles in Kudriavy’s crater. 

Source:  Jones, N., 2000.  Outrageous fortune.  New Scientist, 26 August 2000, p 24-26

A friend from the USA, who visited me a month back, was surprised to find Britain not yet in the throes of a popular insurrection.  He gasped each time I filled up at a fuel station.  Clearly, he has yet to divine the depth of phlegmatic resources endowed to motorists stuck between junctions 8 and 12 on the M6.  Few of us now bother to ponder whether the recent price hikes should be put down to the laws of supply, demand and price, or to the addiction of the British economy to gouging fuel tax and duties from the hapless road user.  The Organization of Petroleum Exporting Countries (OPEC) refound its awesome powers of the 1970’s during 1998-9 and cut back production to drive a near tripling of spot prices.  Concerned that the political impact of this on a now globalized economy might bear down on them, the Saudi delegate to the recent OPEC meeting in Vienna announced an increase in Saudi crude production that halted the upward spiral.  Should Iraq be allowed to pump to capacity and Libya reach peak output, the situation would rapidly reverse.

It is a curious time, for the petroleum sector of the North American and European economies faces dwindling home reserves while their industrial production is hard hit by rising fuel prices – a case of ‘tails you lose, heads we win’, it might seem.  Since the Limits to Growth prognosis in the late 1960’s of rapid exhaustion of petroleum reserves, each decade has seen the ‘evil day’ recede into the future, as exploration frontiers have pushed forward and extractive methods become more efficient.  In its latest assessment of world fossil-fuel reserves, the US Geological Survey has taken everyone by surprise (greenwood.cr.usgs.gov/energy/WorldEnergy/DDS-60).

A new approach to estimation using the latest geological data from around the world’s petroleum-prone basins suggests that undiscovered conventional oil resources are 20 % larger than believed previously.  A substantial proportion of this increased estimate stems from evaluating the formerly overlooked  tendency for ‘finding elephants in elephant country’, i.e. hitting previously undiscovered reservoirs within or just beyond existing fields.  This suggests that old fields should grow by up to a quarter in the future (612 billion barrels or about 9 years of global production), while new exploration should come on stream with 732 billion barrels, eventually.  The estimates are not uniform, however.  European and North American production still remains doomed to rapid exhaustion, with the bulk of new resources adding to the already huge dominance of the Arabian peninsula, and to the worrisome former Soviet Union.

Despite the flurry of optimism among petroleum economists and the industry in general, a sober assessment is that the new USGS assessment delays matters by a decade or two at most, given the annual production of 27 billion barrels per year and 1.5 to 2% annual growth  – business-as-usual and barely a sign of significantly replacing petroleum with alternative, renewable energy sources that do not add to global warming.  Re-emphasis of the overwhelming dominance of the Arabian peninsula, North Africa and the former Soviet Union as suppliers to fuel continuing demand, and the certain increase in one-sideness of the economic relationship have big political implications.  Some analysts foresee a ‘second coming’ of OPEC, and greater tension surrounding the areas formerly in the Soviet sphere of influence.  China barely figures as a significant player, despite former optimism.

Water resources under threat

We now live in an epoch where the ‘first provision of any civilized society, after a system of laws, is a water supply’ has begun to pass definitively from municipal to privatized control.  The private sector in water provision is exploding worldwide, particularly in potentially profitable urban areas of the ‘two-thirds world’; i.e. the poorest countries.  This is a tendency explicitly encouraged by multi- and bilateral sources of developmental aid, such as the World Bank, departments of the EU and Britain’s Department for International Development (DfID).  Popular unrest concerning rapidly rising water prices are sweeping through the townships of South Africa and several South American countries, as people find themselves unable to pay for supplies and find them cut off.

The Water Systems Analysis Group of the University of New Hampshire, USA has released a depressing and highly detailed assessment of the future fragility of global fresh-water supplies (Vörösmarty, C.J, et al., 2000.  Global water resources: vulnerability from climate change and population growth.  Science, v. 289, p 284-288).  Their analysis is based on geographic cells half a degree square (about 55 km), and considers the fresh water flow by surface run-off and movement through shallow aquifers, which constitutes the locally sustainable supply (deep aquifers are non-renewable in the short- to medium-term, without being engineered for recharge by surface water) relative to population density and domestic, industrial and agricultural uses.  Unlike assessment of petroleum reserves (above), which stems from detailed information supplied by giant transnational companies, doing the same for water is at best a sketchy exercise, because of the wide variations in quality of data.

Using aggregations for individual countries suggests that one third of the world’s population lived in 1985 under conditions of water scarcity, and about 450 million faced severe water stress.  However, by looking more closely, on a cell-by-cell basis, the Group shows that levels of stress are grossly underestimated by conventional country assessments.  They found that 1.8 billion people had to survive 15 years ago at the highest level of water shortage.

To model future changes in water stress, the Group considered both climate and population change.  They based the first on a water-balance model that incorporates global hydrological information and the precipitation side of climate change modelling of the anthropogenic ‘greenhouse’ effect.  Climate change is subordinate to growing population and likely shifts in population (the rural to urban drift that is growing at present).  Things seem likely to improve for people living in or moving to relatively water-rich areas, but probably at the expense of worsening water quality.  The most dramatic feature is a possible 85% increase in the population subject to the highest levels of water stress.  Since agriculture that depends on irrigation centres in already water stressed areas for domestic and industrial use, the prognosis is doubly worrisome, since those areas are likely to face even worse food shortages.  Looking at individual drainage basins shows that some, including that of the Huang He (Yellow River) in China, which has the highest population density anywhere, seem destined soon to show an excess of demand over discharge.

It is not difficult to foresee from the Group’s analysis a rapidly approaching period of curtailment of economic activities, mass migration and conflict in transnational river basins.  The danger areas are overwhelmingly in the ‘two-thirds world’, where the search for profits by water companies finds strategic focuses at present.  Being the ultimate in supply-demand forces (demand for water is the least ‘elastic’ imaginable) this is hardly surprising.  It should, however, come as no great surprise if such ventures are expropriated by people themselves.