Rio Tinto Group, the world's second- largest mining company, closed two iron ore mines in Western Australia after a worker died.

The man was fatally injured while working at the Brockman 2 mine at 8 p.m. local time yesterday, the London-based company said in an e-mailed statement today. The mine and the adjacent Nammuldi operation have been closed. The police, the Department of Mines and Petroleum and other relevant authorities have been notified and investigations will begin immediately, it said.

Rio, the second largest iron ore producer, has 14 mines in the Pilbara region, with total production capacity of 225 million metric tons a year, according to the company's website. It's expanding capacity to 333 million tons.

Eoin Treacy's view Iron-ore has been a totem in terms of the secular bull market in commodities. China's apparently insatiable appetite for steel has fuelled a major bull market for the major producers of iron-ore over the last decade. Their dominance of global supply has prompted steel producers to attempt to develop their own supply and a number of new companies, most notably Fortescue Metals have entered the market. Against this background companies such as Rio Tinto among others are planning to expand production significantly through the expansion of current operations and investing in green field sites.

Prolific economic growth across Asia has led to large increases in per capita consumption of just about all commodities. Iron-ore in particular is emblematic of the infrastructure building necessary to create the cities in which massive new middle class populations wish to live. While China has been the clear leader in this regard, India is also slowly but surely developing new cities and the Middle East and ASEAN regions are following a similar trajectory.

Secular bull markets don't generally end because demand dries up. Thinking of the Nasdaq bust, demand for technology, media and telecoms has continued to increase despite the burst investment bubble. An explosion of supply is a symptom of just about every major secular bull market peak. In the late 1970s following more than a decade of price rises, major investment in new supply hit the market around the same time that interest rates were rising aggressively. This served to choke of demand at exactly the wrong time.

The present bull market in iron-ore has been managed effectively by the oligopoly of Vale, Rio Tinto and BHP Billiton. They have so far contained supply and forced prices higher. However, they are now announcing plans to massively increase supply over the medium term. At some point in the future supply will overtake demand however strong the latter is. It is not inconceivable that this could also occur in a higher interest rate environment than is currently present.

I am extremely bullish about the prospects for Asia's growth economies over the long term. Rising living standards across Asia and Latin America are helping to promote demand growth in everything from consumer goods to commodities. However, in the short term, Asian central banks continue to tilt policy towards tightening. Wage pressures and high raw material prices are a headwind and remain so. Rice, Asia's staple food, has just completed a 2-year base and risks are skewed to the upside. Oil remains stubbornly firm. Projections for further demand growth in the commodity sector in such an environment are now more questionable particularly when the chart action for some of the relevant shares is considered.

Vale, in common with the Brazilian market generally, has been hampered by a large increase in supply. The share has posted a large volatile range over the last 18 months and is currently testing the lower side. While oversold in the short term, a sustained move above BRL52 would be required to question the consistency of the 8-month downtrend.

Rio Tinto broke downwards from a 10-month range earlier this month and needs to sustain a push back above 4000p to indicate a return to medium-term demand dominance. Cliffs Natural Resources has a relatively similar pattern.

BHP Billiton has the strongest balance sheet of the three but has not been immune from the recent selling pressure. It has posted a succession of lower rally highs since April, accelerated lower earlier this month and found at least short-term support near last year's lows around 1750p. It will need to hold above that level on a pullback to confirm demand is beginning to return to medium-term dominance.

Fortescue Metals briefly broke downwards from the 10-month range but bounced impressively last week. The medium-term upside can continue to be given the benefit of the doubt provided it holds above A$5.10.

Atlas Iron lost momentum in the region of the 2008 peak from early February and failed to sustain the upward break three weeks ago. It bounced impressively from the lower side of the range and the region of the 200-day MA. The medium-term upside can continue to be given the benefit of the doubt provided it holds above the A$3 area.

Kumba Iron-Ore posted a largely weekly key reversal three weeks ago following a loss of momentum. It continues to hold the progression of rising lows and remains above the 200-day MA. A sustained move below ZAR43,000 would complete a medium-term top.

Ferrexpo broke its almost three-year progression of rising major reaction lows last week and while it has bounced impressively since, a sustained move back above 450p would be required to suggest demand is beginning to regain dominance.

Sesa Goa remains in a consistent medium-term downtrend and a break of the progression of lower rally highs, currently near INR300 would be required to question potential for additional downside. MMX Mineracao e Metalicos has a similar pattern.

Fortescue Metals and Atlas Iron remain the two most consistent trends and should be among some of the better performers if a recovery scenario prevails. Medium-term demand dominance will not be confirmed until they have found support above their lows, suggesting there should be ample opportunity to participate following a retest subject to one's own due diligence.