Shares in Tullow Oil (LSE: TLW) have fallen by as much as 8% today following the release of disappointing news flow. The oil producer said that following a recent inspection of the turret area of the Jubilee Floating Production Storage and Offtake vessel, a potential issue was identified with the turret bearing.

As a precaution, Tullow has put in place additional operating procedures to monitor the turret bearing and reduce the degree of rotation of the vessel. In addition, the turret manufacturer will now undertake further offshore examinations, while Tullow will work with it to decide if any further measures are required.

Although disappointing, oil production and gas export is continuing as normal and despite today’s share price fall, Tullow is still up by 43% in the last month. A key reason for this is the expected increase in its production and profitability in the second half of the year, resulting from its project TEN coming onstream in Ghana. This has the potential to be a game-changer for the company and its shares could continue their upward momentum over the medium term.

Gold standard

Also rising in the last month have been shares in precious metals producer Fresnillo (LSE: FRES). They’re up by 33% and have benefitted from the rising price of gold as investors have flocked to the perceived safe haven during a time of considerable uncertainty.

While markets are now staging a comeback, gold could remain popular and its price may continue to rise since the prospect of interest rate increases in the US has reduced. This should have a positive impact on gold since its lack of interest payments are less problematic while interest rates are near rock bottom.

With Fresnillo forecast to increase its earnings by 81% in the current year, investor sentiment could continue to improve. And with Fresnillo trading on a price-to-earnings growth (PEG) ratio of only 0.4, now seems to be a good time to buy it for the long term – especially since dividends are due to rise by 92% in 2016.

Long-term view

Meanwhile, shares in Rio Tinto (LSE: RIO) have also performed well in the last month, with them rising in value by 15%. Although the prospects for the price of iron ore are relatively downbeat in the short run since China’s GDP growth rate continues to fall, Rio Tinto appears to be well-placed to overcome the present difficulties. Evidence of this can be seen in its recent update that highlighted its strong cash flow and sound cost control.

As a result, Rio Tinto’s position within the iron ore space could improve relative to its peers, and in the long run this may equate to greater market share. While buying now may lead to high long-term profits for investors, there remains a high degree of uncertainty and volatility is likely to be high. But with Rio Tinto trading on a forward price-to-earnings (P/E) ratio of 12.8, it seems to be a strong buy at the present time.

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Peter Stephens owns shares of Rio Tinto. The Motley Fool UK has recommended Rio Tinto and Tullow Oil. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.