It's widely speculated that BHP Billiton's (BLT.L, £14.87 a share) hunger to swallow up world No 2 miner Rio Tinto (RIO.L, £49.53) is likely to trigger a surge in corporate activity in the global resources sector. If BHP Billiton's vision materializes, the resulting entity would boast a market value of at least $350bn, and rank as one of the five most valuable stocks in the world.

The record, however, shows that corporate activity in the global resources sector has been somewhat pedestrian, relative to the strength of the bull market in dollar commodity and metal prices, now in its fifth consecutive year. The way things have turned out can probably be measured around the only really big deal seen in 2005, viz., BHP Billiton's $7.3bn cash acquisition of Australia's WMC Resources.

In the past year or so, Inco fell to CVRD (NYSE: RIO, $32.43), now the world's No 2 miner, after BHP Billiton; Phelps Dodge fell to Freeport McMoRan (FCX, $90.06); Noranda and Falconbridge amalgamated into Falconbridge, only to be swallowed by Xstrata (XTA.L, £28.82) for a rich $18bn in cash.

Then of course there was the mega, friendly white knight $38bn Rio Tinto bid for Alcan, announced July 12. The Rio Tinto offer, when made, was at a huge 33% premium to the value of the bid announced by Alcoa (AA, $35.17) on May 7. The Rio Tinto-Alcan deal went through just as Rio Tinto potentially fell into BHP Billiton's bear hold.

Long life, low cost, top class mining assets remain rare. To see this, track the progress of Anglo Swiss miner Xstrata, which for some time ranked as a leading corporate predator of this minerals cycle. Late in March this year, it bid C$18.50 a share for LionOre, giving a potential transaction value of C$4.6bn, when including outstanding debt and convertibles. Xstrata's bid for LionOre was well covered, but was just an opening salvo: Russia's muscular Norilsk (NILSY, $297.73) announced a far higher counter bid for LionOre.

LionOre had also been especially attractive to Xstrata's acquisition nemesis, BHP Billiton, which outbid Xstrata for WMC. This was a plum of a deal: the BHP Billiton/WMC west Australian nickel assets held potentially intimate synergies with LionOre's Activox hydrometallurgical process technology. Industry experts saw LionOre's Honeymoon Well 1m-ton contained nickel project as a look-alike in many respects for the jewel of BHP Billiton's nickel business, Mt Keith. But BHP Billiton stood aside and LionOre eventually fell to Norilsk.

Xstrata, however, made a rich and successful $1bn bid for South Africa's Eland Platinum. Late last month, it offered A$23 a share for Australian nickel digger Jubilee. The A$3.1bn deal looks strained, given that Jubilee is literally surrounded by BHP Billiton operations, or mines under contact to BHP Billiton.

Xstrata has apparently run out of steam, highlighting the painful reality that the proverbial low-hanging fruit in global resources is no more. BHP Billiton continues to execute a different plan, in showing its hunger for Rio Tinto, underpinned by a host of compelling reasons as to why the two should join.

To put it simply, BHP Billiton seeks to expand its base of world class assets. When it bought WMC in 2005, it acquired a complementary nickel business, plus Olympic Dam, the world's fourth largest copper resource and the world's 10th largest gold deposit. The takeover also established BHP Billiton as a major producer of uranium with the single largest resource base in the world.

The many scavengers in the investment community will continue to speculate about the next big deal, an activity long shown to be a mug's game. Rewind, for instance, to August last year, when JP Morgan speculated that BHP Billiton and Rio Tinto would be swallowed up by private equity. Around the same time, Société Générale reckoned that Anglo American (AAL.L, £28.17) was "predator rather than prey", following speculation that Xstrata, Rio Tinto and CVRD had hired financial advisers ahead of possible action.