Marine phosphate mining hopeful Minemakers Ltd has taken a substantial stake in joint venture partner Union Resources Ltd, which it recently trumped in a takeover war for Bonaparte Diamond Mines NL.

Shares in Union, a phosphate and zinc exploration minnow, jumped 0.2 cent, or 40 per cent, to 0.7 cent at 1251 AEST.

Minemakers purchased a 9.64 per cent interest in Union through a scrip deal with Toronto Stock Exchange-listed base metals miner Lundin Mining AB.

Under the deal, Lundin will be issued one new Minemakers share for every 80 Union shares that Lundin holds.

Lundin's parcel of 2.2 million Minemakers shares is worth about $1.1 million based on Minemakers' share price at 1253 AEST of 52.5 cents, down half a cent.

Minemakers has amassed an 85.84 per cent stake in Bonaparte under a scrip offer that valued the target at $9 million when it was first offered in March.

It took control of the company on May 8.

Minemakers on Wednesday requested a meeting of Bonaparte shareholders with a resolution to de-list the one-time diamond miner from the Australian stock exchange.

It also extended its takeover offer by seven days to July 8 to allow it to mop up the remaining shares in its target.

Minemakers urged Bonaparte shareholders who had accepted Union's now-expired takeover offer to accept the Minemakers offer.

They could do so because Union's offer closed on June 29 while it was conditional.

Union's offer valued the target at about $13 million when it was made in April.

Minemakers investor relations manager, Dean Richardson, told AAP in May that Minemakers' offer, while less on paper than Union's, was a superior bid.

This was because Minemakers offered Bonaparte shareholders greater certainty that the capital required to develop Bonaparte's marine phosphate project offshore from Namibia, in south-west Africa, could be raised within the proposed timeline.

Union and Bonaparte each hold a 42.5 per cent stake in the project.