A total of 405 prospecting licence applications have been accepted from Neptune Minerals (AIM: NPM) by Japan's Ministry for Economic Trade & Industry.

Subsidiary Neptune Minerals Japan KK lodged the applications that cover seafloor massive sulphide (SMS) prospective features in Japanese territorial waters, 500 kilometres south of Tokyo and adjacent to three areas covered by Neptune's existing licence applications.

Neptune's chief executive Dr Simon McDonald, said the 405 applications cover 1,400 square kilometres within the Izu-Bonin Arc, a volcanic island arc and associated back-arc basin.

Neptune's existing applications cover three seamounts - Bayonnaise, Myojin and Myojinsho Knolls - all well-researched SMS deposits.

One of these deposits, Sunrise, has been estimated by Japanese researchers to cover an area of 400 metres x 400m with a sulphide mound accumulations up to 30m thick, said McDonald.

Neptune has utilised its early-mover advantage and good relationships with local researchers to apply for prospective acreage located close to potential customers and resource-hungry markets, he said.

Meanwhile in the Kermadec Trench project which extends off the east coast of NZ's North Island the company has reported that an engineering scoping study has shown attractive economics for seafloor mining.

The report on the NZ operation was by consultancy and engineering company Genesis which is associated with Technip, a leader in engineering and project management for the global oil and gas industry.

McDonald said Neptune was evaluating contract mining operations that could see a contractor build, own and operate all the mining production assets that would minimise Neptune's capital raising requirements.

Technip had recommended a mining system incorporating a dynamically-positioned production vessel, a flexible production riser and an airlift pumping system connected at the seafloor to an ore crusher and seafloor miner.

The advantage of this technology is that it can be used on a range of SMS deposits in multiple locations, the company said.

The scoping study showed the tonnes of SMS ore to be mined could be 16.2 Mt, with operating costs per tonne of $US9 and total capital expenditure of $US501.1 M.

The NZ project is called Project Trident and the company has a target of beginning pilot mining in 2010.

In global mining news terms the quest by Neptune has been over-shadowed by the high profile activities of the TSX and AIM listed Nautilus Minerals Inc which was originally an Australian initiative but which now has some of the world's biggest mining companies on its share registry. Nautilus has advanced seafloor mine assessment projects off Papua New Guinea.