Commodities giant Glencore is expected to kick off a much-anticipated $10 billion listing this week, with the publication of an Intention to Float document that will confirm its plans after months of speculation.

The listing -- which could be the largest to date in London and one of the largest in Europe -- will force the Swiss-based firm to shed its once-fabled secrecy and open up its huge and successful mining and trading operations to increased scrutiny.

It will also create massive paper wealth, dissolving the group's partnership structure and handing the 485 employees who own the group millions of dollars on average in shares -- though all are expected to be locked in for at least a year, with top management unable to sell for five years.

Glencore is expected to list roughly a 20 percent stake, which, along with short lock-ups on some of the existing shares, would give it the free float necessary to secure a spot in London's top share index.

Sources familiar with the matter have said Glencore and its advisors are working to issue the ITF document in London around mid-April -- this week -- though that could still be delayed.

ITFs, which are not a legal requirement, vary from brief statements setting out little more than a company's sketched plan to list at some stage to hefty documents listing details on timing, finances and management.

Glencore is expected to provide extensive detail, including the name of its new chairman. The Sunday Times named Simon Murray, a Hong Kong businessman and former French foreign legionnaire, as a frontrunner among three candidates.

Murray, currently chairman of Asian private equity firm GEMS, could not be reached for comment on Sunday.

Glencore, which has kept its plans under wraps since briefing analysts more than a month ago, has consistently declined to comment on the timeline of any IPO. The firm also declined to comment on Sunday on the search for a chairman.

MUST OWN IN TURBULENT MARKETS?

Sources familiar with the situation have said the firm, valued by one analyst at about $60 billion, has held positive talks with investors in recent weeks, and these are expected to have included discussions with potential cornerstone investors for the Hong Kong portion of the listing.

Citi , Morgan Stanley and Credit Suisse are likely to serve as joint global co-ordinators, with Bank of America Merrill Lynch and BNP Paribas as bookrunners. Barclays Capital , Societe Generale and UBS are likely to make up a third tier of banks advising on the IPO, according to sources familiar with the matter.

Markets, however, remain tough.

Although equities markets have rebounded since a spike in volatility last month on fears of a nuclear crisis in Japan and unrest in the Arab world, bankers say investor willingness to back IPOs in general remains limited.

The tail risks are still quite elevated with concerns over the Middle East, the oil price, the Portuguese bailout, aftershocks in Japan, said one. The market is very jumpy.

A string of companies have pressed ahead with plans for new listings, but are finding that with a glut of issuers competing for attention in a still-uncertain market buyers can afford to be demanding on what price they are willing to pay.

Technology company Edwards scrapped its listing on Friday, the largest European float due last week, after a group of other companies bowed to market pressure and sold shares at the lower end of their planned price ranges.

But people close to the Glencore mega-deal, are confident it will not fall foul of the same problems.

It falls into the 'must own' category, said one source close to the deal. It is appealing to a much broader base of investors and is going to go straight into major indices.

If, as expected, Glencore proceeds with the listing, it would likely be making its debut around mid-May.

Glencore, planning a dual listing in London and Hong Kong, has received listing approval from the Hong Kong exchange. It has not said how it would split the IPO.

(Additional reporting by Quentin Webb; Editing by Sitaraman Shankar and Jon Loades-Carter)