The eight organizations, which include pension funds from across Canada and elsewhere, are objecting to the decision to pay Thornton a signing bonus on top of his regular compensation.
The groups say that together the payments amount to a $17-million package, which they call "unprecedented in Canada."
"This compensation is inconsistent with the governance principle of pay-for-performance and is therefore disproportionate and sets a troubling precedent in Canadian capital markets," the group said in a release.
Others among the concerned investment group include the Canada Pension Plan Investment Board, the Ontario Teachers Pension Plan, the Ontario Municipal Employees Retirement System (OMERS), Alberta Investment Management Corp., the British Columbia Investment Management Corp. and international firm Hermes Equity Ownership Services.
Thornton, who had been a Barrick director, was appointed co-chairman in June 2012 at the same time that chief executive Jamie Sokalsky was promoted from chief financial officer to replace Aaron Regent.
In Barrick's financial filings, the company says in addition to the $11.9-million signing bonus, Thornton received a salary of $1.4 million, $2 million in share-based awards, a bonus of $1.4 million and $213,000 in pension value for 2012.
Barrick said Thornton, who used the after-tax proceeds of the signing bonus to buy 177,500 shares in the company, received the payment "in recognition of his unique skills and expertise and contributions."
The investors say they've expressed their concern in a letter to Barrick's chairman and will vote against both the executive compensation resolution and the election of the compensation committee at Barrick's annual meeting next Wednesday.
The concern by the money managers follows a sharp drop in Barrick shares in recent days amid a plunge in the price of gold and a Chilean court decision last week that ordered a halt to construction at the miner's $8-billion Pascua-Lama project due to environmental concerns.
Moody's Investors Service also placed Barrick under review for a potential ratings downgrade this week.
Barrick shares, which have fallen more than 40 per cent so far this year, closed up 21 cents at $18.65 on the Toronto Stock Exchange on Friday.
Work on Barrick's Pascua-Lama project was suspended by the appeals court in the northern Chilean city of Copiapo amid environmental concerns about the construction of the world's highest-altitude gold and silver mine.
The start date for the mine, which straddles the Andean border with Argentina, has already been delayed by more than six months to the second half of 2014. Cost overruns have seen the price tag rise from $3 billion to more than $8 billion.
Barrick has said it will work to address environmental and other regulatory requirements on the project in Chile, while construction will continue on the portion of the project in Argentina.