(Adds ASX filing, details of executive turnovers, analyst and Andrew Forrest quotes)

By Sameer Manekar and Roushni Nair

Sept 1 (Reuters) - Guy Debelle, the former Reserve Bank of Australia deputy governor, resigned from the board of Fortescue Metals Group's green energy unit on Friday, media reports said, continuing the run of abrupt departures by executives at the world's fourth largest miner.

Debelle has stepped down as a non-executive director from the board of Fortescue Future Industries (FFI), the green energy arm of Fortescue Metals Group, the Australian Financial Review reported.

In an exchange filing, critical minerals firm Tivan said Debelle will be joining its board as a non-executive director, but did not mention if he would leave FFI's board.

Fortescue did not respond to a Reuters request for comment.

This is the third senior executive departure from Fortescue just this week. Shares of the miner were trading 3.7% lower in early trade at A$20.64 as at 0012 GMT.

Debelle's exit comes days after Fortescue's metals division's CEO Fiona Hick announced her departure after just six months in the role, and on Thursday the division's finance chief Christine Morris stepped down after taking on the job three months ago.

Overseen by founder Andrew Forrest as executive chairman, Fortescue has struggled to keep senior management as it sets out to transform itself into a green energy superpower with a global footprint.

The iron ore giant logged a pretax impairment of $1 billion to its flagship Iron Bridge growth project in Western Australia and reported its lowest annual profit since 2020.

"Shareholders are going to be concerned about what and why all these people are leaving, and we're not really getting the answers," said Damian Rooney, Director of Equity Sales at Argonaut said.

"It's all good to wave your arms around and talk about going green, but at the end of the day, you still need to look after your shareholders who are investing money for growth, dividends and alike," Rooney said.

Executive chairman Andrew Forrest, who spoke to local media earlier this week, said CEO Hick stepped aside following differences of opinion over the firm’s green transition.

"What we have now is a literally galloping herd of people who want to see this company go green,” he said, according to The Australian.

"So if you want to step outside that, you’re given a choice. You’re not fired, there’s no disagreement, you’re just given a choice: step back in, or you call it," Forrest was quoted as saying.