By Fabian Cambero and Divya Rajagopal

SANTIAGO, April 14 (Reuters) – Lundin Mining Corp's bid for control of Chile's Caserones copper mine comes despite ongoing uncertainty over potential policy changes to royalties and taxes, an indication that investors may be regaining confidence in the world no.1 copper-producing country.

Lundin last month agreed to pay $950 million for 51% control of the mine, calling the deal "an endorsement that we believe the mining royalty and taxation discussions are trending in the right direction."

The deal caused some surprise. In the past 18 months, mining giants have been vocal about concerns in Chile. BHP Group Ltd said it might reevaluate its investments depending on new tax plans by the government, while Freeport-McMoRan Inc has said it would pause expansion plans in Chile, citing political uncertainty.

But with the outlook looking rosier for investment and global demand surging for the key green energy metal, reluctance has diminished, experts and officials say.

Chile's mining minister, Marcela Hernando, told Reuters on Thursday she felt "confident" that the concerns of the industry had been taken into account with the royalty proposals and that she had seen hints investment was starting to improve.

"What one observes are signs, you see how some investments have materialized, how a very important deal was completed a few weeks ago," she said, referring to the Caserones purchase.

"We aren't worried investments are going to be scared away."

A proposed new constitution that, among other changes, would have given the state greater control over mining was rejected by voters last September, while an ambitious tax overhaul plan was voted down by Congress in March.

Meanwhile, another government plan for new royalties on mining, currently moving through Congress, has also been tempered amid industry complaints that an increased tax burden at a time when deposits were facing decreased production would hurt the country's competitiveness.

"As the proposed bill has moderated, some companies have gotten to a risk level compatible with their investment decisions, as happened with Lundin," said Juan Carlos Guajardo, head of the Plusmining consulting agency in Santiago.

"Some companies have a more optimistic vision about the final evolution of the royalty bill, which is sparking investment decisions, but there are others that are still in 'wait-and-see' mode."

Canada-based Teck Resources has also recently boosted investment in Chile, submitting for environmental approval this year a $3 billion project to increase capacity at its Quebrada Blanca 2 mine.

But BHP said its stance on investment in Chile had not changed. Freeport did not reply to a request for comment.

Lundin said it was considering raising its stake to 70% of the mine for an additional $350 million, but that it would "continue to evaluate any potential royalty and taxation changes" as a factor in that decision.

ENVIRONMENTAL CONCERNS

Lundin's purchase from JX Nippon Mining & Metals comes at a time when companies are seeing longer delays for permits as opposition has risen from local communities. Some projects have been rejected by the state or by courts on environmental impact concerns.

Caserones, located 4,300 meters above sea level, has itself faced strikes by workers and lawsuits by farmers, who have complained about water over-extraction.

Chilean courts have since approved plans from JX Nippon to rectify environmental damage and Lundin told Reuters one of the company's "primary objectives is to minimize potential environmental impacts through implementation of environmental management controls."

The company added that its nearby Candelaria operation uses desalinated water and has a guaranteed minimum of 80% of renewably-sourced electricity.

Lundin remains confident in the future of the Caserones project, which began operations in 2014 and has annual output of 100,000 tonnes of copper. Peter Rockandel, Lundin Mining's CEO, said the firm had "no concerns" of what lay ahead in a conference call following the announcement of the deal.

The purchase is emblematic of the emerging copper industry trend of buy versus build, said Christopher LaFemina, an equity analyst at Jefferies, with falling share prices and ballooning development costs favoring purchasing, rather than constructing, new mines, even at "premium prices."

"The optimal time to pursue sizable acquisitions is now," LaFemina said in a report, adding that the window might close if investors wait for "the macro environment to improve." (Reporting by Fabian Cambero and Divya Rajagopal; editing by Alexander Villegas, Ernest Scheyder and Rosalba O'Brien)