NEW YORK (Reuters) - A U.S. judge on Thursday dismissed some claims in a lawsuit accusing Rio Tinto and its former CEO Jean-Sebastien Jacques of defrauding investors by concealing problems developing the $5.3 billion Oyu Tolgoi copper and gold mine in Mongolia.

U.S. District Judge Lewis Liman in Manhattan addressed recently added claims that Rio Tinto knowingly concealed how it would miss a deadline for "draw bell" blasting, a key milestone, while Jacques hid delays and associated cost overruns.

In a 40-page decision, Liman dismissed the claim against Rio Tinto because it was Turquoise Hill Resources, which owned 66% of the mine with Mongolia owning the rest, that said the draw bell schedule was on track.

Liman said Rio Tinto was not liable for that statement even though an affiliate of the Anglo-Australian mining giant was Turquoise Hill's majority owner.

The judge also dismissed claims that Jacques intended to defraud shareholders in statements about the mine beginning in October 2018, because those statements suggested he believed Rio Tinto's timetable announced that month was accurate.

Claims against Jacques based on earlier statements survived, because shareholders adequately alleged that he knew delays existed when the class period began, Liman said.

Led by funds advised by Pentwater Capital Management, the lawsuit seeks damages on behalf of shareholders of Montreal-based Turquoise from July 17, 2018 to July 31, 2019.

Pentwater's lawyers did not immediately respond to requests for comment. Lawyers for Rio Tinto and Jacques did not immediately respond to similar requests.

Jacques led Rio Tinto for four years before stepping down in March 2021, following pressure from shareholders seeking accountability for the company's destruction of two culturally significant Aboriginal rock shelters in May 2020.

Rio Tinto did not break any laws when working around the Juukan Gorge sites in Western Australia. The sites showed evidence of human habitation dating back 46,000 years.

The case is In re Turquoise Hill Resources Ltd Securities Litigation, U.S. District Court, Southern District of New York, No. 20-08585.