Analyze the relationship between 'Turquoise Hill Resources' and 'gold' within the context of the input sentence.
Options: product/material produced, member of, employer, distribution format

July 15 (Reuters) - A project financing agreement for the underground expansion of Oyu Tolgoi, a massive copper and gold mine in Mongolia, is expected to be signed by year end, mine owner Rio Tinto (LSE: RIO.L - news ) 's Turquoise Hill Resources (Toronto: IVN.TO - news ) unit said on Wednesday.
product/material produced