Jaimes Lomelin, the 77-year-old Chief Executive Officer of silver and gold miner Fresnillo, is to retire next month to be succeeded by Fresnillo veteran Octavio Alvidréz, who is currently General Manager of Madeiro mine, one of the largest zinc mines in Mexico.Alvidréz was the unanimous choice of the board to succeed Lomelín. He will formally take on the role on August 15th, 2012, following a handover period.Lomelin served as Chief Executive Officer of Peñoles, which has an interest in the silver mine at Fresnillo, Mexico, for 26 years before taking on the same role at Fresnillo plc when it listed in London in 2008.Lomelin will remain on the Fresnillo board as a non-executive director.His successor, Octavio Alvidréz, joined Peñoles in August 1998. Since then he has held a number of senior operational and financial positions across Peñoles and Fresnillo, including that of Treasurer, Head of Investor Relations in London and Head of Procurement.Although at his age Lomelin is more than justified in taking retirement, the market does not like uncertainty, and reacted to the news of a new boss by marking down the shares, which were trading at about 1,380p just before the announcement. JH