SUPERIOR, Ariz.—One of the world’s largest untapped copper deposits sits 7,000 feet below the Earth’s surface. It is a lode that operator Rio Tinto RIO +1.70% PLC wouldn’t have touched—until now. Not that long ago, an abundance of high-grade copper could be mined out of shallower open pits. But as those deposits are depleted and high-grade copper becomes tougher to find, firms such as Rio have been compelled to mine deeper underground. Advances in mining technology are making that possible—just as developments in oil and gas drilling heralded the fracking revolution. Now, using everything from sensors and data analytics to...