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A. Mexico is the largest silver mining country in the world, producing 5,541 tonnes (178 million oz) of silver, or 23% of the total mine production and 18% of total silver supply in 2020. Even though silver mining in Mexico goes back thousands of years to the Mayans, and it has dominated modern silver production for hundreds of years, Mexico continues to have some of the best exploration potential worldwide for the discovery of new silver orebodies and the development of new mines. The reasons for this are three-fold:
1) Plate Tectonics – Mexico is situated on the silver-enriched North American crust and when the Cocos plate under the Pacific Ocean was subducted below the North American plate, it partially melted both plates and the magmas rose up to form one of the longest volcanic belts in the world. These volcanoes heated the surrounding rocks, the ground water contained within them also heated up. Since hot water rises, as these waters moved up in the crust, they started dissolving metals out of the rocks they were passing though. When these waters rose within 1-2 kilometers of the then surface (now eroded), the drop of pressure caused these waters to deposit their dissolved minerals in fractures. After erosion removed the overlying rocks, these orebodies were exposed to surface and discovered by people, both ancient and modern.
2) Modern Exploration – Once outcropping orebodies have been discovered and mined, the main challenge for modern day exploration geologists is how to see below the earth’s surface in order to discover buried orebodies hiding below surface. Many new technologies have been developed over the past 70 years to help geologists discover blind orebodies, including detailed geological models of what orebodies look like, advanced geochemical sampling to detect metals that may have leaked upwards from orebodies below into surficial sediments, soils and rocks, and complex geophysical surveys to measure the magnetic, electrical and other effects of buried orebodies. Mexico has enjoyed a resurgence of mineral discoveries and the development of new mines in recent years as a result of modern exploration.
3) Free Trade – From 1961 to 1993, Mexico was effectively closed to foreign investment in the mining sector because of legislation restricting foreign ownership to 49% of Mexican mining companies and mining concessions, this changed to 100% ownership when Mexico joined NAFTA. Therefore, the Mexican mining sector prior to 1993 was dominated by a few very large Mexican companies who did not have easy access to either international sources of financing or modern exploration technologies, so there was very little investment in exploration to discover new orebodies. Since 1993, there has been a boom of foreign investment into exploration and mining in Mexico, which resulted in several new silver discoveries and mine expansions such as Penasquito, Fresnillo and many more.