Overview of the Geology and Mineral Industry of Nicaragua

Abstract

This paper is a synthesis and update of the geology of Nicaragua and a discussion of metallic and non-metallic mineral deposits. Nicaragua is divided into 15 departments and 2 autonomous territories, within an area of 130,700 km2. The geologic environments include Paleozoic crystalline basement rocks, Mesozoic sedimentary and intrusive rocks, nearly continuous sedimentary sequences of Late Cretaceous to Pleistocene age, a broad area of Tertiary volcanic rocks, and Quaternary sedimentary and volcanic rocks that include several active volcanoes. These rocks have a dominant continental crust affiliation and are assigned to the Chortis Block, although there is evidence of fragments of oceanic-crust material. The structural framework is controlled largely by the NW-trending Middle America Trench, which marks the boundary between the Cocos and Caribbean plates. This trend is manifest in the Nicaraguan Depression, the chain of volcanoes that extend from western Panama to El Salvador, as well as fold axes within a forearc depositional basin. East of the Nicaraguan Depression, a northeast structural trend becomes important. There are some 94 metallic and 46 nonmetallic mineral deposits within the various geologic environments. Gold is mined from three deposits—Limon, Bonanza, and La Libertad—and limestone, gypsum, aggregates, and clay minerals are mined at six quarries. Nicaragua is the leading gold-producing country in Central America and the Caribbean Basin. Since the late 1930s more than eight million ounces of gold have been mined, mainly from epithermal and mesothermal veins (Limon, Bonanza), skarn zones (Siuna, Rosita), and various placer deposits. Geologic reserves are estimated at 6.5 million ounces. Other mineral commodities include silver, copper, zinc, limestone, aggregates, gypsum, and clay minerals. Brief descriptions of these and several other commodities are provided along with production statistics and general location maps. As a result of political unrest and nationalization of many foreign assets during the 1970s and 1980s, little exploration was conducted. However, the election of a stable, democratic government in the early 1990s and a revision of foreign investment regulations has resulted in an increase in exploration activity; nevertheless, much of the country remains underexplored.