THE RELATIONSHIP BETWEEN IGNEOUS ACTIVITY AND MINERALIZATION WITHIN THE LEEVILLE MINING COMPLEX

The target of Newmont’s Leeville Mining Complex is a concentration of disseminated gold deposits located 16 km North of Carlin, NV along the Carlin Trend. The deposit is hosted in limestone and crosscut by dozens of igneous dikes that influence ore grade and location. Therefore, understanding the role these dikes played in the development of the Carlin-Type mineralization at Leeville is important for genetic models of the ore formation. One school of thought attributes the dikes to ore formation, as heat sources driving hydrothermal convection. Others believe the dikes play no role in the mineralization. Although the source of the ore bearing fluids remains debated, mineralization along the Carlin trend is firmly established to have occurred in the Eocene. Regionally, four major episodes of magmatism have occurred, and can be summarized as: a Jurassic diorite-granodiorite laccolith emplacement (158 ma), a cretaceous granitic intrusion (112 ma), an abundance of Eocene silicic to intermediate dikes (40-36 ma), and a series of Miocene rhyolite lavas (15 ma). U-Pb dating of zircons from 2 dikes at Leeville is being undertaken to isolate the individual igneous dikes for comparison with major and trace element geochemical and petrographic data. These data will be combined with previous work done in the area to interpret the effects of the igneous dikes on local mineralization, as well as correlate the rocks with regional igneous activity. The end goal is to create a more complete genetic model of the deposit, increase ore control accuracy, and improve near-mine exploration methods at the Leeville Mining Complex.