Chronological sequence of charcas igneous complex and their relationships with Zn–Pb–Ag mineralization events, San Luis Potosi state, Mexico

Abstract

The Charcas Intrusive Complex (CIC), comprised of monzogranites and granodiorites is located at the eastern edge of the Mesa Central in México. The CIC was dated by U/Pb on zircon crystals, from Tithonian to Rupelian ages and three distinct magmatic pulses were identified: (1) Tithonian (∼150 Ma), (3) Ypresian to Lutetian (∼55–∼44 Ma), and (3) Rupelian (∼30–∼27 Ma). The Early Cretaceous to Lutetian major and trace element magma compositions, suggest that the arc monzogranites were emplaced in a growing continental crust while the Ypresian granodiorites show typical boron enrichment observed in central Mexico. The Lutetian and Rupelian granodiorites plot inside the field of cordilleran granites or continental arc magmatism where magma mixing is common and are considered as I-type granites presenting high concentration of Ba and Sr, and high Sr/Y and La/Yb ratio values. The most developed and intensely mineralized (Zn–Pb) hydrothermal event is Lutetian in age, corresponding to the peak of magma fertility conditions determined by zircon trace element chemistry and is well correlated to the skarn occurrences at around ∼47 Ma. The Ag mineralization event is related to the Rupelian dike's emplacement. Inherited zircon grains found in the magmas highlight the shallow position of the magma plumbing and the importance of the early Cretaceous magmatic intrusion in the formation of the Rupelian silver mineralization.