First Insights into the Crystallization Conditions of the Belvís de Monroy Granite-Pegmatite System (Central Iberian Zone, Spain)

The Belvís de Monroy granite-pegmatite system (Cáceres, Spain) is located in the Central Iberian Zone and intrudes the Schist-Graywacke Complex between the Belvís de Monroy granite-pegmatite system and the Navalmoral de la Mata granites. This study presents detailed cartography, structural analysis, and mineralogical and petrographic descriptions of the six types of aplite-pegmatites and the associated quartz dikes occurring in the area. These include aplite-pegmatites with mafic minerals (T1); tourmaline-rich aplite-pegmatites with unidirectional solidification textures (T2); garnet-bearing aplite-pegmatites with unidirectional solidification textures (T3); simple aplites (T4); intragranitic aplite-pegmatites (T5); irregular aplitic masses (T6); and quartz segregates (T7). Structural evidence indicates that these pegmatites are not coeval, with T3, T4, and T7 being the oldest bodies; followed by T2; while T1, T5, and T6 represent the youngest dikes. However, the absence of structural interrelationships between all types does not allow a complete chronological sequence to be established. Textural features such as layering and unidirectional solidification textures indicate significant undercooling in T2 and T3, probably due to temperature drop and flux loss during early stages of crystallization. T2 displays internal zonation (textural, mineralogical, and chemical), suggesting variable undercooling, with stronger undercooling at the margins and a lower undercooling degree in the inner zones. The Belvís de Monroy pluton shares key characteristics with other highly evolved granites of the Central Iberian Zone that are considered parental magmatic chambers of Li-rich pegmatites. Given the fractionation degree and the spatial relationships between the Belvís de Monroy pluton and the nearby aplite-pegmatites, it can be deduced that these igneous materials are petrogenetically related. Nevertheless, despite numerous features shared with other pegmatitic fields from the Central Iberian Zone, the presence of graphic intergrowths and internal zoning in lithium bearing T2, not observed in other pegmatitic fields from Central Iberian Zone, attests to differences in the crystallization conditions. This study provides a detailed map and petrographic and structural characterization of the Belvís de Monroy granite-pegmatite system, including a comprehensive classification of the different types of aplite-pegmatites. This offers a solid basis for future exploration and research of this complex pegmatitic field. Moreover, this paper highlights the importance of the fieldwork in conjunction with detailed petrographic studies as a fundamental aspect of geological research.