Crystal Size Distribution (CSD) as a proxy of granitoid magmatic processes in southern Mexico
Distribución del tamaño de cristales (CSD) como indicador de los procesos magmáticos de granitoides en el Sur de México
María del Sol Hernández-Bernal1,*, Pedro Corona-Chávez2, Guillermo Suazo-Cruz3, Elesbaan Reséndiz-Zarco3, Ninfa Lizbeth Romero-Carrillo4, Stefano Poli5
1 Escuela Nacional de Estudios Superiores, Unidad Morelia, Universidad Nacional Autónoma de México, Antigua Carretera a Pátzcuaro 8701, S/N, Indeco la Huerta, 58190, Morelia, Michoacán, México.
2 Instituto de Investigaciones en Ciencias de la Tierra, Universidad Michoacana de San Nicolás de Hidalgo, Avenida Francisco J. Mújica S/N, Edificio U-3, Ciudad Universitaria, 58030, Morelia, Michoacán, México.
3 Maestría en Geociencias y Planificación del Territorio, Universidad Michoacana de San Nicolás de Hidalgo, Avenida Francisco J. Mújica S/N, Edificio U-3, Ciudad Universitaria, 58030, Morelia, Michoacán, México.
4 Facultad de Ciencias de la Tierra, Universidad Autónoma de Nuevo León, Carretera a Cerro Prieto Km 8, Ejido Ex-hacienda de Guadalupe, 67700 Linares, Nuevo León, México.
5 Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Sandro Botticelli, 23, 20133, Milano, Italy.
Corresponding author: (M.S. Hernández-Bernal) This email address is being protected from spambots. You need JavaScript enabled to view it.
How to cite this article:
Hernández-Bernal, M.S., Corona-Chávez, P., Suazo-Cruz, G., Reséndiz-Zarco, E., Romero- Carrillo, N.L., Poli, S., 2025, Crystal Size Distribution (CSD) as a proxy of granitoid magmatic processes in southern Mexico: Boletín de la Sociedad Geológica Mexicana, 77(2), A120325. http://dx.doi.org/10.18268/BSGM2025v77n2a120325
Manuscript received: February 2, 2025; Corrected manuscript received: February 28, 2025; Manuscript accepted: March 3, 2025.
ABSTRACT
Magmatic differentiation is a key process behind the diversity of continental crust rocks. Crystal Size Distribution (CSD) is a stereological-textural method that provides insights into nucleation and crystal growth, especially when integrated with geochemical and petrological data. While most CSD studies focus on igneous textures in volcanic rocks, particularly in K-feldspar and plagioclase crystals, fewer address granitoid textures. This study presents CSD analyses of eight plutonic bodies from Michoacán, southern Mexico, supported by geochemical, chronological, and thermobarometric data. These granitoids range in composition from tonalite to granite and display calc- alkaline arc signatures in major and trace elements. U-Pb zircon ages span from the Jurassic to the Miocene (164.8-20.6 Ma), suggesting long-term magmatic activity. CSD plots of plagioclase crystals indicate open magmatic systems with variable conditions, inconsistent with simple cooling. Granitoids hosting mafic microgranular enclaves show concave-up CSD trends and abrupt slope changes, implying magma mixing. Estimated average residence times (τ) range from 17 to 67 years for crystals <0.5 mm and 86 to 187 years for larger crystals (>0.5 mm), aligning with theoretical diffusion times during magma mixing and assimilation in intermediate to silicic systems. Combined CSD and thermobarometric data propose an inverse relationship between magma temperature, silica content, and crystal residence time at shallow emplacement levels. These findings provide new insights into the dynamics of crustal magma chambers and the physical parameters influencing pluton emplacement in arc-related settings.
Keywords: Crystal Size Distribution, Residence Times, Magmatic Processes, Magmatic arc, southern México.
