Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia

Petrología Magnética aplicado a la caracterización de Diques Pegmatíticos en el Oriente Colombiano



Magnetite; oxygen fugacity; geothermobarometry; pegmatites; ilmenite (en)
magnetita, fugacidad de oxígeno, geotermobarometría, pegmatitas, ilmenita (es)



  • Carlos José Charry Universidad Nacional de Colombia
  • Juan Carlos Molano Universidad Nacional de Colombia
  • Leonardo Santacruz Universidad Nacional de Colombia
  • Janeth Sepulveda Servicio Geológico Colombiano

In the sector of San Jose, Macanal, and Tabaquen, in eastern Colombia, granitic rocks cut by pegmatite dikes and quartz veins appear with the presence of magnetite, ilmenite, and ilmenorutile. Using magnetic petrology and geochemistry concepts and methods, the main objective is to determine if these types of rocks are genetically related and how the fluid chemically evolves during its crystallization and cooling. This work was conducted in three stages. Petrography and opaque metallography for identifying the occurrence, paragenesis, and secondary processes that transform the oxides. In a second stage and utilizing an Electron Probe Microanalyzer (EPMA), 214 quantitative analyses (WDS) and four compositional maps for magnetite, ilmenite, and ilmenorutile were performed, measu- ring the oxides FeO, TiO2, V2O3, MgO, MnO, Nb2O5, Ta2O5, Al2O3, Ga2O3, NiO, CaO, Cr2O3, SnO, and WO3. Since magnetite and ilmenite are favorable geothermometers that also allow the calculation of oxygen fugacity, the ILMAT program was used to calculate these values. In closing, integrate the data with the magnetic susceptibility values. The results determine crystallization temperatures between 358-414 °C for the granitic-host rock and 402- 499 °C for pegmatites dykes, in a system where oxygen fugacity increases, the Mn2+ is enriched in the ilmenite, and magnetite preserves a low content of trace elements thorough the evolution of the fluid. Taken together with the martitization and exsolution of hematite and rutile within ilmenite found in the petrography, these results allow us to conclude that an oxide-silicate re-equilibration process controls the evolution of this magmatic-hy- drothermal fluid with a KUIlB cooling trend-type reaction. Based on the Al + Mn vs. Ti + V ratio, the signature of the magnetite is like the Lucky Friday mine’s signature studied by Nadoll. However, the analysis of the 95th percentile shows a different concentration of trace elements in the magnetite of both sectors. Therefore, a new field of discrimination is proposed for this environment of anorogenic pegmatites of the NYF family. Finally, the magnetic susceptibility is controlled only by the abundance of magnetite in each type of rock. The granitic host rocks have the highest susceptibility values, followed by pegmatites and quartz veins with the lowest.

En el sector de San José, Macanal y Tabaquén, en el oriente colombiano, afloran rocas graníticas cortadas por diques pegmatíticos y venas de cuarzo con presencia de magnetita, ilmenita e ilemnorutilo, estos tipos de rocas se encuentran relacionadas genéticamente. La magnetita y la ilmenita son buenos geotermómetros y permiten calcular la fugacidad de oxígeno con base en el contenido de elementos trazas. Con la microsonda electrónica EPMA se realizaron 214 análisis cuantitativos (WDS) y 4 mapas composicionales en estos tres minerales en los que se miden 14 elementos químicos. Los resultados permiten suponer temperaturas de cristalización entre 358 y 414°C para roca caja y 402 – 499°C en pegmatitas, un incremento de la fugacidad de oxígeno en el sistema, un enriquecimiento de Mn 2+ en la ilmenita y un bajo contenido de elementos trazas en la magnetita. Estos resulta- dos, sumados al registro de martitización y exsolución de hematita y rutilo en la ilmenita, permiten concluir que la evolución del fluido magmático – hidrotermal está siendo controlada por la reacción de reequilibrio KUILB del tipo óxido –silicato. La relación Al+Mn vs Ti+V ubica la firma de la magnetita en el campo de la mina Lucky Friday estudiado por Nadoll, sin embargo, el análisis del percentil 95 muestra un comportamiento distinto en los elementos trazas de la magnetita de ambos sectores, por lo tanto, se propone un nuevo campo de discrimina- ción para este ambiente de pegmatitas anorogénicas de la familia NYF. Por último, la susceptibilidad magnética está controlada únicamente por la abundancia de la magnetita en cada tipo de roca, encontrando que los grani- tos tienen los valores más altos de susceptibilidad, seguidas por las pegmatitas y por último las venas de cuarzo.


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How to Cite


Charry, C. J., Molano, J. C., Santacruz, L. and Sepulveda, J. (2023). Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia. Earth Sciences Research Journal, 27(1), 11–25.


Charry, C.J., Molano, J.C., Santacruz, L. and Sepulveda, J. 2023. Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia. Earth Sciences Research Journal. 27, 1 (May 2023), 11–25. DOI:


Charry, C. J.; Molano, J. C.; Santacruz, L.; Sepulveda, J. Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia. Earth sci. res. j. 2023, 27, 11-25.


CHARRY, C. J.; MOLANO, J. C.; SANTACRUZ, L.; SEPULVEDA, J. Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia. Earth Sciences Research Journal, [S. l.], v. 27, n. 1, p. 11–25, 2023. DOI: 10.15446/esrj.v27n1.102683. Disponível em: Acesso em: 26 sep. 2023.


Charry, Carlos José, Juan Carlos Molano, Leonardo Santacruz, and Janeth Sepulveda. 2023. “Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia”. Earth Sciences Research Journal 27 (1):11-25.


Charry, C. J., Molano, J. C., Santacruz, L. and Sepulveda, J. (2023) “Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia”, Earth Sciences Research Journal, 27(1), pp. 11–25. doi: 10.15446/esrj.v27n1.102683.


C. J. Charry, J. C. Molano, L. Santacruz, and J. Sepulveda, “Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia”, Earth sci. res. j., vol. 27, no. 1, pp. 11–25, May 2023.


Charry, C. J., J. C. Molano, L. Santacruz, and J. Sepulveda. “Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia”. Earth Sciences Research Journal, vol. 27, no. 1, May 2023, pp. 11-25, doi:10.15446/esrj.v27n1.102683.


Charry, Carlos José, Juan Carlos Molano, Leonardo Santacruz, and Janeth Sepulveda. “Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia”. Earth Sciences Research Journal 27, no. 1 (May 23, 2023): 11–25. Accessed September 26, 2023.


Charry CJ, Molano JC, Santacruz L, Sepulveda J. Magnetic Petrology applied to the characterization of Pegmatite Dykes in Eastern Colombia. Earth sci. res. j. [Internet]. 2023 May 23 [cited 2023 Sep. 26];27(1):11-25. Available from:

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