Boletín de la Sociedad Geológica Mexicana

Volumen 74, núm. 3, A200722, 2022



Subducted iron and glassy spherules in the upper mantle?

¿Esférulas de hierro y vítreas subducidas en el manto superior?


José M. González-Jiménez1,2,*, Ivanina Sergeeva3, Thomas N. Kerestedjian3, Fernando Gervilla1,2


Instituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad de Granada, Avda. de las Palmeras 4, 18100, Armilla, Granada, Spain.

Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, 18002, Granada, Spain.

Geological Institute, Bulgarian Academy of Sciences, 24 Georgi Bonchev Str., 1113, Sofia, Bulgaria.

* Corresponding author: (J.M. González- Jiménez) This email address is being protected from spambots. You need JavaScript enabled to view it.


How to cite this article:

González-Jiménez, J.M., Sergeeva, I., Kerestedjian, T.N., Gervilla, F., 2022, Subducted iron and glassy spherules in the upper mantle?: Boletín de la Sociedad Geológica Mexicana, 74 (3), A200722.

Manuscript received: June 26, 2022; Corrected manuscript received: July 19, 2022; Manuscript accepted: July 24, 2022.



Spherules are documented in ophiolitic mantle rocks such as peridotites and associated chromitites. They consist of: (1) native iron having variable amounts of Ni with/without inclusions of silicate glass or oxides (wüstite), (2) dendritic intergrowth of oxides (magnetite, wüstite and hematite) with/without silicate glass and, (3) silicate glass. Consensually, they are interpreted as indigenous to chromitites and related with high-temperature processes operating in the Earth’s upper mantle. However, their similarity with terrestrial and extraterrestrial spherules found in other settings of the geological record is remarkable. We raise the question on such indigenous origin, relating them to volcanic and cosmic material recycled back to the mantle wedge where chromitites form during subduction.

Keywords: spherules, iron, glass, upper mantle, chromitite, subduction.