28/09/2026
Pegmatite emplacement during post-orogenic cooling and extension: Constraints from multi-sensor high resolution remote sensing and structural analysis of one of the largest pegmatite swarms on Earth
Abstract
"Pegmatites form typically in swarms of tens to thousands of sheeted intrusions that may display regional fractionation trends that indicate zones of pegmatite mineralization or a potential parental granite. To substantiate these and other spatial relationships concerning pegmatite formation, studies that address the structural–tectonic relationships of an entire swarm are necessary. In the Seridó Pegmatite Province (NE Brazil), we employed remote sensing multispectral images with subsequent field validation, and identified more than 10,000 pegmatite bodies, with length and orientation precision, over the southeastern 20% of the Seridó Belt. Structural criteria, from distribution of pegmatite-host rock discordance to power law length scaling indicate the Seridó Pegmatite Province was formed mainly after regional transcurrent shearing and without control of bounding shear zones, by a combination of forceful migration through intact rock, and injection of pegmatite-forming melts in pre-existing fracture networks. Orientation distributions of discordant pegmatites are compatible with a near-hydrostatic extensional stress setting developed in an episode of renewed regional cooling, and match the NNE trend of deep-seated modeled elongate dome structures. Due to the 65 Myr hiatus separating pegmatite emplacement from the peak of HT-LP metamorphism, and the lack of a parental granite, we estimate that the ca. 3,160×106 m3 of pegmatite in over 10,000 bodies could potentially constitute the largest pegmatite swarm on Earth. It was likely formed after orogeny by release of residual melts fractionated from deep, slowly cooled plutons generated by melting of diverse rock types in the orogenic crust. This new survey may help guide future critical mineral exploration efforts and testing pegmatite petrogenesis models."
"Fig. 1. Geological map of the eastern Seridó Belt. The three largest sub-swarms are named in white (i.e. Mufumbu-Trigueiro, Boa Sorte and Malhada Limpa). All pegmatite traces were drawn with 0.26 mm width, equivalent to 117 m at this scale. Crystallization ages for the Acari and Totoró plutons were obtained by Archanjo et al. (2013) from U-Pb zircon ages, for the Picuí granite was obtained by Hollanda et al. (2017), and for the pegmatites of the Mufumbu-Trigueiro region by Baumgartner et al. (2006) from U-Pb columbite ages (except for the 528 Ma monazite age which is for a pegmatitic granite). All geological features (geological units, pegmatites and structures) were mapped based on remote sensing, field data, and airborne geophysics, while comparing and observing geological maps in Archanjo et al. (2013), Cioffi et al. (2021), Araújo et al. (2001), and Costa et al. (2019). All maps and geolocations shown in this study are in WGS84 (geographic coordinates or UTM24S)."
Source:
Ávila, C. F., Hollanda, M. H. B., Neto, J. A. S., Figueiredo, E., Rodrigues, M., Macêdo Filho, A. A., & Fossen, H. (2026). Pegmatite emplacement during post-orogenic cooling and extension: Constraints from multi-sensor high resolution remote sensing and structural analysis of one of the largest pegmatite swarms on Earth. Journal of Structural Geology, 105811.
https://doi.org/10.1016/j.jsg.2026.105811
