Timing of Proterozoic magmatism in the Sunsas belt, Bolivian Precambrian Shield, SW Amazonian Craton

We present new U-Pb zircon and monazite ages from the Sunsas belt granitic magmatism in Bolivia, SW Amazonian Craton. The geochronological results revealed four major magmatic events recorded along the Sunsas belt domains. The older igneous event formed a granitic basement coeval to the Rio Apa Terrane (1.95 - 1.85 Ga) in the southern domain. The second magmatic episode is represented by 1.68 Ga granites associated to the Paragua Terrane (1.69-1.66 Ga) in the northern domain. The 1.37-1.34 Ga granites related to San Ignacio orogeny represent the third and more pervasive magmatic event, recorded throughout the Sunsas belt. Moreover, magmatic ages of-1.42 Ga revealed that the granitogenesis associated to the Santa Helena orogeny also affected the Sunsas belt, indicating that it was not restricted to the Jauru Terrane. Lastly, the 1.10-1.04 Ga youngest magmatism was developed during the Sunsas orogeny and represents the final magmatic evolution related to Rodinia assembly. Likewise, the 1.95-1.85 and 1.68 Ga inherited zircon cores obtained in the-1.3 Ga and 1.0 Ga granite samples suggest strong partial melting of the Paleoproterozoic sources. The 1079 +/- 14 Ma and 1018 +/- 6 Ma monazite crystallization ages can be correlated to the collisional tectono-thermal event of the Sunsas orogeny, associated to reactions of medium-to high-grade metamorphism. Thus, the Sunsas belt was built by heterogeneous 1.95- 1.85 Ga and 1.68 Ga crustal fragments that were reworked at 1.37-1.34 Ga and 1.10-1.04 Ga related to orogenic collages. Furthermore, the 1.01 Ga monazite age suggests that granites previously dated by zircon can bear evidence of a younger thermal history. Therefore, the geochronological evolution of the Sunsas belt may have been more complex than previously thought. (c) 2021 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Automated summary

The Sunsas belt in Bolivia has experienced four major magmatic events at different geological periods, including the formation of granitic basement in coeval terranes, a magmatic association with various terranes, and multiple magmatic events related to orogenies. The ages obtained from monazite and zircon data suggest a complex geological evolution with evidence of multiple reworking events in the Sunsas belt.