Fractionation by compositional magma splitting: An example from Cerro Munro, Argentina Rodríguez, Carmen Castro, Antonio Sánchez Navas, Antonio Calc-alkaline magmatism Fractionation Mafic microgranular enclaves Second boiling Geochronology Cathodoluminiscence The manuscript has been benefited from valuable suggestions from Mattia Pistone and Jiri Zak. This work is supported by IBERCRUST project (PGC2018-096534-B-I00). C. R. is grateful for her AUIP grants (Asociacion Universitaria Iberoamericana de Postgrado) for both stays at the Universidad Nacional de La Plata (Argentina), during 2015 and 2018, and for her postdoctoral contract from the University of Huelva (under the Estrategia Politica Cientifica de la UHU 2016/2017). This is the IBERSIMS publication n.85. JM is funded by the MINECO grant CGL2017-84901-C2-P1. The Paleocene-Eocene Cerro Munro pluton, to the east of the North Patagonian Batholith (NPB), is a tonalitic intrusion emplaced as a shallow, small, sub-circular tonalite-granodiorite body hosting abundant co-magmatic mafic microgranular enclaves (MME). Besides, the intrusive body is crosscut by radial porphyritic dikes and has been related to andesitic, dacitic and rhyolitic dikes, lava flows and ignimbrites cropping out at neighboring areas. Magmatic contacts between MME and host tonalites, together with their common geochemical features, suggest derivation from a common parental magma, although short-range mineralogical and geochemical differences point to an early crystallization of MME (chilled margins) at the sidewalls of ascent conduits or at shallow reservoirs. The established thermal gradient and the advance of the solidification front were responsible for the presence of the mafic microgranular and tonalitic subsystems and, in a continuous process, promoted the water saturation and the second boiling that finally account for the segregation of a water rich highly differentiated residual liquid. Hbl-Pl cumulate textures observed in the tonalites and mafic enclaves, as well as incompatible element-enriched rhyolitic melts record the results of this in-situ differentiation process. U–Pb zircon ages obtained from tonalites (57.1 ± 1.4 Ma), dacitic (55.4 ± 0.6 Ma) and rhyolitic (54.1 ± 0.7 Ma) dikes constrain an age of around 54 Ma for the final consolidation of the tonalitic magma and the crystallization of the expelled highly differentiated melts. This age coincides with the deposition of dacitic volcanic and volcanoclastic deposits to the north of the Cerro Munro pluton, which suggests that the fractionation process led to the extrusion of segregated melts, favored by extension, uplift and exhumation of an active rift tectonic setting. 2021-10-22T08:03:49Z 2021-10-22T08:03:49Z 2021-07-27 info:eu-repo/semantics/article Carmen Rodríguez... [et al.]. Fractionation by compositional magma splitting: An example from Cerro Munro, Argentina, Lithos, Volumes 400–401, 2021, 106396, ISSN 0024-4937, [https://doi.org/10.1016/j.lithos.2021.106396] http://hdl.handle.net/10481/71039 10.1016/j.lithos.2021.106396 eng http://creativecommons.org/licenses/by-nc-nd/3.0/es/ info:eu-repo/semantics/openAccess Atribución-NoComercial-SinDerivadas 3.0 España Elsevier