Laurentia, Baltica and Amazonia formed the last fragment of the Rodinia supercontinent that broke apart during the Early Ediacaran (~630-600 Ma), leading to opening of the Iapetus Ocean. An essential record to establish such reconstructions and to identify Large Igneous Provinces (LIPs) are coeval dyke swarms that occur over large extensions on formerly adjacent cratons. Plume-related mafic dykes from Baltica (Egersund dykes, [1]) and Laurentia (Long Range dykes, [2]) are reliably dated at 616 ±3 and 615 ±2 Ma, respectively (baddeleyite [ZrO2] U-Pb); however, the occurrence of similar dykes is still unrecognized in the Amazonia craton or in the Oaxaquia Terrane of Mexico, a Late Mesoproterozoic basement block located in Rodinia reconstructions between Amazonia and Baltica. Here we report new dating approaches by Secondary Ion Mass Spectrometry (SIMS) from two exposures in Mexico: 
1. Polymetamorphic basement of the Chiapas Massif Complex (southeastern Mexico) contains ~1.0 Ga gneisses and anorthosites that were intruded by E-MORB magmas prior to Ordovician high-grade metamorphism [3]. Direct dating of these mafic intrusions is impossible because zircon is either inherited from the basement or metamorphic. This new approach is based on the fact that zirconium exsolved from rutile and ilmenite of anorthosite during thermal overprints, forming metamorphic zircon coronas. The metamorphic zircon grains typically have distinctive growth zones, of which “dark” zircon zones yielded Concordia ages of 619±4 Ma and 615±8, reflecting zircon growth in host anorthosite during the intrusion of the “hot” mafic dykes. 
2. A plume-related dike swarm is known from the Rodinia-type Novillo gneiss (northeastern Mexico), preciously dated with the 40Ar-39Ar method yielding a cooling age of ~545 Ma [4]) that reflects greenschist facies overprint postdating the time of intrusion. In-situ U-Pb micro-baddeleyite (7-10µm) dating yielded the first reliable intrusion age of Novillo dykes at 619 ± 9 Ma coeval with Chiapas E-MORB amphibolites, Egersund and Long Range dykes. In addition, a second age group of baddeleyite yielding 545 ± 9 Ma is consistent with the earlier 40Ar-39Ar age suggesting recrystallization or Pb-loss during greenschist facies metamorphic overprint. 
The results indicate a previously unrecognized LIP that produced plume-related magmas over large distances across all cratonic masses involved in final Rodina brake-up and birth of the Iapetus Ocean. 
[1] Bingen et al., 1998, J. Geology 106, 565–574; [2] Kamo et al., 1989, Geology 17, 602–605; [3] Weber et al., 2018, Lithos 300–301, 177–199; [4] Keppie et al., 2006, Precamb. Res. 147, 342–353.