42-8 Rare metal mineralization associated with agpaitic syenites in the northern Eastern Mexican Alkaline Province

Session: Cordilleran Mineral Systems: Interdisciplinary Perspectives on Critical Metal Ore Deposits

Presenting Author:

Néstor Cano

Authors:

Cano, Néstor¹, Díaz-Martínez, Roberto², Brito-Calderón, Luis³, Camprubi, Antoni⁴, Villanova-de-Benavent, Cristina ⁵, Domínguez-Carretero, Diego⁶, Llovet, Xavier⁷, González-Partida, Eduardo⁸, Proenza, Joaquín Antonio⁹

(1) Instituto de Geología, Universidad Nacional Autónoma de México, Mexico City, CDMX, Mexico; Laboratorio Nacional de Geoquímica y Mineralogía, Universidad Nacional Autónoma de México, Mexico City, CDMX, Mexico, (2) Escuela Superior de Ingeniería Lic. Adolfo López Mateos, Universidad Autónoma de Coahuila, Nueva Rosita, Coahuila, Mexico, (3) Escuela Superior de Ingeniería Lic. Adolfo López Mateos, Universidad Autónoma de Coahuila, Nueva Rosita, Coahuila, Mexico, (4) Instituto de Geologia, Universidad Nacional Autónoma de México, Mexico City, CDMX, Mexico, (5) Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Barcelona, Barcelona, Spain, (6) Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Barcelona, Barcelona, Spain, (7) Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Barcelona, Barcelona, Spain, (8) Instituto de Geociencias, Univerisdad Nacional Autónoma de México, Mexico City, CDMX, Mexico, (9) Departament de Mineralogia, Petrologia i Geologia Aplicada, University of Barcelona, Barcelona, Barcelona, Spain,

Abstract:

Alkaline magmatism in the Eastern Mexican Alkaline Province (EMAP) extends from the Gulf of Mexico to the Mexico-USA border, yet its northern sector remains poorly characterized in terms of rare-metal potential. This study documents the mineralogical and petrogenetic evolution of alkaline complexes in the Sierra Maderas del Carmen region, with particular emphasis on eudialyte-group-mineral (EGM)-rich syenites identified as the most prospective lithologies for Zr-Nb-REE mineralization. Magmatism defines an evolutionary sequence from alkali gabbros and intermediate intrusions to silica-saturated and silica-undersaturated syenites derived from enriched, OIB-like mantle melts emplaced in an intracontinental setting. EGM-rich syenites occur as narrow dikes, sills, and small plugs, locally associated with well-developed calc-silicate skarn haloes in carbonate host rocks. Five syenite types are recognized, ranging from fine-grained agpaitic to transitional agpaitic assemblages dominated by EGM, aegirine-augite, alkali feldspar, and sodalite ± analcime. The most metal-enriched syenites are characterized by early crystallization of EGM, feldspar, and aegirine-augite, followed by late-stage albite + calcite + gittinsite assemblages, reflecting extreme differentiation under dry, reducing conditions. These processes promoted increasing peralkalinity and the concentration of Zr, Nb, REE, Th, and Ti into late magmatic and magmatic-hydrothermal assemblages. Scanning electron microscopy reveals a diverse suite of rare-metal minerals, including eudialyte, britholite-(Ce), thorite, pyrochlore, ancylite-(Ce), gittinsite, and baddeleyite, occurring both within syenites and associated skarns. Regionally, emplacement ages (~48–28 Ma) coincide with slab detachment beneath northeastern Mexico, linking intraplate alkaline magmatism to rare-metal fertility. These results highlight the northern EMAP as an underexplored province for agpaitic-related Zr-Nb-REE mineralization in the North American Cordillera.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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