9 From Grenvillian Basement to Neotectonics in Northeast Mexico: A 1.3-Billion-Year Journey of Geological Development

Monday, 14 March 2022
1:30 PM - 5:30 PM
Online

AGE AND PETROGENESIS OF THE RINCÓN MURILLO GABBRO OF THE SIERRA DE SAN CARLOS ALKALINE COMPLEX, NE MEXICO

Paper number: 9-4
Program: Theme Sessions
Time: 2:30 PM – 2:50 PM

Authors

Abstract

The Sierra de San Carlos (SC) is located in the state of Tamaulipas and is the northernmost expression of the Sierras Tamaulipecas, which is a broad anticlinorium orientated NNW-SSE. It is constituted by Mesozoic limestone and marls, slightly folded an uplifted by the Laramide Orogeny during the Late Cretaceous to the Early Cenozoic (93-43 Ma).

Later in the Eocene, magmatic bodies intruded in the Sierra de San Carlos, building plutonic ultrabasic-acid plutons grouped in four major units: (a) San José Monzodiorites, (b) Rincón Murillo Gabbros, (c) Ell Bagre Alkaline Syenites, and (d) El Rosario Nepheline Syenites. After the plutonic emplacement, the magmatism continued with the formation of basic-intermediate subvolcanic and volcanic rocks in the periphery of the SC. In this work, we present a petrological approach of the Rincón Murillo Gabbro based on whole-rock, isotopic and geochronological data.

The Rincón Murillo Gabbro has a nepheline-normative alkaline character, enriched in LILE (Rb, Sr), HSFE (Nb, Y) and LREE. In this work we present the first two U-Pb LA-ICP-MS geochronological analysis performed on titanite crystals yielding Oligocene (Rupelian) crystallization ages of 31.38 ± 1.80 and 31.04 ± 1.72 Ma. This unit presents 87Sr/86Sr ratios between 0.70341 - 0.70417 and 143Nd/144Nd ratios between 0.51276 - 0.51284, which correspond to a mantle origin with a source close to the HIMU-type, without evidence of crustal contamination. The PM-normalized spider diagrams patterns, the tectonomagmatic discrimination diagrams and batch-partial melting modeling, show that the Rincón Murillo Gabbro unit was generated in a continental intraplate tectonic setting, under moderate degrees of partial melt (5-13 %) of a partially metasomatized mantle region with garnet-rich lithologies (peridotites / pyroxenites) with amphibole, in a post-orogenic stage after the formation of the Mexican Orogenic Belt.

Geological Society of America Abstracts with Programs. Vol. 54, No. 1

doi: 10.1130/abs/2022SC-374008

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