Arcos magmáticos del ordovícico y del carbonífero en el basamento de la Sierra Madre Oriental en el Anticlinorio Huizachal Peregrina.

El Anticlinorio Huizachal-Peregrina (AHP) al W de Cd. Victoria, Tamaulipas, exhibe un amplio catálogo de litologías precámbricas y paleozoicas. Previo a este trabajo, las implicaciones tectónicas de las unidades magmáticas paleozoicas no habían sido estudiadas a fondo, lo que generaba inconsistencia en los modelos para el área. Estos cuerpos ígneos son clave para entender las condiciones geodinámicas de la evolución del NE de México durante el Paleozoico. Dentro de estas unidades ígneas del AHP se encuentran dos cuerpos félsica, que hasta ahora habían sido asociados al arco magmático del Carbonífero de la margen NW de Gondwana. A la primera unidad se le ha denominado Tonalita Peregrina y se encuentra en contacto tectónico entre las unidades metamórficas del Precámbrico y Paleozoico. La segunda unidad, la Riolita Aserradero, está ubicada entre la Secuencia Sedimentaria Paleozoica. El estudio petrográfico arrojó una composición de plagioclasa, cuarzo, ortopiroxeno, muscovita y clorita, y con calcita, ortoclasa, circón y titanita como accesorios para la Tonalita Peregrina, mientras que para la Riolita Aserradero presenta plagioclasa, cuarzo, sanidino y biotita en una matriz microcristalina y con clorita y sericita como minerales secundarios, con fracturas rellenas de calcita y en algunas ocasiones cuarzo, además de pirita diseminada. La geoquímica de elementos mayores confirma la ausencia de relaciones genéticas entre ambas unidades. Por otra parte, los elementos traza indican un ambiente de arco magmático para ambas unidades. Los nuevos datos geocronológicos LA-ICP-MS por el método de U-Pb en circones para la Tonalita Peregrina arrojan diversas poblaciones pertenecientes a edades grenvillianas, panafricanas y las más jóvenes, interpretadas como edad de cristalización, presentan una edad de 449.2 ± 2.9 Ma Ma, pertenecientes al Katiense (Ordovícico Superior). Los resultados para la Riolita Aserradero no fueron concluyentes dada la escasa población de circones, pero el circón analizado con edad más joven (331.9 ± 5.2 Ma, Pensilvánico Medio) es congruente tanto con la posición estratigráfica de esta unidad en la Secuencia Sedimentaria Paleozoica como con las edades radiométricas previamente reportadas en la literatura. Con la información generada se propone un nuevo modelo tectónico en el cual la Tonalita Peregrina es el producto de un arco magmático desarrollado en Oaxaquia durante el Ordovícico Superior, del cual no se tenía hasta ahora evidencia petrológica en el NE de México. El origen de la Riolita Aserradero permanece asociado al arco magmático Permo-Carbonífero del W de Pangea Gondwana. ABSTRACT The Huizachal-Peregrina Anticlinorium (HPA) located W of Cd. Victoria, Tamaulipas, displays a wide variety of Precambrian and Paleozoic lithologies. Before this work, tectonic implications of the Paleozoic magmatic units had not been deeply studied, generating inconsistencies in preexisting models. The igneous units set key points for the understanding of geodynamic conditions during the evolution of NE Mexico through Paleozoic times. The HPA comprises two felsic bodies, which prior of this work had been associated to the magmatic arc along NW Gondwana margin during Carboniferous. The first unit, Peregrina Tonalite, is tectonically emplaced between the Precambrian and Paleozoic metamorphic units. The second unit, referred as Aserradero Rhyolite, is interbedded in the Paleozoic Sedimentary Sequence. Petrographic analysis shows a modal composition of plagioclase, quartz, ortopyroxene, muscovite and chlorite, with calcite, orthoclase, zircon and titanite as accessory minerals for the Peregrina Tonalite, while plagioclase, quartz, sanidine, biotite in a microcrystalline matrix with chlorite and sericite as secondary minerals, as well as disseminated pyrite, for the Aserradero Rhyolite. Major elements confirms the lack of genetic relationships between both acid units, while trace element point out to a magmatic arc setting for the origin of both units. New U-Pb LA-ICP-MS data obtained from zircons from Peregrina Tonalite shows several populations, the oldest from Grenvillian and Panafrican ages, while the younger, interpreted as crystallization age, is 449.2 ± 2.9 Ma (Katien, Upper Ordovician). Aserradero Rhyolite results were inconclusive because of the limited population of zircon crystals in the rock, but the younger age (331.9 ± 5.2 Ma, Pensilvánico Medio) is congruent with its stratigraphic position in the Paleozoic Sedimentary Sequence, and radiometric ages previously reported on literature. With this new information, a new tectonic model is proposed. Peregrina Tonalite is generated as part of a magmatic arc developed during Upper Ordovician in Oaxaquia, which has not been reported yet in NE Mexico. Aserradero Rhyolite is still considered as a product associated to the Permo-Carboniferous magmatic arc along Western Pangea

Petrology and geochemistry of meta-ultramafic rocks in the Paleozoic Granjeno Schist, northeastern Mexico: Remnants of Pangaea ocean floor

Abstract: The Granjeno Schist is a meta-volcanosedimentary upper Paleozoic complex in northeastern Mexico. We suggest different tectonic settings for metamorphism of its serpentinite and talc-bearing rocks based on petrographic and geochemical compositions. According to the REE ratios (LaN/YbN = 0.51–20.0 and LaN/SmN = 0.72–9.1) and the enrichment in the highly incompatible elements Cs (0.1 ppm), U (2.8 ppm), and Zr (60 ppm) as well as depletion in Ba (1 – 15 ppm), Sr (1–184ppm),Pb(0.1–14ppm),andCe(0.1–1.9ppm)the rocks have mid-ocean ridge and subduction zones characteristics.TheserpentinitecontainsAl-chromite,ferrian chromiteandmagnetite.TheAl-chromiteischaracterized byCr#of0.48to0.55suggestingaMORBorigin,andCr#of 0.93 to 1.00 for the ferrian chromite indicates a prograde metamorphism.Weproposeatleasttwoserpentinization stagesoflithosphericmantlefortheultramaficrockofthe GranjenoSchist,(1)afirstinanocean-floorenvironment atsub-greenschisttogreenschistfaciesconditionsand(2) later a serpentinization phase related to the progressive replacement of spinel by ferrian chromite and magnetite atgreenschisttolowamphibolitefaciesconditionsduring regional metamorphism. The second serpentinization phase took place in an active continental margin during the Pennsylvanian. We propose that the origin of the ultramaficrocksisrelated toanobductionandaccretional eventatthewesternmarginofPangea. Keywords: ultramafic rocks; serpentinite; Granjeno Schist;northeasternMexico,Gondwana,Pange

Petrological, geochemical (major, trace, and rare earth elements), and U–Pb zircon data of the Tamatán Group, NE Mexico

From samples of the Paleozoic Tamatán Group (Huizachal–Peregrina Anticlinorium, Tamaulipas, Mexico), petrographic (qualitative and modal) and geochemical analyses (major, trace, and rare earth elements) were conducted. The first U–Pb geochronological data on detrital zircons of the Tamatán Group were generated using four samples. The data presented here contains a broad overview of photomicrography, recalculated modal point-count data, raw geochemical data, and simple statistics of selected geochemical parameters. The data presented in this article are interpreted and discussed in the research article titled “Provenance and tectonic setting of the Tamatán Paleozoic sequence, NE Mexico: Implications for the closure of the Rheic Ocean at the northwestern part of Gondwana” [1]

Early Mississippian precollisional, peri-Gondwanan volcanic arc in NE-Mexico: Aserradero Rhyolite from Ciudad Victoria, Tamaulipas

The study of the pre-Mesozoic geological history of NE Mexico offers the opportunity to reconstruct the processes that occurred at the NW margin of Gondwana. The Huizachal–Peregrina Anticlinorium, which is located west of Ciudad Victoria (Tamaulipas) is a regional structure produced during the Cretaceous–Palaeogene Laramide Orogeny. Its eroded core exposes Precambrian and Palaeozoic units that together comprise the Sierra Madre Oriental basement. These units are the Neoproterozoic metamorphic Novillo Complex, the Ordovician Peregrina Tonalite, the metamorphic Pennsylvanian Granjeno Complex, and the sedimentary Silurian–Permian Tamatán Group. Aserradero Rhyolite belongs to the Tamatán Group, occurring between the siliciclastic deposits of the Early Mississippian Vicente Guerrero and the Pennsylvanian Del Monte Formations. The studied rhyolites display geochemical characteristics corresponding to high-K, low-Sr, and S-type granitoid rocks that may have been produced by upper-crustal anatexis from a source similar to that of the Novillo Complex. New LA-ICP-MS U–Pb geochronological analysis on zircons separated from the Aserradero Rhyolite yielded Early to Middle Mississippian crystallisation ages of 347.8 ± 2.7 Ma and 340.7 ± 3.6 Ma, confirming that this acidic unit is in its original stratigraphic position despite the pervasive deformation of the Tamatán Group. Based on the correlation with other Carboniferous–Early Permian magmatic complexes in Mexico and Central America, it is suggested that the Aserradero Rhyolite represents an early stage of a precollisional Carboniferous–Permian peri-Gondwanan arc, occurring also in the Las Delicias, Oaxaquia, the Acatlán Complex, the Maya Block, as well as in the buried crystalline basement along the Western Gulf of Mexico. The assembly of the Precambrian and Palaeozoic basement units from the Huizachal–Peregrina Anticlinorium were integrated with the Ciudad Victoria Block, which was dismembered from Oaxaquia and their peripheral units during the Upper-Jurassic Gulf of Mexico opening.Fil: Ramírez Fernández, Juan Alonso. Geonetwork of Latin-American German Alumni; Perú. Universidad Autónoma de Nuevo León; MéxicoFil: Alemán Gallardo, Eduardo Alejandro. Universidad Autónoma de Nuevo León; MéxicoFil: Cruz Castillo, Denisse. Universidad Autónoma de Nuevo León; MéxicoFil: Velasco Tapia, Fernando. Universidad Autónoma de Nuevo León; MéxicoFil: Jenchen, Uwe. Geonetwork of Latin-American German Alumni; PerúFil: Becchio, Raul Alberto. Geonetwork of Latin-American German Alumni; Perú. Geomap S.a.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: De León Barragán, Lorena. Universidad Autónoma de Nuevo León; MéxicoFil: Casas Peña, Juan Moisés. Universidad Autónoma de Nuevo León; Méxic