Search

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 Tamatan Group. Aserradero Rhyolite belongs to the Tamatan 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 Tamatan 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 Acatlan 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.

The origin of the Eastern Mexican Alkaline Province has been explained by landward arc migration and subsequent asthenospheric upwelling after slab roll-back of the Farallon Plate. In this work, we present new petrographic, mineral chemical, geochemical, and geochronological data of the Sierra de San Carlos-Cruillas (SSCC), one of the most important complexes in the province. This information, together with published data, helped us to reinterpret the tectonic processes operating during the generation of this province, as well as the mantle sources involved in the partial melting process. Detailed geochemical analysis suggests the participation of two types of metasomatized mantle regions: a lithospheric source modified by past subduction processes and an asthenospheric source slightly affected by carbonatite-related metasomatism. Variations in the partial melting degrees controlled the extent of magma enrichment in the latter. Major and trace element geochemistry, together with geochronological data and field relations, evinced an older post-orogenic setting related to the arc-like rocks (Eocene) and a younger intraplate extensional environment associated with all enriched igneous rocks (Oligocene-Miocene). Bivariate diagrams of SiO2-trace element ratios and multi-element patterns indicate that magmas from the SSCC complex dominantly evolved through fractional crystallization with a limited crustal contribution. Petrographic and mineral chemistry features suggest that some of these magmas experienced open-system processes (e.g. recharge events) in a complex and dynamic magmatic feeding system. In contrast to the traditional petrotectonic model, we propound that the passage and subsequent foundering of the Hess conjugate under northeastern Mexico resulted in its eclogitization and triggered slab tearing and succeeding detachment. This latter process occasioned mantle upwelling and the partial melting of the two recognized metasomatized mantle sources, thus generating the San Carlos-Cruillas magmatism.

The Huizachal–Peregrina Anticlinorium basement of the Sierra Madre Oriental in north-eastern (NE) Mexico comprises a wide variety of Precambrian and Paleozoic units. A granitic unit, described in this work as the Peregrina Tonalite (PTo), intruded the Neoproterozoic Novillo Gneiss, which is the northernmost expression of the Oaxaquia microcontinent. In contrast, the PTo’s contact with the Carboniferous Granjeno Schist is tectonic along vertical faults with a strike-slip component. This Paleozoic lithodeme is part of the Granjeno–Acatlan Belt. The PTo has been described as an orphaned block associated with an enigmatic Carboniferous magmatic arc located along the north-western (NW) margin of Gondwana. In this study, new U–Pb LA–ICP–MS data from PTo zircons included a youngest Late Ordovician (Katian stage) population at 448.8 ± 2.9 Ma, interpreted as the crystallisation age, and an oldest Grenvillian population interpreted as the potential age of its protolith. Additionally, major and trace element concentrations and ratios indicate a link to a continental arc that developed along the NW margin of Gondwana. Given this proposed arc’s age and position, a comprehensive model for the development of the NE Mexican basement without the involvement of exotic or orphaned terranes is now proposed. The PTo outcropping near Ciudad Victoria, Tamaulipas, is interpreted to be part of a previously unreported magmatic arc in NE Mexico established during the Late Ordovician, herein described as the Peregrina–Mochonian Orogeny. It represents an extension of the South American Famatinian arc into Mexico.

From samples of the Paleozoic Tamatan 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 Tamatan 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 Tamatan Paleozoic sequence, NE Mexico: Implications for the closure of the Rheic Ocean at the northwestern part of Gondwana" [1].

The Precambrian metamorphic basement exposed in the eroded core of the Huizachal-Peregrina Anticlinorium (Cd. Victoria, Mexico) is described in this contribution as Novillo Metamorphic Complex (NMC). Based on field relations, modal content, whole rock geochemistry and Nd-isotopic ratios is possible to recognize two major units: (a) Metaigneous Unit (MIU) and (b) Metasedimentary Unit (MSU). The MIU is subdivided into the Old Suite, constituted by (a) felsic gneisses from Novillo canyon, (b) felsic gneisses from Peregrina canyon, (c) metagranites, (d) mafic gneisses, and (d) migmatites; and the AMCG Suite, composed by (a) meta-anorthosites, (b) metagranite-gabbro intercalations, (c) metacharnockites, (d) garnet-rich metaferrodiorite dykes, and (e) metanelsonites. The MSU is represented by (a) meta-arkose – amphibolite intercalations and (b) calcsilicate marbles. Tectonic discrimination diagrams based on linear discriminant analysis of natural logarithm transformed ratios of elements show an island arc tectonic setting for the MIU. Nd isotopic ratios show crustal residence TDM ages of 1.49–1.44 Ga for the Old Suite (2 samples) and 1.63–1.33 Ga for the AMCG Suite (7 samples). The MSU have TDM between 1.39 a 1.25 Ga (3 samples) that support the interpretation that the protoliths were possibly deposited in a basin with sediment input from the younger MIU members. These deposits were later thrusted over MIU rather than intruded, and together metamorphosed under granulite facies conditions by the ca. 1.0 Ga Zapotecan orogeny. However, since the metaferrodioritic bodies cut discordantly the meta-anorthosites fabric, they represent a younger tectonothermal event, not yet described for the NMC.

The geochemistry of the metavolcanic rocks from the Granjeno Schist in northeastern Mexico indicates an origin in different tectonic environments: mid-ocean ridge and ocean island. High ratios of Hf/Th and Th/Nb (4.4-14 and 0.08-0.15), low ratios of LaN/YbN and LaN/SmN (0.74-1.7 and 0.60-1.4) and depleted LREE patterns in metabasalt display mid-ocean ridge characteristics. In contrast, the pattern of trace-element ratios and REEs in metabasalt and metapillow lava 60km to the west indicates a magma source with ocean-island basalt characteristics. Both areas were metamorphosed during the Late Carboniferous (300±4Ma). Estimated metamorphic conditions deduced from white mica and chlorite compositions, distinguish greenschist facies (350°C and 4kbar) for the mid-ocean ridge basalt, and prehnite-pumpellyite facies (250°C and 2.5kbar) for the ocean-island-type basalt. This metamorphism took place at an active continental margin during Pennsylvanian time. Our new tectonic model, which differs from earlier models, suggests that the origin of the Granjeno Schist is related to a subduction zone located at the western margin of Pangaea, active after Laurentia-Gondwana collision. (Less)

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,Pangea

El valle de Huizachal es el cañón más austral que corta al Anticlinorio Huizachal-Peregrina de la Sierra Madre Oriental (Ciudad Victoria, Tamaulipas). En el presente estudio, se realizó el estudio petrológico preliminar de las unidades volcánicas y clásticas (lechos rojos: lutitas, limolitas, areniscas y conglomerados) que conforman a las rocas jurásicas de las Formaciones La Boca y La Joya. La Formación La Boca ha sido dividida en dos miembros, el más antiguo se encuentra con echados casi verticales, mientras que el superior es sub-horizontal. Estos son suprayacidos por los lechos rojos de la Formación La Joya. El relleno sedimentario consiste de depósitos aluviales y fluviales distribuidos de manera irregular, con una alta influencia de detritos volcánicos derivados de rocas ígneas emplazadas a lo largo de la base y parte media de la sección geológica medida. Las rocas volcánicas comprenden derrames de lavas basáltico-andesíticas y depósitos piroclásticos en la base y domos riolíticos y complejos depósitos volcaniclásticos (lahares, ignimbritas y otros tipos de tobas) hacia la parte superior de la secuencia. El estudio petrográfico de los componentes principales de las areniscas de ambas formaciones ha revelado la presencia de dos petrofacies. La primera corresponde al miembro basal de la Formación La Boca, mientras que la segunda involucra al miembro superior de la misma formación y a la Formación La Joya. La primera petrofacies está constituida por arenitas feldespáticas a líticas depositadas en zonas de arco transicional con tendencia a arco disectado. La segunda petrofacies se compone de arenitas líticas depositadas en un ambiente de orógeno reciclado. Las petrofacies reflejan una procedencia a partir del contenido de cuarzo en rocas metamórficas de grado bajo a medio (esquistos, serpentinitas y gneises) y rocas ígneas (riolitas). Adicionalmente, la distinción de líticos metamórficos validó la procedencia de detritos del basamento del NE de México. La diferenciación del contenido lítico volcánico a partir de la caracterización textural ha confirmado la posición normal de la secuencia, y ha demostrado la influencia del reciclamiento y/o exhumación de la secuencia volcánica, sedimentaria y cristalina del basamento. La composición de las areniscas en el valle del Huizachal varía de base a techo debido a la compleja historia tectónica de la región, que involucra la presencia del basamento cristalino heterogéneo del Precámbrico-Paleozoico, el régimen extensional asociado a la apertura del Golfo de México y la instauración de un arco volcánico jurásico.

En este articulo se presenta el primer mapa de la regionalizacion sismica del Estado de Nuevo Leon, escala 1:250000. Este fue elaborado usando informacion geologica y datos de velocidad de propagacion de ondas P y S. Para la obtencion de las velocidades de propagacion de ondas se utilizo la metodologia de refraccion sismica. Se realizaron un total de 708 perfiles sobre diferentes unidades geologicas que afloran y conforman la columna litologica tipo del Estado de Nuevo Leon. Los afloramientos en donde se realizaron los perfiles sismicos comprenden rocas sedimentarias, igneas, metamorficas y depositos del Cuaternario. La generacion del mapa de las condiciones sismicas de sitio esta basada en codigos de efectos de sitio, como propone el National Earthquake Hazards Reduction Program (NEHRP, EE.UU.), a partir de la determinacion de V S30 y su correlacion con informacion litologica. El mapa de regionalizacion por V S30 , revelo los sitios clase A (V S30 > 1500 m/s), clase B (760 < V S30 ≤ 1500) y clase C (360 < V S30 ≤ 760) predominan en el area de estudio. En las regiones caracterizadas por material aluvial muestran valores mas bajos de V S30 (560 m/s), mientras que las rocas mas consolidadas como, por ejemplo, las que conforman la secuencia mesozoica, presentan valores altos de propagacion de ondas sismicas (V S30 = 1200 - 3500 m/s). Los resultados generados en este trabajo proveen de una primera aproximacion de la respuesta sismica de los materiales someros en el estado, cuya aplicacion es de importancia en la planeacion del uso de suelo, desarrollo urbano, asi como para el calculo del riesgo sismico u otros peligros geologicos, particularmente para regiones donde existe evidencia historica de actividad sismica, pero con escasa o nula instrumentacion sismica

Alkaline magmas along the periphery of Sierra de San Carlos-Cruillas and Sierra de Tamaulipas (Eastern Alkaline Province, northeast Mexico) contain ultramafic xenoliths. Most of the host rocks are mafic (e.g., basalts, basanites, trachybasalts, phonotephrites), and have geochemical characteristics of nearly primary magmas generated in subcontinental zones (SiO2 = 42.6-48.4%, MgO = 6.3-11.2%, Mg# = 59.2-69.7). MORB-normalized patterns are similar to those displayed by extensionrelated mafic magmas. This hypothesis is supported by an enrichment in light REE ([La/Yb]N = 10.8-27.1; chondrite-normalized ratios) and the behavior of relatively immobile trace elements. Using a partial melting model for REE, the source for the mafic magmas apparently was in the garnet P-T stability field. On the other hand, peralkaline phonolites and tephriphonolites (SiO2 = 52.9-54.1%, MgO = 1.5-1.8%, Mg# = 33.1-39.8) also contain mantle xenoliths. These evolved magmas show MORB-normalized multi-element diagrams characterized by ...

En el noreste de Mexico, el Esquisto Granjeno aflora en los nucleos de estructuras plegadas de la Sierra Madre Oriental, como el Anticlinorio Huizachal-Peregrina o los altos de Miquihuana y Bustamante, en Tamaulipas, y Aramberri en Nuevo Leon. El trabajo de campo y el estudio petrografico han permitido reconocer las distintas litofacies y relaciones estratigraficas presentes en las diferentes localidades, asi como el grado y estilo de deformacion. Aunque la geocronologia de circones detriticos, en muestras de los diferentes protolitos clasticos, permite reconocer procedencias principalmente grenvillianas (1250-920 Ma) y panafricanas (730-530 Ma), es relevante destacar algunas diferencias en la edad maxima del deposito que se puede interpretar para las muestras procedentes de las distintas localidades, que abarcan desde el Neoproterozoico hasta el Silurico o posiblemente el Devonico. Asimismo, se observan algunas poblaciones con menor representacion de circones, de edades proterozoicas y paleozoicas, que corresponden aparentemente a eventos tectonomagmaticos poco estudiados hasta el momento, como el magmatismo ordovicico-silurico. El presente estudio sustenta un origen del Esquisto Granjeno estrechamente ligado a la porcion noroccidental de Gondwana, sumandose asi, dada la ausencia de procedencias caracteristicas del suroeste del craton de Norteamerica, a la serie de argumentos en oposicion al desplazamiento lateral izquierdo de Mexico de varios cientos de kilometros durante el Jurasico Superior, previamente propuesto por la hipotesis de la megacizalla Mojave-Sonora. El metamorfismo del Esquisto Granjeno, ocurrido en el Paleozoico tardio, estaria relacionado a un proceso de subduccion en la margen occidental de Pangea (Cinturon Granjeno-Acatlan), en etapa posterior a la colision de Laurencia y Gondwana (Cinturon Sonora-Ouachita-Marathon). Lo anterior resulta acorde con la presencia del arco magmatico permo-triasico en la porcion oriental de Mexico, el cual es claramente un producto de la misma subduccion en su etapa de gran angulo, inmediatamente posterior a la deformacion y metamorfismo durante la fase de subduccion inicial de bajo angulo.