Papers by Elena Centeno-Garcia
4. Los depósitos de tipo Óxido de Fe-(Cu-U-Au-REE): Polémicas sobre su origen y su posible existencia en territorio mexicano
The brachiopods Krotovia sp., Dasysaria sp., Derbyoides cf. D. dunbari, Neospirifer cf. N. amphig... more The brachiopods Krotovia sp., Dasysaria sp., Derbyoides cf. D. dunbari, Neospirifer cf. N. amphigyus, Neospirifer sp., Spiriferellina tricosa and ?Holosia sp., and the trilobite Anisopyge whitei are described from Lower Permian (Wolfcampian-Leonardian) rocks from Otlamalacatla region, northwest of Hidalgo State. The association is similar to Permian faunas from west Texas and almost all these taxa are recorded for the first
Revista Mexicana de Ciencias Geológicas, 2013
Based on the recognition of a major angular unconformity, magmatic and detrital zircons dating, a... more Based on the recognition of a major angular unconformity, magmatic and detrital zircons dating, as well as facies analysis of pre-Oxfordian clastic succession in the Ayuquila basin, we propose to subdivide the succession into two formations. We documented that the succession accumulated in braided fluvial systems, draining mainly southwards. During Bajocian-Bathonian time, at the beginning of sedimentation, the climate conditions were semiarid and became wet during Callovian time, probably because of the shifting of southern Mexico towards a more equatorial setting. We formally propose the Ayuquila Formation to name the succession below the unconformity, which consists of monomictic conglomerate of metamorphic or sandstone clasts, and lithic and feldspathic greywacke. Ayuquila Formation bears fossil flora reported in the region and includes some lacustrine beds; these accumulated during Bajocian- Bathonian time. We propose as type locality of the Ayuquila Formation, the succession exposed north of Chilixtlahuaca, Oaxaca. We intend to retain the name Tecomazúchil Formation for the Callovian quartzrich succession above the unconformity exposed in the arroyo Tecomazúchil. Tecomazúchil Formation consists of a succession of subarkose, sublitharenite and conglomerate with quartz lenses; the sequence has thinner beds and is finer upwards. Magmatic zircons from the intrusive hosted in the Ayuquila Formation have ages U-Pb of 164.3 ± 3.6 and 156.9 ± 3.5 Ma. Detrital zircons in the Ayuquila and Tecomazúchil formations have ages ranging from1464 Ma to 174 Ma, which are compatible with a provenance from metamorphic and magmatic terranes of southern Mexico. Permian-Triassic detrital zircons might have come from the La Mora formation. The youngest zircon in the Tecomazúchil Formation has an age of 174 Ma; its most possible source might have been the San Miguel intrusives emplaced in the migmatitic Chazumba Lithodem (Magdalena Migmatite).This fact might constraint the Ayú Complex exhumation before Oxfordian time. Dislocation along Petlalcingo-Huajuapan fault conditioned the Ayuquila basin formation, therefore the fault was active during Middle Jurassic time. According to the timing reported for the migmatization process of Ayú Complex, the pre-Oxfordian clastic succession began its accumulation after 171 Ma in the Ayuquila basin. This one is a small, asymmetric, extensional basin formed on a tectonic setting of continental break-up with SSE-NNW strike extension. This extensional process associated with the rupture of Pangaea during Middle Jurassic was simultaneous in the region with the migmatization and exhumation of the Ayú Complex, and probably with the magmatic event of Diquiyú unit.
Revista Mexicana de Ciencias Geológicas, 2009
The Matzitzi Formation (Permian), located in the southern part of Puebla State, constitutes one o... more The Matzitzi Formation (Permian), located in the southern part of Puebla State, constitutes one of the few exposures of Paleozoic rocks in southern Mexico. Rocks of this formation were recognized since 1896 by Aguilera, and ever since they are known for its paleobotanical significance, because of their diverse fossil flora. This unit overlies or is in fault contact with the Oaxacan Complex and is unconformably overlain by Mesozoic conglomerates. Measured columns along the dirt road between Los Reyes Metzontla and Coatepec allowed us to characterize six facies association. Based on these facies associations, we recognized debris flow deposits, sandy channel-fill, overbank, and crevasse splays deposits. These facies are interpreted as related to an anastomosed river system. In addition, evidence of an extrusive origin for the felsic rocks that crop out in San Luis Atolotitlán town are also discussed in this paper. These igneous rocks were previously interpreted as a shallow stock, or a sill or a dike. However, field observations corroborated a volcanic origin, those are: 1) the basal contact is conformable, it shows no evidence of contact metamorphism, and is formed by a minor erosional surface due to flow (surge ondulite); 2) the upper contact is also conformable, and mildly erosional as well, and sandstone and conglomerate that rest upon contain abundant clasts of the underlying felsic rock; 3) rocks show reomorphic structures and cooling hexagonal prisms. Thus, we interpret these rocks as part of a pyroclastic flow, named as the Atolotitlán Tuff. Geochemical data suggests a volcanic-arc affinity for this tuff, since it has low Ce, P, Nb and Ti, enriched light rare earth element (LREE) patterns, flat heavy rare earth element (HREE) patterns, and negative Eu anomaly. This last interpretation is valid only if there was no considerable amount of crustal melts involved in the magma generation. The fact that the Matzitzi Formation contains volcanic rocks is important for the paleogeographic and tectonic reconstruction of southern Mexico, because it corroborates that the paleo Pacific continental margin was active during Permian time. Permian arc related volcanic rocks have been already recognized, but only to the north of the studied area. This is also the first record of upper levels of Paleozoic igneous activity, since only granitoids of Permian age have been found southern Mexico.
Pb (%) 235 U* (%) 238 U (%) corr. 238 U* (Ma) 235 U (Ma) 207 Pb * (Ma) (Ma) AYU-127
Gondwana Research, 2015
The La Mora Formation is the oldest Mesozoic floodplain succession in the Mixteca Terrane of Sout... more The La Mora Formation is the oldest Mesozoic floodplain succession in the Mixteca Terrane of Southern Mexico. The presence of Amazonian detrital zircons in the La Mora Formation and in the overlying volcanic Diquiyú Unit indicates a major fluvial system that drained the Mixteca Terrane. The La Mora Paleo-River crossed the Oaxaquia microcontinent and the Mixteca Terrane prior to the breakup of Pangea, during Late Triassic-Early Jurassic time, when the Acatlán-Oaxaquia block was part of the northwestern portion of the Amazonian craton. Detrital zircons in the La Mora Formation have ages between 3307 ± 31 and 210 ± 12 Ma, which suggest that they originated in Amazonia and Southern Mexico: 33.2% of the detrital zircons have ages that are found only in Amazonian sources; whereas 66.7% of the zircons may be associated with either the Amazonian craton, the Andean Basement, or Southern Mexico. We propose that the La Mora fluvial system drained the Amazon basin in a westward direction, with its mouth in central Pangea, and that it most likely fed the Tolimán submarine fan. The inferred location of the Acatlán-Oaxaquia tectonic block at the time of the La Mora fluvial system implies that the basement of Southern Mexico experienced a right lateral displacement of at least 2300 km with respect to South America during the Mesozoic.
Sedimentary Geology, 2006
A depositional model of the Eocene-Oligocene Coatzingo Formation in Tepexi de Rodríguez (Puebla, ... more A depositional model of the Eocene-Oligocene Coatzingo Formation in Tepexi de Rodríguez (Puebla, Mexico) is proposed, based on facies analysis of one of the best-preserved sections, the Axamilpa Section. The sedimentary evolution is interpreted as the retrogradation of an alluvial system, followed by the progressive expansion of an alkaline lake system, with deltaic, palustrine, and evaporitic environments. The analysis suggests a change towards more arid conditions with time. Fossils from this region, such as fossil tracks of artiodactyls, aquatic birds and cat-like mammals, suggest that these animals traversed the area, ostracods populated the lake waters, and plants grew on incipient soils and riparian environments many times throughout the history of the basin. The inferred habitat for some fossil plants coincides with the sedimentological interpretation of an arid to semiarid climate for that epoch. This combined sedimentological-paleontological study of the Axamilpa Section provides an environmental context in which fossils can be placed and brings into attention important biotic episodes, like bird and camelid migrations or the origin of endemic but extinct plants in this area.
Journal of South American Earth Sciences, 1999
Analyses of Lower Permian or older basalts and associated dykes of the Juchatengo sequence indica... more Analyses of Lower Permian or older basalts and associated dykes of the Juchatengo sequence indicate that they are rift tholeiites that formed in a continental rift or back-arc tectonic setting. Age constraints include a Middle Permian fossil recovered from the tectonically overlying sediments and a cross-cutting, post-tectonic pluton dated by K/Ar on hornblende at 2822 6 Ma. A location adjacent to the Oaxacan Complex or other old continental crust is suggested by (1) an eNd i isotopic value of À8.95 and a T DM age of 1487 Ma in the overlying sediments, which are similar to the Oaxacan Complex; (2) enrichment of incompatible elements in the lavas, suggesting old crustal contamination; and (3) the presence of Permian±Triassic calc-alkaline plutons that stitch the Juchatengo±Oaxaca boundary. The possible tectonic models depend on the age of the Juchatengo basalts, which requires future geochronological work. If the Juchatengo basalts are Permo-Carboniferous, they could have formed near the eastern edge of a back-arc basin: the contemporaneous arc would have rifted away to the west. Eastward migration of the arc magmatism indicated by the Permian±Triassic calc-alkaline plutonism may re¯ect shallowing of the dip of the subduction zone, which probably also produced the deformation of the Juchatengo sequence.
Geology, 1995
Grenville-age granulite facies rocks in southern, central, and northeastern Mexico have distincti... more Grenville-age granulite facies rocks in southern, central, and northeastern Mexico have distinctive geologic features that suggest a common tectonic evolution. The similarities include northwesttrending structural grain from Oaxaca to Tamaulipas, massif-type anorthosite-charnockite complexes, protoliths rich in sedimentary rocks of shallow-marine platform or continental rift-related facies devoid of calc-alkaline volcanic rocks, common metamorphism under granulite facies conditions, U-Pb zircon ages of about 1.0 Ga., and an apparently common history of uplift and cooling. Altogether, this evidence strongly suggests a coherent geologic history for this block. Paleontologic data from the overlying sedimentary sequences indicate that Oaxaquia was not part of Laurentia during most of the Paleozoic. This precludes emplacement of Oaxaquia in its present position by simple lateral displacement from the southern United States as well as a Taconic time of emplacement. Oaxaquia was probably emplaced to its present position during late Paleozoic time. The concept of a Mesoproterozoic ''Oaxaquia'' microcontinent extending for about 1000 km in Mexico needs to be considered in the reconstruction of the Grenville orogen as a whole and for the Paleozoic tectonic interactions between eastern Laurentia and western Gondwana.
Earth and Planetary Science Letters, 2010
The Chivillas Formation is the easternmost record of Mesozoic marine volcanism in Mexico. It cons... more The Chivillas Formation is the easternmost record of Mesozoic marine volcanism in Mexico. It consists of thick intervals of pillow lavas interbedded with siliciclastic turbidites, and debrites, containing clasts derived from metamorphic, sedimentary and volcanic sources. Clast composition and detrital zircon geochronology indicate a continental provenance, with sources located south of the studied rocks. Detrital zircon ages range from 1573 ± 60 to 125 ± 1.6 Ma. The probability curves have peaks at 124 to 130 Ma (mean 126 Ma); 188 Ma and 921-1236 Ma (the latter with peaks at ∼ 1022 and ∼ 1157 Ma). Subordinate peaks at 277, 419 and 535 Ma are also present. We interpret the youngest zircon population ∼ 126 Ma (Barremian), as the maximum depositional age. Other peaks suggest Grenvillian-type basement and Permo-Triassic arc sources. Late Jurassic detrital zircons were probably derived from the Sierra de Juárez Mylonitic belt. Pillow lavas are mostly alkaline basalts, with SiO 2 46%-53%, and alkali oxide (K 2 O+ Na 2 O) 5-8 wt.%; all samples have low-TiO 2 (b 1.6 wt.%) and low V (180-242 ppm), with Ti/V between 30 and 50. 206 Pb/ 204 Pb isotopic ratios are 18.6-20.5, and 208 Pb/ 204 Pb are within OIB and MORB ranges. Initial εNd(126) are 0.3 to 4.1, and T DM are 632-1520 Ma. Lava compositions are similar to alkaline basalts along the margins of the Atlantic Ocean, particularly to basalts from the Central Atlantic Magmatic Province (CAMP), and to the Cretaceous Peri-Atlantic Alkaline Pulse (PAAP). Volcano-sedimentary rocks from Chivillas Formation probably formed in a subsiding marine rift basin, at a ridge-transform intersection. This basin received sediments transported throughout longitudinal canyons along the major Jurassic-Cretaceous strike-slip fault. In this model, extension of the rift basin was controlled by right-lateral displacement of the strike-slip fault, which acted as a transform fault at this time. This rift is interpreted as a segment of the rift system of the Gulf of Mexico.
Computational Geometry, 1999
The greedy triangulation of a finite planar point set is obtained by repeatedly inserting a short... more The greedy triangulation of a finite planar point set is obtained by repeatedly inserting a shortest diagonal that does not cross those already in the plane. The Delaunay triangulation, which is the straight-line dual of the Voronoi diagram, can be produced in O(n log n) worst-case time, and often even faster, by several practical algorithms. In this paper we show that for any planar point set S, if the Delaunay triangulation of S is given, then the greedy triangulation of S can be computed in linear worst-case time (and linear space).
Revista mexicana de …, 1997
donde las rocas están prácticamente sin deformar. La Formación Chivillas consiste en derrames bas... more donde las rocas están prácticamente sin deformar. La Formación Chivillas consiste en derrames basálticos frecuentemente con estructura en almohadilla y depósitos siliciclásticos producto de corrientes turbidíticas y flujos de escombros que forman una sucesión volcanosedimentaria muy gruesa cortada por diques de composición similar a los derrames. Se estima un espesor total de más de 4875 m. La Formación Chivillas se asigna al Barremiano con base en la edad máxima de depósito por circones detríticos, edad que es congruente con el contenido fósil previamente reportado. En la formación se identificaron 16 facies en cinco clases: conglomerática, arenosa, fina, calcárea e ígnea, las cuales se agruparon en ocho asociaciones de facies: A) Turbiditas de grano medio; B) Turbiditas de grano grueso; C) Turbiditas de grano fino; D) Areniscas sin estructura interna; E) Debritas soportadas por clastos; F) Debritas soportadas por matriz; G) Pliegues disarmónicos sinsedimentarios y H) Derrames y lavas almohadilladas. Con las asociaciones de facies reconocidas se interpreta un ambiente de depósito de abanico submarino. Las rocas volcánicas de la Formación Chivillas tienen una composición máfica a intermedia alcalina con afinidad geoquímica tipo MORB u OIB, con valores isotópicos de plomo común similares a los valores de manto enriquecido, la firma isotópica Pb/Pb de los derrames de la Formación Chivillas sugiere una fuente asociada a la corteza inferior. Las areniscas estudiadas están conformadas principalmente de cuarzo monocristalino, cuarzo policristalino milonítico, cuarzo policristalino en mosaico, microclina pertítica, y algunas plagioclasas; también son muy abundantes los líticos de limolita y caliza, y en menor cantidad líticos volcánicos y metamórficos, y otros similares a granito o gneis granulítico; texturalmente, los clastos son angulosos a subredondeados. Los clastos en los conglomerados son de caliza, arenisca (con estratificación cruzada) y gneis. Estas litologías son características de los complejos Milonítico Sierra de Juárez y Oaxaqueño, y su cubierta sedimentaria. Se observaron escasos líticos volcánicos en las areniscas, y algunos niveles con piroclastos de caída. Las areniscas tienen su procedencia en bloques continentales, específicamente en un cratón interior o de un basamento levantado, por lo que podemos suponer que proceden de la erosión de Oaxaquia. La presencia de circones de edad Pan-Africano-Brasiliano indica una procedencia de Gondwana probablemente transportados por sistemas fluviales complejos en una etapa evolucionada del proceso de rifting del Golfo de México.
Reinterpretación metalogenética del mineral de hierro de La Chula: Yacimiento de Peña Colorada, Edo de Colima, México
ABSTRACT
Revista Mexicana de Ciencias Geológicas
El depósito de hierro de Peña Colorada está constituido por tres tipos de mineralización caracter... more El depósito de hierro de Peña Colorada está constituido por tres tipos de mineralización característicos: (1) un cuerpo superior masivo de magnetita , subconcordante con la estratificación y de hasta 20 metros de potencia, que contiene fragmentos decimétricos a métricos de granatitas pre-existentes, completamente reemplazadas por feldespato potásico; (2) un cuerpo con magnetita diseminada, también subconcordante con la estratificación, situado por debajo del anterior y de una potencia reconocida, por sondeos, de hasta 150 metros, constituido por alternancias rítmicas de pirita-magnetita-piroxeno junto con cristales idiomórficos de feldespato potásico poiquilítico de origen metasomático que, localmente, llegan a constituir una episienita "sensu lato"; y (3) una brecha polimícitica, con evidencias de fracturación hidráulica, que corta a toda la serie estratigráfica local, con morfología general de diatrema, que incluye en sus niveles inferiores xenolitos de "nelsonitas pobres en Ti", en el sentido de Fooses y Grauch, así como fragmentos de los otros cuerpos mineralizados. En este trabajo reportamos los dos primeros fechamientos, efectuados mediante el método K-Ar, en los cuerpos mineralizados de Peña Colorada. Una muestra de feldespato potásico de las episienitas del cuerpo diseminado inferior presenta la edad más antigua del depósito (65.3±1.5 Ma); en cambio, una muestra de feldespato potásico del cuerpo masivo superior presenta una edad sensiblemente menor (57.3±2.1 Ma). Estos fechamientos sitúan la formación de dicho depósito entre el límite Cretácico Superior-Paleoceno y el Paleoceno medio. Dado que los cuerpos fechados representan al segundo y tercer evento de formación del depósito (de cinco), se puede argumentar que el tiempo total de formación del depósito es superior a 4.4 Ma, pudiendo haber sido, muy posiblemente, mucho mayor. La disposición espacial de los diferentes cuerpos mineralizados, sus características texturales, y
sismos de 19 (Ms = 8.1) y 20 (Ms = 7.5) de septiembre de 1985, comprendido entre la Playa de Tizu... more sismos de 19 (Ms = 8.1) y 20 (Ms = 7.5) de septiembre de 1985, comprendido entre la Playa de Tizupan, Michoacán y Zihuatanejo, Guerrero (aproxi-madamente180 km), permitió establecer con certeza razonable el levantamiento quesufriola costa como consecuencia directa de dichos terremotos. En ausencia de mareógrafos en el área, el levantamiento se cuantificó comparando el nivel de una franja blanca horizontal marcada en las costas acantiladas, constituida por organismos sésiles muertos al ser desplazadas de su habitat por el levantamiento, y el nivel en el que éstos debieron encontrarse antes del sismo; estos organismos son principalmente el balano Chthamalus fissus Darwin y algas coralinas costrosas que se desarrollan en la zona alta de intermareas y la zona de salpicadura de las olas, respectivamente. Esta franja de organismos se observó a 0.50 m sobre su nivel normal en Neixpa, a 0.60 m en el km 46 de la Carretera Playa Azul-Caletade Campos, a 0.45 m en Chuquiapan y a 0.35 m en Las Penas, lo que permite concluir que el segmento levantado tiene una longitud minima de 32km. La presenciaen este tramo de costas acantiladas con terrazas de erosión marina de hasta 60 m de altitud, flanqueadas por tramos largos de playas de perfil suave, sugiere que el segmento levantado ha sufrido una historia sísmica reiterada y de gran intensidad relativa durante los últimos miles de años. La disminución sistemática del levantamiento de WNWa ESE observada a lo largo de los32 km indica que el bloque fue basculado en esta ultima dirección.
Boletin de la Sociedad Geologica Mexicana
Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto En la pr... more Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto En la presente nota se propone que la sucesión de terrígenos más antigua que aflora en la región de Tolimán, sea dividida en dos unidades: El complejo El Chilar, constituido por turbiditas siliciclásticas intensamente deformadas y la Formación San Juan de la Rosa como compuesta por una sucesión volcano-sedimentaria depositada en condiciones marinas. El volcanismo
Chromite deposits at Loma Baya: petrogenesis and clues for the origin of the coastal Guerrero Composite Terrane in Mexico
The high-Al podiform Loma Baya chromitite deposits occur hosted within an ultramafic massif repre... more The high-Al podiform Loma Baya chromitite deposits occur hosted within an ultramafic massif representative of ophiolitic mantle produced in a back-arc basin near to the westernmost edge of the Guerrero Composite Terrane, SW Mexico. Such conclusion is drawn from the tholeiitic (i.e., back-arc basin basalt) affinity of the parental melts of the chromitite, deduced from major and trace element distribution in chromite, and the nature of the platinum-group elements mineralization.
Contributions to Mineralogy and Petrology, 2015
event, confirming previous thermodynamic predictions. Understanding these complex features is of ... more event, confirming previous thermodynamic predictions. Understanding these complex features is of particular interest due to the fact that changes in temperature and variable degrees of fluid/rock interaction during metamorphism and intrusion have also significantly affected the chromitehosted IPGE carrier phases. Here, we propose that the metamorphic fluids involved in the hydrous metamorphism have caused the desulphurization of laurite RuS 2 , releasing minute particles of Ru-Os-Ir alloys <50 nm in diameter. The following short-lived thermal event that promoted dehydration in the chromitite had the opposite effect on nanoparticle stability, producing a significant coarsening of metal nanoparticles to dimensions larger than a micron. Based on such observations, we argue that IPGE nanoparticles can be exsolved and grown (or coarsen) from sulphide matrices during prograde metamorphism or heating and not exclusively upon cooling under magmatic conditions as it has been previously suggested. These results provide new insights on the relevant role of temperature and nanoparticle-host interaction phenomena in natural systems, shedding new light on the kinetic controls of nano-to micronscale IPGE particle distributions during metamorphism.
The aquatic and semiaquatic biota in Miocene amber from the Campo LA Granja mine (Chiapas, Mexico): Paleoenvironmental implications
Journal of South American Earth Sciences, 2015
Abstract Amber from the Campo La Granja mine in Chiapas, Mexico, is distinct from other sources o... more Abstract Amber from the Campo La Granja mine in Chiapas, Mexico, is distinct from other sources of amber in Chiapas. Campo La Granja amber has distinct layers created by successive flows of resin with thin layers of sand on most surfaces. Aquatic and semi-aquatic arthropods are commonly found. Together these pieces of evidence suggest an estuarine environment similar to modern mangrove communities. The aquatic crustaceans are the most intriguing aspect of the biota. A large number of ostracods have been found in the amber—many with their carapaces open, suggesting that they were alive and submerged in water at the time of entombment. The only known examples of brachyuran crabs preserved in amber are found in the Campo La Granja amber. Amphipods, copepods, isopods, and tanaids are also members of the crustacean fauna preserved in amber.
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Papers by Elena Centeno-Garcia