Time filter

Source Type

Salinas-Marquez F.M.,Autonomous University of Baja California | Flores-Trujillo J.G.,Autonomous University of Carmen | Helenes J.,Research Center Cientifica tudios Superiores Of Ensenada | Tellez-Duarte M.A.,Autonomous University of Baja California | Aranda-Manteca F.J.,Autonomous University of Baja California
Boletin de la Sociedad Geologica Mexicana | Year: 2016

The aim of the present study is to identify and analyze the paleoenvironmental and biostratigraphic aspects of the diatoms, in the sediments of the Mesa La Misión outcrop. The Mesa La Misión in Baja California is an outcrop of the Member Los Indios, part of the Rosarito Beach Formation. This formation consists of a volcanoclastic sequence with abundant and diverse vertebrate fauna named "La Misión Local Fauna". The presence of 15 different diatom species were found in samples taken from four stratigraphic levels of the Mesa La Misión outcrop. Deposition of the Los Indios Member occurred in a marine progradational platform. Benthic diatoms are abundant in the lower part of the sequence and become less abundant at higher stratigraphic levels. Most of the diatom species found indicate temperate waters. However, mixing of water may have been present due to some tropical and cold water specimens that were found. An increase of the deposition depth towards the top of the section was found. This was due to the occurrence of diatoms from different temperature gradients, combined with the reduction of benthic diatoms towards the top of the section. This sea level can be associated with the Middle Miocene Climatic Optimum. It may correspond to the global cycle TM 2.2. In addition, the presence of Actynocyclus ingens var. nodus, a biostratigraphical taxon, places the deposition of the sediments during the middle Miocene. More specifically, between 15.6 and 13.0 million years (middle Langhian). This age correlates with the radiometric dating of the underlaying and overlaying basalts dated 16.1 ± 2.1 and 14.3 ± 2.6, respectively.

Maya-Sanchez M.C.,Research Center Cientifica tudios Superiores Of Ensenada | Reynoso-Hernandez J.A.,Research Center Cientifica tudios Superiores Of Ensenada
Microwave and Optical Technology Letters | Year: 2011

A new bandstop-coupled line filter using spurline structures has been presented in this work. The new bandstop filter enhances the rejection bandwidth of bandstop coupled line filters in a 50%. To demonstrate the idea, classical bandstop-coupled line filters with and without simple spurlines structure were designed using Rogers material, and their frequency response were compared. Simulations performed with momentum agree with experimental results, demonstrating the usefulness of spurlines structures in the enhancement of the bandwidth of coupled line filters. © 2011 Wiley Periodicals, Inc.

Garcia-Osorio A.,Research Center y Estudios Avanzados | Loo-Yau J.R.,Research Center y Estudios Avanzados | Reynoso-Hernandez J.A.,Research Center Cientifica tudios Superiores Of Ensenada | Ortega-C. S.,Research Center y Estudios Avanzados | Del Valle-Padilla J.L.,Research Center y Estudios Avanzados
Microwave and Optical Technology Letters | Year: 2011

This article presents an improved nonlinear IDS(VGS, VDS) model useful for modeling the experimental pulsed I-V measurement data of GaN FETs operated at large drain-source voltages. This improved IDS(VGS, VDS) model is based on the Chalmers model. The main features of the improved nonlinear I DS(VGS, VDS) model are the two analytical expressions that are incorporated to model the output conductance and the saturation voltage. The new model only requires 13 parameters easily determined from experimental pulsed I-V data. Comparison between simulated and measured data of an inverse class F PA designed with a commercial GaN FET at 1.5 GHz demonstrate that the proposed model is suitable for microwave circuit design based on GaN transistors. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1256-1259, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25980 Copyright © 2011 Wiley Periodicals, Inc.

Camprubi A.,National Autonomous University of Mexico | Gonzalez-Partida E.,National Autonomous University of Mexico | Lopez-Martinez M.,Research Center Cientifica tudios Superiores Of Ensenada | Iriondo A.,National Autonomous University of Mexico | And 7 more authors.
Ore Geology Reviews | Year: 2016

The Guaynopa and Guaynopita mineralized areas in central-western Chihuahua are conterminous sets of ore deposits that formed in association with gabbroic and granitic intrusions that correspond to the Lower Volcanic Complex of the Sierra Madre Occidental silicic large igneous province. The Guaynopa IOCG deposit consists of (1) early iron oxide-copper-gold mantos accompanied by potassic (fuchsite, biotite and potassium feldspar) and/or calcic-sodic alteration (tremolite-actinolite) and hosted by marmorized limestones near the contact with intrusive granites, (2) later copper-rich stockworks and gold disseminations, and (3) late gold- and copper-rich quartz-calcite veins. Mantos contain most of the copper and gold ores in this deposit, and their hypogene mineralogy consists of magnetite, fuchsite, chalcopyrite, Ag-rich gold, cuprite, and late hematite. The Guaynopita porphyry copper deposit consists mainly of stockworks within potassic alteration zones, and includes ancillary sulfide copper- and lead-rich skarn deposits. Microthermometric studies of fluid inclusions were carried out on most mineral associations of the Guaynopa IOCG and in the Guaynopita porphyry copper deposits. In IOCG mantos, temperatures of homogenization (Th) in calcite and quartz vary between 152° and 310°C, and apparent salinities between 10.7 and 24.2wt.% NaCl equiv. In IOCG veins, Th in quartz vary between 310° and 400°C, and apparent salinities between 11.1 and 21.0wt.% NaCl equiv. In IOCG stockworks, Th in tremolite vary between 330° and 410°C, and the apparent salinity is 16.0wt.% NaCl equiv. In porphyry-copper stockworks, Th in quartz vary between 205° and 448°C, and apparent salinities between 8.1 and 21.3wt.% NaCl equiv. δ34S values for sulfides (mostly chalcopyrite) in IOCG associations range between -15.1 and 7.0‰ in mantos, between -3.7 and -0.2‰ in veins, and between -1.6 and 0.2‰ in stockworks. δ13CVPDB values from calcite in IOCG mantos range between -5.22 and 3.45‰, and δ18OVSMOW values between 9.61 and 17.23‰, which correspond to the interaction of magmatic fluids with host limestones at a broad range of temperatures and water to rock volume ratios. Likely ore-formation processes are isothermal mixing, conductive cooling, and boiling. In the case of the Guaynopita porphyry copper deposit, similar possible magmatic-dominated fluids underwent progressive dilution and cooling with time, with the occurrence of boiling at some extent.New geochronological data from hydrothermal minerals and host rocks for these deposits suggest a minimum ~14m.yr. span of conjoined magmatic and hydrothermal activity: biotite and chromian muscovite (fuchsite) from mantos at the Guaynopa IOCG deposits yielded 40Ar/39Ar plateau ages at 98.12±0.37 and 95.42±0.71Ma (Cenomanian), respectively, whereas U-Pb dating in zircons from diorite and granodiorite host intrusives, and a potassic alteration assemblage at Guaynopita yielded ages at 92.4±0.5Ma, 89.1±0.7Ma (Turonian to Coniacian), and 84.4±1.0Ma (Santonian), respectively. These ages place the Guaynopa-Guaynopita ensemble within the Mesozoic metallogenic provinces and epochs in northwestern Mexico. Unlike the majority of Mesozoic generic magmatic-hydrothermal iron oxide deposits in Mexico, Guaynopa in Chihuahua and Cerro del Oro in Sonora formed at a distal position from the paleo-Pacific margin (~500km inland) and therefore it cannot be ascribed to a general intra-arc "Coastal Andes Cordillera-type" tectonomagmatic setting. Therefore, this region may constitute a part of a previously unnoticed metallogenetic region, and petrogenetic studies should follow in order to properly evaluate the hypothetical possibility for a back-arc setting there during the Late Cretaceous. © 2016 Elsevier B.V.

Loading Research Center Cientifica tudios Superiores Of Ensenada collaborators
Loading Research Center Cientifica tudios Superiores Of Ensenada collaborators