Martin Valencia - Profile on Academia.edu (original) (raw)
Papers by Martin Valencia
Temporal constraints on the eastward migration of the Late Cretaceous–early Tertiary magmatic arc of NW Mexico based on new 40Ar/39Ar hornblende geochronology of granitic rocks
Journal of South American Earth Sciences, 2006
... late 1970s (eg, Coney and Reynolds, 1977, Gastil and Krummenacher, 1977, McDowell and Clabaug... more ... late 1970s (eg, Coney and Reynolds, 1977, Gastil and Krummenacher, 1977, McDowell and Clabaugh, 1979, Damon et al., 1983a, Damon et al., 1983b, Silver and Chappell, 1988, Kimbrough et al., 2001, Staude and Barton, 2001, Henry et al., 2003 and Ortega-Rivera, 2003). ...
Canadian Journal of Earth Sciences, 2003
Figure 11 and caption were mistakenly left out of the printed text. They are presented here. The ... more Figure 11 and caption were mistakenly left out of the printed text. They are presented here. The NRC Research Press apologizes for any inconveniences to the authors and readers.
Los Alisos prospect is a porphyry copper deposit located in northeastern Sonora, at about 10 km n... more Los Alisos prospect is a porphyry copper deposit located in northeastern Sonora, at about 10 km northeast of La Caridad mine. It is a relatively small deposit, characterized by an intense hypogene oxidation zone exposed over 20 km 2 . According to the new U-Pb zircon dates reported in this work, the oldest rocks outcropping in this region consist of andesitic volcanic flows of Late Cretaceous age dated at 73.6 ± 1.0 Ma, which were intruded during the Paleocene by a 60.2 ± 0.8 Ma old quartz-feldspar porphyry stock. These rocks were unconformably covered by Eocene-Oligocene rhyolite lava flows and tuffs. Locally, these rocks were in turn covered by a sequence of conglomerate and sandstone with basaltic lava flows, which regionally correlates with the Miocene Baucarit Formation. The geochemical and isotopic composition of the quartz-feldspar porphyry is characterized by a light rare earth enriched pattern (LREE), coupled with Sr and eNd initial values of 0.7067 and -5.5, respectively. ...
Boletín de la …, 2006
La abundante actividad magmática ocurrida durante el fi n del Mesozoico y el inicio del Cenozoico... more La abundante actividad magmática ocurrida durante el fi n del Mesozoico y el inicio del Cenozoico a lo largo de la Cordillera oeste de Norte América, produjo el emplazamiento de numerosos centros de mineralización de tipo pórfi do de cobre. Esta actividad se extendió también por todo el occidente de México, particularmente por la región noroeste del país. Esta región junto a las regiones aledañas de Arizona y New Mexico, en el suroeste de los Estados Unidos, constituye uno de los centros con mineralización de cobre más importantes en el mundo, que puede competir en tamaño con los famosos depósitos de la Cordillera oeste de Sur América. La mayor parte de los depósitos de cobre en México se localizan en la porción oriental del cinturón magmático Laramide (90-40 Ma) y predominantemente tienen edades entre 75 y 50 Ma. Los depósitos más grandes y mejor preservados se localizan en el noreste de Sonora, en la parte norte del cinturón, donde Cananea (~30 Mt Cu) y La Caridad (~8 Mt Cu) contienen acumulaciones de metal de gran relevancia a escala mundial. La mineralización de cobre está comúnmente acompañada por concentraciones localmente importantes de molibdeno, tungsteno y oro. La distribución de estos metales está aparentemente asociada a cambios regionales en el tipo de basamento en el cual se emplazó la mineralización. En general se distinguen tres dominios principales: el dominio norte caracterizado por un basamento cristalino proterozoico asociado a los terrenos Norte América y Caborca; un dominio central compuesto por rocas paleozoicas de cuenca marina profunda subyacidas por las rocas cristalinas del terreno Caborca, también defi nido como el terreno Cortés; y un dominio sur representado por secuencias mesozoicas de arco de islas del Terreno Guerrero. Los datos isotópicos de Sr y Nd disponibles muestran que los plutones laramídicos en los dominios norte y central tienen fi rmas más evolucionadas en comparación con las del dominio sur, lo cual sugiere que el tipo de basamento intrusionado tuvo una infl uencia importante en la composición fi nal de los magmas laramídicos, y pudo haber actuado también como un importante control en la distribución espacial de los metales asociados a los sistemas de tipo pórfi do cuprífero del noroeste de México. En general, aunque los metales no están limitados geográfi camente, se puede apreciar una predominancia de depósitos de Cu-MoW en la parte norte y central del cinturón subyacida por rocas antiguas de afi nidad norteamericana, la cual hospeda los depósitos más importantes. Además, existen varias chimeneas brechoides con altas leyes de molibdeno en esta misma porción del cinturón, justo al sur de la región de Cananea y La Caridad, lo cual sugiere un levantamiento tectónico y erosión relativamente mayor. Más hacia el sur, el cinturón está subyacido por rocas más jóvenes de afi nidad oceánica, caracterizadas por el Terreno Guerrero. La mineralización es típicamente de Cu-Au y se encuentra bien distribuida en esta parte del cinturón; sin embargo, las dimensiones de los centros mineralizados conocidos hasta ahora son relativamente pequeñas, siendo los depósitos de El Arco en Baja California (~3.6 Mt Cu) y Santo M E X IC ANA A .C .
Late Cretaceous to early Eocene magmatic evolution of the Laramide arc in the Nacozari quadrangle, northeastern Sonora, Mexico and its regional implications
Ore Geology Reviews, 2016
Abstract Late Cretaceous to early Eocene volcanic and plutonic rocks that crop out in the Nacozar... more Abstract Late Cretaceous to early Eocene volcanic and plutonic rocks that crop out in the Nacozari quadrangle compose the Laramide magmatic arc in northeastern Sonora, northwestern Mexico. The purpose of this work is to characterize the arc rocks based on new cartography, stratigraphy, U-Pb and K-Ar geochronology, and major, trace and isotope geochemical data and interpret them in the regional context of evolution of the arc. The study area lies within the Proterozoic Mazatzal crustal block which is limited to the south by the Caborca block. The volcanic rocks regionally correlate with the Tarahumara Formation and consist of volcanic flows, breccias, tuffs and volcaniclastic sandstones with an estimated thickness of 4 km. They range in composition from andesite to rhyolite and have isotopic ages from 76.8 ± 0.4 to 57.1 ± 0.4 Ma. The granitic plutons and rhyolitic domes that intrude them yielded ages from 59.3 ± 0.8 to 53.3 ± 1.6 Ma. Initial 87 Sr/ 86 Sr and epsilon Nd values for these rocks vary from 0.70553 to 0.70841 and − 3.7 to − 8.5, respectively, and have 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb isotope ratios that range from 18.05 to 19.05, 15.52 to 15.63, and 38.25 to 39.07, respectively. Regional integration of our U-Pb ages suggests that the volcanic activity lasted between ca. 81 and 57 Ma, with two main peaks of activity at 74.5 and 61 Ma. Similarly, regional magmatic activity indicated by dated plutons initiated at ca.91 and ended by 50 Ma, after main peaks of activity at 71 and 60–55 Ma. The plutonism between 91 and 80 Ma was subordinate and regionally restricted to coastal and central Sonora and might represent an older event unrelated to the Laramide arc. Two K-Ar cooling ages of 55.4 ± 0.7 and 48.5 ± 0.7 Ma obtained from La Purica granite dated at ca. 59 Ma (U-Pb) in the study area, correlate regionally with a possible event of rapid uplift between 68 and 50 Ma. The geochemical composition of the studied rocks indicate high-K, calc-alkaline, metaluminous to weakly peraluminous compositions, typical of subduction arc-related magmas which characterize the Laramide magmatic belt in northwestern Mexico. The Nd, Sr and Pb isotope compositions of these and other samples documented for northeastern Sonora, closely correlate with isotope signatures of the Mazatzal crustal block in southeastern Arizona and differ from those in the Caborca block, which display affinity with the Mojave-Yavapai province. The data also allow to best constrain the location of the boundary between the Mazatzal and Caborca crustal blocks in east-central Sonora.
Cretaceous and Tertiary sedimentary, magmatic, and tectonic evolution of north-central Sonora (Arizpe and Bacanuchi Quadrangles), northwest Mexico
Geological Society of America Bulletin, Apr 2000
The Arizpe and Bacanuchi Quadrangles provide a geologic history representative of the north-centr... more The Arizpe and Bacanuchi Quadrangles provide a geologic history representative of the north-central part of Sonora, where lithologies are dominated by late Mesozoic and Cenozoic igneous rocks. In this study, new geologic mapping, 40Ar/39Ar dating, and geochemical analyses have been combined to provide a stratigraphic framework for this area. Ten lithostratigraphic units and several igneous and tectonic events can be recognized. The oldest outcropping rocks are Lower Cretaceous strata of the Bisbee Group, which along with the Picacho conglomerate record a middle Cretaceous compressive tectonic event and associated sedimentation. Laramide igneous activity is widespread and represented by (1) highly altered andesitic flows and volcaniclastic rocks (Arroyo Alcaparros andesitic rocks) of late Campanian to Maastrichtian age, (2) less altered andesitic and dacitic flows (Cerro Las Jarillas volcanic rocks) of late Paleocene age, and the intrusive bodies of (3) Sierra El Manzanal granodiorite and (4) Rancho Vaquería quartz monzonite. The Sierra El Manzanal granodiorite was emplaced at ca. 68 Ma on the basis of a 40Ar/39Ar biotite age (67.97 ± 0.19 Ma) and cooled relatively rapidly according to less precise 40Ar/39Ar hornblende and K-feldspar ages from the same sample (64.8 ± 1.0 Ma and 62.8 ± 0.3 Ma, respectively). The Cerro Las Jarillas volcanic rocks are slightly younger (40Ar/39Ar biotite age of 58.67 ± 0.17 Ma). The Rancho Vaquería quartz monzonite was emplaced at ca. 57 Ma (40Ar/39Ar biotite age of 56.73 ± 0.14 Ma and a less precise 40Ar/39Ar hornblende age of 55.0 ± 0.7 Ma); a protracted cooling history of this pluton is indicated by the age spectrum of K-feldspar from the same sample. A probable magmatic lull and denudation seem to have occurred between middle and late Eocene time and probably until the early Oligocene. Subsequently, rhyolitic to mafic volcanism began close to late Oligocene time and lasted until the early Miocene. Felsic volcanism is represented by the Cerro Cebadéhuachi volcanic rocks, from which 40Ar/39Ar hornblende ages of 27.25 ± 0.09 and 27.32 ± 0.06 Ma and a biotite age of 26.97 ± 0.06 Ma were obtained at three different localities. The Mesa Pedregosa volcanic rocks represent the transition to younger, mafic volcanic activity that occurred during the late Oligocene, as indicated by a sanidine 40Ar/39Ar age of 25.48 ± 0.05 Ma. This late Oligocene and early Miocene magmatism was paired by two episodes of extensional deformation. The first phase is characterized by northwest-striking normal faults and folds, which expose the deepest structural levels of the area, and by the related basin fill, the Bacanuchi conglomerate. The second phase is represented by north-striking normal faults and by the syntectonic basin fill, the Arizpe conglomerate. Basaltic andesite volcanic flows at the base of the Arizpe conglomerate yielded 40Ar/39Ar (whole-rock) ages of 23.52 ± 0.17 and 21 ± 0.20 Ma. The extensional deformation (27 to 23 Ma) in the study area is coeval with the development of metamorphic core complexes in neighboring areas of Sonora and with the onset of extension in southern Sonora. The mafic volcanic rocks and clastic sedimentary units associated with this extension resemble the basin fills that in other parts of Sonora are assigned to the Báucarit Formation.
Geochemical information from samples representing each of the igneous events displayed high-K calc-alkalic and mostly metaluminous compositions. The older units including the Arroyo Alcaparros andesitic rocks, the Cerro Las Jarillas volcanic rocks, the Sierra El Manzanal granodiorite, and the Rancho Vaquería quartz monzonite are characterized by steep chondrite-normalized REE (rare earth element) slopes and generally well-developed negative Eu anomalies, suggesting garnet and plagioclase removal in the source. The younger igneous events including the Cerro Cebadéhuachi and Mesa Pedregosa volcanic rocks, and the basaltic flows associated with the Arizpe conglomerate, showed basin-shaped REE slopes with no Eu anomalies, suggesting clinopyroxene or amphibole fractionation.
… Society of America …, 2001
Along the Laramide belt of northwestern Mexico, granitic rocks of similar bulk composition show i... more Along the Laramide belt of northwestern Mexico, granitic rocks of similar bulk composition show isotopic and trace element signatures that help to delineate the position of the southern edge of the North American Precambrian basement. In the northern part, the Laramide plutons (the ''northern granites'') intruded Proterozoic crystalline rocks and a thick Late Proterozoic through Paleozoic miogeoclinal cover of North American affinity. In the central part, the granitic bodies (the ''central granites'') were emplaced into a sequence of Paleozoic eugeoclinal rocks overlain by Late Triassic clastic units. The southern part of the belt (the ''southern granites'') intruded a less-known crust characterized by middle to late Mesozoic island-arc-related volcanic and sedimentary rocks of the Guerrero terrane. Data from a suite of metaluminous to slightly peraluminous calc-alkalic granitic rocks along the belt display north-to-south geochemical and isotopic variations, which could correlate with the type of intruded basement. The northern and central granites are characterized by strongly fractionated, light rare earth element (REE)-enriched patterns, which display generally pronounced negative europium anomalies, whereas the southern granites have lower total REE enrichments and much flatter chondrite-normalized slopes displaying almost no europium anomalies. Isotopic results also suggest regional variations, as shown by the following initial Sr and ⑀ Nd ranges: 0.7070 to 0.7089 and؊4.2 to؊5.4, respectively, for the northern granites; 0.7060 to 0.7079 and؊3.4 to؊5.1 for the central granites; and 0.7026 to 0.7062 and؊0.9 to ؉4.2 for the southern granites. On the basis of their isotopic similarities, the Proterozoic mafic to intermediate lower crust revealed by xenoliths from young volcanic flows in southern Arizona and northern Mexico is interpreted as *E-mail: valencia@geologia.unam.mx. a reasonable parental source for the northern and central granites; however, mantle-derived melts are not excluded. The more primitive southern granites are interpreted to come from a source that lacked Proterozoic basement. Instead, they were probably derived by mixing of juvenile mantle melts with partial melts of the lower parts of the Guerrero terrane. In general, the north-to-south compositional variations of the Laramide granitic rocks of northwestern Mexico reflect the crustal structure underneath the batholiths. The Sr and Nd data indicate that the edge of the North American Precambrian basement extends approximately southeastward from the coastal batholith of central Sonora; then, about 200 km south of Hermosillo in southern Sonora, the edge bends eastward and continues to the east beneath the Sierra Madre Occidental volcanic province.
Cretaceous and Tertiary sedimentary, magmatic, and tectonic evolution of north-central Sonora (Arizpe and Bacanuchi Quadrangles), northwest Mexico
… Society of America …, 2000
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… SOCIETY OF AMERICA, 2007
(2) Eocene andesites and lesser rhyolites, traditionally grouped into the so-called Lower Volcani... more (2) Eocene andesites and lesser rhyolites, traditionally grouped into the so-called Lower Volcanic Complex; (3) silicic ignimbrites mainly emplaced during two pulses in the Oligocene (ca. 32-28 Ma) and Early Miocene (ca. 24-20 Ma), and grouped into the "Upper Volcanic Supergroup"; (4) transitional basaltic-andesitic lavas that erupted toward the end of, and after, each ignimbrite pulse, which have been correlated with the Southern Cordillera Basaltic Andesite Province of the southwestern United States; and (5) postsubduction volcanism consisting of alkaline basalts and ignimbrites emplaced in the Late Miocene, Pliocene, and Pleistocene, directly related to the separation of Baja California from the Mexican mainland. The products of all these magmatic episodes, partially overlapping in space and time, cover a poorly exposed, heterogeneous basement with Precambrian to Paleozoic ages in the northern part (Sonora and Chihuahua) and Mesozoic ages beneath the rest of the Sierra Madre Occidental. The oldest intrusive rocks of the Lower Volcanic Complex (ca. 101 to ca. 89 Ma) in Sinaloa, and Maastrichtian volcanics of the Lower Volcanic Complex in central Chihuahua, were affected by moderate contractile deformation during the Laramide orogeny. In the fi nal stages of this deformation cycle, during the Paleocene and Early Eocene, ~E-W to ENE-WSW-trending extensional structures formed within the *E-mails, Ferrari and Valencia-Moreno: luca@geociencias.unam.mx; valencia@ geologia.unam.mx. Current address, Bryan: School of Earth Sciences & Geography, Kingston University, Kingston Upon Thames, Surrey KT1 2EE, UK; s.bryan@kingston.ac.uk.
Geochemistry of the coastal Sonora batholith, northwestern Mexico
… Journal of Earth …, 2003
... to the Pacific side (Fig. 7d). One likely explanation to this behavior may be involvement of ... more ... to the Pacific side (Fig. 7d). One likely explanation to this behavior may be involvement of deep sea clay in the magma source, according to the average content of Sr in these sediments (Faure 1986). In any case, the lateral variations ...
Geochemistry of Laramide granitic rocks across the southern margin of the Paleozoic North American continent, Central Sonora, Mexico
International geology …, 1999
The geochemistry of Laramide granitic rocks from central Sonora was studied to relate possible co... more The geochemistry of Laramide granitic rocks from central Sonora was studied to relate possible compositional variations to the assimilation of different crustal sources. Most of the studied rocks are granodiorites collected near the southern boundary of the Paleozoic North American continent. North of this boundary, the Laramide plutons intruded a thick section of Upper Proterozoic and Paleozoic miogeoclinal strata, whereas
Temporal constraints on the eastward migration of the Late Cretaceous–early Tertiary magmatic arc of NW Mexico based on new 40Ar/39Ar hornblende geochronology of granitic rocks
Journal of South American Earth Sciences, 2006
... late 1970s (eg, Coney and Reynolds, 1977, Gastil and Krummenacher, 1977, McDowell and Clabaug... more ... late 1970s (eg, Coney and Reynolds, 1977, Gastil and Krummenacher, 1977, McDowell and Clabaugh, 1979, Damon et al., 1983a, Damon et al., 1983b, Silver and Chappell, 1988, Kimbrough et al., 2001, Staude and Barton, 2001, Henry et al., 2003 and Ortega-Rivera, 2003). ...
Canadian Journal of Earth Sciences, 2003
Figure 11 and caption were mistakenly left out of the printed text. They are presented here. The ... more Figure 11 and caption were mistakenly left out of the printed text. They are presented here. The NRC Research Press apologizes for any inconveniences to the authors and readers.
Los Alisos prospect is a porphyry copper deposit located in northeastern Sonora, at about 10 km n... more Los Alisos prospect is a porphyry copper deposit located in northeastern Sonora, at about 10 km northeast of La Caridad mine. It is a relatively small deposit, characterized by an intense hypogene oxidation zone exposed over 20 km 2 . According to the new U-Pb zircon dates reported in this work, the oldest rocks outcropping in this region consist of andesitic volcanic flows of Late Cretaceous age dated at 73.6 ± 1.0 Ma, which were intruded during the Paleocene by a 60.2 ± 0.8 Ma old quartz-feldspar porphyry stock. These rocks were unconformably covered by Eocene-Oligocene rhyolite lava flows and tuffs. Locally, these rocks were in turn covered by a sequence of conglomerate and sandstone with basaltic lava flows, which regionally correlates with the Miocene Baucarit Formation. The geochemical and isotopic composition of the quartz-feldspar porphyry is characterized by a light rare earth enriched pattern (LREE), coupled with Sr and eNd initial values of 0.7067 and -5.5, respectively. ...
Boletín de la …, 2006
La abundante actividad magmática ocurrida durante el fi n del Mesozoico y el inicio del Cenozoico... more La abundante actividad magmática ocurrida durante el fi n del Mesozoico y el inicio del Cenozoico a lo largo de la Cordillera oeste de Norte América, produjo el emplazamiento de numerosos centros de mineralización de tipo pórfi do de cobre. Esta actividad se extendió también por todo el occidente de México, particularmente por la región noroeste del país. Esta región junto a las regiones aledañas de Arizona y New Mexico, en el suroeste de los Estados Unidos, constituye uno de los centros con mineralización de cobre más importantes en el mundo, que puede competir en tamaño con los famosos depósitos de la Cordillera oeste de Sur América. La mayor parte de los depósitos de cobre en México se localizan en la porción oriental del cinturón magmático Laramide (90-40 Ma) y predominantemente tienen edades entre 75 y 50 Ma. Los depósitos más grandes y mejor preservados se localizan en el noreste de Sonora, en la parte norte del cinturón, donde Cananea (~30 Mt Cu) y La Caridad (~8 Mt Cu) contienen acumulaciones de metal de gran relevancia a escala mundial. La mineralización de cobre está comúnmente acompañada por concentraciones localmente importantes de molibdeno, tungsteno y oro. La distribución de estos metales está aparentemente asociada a cambios regionales en el tipo de basamento en el cual se emplazó la mineralización. En general se distinguen tres dominios principales: el dominio norte caracterizado por un basamento cristalino proterozoico asociado a los terrenos Norte América y Caborca; un dominio central compuesto por rocas paleozoicas de cuenca marina profunda subyacidas por las rocas cristalinas del terreno Caborca, también defi nido como el terreno Cortés; y un dominio sur representado por secuencias mesozoicas de arco de islas del Terreno Guerrero. Los datos isotópicos de Sr y Nd disponibles muestran que los plutones laramídicos en los dominios norte y central tienen fi rmas más evolucionadas en comparación con las del dominio sur, lo cual sugiere que el tipo de basamento intrusionado tuvo una infl uencia importante en la composición fi nal de los magmas laramídicos, y pudo haber actuado también como un importante control en la distribución espacial de los metales asociados a los sistemas de tipo pórfi do cuprífero del noroeste de México. En general, aunque los metales no están limitados geográfi camente, se puede apreciar una predominancia de depósitos de Cu-MoW en la parte norte y central del cinturón subyacida por rocas antiguas de afi nidad norteamericana, la cual hospeda los depósitos más importantes. Además, existen varias chimeneas brechoides con altas leyes de molibdeno en esta misma porción del cinturón, justo al sur de la región de Cananea y La Caridad, lo cual sugiere un levantamiento tectónico y erosión relativamente mayor. Más hacia el sur, el cinturón está subyacido por rocas más jóvenes de afi nidad oceánica, caracterizadas por el Terreno Guerrero. La mineralización es típicamente de Cu-Au y se encuentra bien distribuida en esta parte del cinturón; sin embargo, las dimensiones de los centros mineralizados conocidos hasta ahora son relativamente pequeñas, siendo los depósitos de El Arco en Baja California (~3.6 Mt Cu) y Santo M E X IC ANA A .C .
Late Cretaceous to early Eocene magmatic evolution of the Laramide arc in the Nacozari quadrangle, northeastern Sonora, Mexico and its regional implications
Ore Geology Reviews, 2016
Abstract Late Cretaceous to early Eocene volcanic and plutonic rocks that crop out in the Nacozar... more Abstract Late Cretaceous to early Eocene volcanic and plutonic rocks that crop out in the Nacozari quadrangle compose the Laramide magmatic arc in northeastern Sonora, northwestern Mexico. The purpose of this work is to characterize the arc rocks based on new cartography, stratigraphy, U-Pb and K-Ar geochronology, and major, trace and isotope geochemical data and interpret them in the regional context of evolution of the arc. The study area lies within the Proterozoic Mazatzal crustal block which is limited to the south by the Caborca block. The volcanic rocks regionally correlate with the Tarahumara Formation and consist of volcanic flows, breccias, tuffs and volcaniclastic sandstones with an estimated thickness of 4 km. They range in composition from andesite to rhyolite and have isotopic ages from 76.8 ± 0.4 to 57.1 ± 0.4 Ma. The granitic plutons and rhyolitic domes that intrude them yielded ages from 59.3 ± 0.8 to 53.3 ± 1.6 Ma. Initial 87 Sr/ 86 Sr and epsilon Nd values for these rocks vary from 0.70553 to 0.70841 and − 3.7 to − 8.5, respectively, and have 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb isotope ratios that range from 18.05 to 19.05, 15.52 to 15.63, and 38.25 to 39.07, respectively. Regional integration of our U-Pb ages suggests that the volcanic activity lasted between ca. 81 and 57 Ma, with two main peaks of activity at 74.5 and 61 Ma. Similarly, regional magmatic activity indicated by dated plutons initiated at ca.91 and ended by 50 Ma, after main peaks of activity at 71 and 60–55 Ma. The plutonism between 91 and 80 Ma was subordinate and regionally restricted to coastal and central Sonora and might represent an older event unrelated to the Laramide arc. Two K-Ar cooling ages of 55.4 ± 0.7 and 48.5 ± 0.7 Ma obtained from La Purica granite dated at ca. 59 Ma (U-Pb) in the study area, correlate regionally with a possible event of rapid uplift between 68 and 50 Ma. The geochemical composition of the studied rocks indicate high-K, calc-alkaline, metaluminous to weakly peraluminous compositions, typical of subduction arc-related magmas which characterize the Laramide magmatic belt in northwestern Mexico. The Nd, Sr and Pb isotope compositions of these and other samples documented for northeastern Sonora, closely correlate with isotope signatures of the Mazatzal crustal block in southeastern Arizona and differ from those in the Caborca block, which display affinity with the Mojave-Yavapai province. The data also allow to best constrain the location of the boundary between the Mazatzal and Caborca crustal blocks in east-central Sonora.
Cretaceous and Tertiary sedimentary, magmatic, and tectonic evolution of north-central Sonora (Arizpe and Bacanuchi Quadrangles), northwest Mexico
Geological Society of America Bulletin, Apr 2000
The Arizpe and Bacanuchi Quadrangles provide a geologic history representative of the north-centr... more The Arizpe and Bacanuchi Quadrangles provide a geologic history representative of the north-central part of Sonora, where lithologies are dominated by late Mesozoic and Cenozoic igneous rocks. In this study, new geologic mapping, 40Ar/39Ar dating, and geochemical analyses have been combined to provide a stratigraphic framework for this area. Ten lithostratigraphic units and several igneous and tectonic events can be recognized. The oldest outcropping rocks are Lower Cretaceous strata of the Bisbee Group, which along with the Picacho conglomerate record a middle Cretaceous compressive tectonic event and associated sedimentation. Laramide igneous activity is widespread and represented by (1) highly altered andesitic flows and volcaniclastic rocks (Arroyo Alcaparros andesitic rocks) of late Campanian to Maastrichtian age, (2) less altered andesitic and dacitic flows (Cerro Las Jarillas volcanic rocks) of late Paleocene age, and the intrusive bodies of (3) Sierra El Manzanal granodiorite and (4) Rancho Vaquería quartz monzonite. The Sierra El Manzanal granodiorite was emplaced at ca. 68 Ma on the basis of a 40Ar/39Ar biotite age (67.97 ± 0.19 Ma) and cooled relatively rapidly according to less precise 40Ar/39Ar hornblende and K-feldspar ages from the same sample (64.8 ± 1.0 Ma and 62.8 ± 0.3 Ma, respectively). The Cerro Las Jarillas volcanic rocks are slightly younger (40Ar/39Ar biotite age of 58.67 ± 0.17 Ma). The Rancho Vaquería quartz monzonite was emplaced at ca. 57 Ma (40Ar/39Ar biotite age of 56.73 ± 0.14 Ma and a less precise 40Ar/39Ar hornblende age of 55.0 ± 0.7 Ma); a protracted cooling history of this pluton is indicated by the age spectrum of K-feldspar from the same sample. A probable magmatic lull and denudation seem to have occurred between middle and late Eocene time and probably until the early Oligocene. Subsequently, rhyolitic to mafic volcanism began close to late Oligocene time and lasted until the early Miocene. Felsic volcanism is represented by the Cerro Cebadéhuachi volcanic rocks, from which 40Ar/39Ar hornblende ages of 27.25 ± 0.09 and 27.32 ± 0.06 Ma and a biotite age of 26.97 ± 0.06 Ma were obtained at three different localities. The Mesa Pedregosa volcanic rocks represent the transition to younger, mafic volcanic activity that occurred during the late Oligocene, as indicated by a sanidine 40Ar/39Ar age of 25.48 ± 0.05 Ma. This late Oligocene and early Miocene magmatism was paired by two episodes of extensional deformation. The first phase is characterized by northwest-striking normal faults and folds, which expose the deepest structural levels of the area, and by the related basin fill, the Bacanuchi conglomerate. The second phase is represented by north-striking normal faults and by the syntectonic basin fill, the Arizpe conglomerate. Basaltic andesite volcanic flows at the base of the Arizpe conglomerate yielded 40Ar/39Ar (whole-rock) ages of 23.52 ± 0.17 and 21 ± 0.20 Ma. The extensional deformation (27 to 23 Ma) in the study area is coeval with the development of metamorphic core complexes in neighboring areas of Sonora and with the onset of extension in southern Sonora. The mafic volcanic rocks and clastic sedimentary units associated with this extension resemble the basin fills that in other parts of Sonora are assigned to the Báucarit Formation.
Geochemical information from samples representing each of the igneous events displayed high-K calc-alkalic and mostly metaluminous compositions. The older units including the Arroyo Alcaparros andesitic rocks, the Cerro Las Jarillas volcanic rocks, the Sierra El Manzanal granodiorite, and the Rancho Vaquería quartz monzonite are characterized by steep chondrite-normalized REE (rare earth element) slopes and generally well-developed negative Eu anomalies, suggesting garnet and plagioclase removal in the source. The younger igneous events including the Cerro Cebadéhuachi and Mesa Pedregosa volcanic rocks, and the basaltic flows associated with the Arizpe conglomerate, showed basin-shaped REE slopes with no Eu anomalies, suggesting clinopyroxene or amphibole fractionation.
… Society of America …, 2001
Along the Laramide belt of northwestern Mexico, granitic rocks of similar bulk composition show i... more Along the Laramide belt of northwestern Mexico, granitic rocks of similar bulk composition show isotopic and trace element signatures that help to delineate the position of the southern edge of the North American Precambrian basement. In the northern part, the Laramide plutons (the ''northern granites'') intruded Proterozoic crystalline rocks and a thick Late Proterozoic through Paleozoic miogeoclinal cover of North American affinity. In the central part, the granitic bodies (the ''central granites'') were emplaced into a sequence of Paleozoic eugeoclinal rocks overlain by Late Triassic clastic units. The southern part of the belt (the ''southern granites'') intruded a less-known crust characterized by middle to late Mesozoic island-arc-related volcanic and sedimentary rocks of the Guerrero terrane. Data from a suite of metaluminous to slightly peraluminous calc-alkalic granitic rocks along the belt display north-to-south geochemical and isotopic variations, which could correlate with the type of intruded basement. The northern and central granites are characterized by strongly fractionated, light rare earth element (REE)-enriched patterns, which display generally pronounced negative europium anomalies, whereas the southern granites have lower total REE enrichments and much flatter chondrite-normalized slopes displaying almost no europium anomalies. Isotopic results also suggest regional variations, as shown by the following initial Sr and ⑀ Nd ranges: 0.7070 to 0.7089 and؊4.2 to؊5.4, respectively, for the northern granites; 0.7060 to 0.7079 and؊3.4 to؊5.1 for the central granites; and 0.7026 to 0.7062 and؊0.9 to ؉4.2 for the southern granites. On the basis of their isotopic similarities, the Proterozoic mafic to intermediate lower crust revealed by xenoliths from young volcanic flows in southern Arizona and northern Mexico is interpreted as *E-mail: valencia@geologia.unam.mx. a reasonable parental source for the northern and central granites; however, mantle-derived melts are not excluded. The more primitive southern granites are interpreted to come from a source that lacked Proterozoic basement. Instead, they were probably derived by mixing of juvenile mantle melts with partial melts of the lower parts of the Guerrero terrane. In general, the north-to-south compositional variations of the Laramide granitic rocks of northwestern Mexico reflect the crustal structure underneath the batholiths. The Sr and Nd data indicate that the edge of the North American Precambrian basement extends approximately southeastward from the coastal batholith of central Sonora; then, about 200 km south of Hermosillo in southern Sonora, the edge bends eastward and continues to the east beneath the Sierra Madre Occidental volcanic province.
Cretaceous and Tertiary sedimentary, magmatic, and tectonic evolution of north-central Sonora (Arizpe and Bacanuchi Quadrangles), northwest Mexico
… Society of America …, 2000
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… SOCIETY OF AMERICA, 2007
(2) Eocene andesites and lesser rhyolites, traditionally grouped into the so-called Lower Volcani... more (2) Eocene andesites and lesser rhyolites, traditionally grouped into the so-called Lower Volcanic Complex; (3) silicic ignimbrites mainly emplaced during two pulses in the Oligocene (ca. 32-28 Ma) and Early Miocene (ca. 24-20 Ma), and grouped into the "Upper Volcanic Supergroup"; (4) transitional basaltic-andesitic lavas that erupted toward the end of, and after, each ignimbrite pulse, which have been correlated with the Southern Cordillera Basaltic Andesite Province of the southwestern United States; and (5) postsubduction volcanism consisting of alkaline basalts and ignimbrites emplaced in the Late Miocene, Pliocene, and Pleistocene, directly related to the separation of Baja California from the Mexican mainland. The products of all these magmatic episodes, partially overlapping in space and time, cover a poorly exposed, heterogeneous basement with Precambrian to Paleozoic ages in the northern part (Sonora and Chihuahua) and Mesozoic ages beneath the rest of the Sierra Madre Occidental. The oldest intrusive rocks of the Lower Volcanic Complex (ca. 101 to ca. 89 Ma) in Sinaloa, and Maastrichtian volcanics of the Lower Volcanic Complex in central Chihuahua, were affected by moderate contractile deformation during the Laramide orogeny. In the fi nal stages of this deformation cycle, during the Paleocene and Early Eocene, ~E-W to ENE-WSW-trending extensional structures formed within the *E-mails, Ferrari and Valencia-Moreno: luca@geociencias.unam.mx; valencia@ geologia.unam.mx. Current address, Bryan: School of Earth Sciences & Geography, Kingston University, Kingston Upon Thames, Surrey KT1 2EE, UK; s.bryan@kingston.ac.uk.
Geochemistry of the coastal Sonora batholith, northwestern Mexico
… Journal of Earth …, 2003
... to the Pacific side (Fig. 7d). One likely explanation to this behavior may be involvement of ... more ... to the Pacific side (Fig. 7d). One likely explanation to this behavior may be involvement of deep sea clay in the magma source, according to the average content of Sr in these sediments (Faure 1986). In any case, the lateral variations ...
Geochemistry of Laramide granitic rocks across the southern margin of the Paleozoic North American continent, Central Sonora, Mexico
International geology …, 1999
The geochemistry of Laramide granitic rocks from central Sonora was studied to relate possible co... more The geochemistry of Laramide granitic rocks from central Sonora was studied to relate possible compositional variations to the assimilation of different crustal sources. Most of the studied rocks are granodiorites collected near the southern boundary of the Paleozoic North American continent. North of this boundary, the Laramide plutons intruded a thick section of Upper Proterozoic and Paleozoic miogeoclinal strata, whereas