Andean Geology最新文献

{"title":"Los mármoles cálcicos de El Escorial (Complejo Metamórfico Cushamen, Macizo Norpatagónico): caracterización isotópica de 87Sr-86Sr y edad de sedimentación","authors":"J. A. Murra, Edgardo G. Baldo, Sebastián O. Verdecchia, Carlos D. Ramacciotti, C. Galindo","doi":"10.5027/andgeov49n1-3387","DOIUrl":"https://doi.org/10.5027/andgeov49n1-3387","url":null,"abstract":"The El Escorial marbles (Cushamen Metamorphic Complex) along with amphibolites form metamorphic septa within the permian granitoids of the Mamil Choique Formation (261-286 Ma). The metamorphism, determined in granulite facies migmatic gneisses septa cropping out 120 km southwest of El Escorial, occurs at 311 ± 27 Ma (CHIME method in monazite). The marbles are calcitic (calcite > 95%, R.I.: 0.5 to 2.5%) and show 87Sr/86Sr values between 0.70768 and 0.70825 (n = 10). The data provided in this work, added to previous contributions, allow to constraints the sedimentation age of the silicic-carbonate successions of the Cushamen Metamorphic Complex between ca. 385 and 335 Ma. This suggests the existence of a mixed carbonate-siliciclastic platform at least in the southernmost portion of southwestern Gondwana between Middle Devonian and early Carboniferous (Middle Mississippian).","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46990113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CARACTERIZACIÓN DE LA INESTABILIDAD DE LADERAS DEL CANAL UPSALA: DESLIZAMIENTO AGASSIZ, PATAGONIA AUSTRAL, ARGENTINA","authors":"S. Moragues, M. G. Lenzano, S. Rivera, Jonathan Oberreuter","doi":"10.5027/ANDGEOV48N3-3350","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3350","url":null,"abstract":"","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43226827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Local Cuban bentonite clay: composition, structure and textural characterization","authors":"P. C. Quero-Jiménez, Lester Alejandro Arias Felipe, Julio Omar Prieto García, M. E. Rodriguez, Jorge Lopez, O. Montenegro, Reinaldo Molina Ruiz, I. Tiscornia","doi":"10.5027/ANDGEOV48N3-3362","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3362","url":null,"abstract":"The Cuban bentonite clays have a specific surface area of 79.9098 m2.g-1, a pore volume of about 0.077612 cm3.g-1 and both isotherms exhibited a hysteresis loop of IV type. X-ray diffractogram of raw bentonite shows that the main mineralogical component is montmorillonite (> 90%). The mineral object study presents the first endothermic peak, characteristic of montmorillonite, in 48.11 ºC and others less accentuated (80.81, 94.01, 119.81 ºC) characteristic of calcium montmorillonite, that corresponds to the loss of water, and can be extended up to 250 ºC. The FTIR spectra showed the existence of Si-OH, Al-Al-OH, Al-Fe-OH, Al-Mg-OH and Si-O-Si functional groups in all clay samples, confirmed the presence of hydrated aluminosilicate in the clay, bands between 1120 and 461 cm-1 correspond to phyllosilicate structures and OH stretching vibrations were observed. The pH at the point of zero charge (pHPZC) obtained has a value of 8.1, which allows montmorillonite to be classified as basic. The structural formula for one-layer unit of montmorillonite was determined as (Na3.99Al0.01)(Al1.11Fe3+0.49Mg0.18Ti0.07)(Ca0.24Na0.15K0.01)O10(OH)2, indicate the location of the different cations in metal oxide octahedrons or tetrahedrons, respectively. From the results obtained by different methods and the analysis of the calculated structural formula, it can be concluded that the bentonite under study is a calcium montmorillonite, with a low specific surface area and little porosity.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44300773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MONDACA VOLCANO LAHAR OF DECEMBER 3, 1762, MAULE REGION (35°28’S): ONE OF THE LARGEST VOLCANIC DISASTERS IN CHILEAN HISTORY","authors":"J. A. Naranjo, F. Hevia, E. Polanco","doi":"10.5027/ANDGEOV48N3-3361","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3361","url":null,"abstract":"The Mondaca volcano comprises a thick rhyolitic lava-field and a dome of similar composition, located near the Lontué River Valley headwaters in the northern part of the Southern Andes Volcanic Zone. It reaches a total volume of ~ 0.85 km, and it is formed by 4 subunits, named Mondaca 1, 2, 3 and 4, which correspond to successive rhyolitic blocky lava flows, emitted from a rounded dome structure. They present well-preserved flow structures and, in the surroundings, restricted to the south and east of the dome, pyroclastic fall, as well as block and ash deposits are also exhibited. Downstream, along the Lontué River, a laharic deposit is recognized. The lahar was produced after the collapse of an ephemeral ~0.44 km3 lake generated after the river obstruction by viscous lavas, during the 1762 first eruptive phase. Proximal lahar facies are well exposed between 5 and 30 km from their source. The profuse agricultural activity has completely obliterated the lahar's medium facies deposits along the Central Depression, but are well identified at the mouth of the Mataquito River, 180 km downstream, as a beige-coloured layer, interbedded within dark coastal beach-sands. The identification of overflows and super-elevation deposits formed during the debris flow emplacement along the Lontué River valley, allows to determine a high flow mobility, with estimated velocities that locally reached up to 114 km/h. Petrographic characteristics in addition to chemical composition of lavas from the volcano, pyroclasts and juvenile blocks of the laharic deposit, indicate that all they correspond to high K calcoalkaline rhyolites with subalkaline affinity. These backgrounds, together with the geographical continuity between the lavas and debris deposits along the Lontué and Mataquito rivers, verify facies correlation and common origin as the result of the 1762 Mondaca volcano eruption complex evolution. IN PR ES S Andean Geology 48 (3): xxx-xxx. September, 2021 doi: 10.5027/andgeoV48n3-3361 2 Although it was a mainly effusive eruption that could not be observed from Curicó, the collateral consequences would have been catastrophic over a vast area to the south of that city, and evidences one of the largest volcanic disasters in Chilean history. Probably because of the low density polulation at that time, the consequences could have been minor.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47189789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diagenesis and Thermal Maturity of the Cogollo Group rocks in the ANH-CR-Montecarlo-1X well, Cesar-Ranchería Basin, Colombia","authors":"Carlos A Ríos, M. Vargas, Mario Garcia","doi":"10.5027/ANDGEOV48N3-3329","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3329","url":null,"abstract":"In ANH-CR-Montecarlo-1X well located in the southern sector of the Cesar-Ranchería basin, Colombia, rocks of the middle Cretaceous outcrop, which have been defined as belonging to the Cogollo Group. The present study concerns with the diagenetic evolution and thermal maturity of this geological unit, integrating petrographic techniques (thin section microscopy and scanning electron microscopy), geochemistry (total organic carbon and pyrolysis rock-eval) and basic petrophysics, to establish the thermal maturity and the potential of rocks as reservoirs of conventional and unconventional hydrocarbons. The results of petrographic and diagenetic analysis revealed that the rocks compositionally correspond to quartz sandstones and graywackes and carbonate rocks to mudstones and wackestones; which were affected by diagenetic processes such as compaction, mineral neoformations distinguishing minerals from the group of clays that cover the grains of the framework, and other types of precipitates of cements such as silica, ferrous and non-ferrous carbonate, some of these present partial and/or total dissolution, for which secondary porosity is recognized, also metasomatisms, where processes of chloritization and illitization of the argillaceous matrix are observed, alteration of feldspars to ferrous and non-ferrous carbonate, which affects the porosity and permeability of the rock; and recrystallization from micrite to sparite and carbonate precipitation in calcareous rocks. The study also showed that the rocks were more affected by compaction than precipitation of the different cements. The research contributes to the understanding of the impact of diagenetic processes on porosity, as well as their spatial and temporal distribution, providing diagenetic paragenesis for both siliciclastic and carbonatic rocks. When we classifying siliciclastic rocks as potential reservoir rocks, low potential results were obtained as conventional reservoirs but has good potential as non-conventional reservoirs (tight sandstones), this respect to porosity and permeability data. The geochemical studies in the calcareous rocks exhibited low to good content of total organic carbon, overmaturity state and a low generation potential with type III and IV kerogens.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45552739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cenozoic plutonism geochemistry in the extra-andean southern Patagonia as evidences of arc migration process","authors":"Alejandro Sánchez Valenzuela, M. Saint-Blanquat, F. Hervé, M. Polvé, D. Morata, Phillipe De Parseval, M. Benoit","doi":"10.5027/ANDGEOV48N3-3158","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3158","url":null,"abstract":"In this work, we present the results of the first study which involves most of several cenozoic satellite plutons located in a 'back-arc' position in west Patagonia, south of the present Chile Triple-Junction. 4 plutons were studied in the northern tip, and 3 in the southern one. The petrographic and geochemical character of these plutons is different enough between them to propose a further classification for them: alkaline (sensu stricto): only the Monte Balmaceda Igneous complex, in the southern extremity; \"intra-plate transitional\" calc-alkaline: Río de Las Nieves and San Lorenzo plutons in the northern area, and the Torres del Paine Igneous Complex, in the southern area; and \"arc transitional\" calc-alkaline: the Paso de Las Llaves and Cerro Negro del Ghío plutons in the northern area, and the Cerro Donoso Pluton in the southern area. The \"transitional\" character, together with the plutons location, and regional context, can be explained by a Mio-Pliocene eastward arc migration coeval with the beginning of the Chile Rise subduction . Slab flattening hypothesis is favoured to explain the arc-migration, and together with the different length and time of arrival of the Chile Rise segments, contributed to the plutons heterogeneous geochemistry.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46318933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EL PLUTÓN SINTECTÓNICO ORDOVÍCICO EL LEÓN, EXTREMO SUROCCIDENTAL DEL CORDÓN DE LILA, REGIÓN DE ANTOFAGASTA","authors":"Hans Niemeyer Rubilar","doi":"10.5027/ANDGEOV48N3-3351","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3351","url":null,"abstract":"","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48144686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THE NICO PÉREZ TERRANE AND ITS ARCHEAN AND PALEOPROTEROZOIC INHERITANCE","authors":"Leda Sánchez Bettucci, U. Cordani, J. Loureiro, E. Peel, S. Fort","doi":"10.5027/ANDGEOV48N3-3345","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3345","url":null,"abstract":"Se realizó un estudio geocronológico U-Pb SHRIMP en circones en el Terreno Nico Pérez, localizado en la porción centro-oriental de Uruguay. El Terreno Nico Pérez es parte del Cratón del Río de La Plata y está limitado al oeste por el Terreno Piedra Alta a través de la mega zona de cizalla Sarandí del Yí. Al este se encuentra en contacto tectónico con el Cinturón Dom Feliciano, que constituye un elemento importante resultado el ciclo Orogénico Brasiliano. Litológicamente, está compuesto por cinturones metamórficos de grado medio a alto (bloques Pavas, Valentines y Rivera) representados principalmente por rocas de tipo granitoide, así como rocas orto y parametamórficas, como anfibolitas, metapiroxenitas, BIF, esquistos, cuarcitas con fucsita, entre otros. La corteza del Terreno Nico Pérez se generó principalmente durante el Riaciano, como lo muestran las edades isotópicas disponibles, que normalmente también están presentes en otras partes del Cratón del Río de la Plata, como los Terrenos Piedra Alta y Tandilia. Escamas tectónicas de edad Arqueanas retrabajadas arrojaron edades de 3.1 Ga y 2.7 Ga, corroborando resultados disponibles anteriores. También se obtuvo una edad de 1,73 Ga para el granito rapakivi de Illescas. Además, se obtuvieron edades robustas Ediacaranas (ca. 580 Ma) en plutones graníticos que se encuentran intruyendo el Terreno Nico Pérez. Estas se encuentran afectadas por el ciclo Orogénico Brasiliano. Se sugiere que las rocas de grado medio-alto del Terreno Piedra Alta y aquellas del Bloque Valentines formaban parte de un mismo fragmento cortical cuando se formó el cinturón Dom Feliciano, ya que muestran una evolución tectónica con arcos magmáticos maduros de edad Riaciana. Además, el enjambre de diques máficos de Florida, del Terreno Piedra Alta, y el granito rapakivi Illescas, del Terreno Nico Pérez, podrían ser parte del mismo episodio magmático que ocurrió alrededor de los 1.73 Ga. El Terreno Nico Pérez muestra como carácter distintivo el haber sido fuertemente afectado por la Orogenia brasiliana. Esto sugiere que es resultado de la metacratización Ediacarana del Cratón del Río de La Plata.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48603803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Quaternary Active El Arrayan Fault, Santiago, Chile","authors":"J. Araya, G. Pascale, S. Sepúlveda","doi":"10.5027/ANDGEOV48N3-3256","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3256","url":null,"abstract":"Understanding the location and nature of Quaternary active crustal faults is critical to the reduction of both fault rupture and strong ground motions hazards in the built environment. Recent work along the San Ramon Fault in Santiago, Chile demonstrates that crustal seismic sources are important hazards. We present the results of a second likely Quaternary active fault (the El Arrayan Fault, EAF) that runs through the City of Santiago. The EAF was discovered at an outcrop in El Arrayan (Lo Barnechea) with up to the North reverse motion and sinistral (left-lateral) motion clearly visible and coincident with fault rocks (gouge, cataclasite, and breccia) and higher topography (i.e. uplift) in the hanging wall. The EAF is at least 12 km long, strikes North-Northwest to South-Southeast, and is steeply dipping (mean dip 77º NE). Clear geomorphic expression with sinistral displaced streams (up to ~210 m) suggest that this fault is Quaternary active and an important local source of fault rupture and crustal strong ground motions. Because no fault zone avoidance criteria in Chile, there is need for enhanced fault mapping, legislation, implementation of active fault rupture avoidance areas in Chile to reduce the risk posed by active crustal structures.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":"48 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41555454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diffuse gases in soil of Araro-Simirao geothermal system, Michoacan, Mexico","authors":"I. Pérez-Martínez, R. Villanueva-Estrada, A. Rodríguez-Díaz, C. Canet, R. García, Alfredo Ramos-Leal, D. Garcia, Froylan Cambrón","doi":"10.5027/ANDGEOV48N3-3327","DOIUrl":"https://doi.org/10.5027/ANDGEOV48N3-3327","url":null,"abstract":"The Araró-Simirao geothermal system is in the southeast part of the Cuitzeo Lake depression. Physiographically, it is located in the eastern portion of the central part of the TransMexican Volcanic Belt province (TMVB). It is a convective hydrothermal system of dominant liquid, with chlorinated sodium waters and high boron content. The principal gas emitted by the thermal springs is CO2 and, in lower concentrations, H2S, H2 and noble gases (He, Ne, Ar). The aim of this study was to delimit fluid ascent areas in the geothermal system by determining the relationships between diffuse gas emission concentrations in soils and the greatest permeability plausible zones (principal faults). Three sampling campaigns were carried out during 2018 (August and November) and 2019 (May), in which diffuse gas emission measurements (CO2, Rn and mercury vapors) across the soils and soil temperature measurements were carried out. For a sampling campaign, the CO2 flux ranged between 4.38 and 94.61 g m-2 d-1 and the gaseous elemental mercury (GEM) concentration ranged between 0.5 and 365 ng/m3. For the other sampling campaign, the CO2 flux ranged between 0.8 and 1,421 g m-2 d-1 and the GEM values ranged between 0.49 and 2,914ng/m3. In the last sampling campaign the222Rn and 220Rn were also measured, and these values oscillated between 1,060 and 124,100 Bq/m3 and from 0 to 7,511 Bq7m3, respectively. Several anomalous zones of CO2 fluxes, GEM and 222Rn concentrations were found, which match the greatest permeability zones (faults and lineaments). The zone with the highest values in these three parameters is located in the so-called «mud pool», at the crossing of the Araró-Simirao fault with a lineament NW-SE (south zone), which is associated with the upflow zone of the system. Other anomalous zones were also located in the fracture and/or lineaments zones in the central and north parts of the system, which are associated with the outflow zone. According to the data obtained, CO2 could be functioning as a carrier of Hg and 222Rn in the area of vertical rise of gases and, in the outflow zone this gas may be found dissolved in the groundwater.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47867238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}