Probabilistic Volcanic Hazard Assessment of the 22.5–28°S Segment of the Central Volcanic Zone of the Andes

Evaluation of volcanic hazards typically focusses on single eruptive centres or spatially restricted areas, such as volcanic fields. Expanding hazard assessments across wide regions (e.g., large sections of a continental margin) has rarely been attempted, due to the complexity of integrating temporal and spatial variability in tectonic and magmatic processes. In this study, we investigate new approaches to quantify the hazards of such long-term active and complex settings, using the example of the 22.5–28°S segment of the Central Volcanic Zone of the Andes. This research is based on the estimation of: 1) spatial probability of future volcanic activity (based on kernel density estimation using a new volcanic geospatial database), 2) temporal probability of future volcanic events, and 3) areas susceptible to volcanic flow and fall processes (based on computer modeling). Integrating these results, we produce a set of volcanic hazard maps. We then calculate the relative probabilities of population centres in the area being affected by any volcanic phenomenon. Touristic towns such as La Poma (Argentina), Toconao (Chile), Antofagasta de la Sierra (Argentina), Socaire (Chile), and Talabre (Chile) are exposed to the highest relative volcanic hazard. In addition, through this work we delineate five regions of high spatial probability (i.e., volcanic clusters), three of which correlate well with geophysical evidence of mid-crustal partial melt bodies. Many of the eruptive centres within these volcanic clusters have poorly known eruption histories and are recommended to be targeted for future work. We hope this contribution will be a useful approach to encourage probabilistic volcanic hazard assessments for other arc segments.Fil: Bertin, Daniel. University of Auckland; Nueva ZelandaFil: Lindsay, Jan M.. University of Auckland; Nueva ZelandaFil: Cronin, Shane J.. University of Auckland; Nueva ZelandaFil: de Silva, Shanaka L.. State University of Oregon; Estados UnidosFil: Connor, Charles B.. University of Florida; Estados UnidosFil: Caffe, Pablo Jorge. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Grosse, Pablo. Fundación Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Báez, Walter. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Bustos, Emilce. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Constantinescu, Robert. University of Florida; Estados Unido

AFC3D: A 3D graphical tool to model assimilation and fractional crystallization with and without recharge in the R environment

AFC3D is an original graphical free software developed in the framework of the R scientific environment and dedicated to the modelling of assimilation and fractional crystallization without (AFC) and with (AFC-r) recharge, facilitating the search for the solutions of the equations originally proposed by DePaolo (1981, 1985) and first solved in a graphical way by Aitcheson and Forrest (1994). The software presented here allows a graphical 3D representation of \u3c1 (mass of assimilated crust/mass of original magma) as a function of r (rate of crustal assimilation/rate of fractional crystallization) and \u3b2 (recharge rate of magma replenishment. /. rate of assimilation) for each element/isotope, finding a coherent set of (. r, \u3b2, \u3c1) parameter triples in a mostly automated way. Mathematically optimized solutions are derived, which can and should then be discussed and evaluated from a geological and petrological point of view by the end user. The presented contribution presents the software and a series of models published in the literature, which are discussed as case studies of application and whose solutions are sometimes enhanced based on the results provided by the softwar

Paleomagnetic evidence of earliest Paleocene deformation in Calama (∼22°S), northern Chile: Andean-type or ridge-collision tectonics?

A paleomagnetic study from the earliest Paleocene Cerros de Montecristo Quartz Monzonite and its Jurassic to uppermost Cretaceous host rock (northern Chile, ∼22°S) provided high-temperature, high-coercivity magnetizations of dominantly reversed polarity. The remanences of the tilted host rock gave a negative fold-test and are indistinguishable from the remanences found in the pluton, indicating that the uppermost Cretaceous rocks underwent deformation before intrusion of the earliest Paleocene pluton, thus documenting a K-T deformation at the locality. Although this deformation may be another product of typical subduction-related noncollisional tectonics in the Central Andes, an alternative hypothesis, permitted by plate reconstructions, is that the event was associated with collision of an oceanic plate boundary. This latter hypothesis may also provide a context for several other tectonic events from northern Chile to the Patagonian Andes, wherein deformation would the consequence of a southward migrating triple junction between the latest Maastrichtian and Early Eocene.Fil: Somoza, Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Tomlinson, A. J.. Servicio Nacional de Geologia y Mineria; ChileFil: Caffe, Pablo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Vilas, Juan Francisco A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentin

Li content and Li-Sr-Nd isotope composition of salar deposits from southern Puna salars (Argentina)

The Central Andes of South America hosts the largest known lithium (Li) anomalies in a restricted area, but the primary lithium sources of the salar deposits and the mobilization process of lithium are still a matter of speculation. Chemical weathering at or near the surface and leaching in hydrothermal systems of the active magmatic arc are considered as the two main mechanisms of Li extraction from the source rock. The lithium and strontium isotope composition of typical salar deposits offer insights into the processes on how Li brine deposits in Andean evaporites are formed. To further the understanding of the different processes of Li mobilization (weathering and/or hydrothermal leaching) and accumulation that play an important role in the salars of the southern Puna in north-western Argentina, we study the Centenario, Ratones and Diablillos salars, the smallest salars that are among the world-class brine deposits in the Central Andes Li-rich salars. We use Sr isotopes (87Sr/86Sr) for source tracing and Li contents and Li isotopes (δ7Li) to constrain Li mobilization from source to deposition. Nd isotope compositions (143Nd/144Nd) were also determined in clastic sediment samples from salar to provide additional constrains to the rock sources. The studied materials include surface catchment and salar surface samples from the three studied closed basins (rocks, freshwater, brines, salts, travertine, siliciclastic sediments) and core samples (siliciclastic sediments and rocks) and fluid (brines) samples to a depth of 250 m, obtained from Salar de Diablillos (southern Puna in north-western Argentina)

Li content and Li and Sr isotopic compositions of deep brines from wells DRC-01 and DDD-02, and core samples (sediments, and basement rocks) from core DDD-07 - Salar de Diablillos, Argentina

Sr isotopes (87Sr/86Sr), Li contents and Li isotopes (δ7Li) were determined in drill core samples (sediments and rocks) and fluid (brine) samples to a depth of 250 m, obtained from Salar de Diablillos (southern Puna in north-western Argentina). For clastic sediment samples, Nd isotope compositions (143Nd/144Nd) were also determined. The Central Andes of South America hosts the largest known lithium (Li) anomalies in a restricted area, but the primary lithium sources of the salar deposits and the mobilization process of lithium are still a matter of speculation. Chemical weathering at or near the surface and leaching in hydrothermal systems of the active magmatic arc are considered as the two main mechanisms of Li extraction from the source rock. The lithium, strontium and neodimium isotope composition of typical salar deposits offer insights into the processes on how Li brine deposits in Andean evaporites are formed

Li, δ7Li, 87Sr/86S and 143Nd/144Nd of surface samples from Salares Diablillos, Ratones and Centenario

The Central Andes of South America hosts the largest known lithium (Li) anomalies in a restricted area, but the primary lithium sources of the salar deposits and the mobilization process of lithium are still a matter of speculation. Chemical weathering at or near the surface and leaching in hydrothermal systems of the active magmatic arc are considered as the two main mechanisms of Li extraction from the source rock. The lithium and strontium isotope composition of typical salar deposits offer insights into the processes on how Li brine deposits in Andean evaporites are formed. To further the understanding of the different processes of Li mobilisation (weathering and/or hydrothermal leaching) and accumulation that play an important role in the salars of the southern Puna in north-western Argentina, we study the Centenario, Ratones and Diablillos salars, the smallest salars that are among the world-class brine deposits in the Central Andes Li-rich salars. We use Sr isotopes (87Sr/86Sr) for source tracing and Li contents and Li isotopes (δ7Li) to constrain Li mobilization from source to deposition. Nd isotope compositions (143Nd/144Nd) were also determined in clastic sediment samples from salar to provide additional constrains to the rock sources. The studied materials include catchment and basin surface samples from the three studied closed basins