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Oceanic intraplate volcanoes sometimes experience late-stage eruptive activity known as rejuvenated volcanism, and contrasting interpretations for its petrogenesis depend on the compositional characteristics. In the Juan Fernández Ridge (JFR), a volcanic chain approximately 800 km in length emplaced on the Nazca Plate, some subaerial occurrences of rejuvenated volcanism have been recognized on the Robinson Crusoe and Santa Clara Islands, both part of the same deeply eroded shield volcano complex. This study aims to understand the origin and magmatic evolution of rejuvenated volcanism on Santa Clara Island, emplaced after ~2.15 Ma of quiescence above the shield sequence, mainly via the analysis of unpublished geochemical and isotopic data. Field reconnaissance identified two nearly coeval rejuvenated sequences on Santa Clara Island: Bahía W (BW) and Morro Spartan (MS), both formed by basanitic and picro-basaltic lava flows with brecciated levels and local intercalations of sedimentary and pyroclastic deposits. In comparison to the chemical signature of the preceding shield-building stage (comprised mainly of basalts and picrites), the two rejuvenated sequences exhibit a notable enrichment in incompatible elements, but the Sr, Nd, and Pb isotopes are very similar to the FOZO mantle endmember, with an apparent additional contribution of HIMU and EM1 components. The geochemistry of lavas revealed the involvement of various processes, including contamination by ultramafic xenoliths, high-pressure fractional crystallization of olivine and clinopyroxene, and potential partial assimilation of oceanic lithospheric components. While the oceanic lithosphere has been considered as a potential source, the isotopic data from Santa Clara lies outside of the mixing curve between depleted mantle (DM, here represented by the North Chile Rise and the East Pacific Rise) and the previous shield stage, suggesting that a lithospheric mantle is not the primary source for the rejuvenated stage volcanism. Therefore, we favor an origin of the rejuvenated volcanism from the mantle plume forming the JFR, supported by similarities in isotopic signatures with the shield stage and high values of 208Pb/204Pb (only comparable to San Félix—San Ambrosio in the vicinity of JFR), implying the presence of a regional source with radiogenic 208Pb/204Pb isotope ratios. In addition, isotopic variations are subparallel to the mixing line between HIMU and EM1 components, whose participation in different proportions might explain the observed trends. In conclusion, we propose that the source of the rejuvenated volcanism on Santa Clara Island is a heterogeneous mantle plume, the same one that fed the shield stage. The rejuvenated volcanism is derived from a secondary melting zone away from the main axis of the plume. [ABSTRACT FROM AUTHOR]

Las islas Juan Fernández, uno de los últimos territorios poblados por humanos, han sido históricamente representadas como un paraíso edénico detenido en el tiempo. Este artículo examina las representaciones de las islas en tanto frontera ambiental y civilizacional, centrándose particularmente en el papel del turismo de cruceros a la isla Robinson Crusoe que alcanzó su punto máximo en el período de entreguerras. Sostenemos que el turismo de cruceros fue fundamental para cimentar una imagen de Juan Fernández como un lugar primitivo, congelado en el momento en que Alexander Selkirk abandonó la isla en el siglo XVIII. Más aún, esta figura, inmortalizada en la novela Robinson Crusoe del británico Daniel Defoe, inspiró el establecimiento de rutas turísticas a las islas desde Valparaíso, en el que tanto chilenos como extranjeros entablaron discursos en torno al archipiélago como un espacio de ocio, que fue contingentemente espacio geoestratégico clave del Chile insular, pese a sus desafíos de infraestructura. Basándose en los conceptos de “frontera” y “paisaje”, el artículo dilucida cómo este destino-imagen idealizada de un Juan Fernández romántico se ha visto reforzado por el establecimiento de las islas como espacios turísticos relevantes tanto en el ámbito nacional como internacional.

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Se citan cuatro nuevas localidades para Robinsonia (Rhetinodendron) berteroi, en la isla Robinson Crusoe, Chile, documentadas mediante colecciones de herbario hechas por la bióloga Marcia Ricci en los años 1988 y 1990 depositadas en el herbario del Jardín Botánico Nacional (JBN) de Chile, las que permanecieron como especies indeterminadas hasta septiembre de 2021.

A new combination, Trimeris anceps (L. f.) E. B. Knox, is established for the species previously known as Lobelia anceps L. f. Lobelia L. is the "core" genus of the Lobeliaceae, which has more than 30 segregate genera that have been recognized based on their evolutionarily divergent reproductive morphology. Wimmerella Serra, M. B. Crespo & Lammers is a segregate South African genus with completely fused corollas (which affect pollinator access), yet one of its descendant lineages has somehow reverted to the Lobelia-like condition of the corolla split to the base on the back. Recent discovery that the St. Helena--endemic T. scaevolifolia (Roxb.) Mabb. is sister to L. anceps provides an established segregate genus into which both of these morphologically anomalous species can be placed. [ABSTRACT FROM AUTHOR]

A submarine eruption in Cumberland Bay, Robinson Crusoe Island, was reported by Thomas Sutcliffe, the former British Governor, shortly after the earthquake that struck the coast of Chile on 20 February 1835. This episode was described by Charles Darwin in his Voyage of the Beagle and extensive mention has been made since then, especially stimulated by a renowned painting by J.M. Rugendas. Because of the apparent causal relation, this event has also been widely cited as an example of remote tectonically triggered eruption. However, there are inconsistencies that pose doubts about the actual occurrence of an eruption. Here we present evidence against the hypothetical eruption based on both the absence of any geological evidence and a reinterpretation of the historical accounts. We first observe that no bathymetric anomaly is present immediately below the place of the depicted 'eruptive column'. We also note the absence of any deposit or recent volcano morphology and then unravel some incompatibility between the expected volcanological parameters and the featured column. In addition, we analyse the historical records and conclude that they are compatible with a tsunami entering the bay. By means of numerical simulations we further demonstrate that the accounts well match with the expected behaviour of a distant earthquake-triggered tsunami. We infer that some tsunami-related processes (sound waves, rockfalls, lightning) may have been misunderstood at that time. The latter corresponds to the current knowledge of natural processes but also could have been deliberatively amplified in Sutcliffe's report. Our multidisciplinary approach provides full consistent geographical evidence of a fact that did not happen. This finding is relevant from the hazard's perspective, but also for the science of earthquakes and eruptions, or the knowledge of processes that control the late secondary volcanism at oceanic islands and seamounts. [ABSTRACT FROM AUTHOR]

It is unknown if any Juan Fernández native plants may tolerate the aggressive invasion of the introduced shrub Ugni molinae. We found sixteen native species growing within these highly invaded patches. The endemic shrub Gaultheria racemulosa (syn. Pernettya rigida) was the most important species according to vegetation cover in invaded patches, therefore relevant in future control management options.

The Juan Fernández Ridge (JFR) is an age-progressive volcanic chain (∼800 km long) related to a fixed mantle plume in the Southeast Pacific offshore central Chile. The high 3He/4He ratio (up to 18 times higher than that of the atmosphere) and spatiotemporal 40Ar/39Ar geochronology suggest that the source material of the JFR is derived from the lower mantle and transferred to the surface by a relatively stationary plume. We used new whole-rock geochemical data (major-element, trace-element, and Sr–Nd–Pb isotopic data) for representative samples from the shield-stage of volcanism in the JFR (from O'Higgins Guyot, Alpha Seamount, Robinson Crusoe Island, and Alejandro Selkirk Island) to develop a petrogenetic model with the goal of understanding the temporal and spatial evolution of magmatism along the JFR. The shield-building lavas of JFR consist primarily of tholeiitic to alkalic basalts. Their compositional differences are explained by the fractional crystallization of olivine and clinopyroxene ± plagioclase, magmatic recharge, melt mixing, and olivine accumulation. Radiogenic Sr–Nd–Pb isotopes show a narrow field within the compositional range of the common FOZO mantle. The 206Pb/204Pb and 207Pb/204Pb ratios of JFR lavas are similar to those of other islands on the Nazca Plate (e.g., San Félix and San Ambrosio). However, the JFR lavas are more radiogenic and show a narrower compositional range compared to the Easter Seamount Chain. The low CaO content at a given MgO content, moderate Ti–Ta–Nb 'TITAN' anomaly, fractionated heavy rare earth element values, and isotopic composition of JFR lavas are consistent with the presence of pyroxenite (recycled oceanic crust) in the mantle source. To estimate source parameters, we used OBS1 software (Kimura and Kawabata, 2015) to calculate the potential temperature (1316–1412 °C), total degree of melting (3.4–19.2 wt%), and pyroxenite fraction (0.6–18.4 wt%) of the mantle beneath JFR. The temporal changes in the thermal, compositional, and lithologic characteristics of the source material can explain the chemical differences observed between different JFR volcanoes. We propose that shield-stage volcanism in JFR is largely generated by the melting of pyroxenite in a relatively low-temperature mantle plume. As a result, this weak plume containing low mantle He is difficult to image using seismic tomography. [ABSTRACT FROM AUTHOR]

The Juan Fernandez Islands in the southeastern Pacific are an atypical linear volcanic chain that exhibits a considerable range in 3 He/ 4 He ratios (8 to 18 R A, where R A is the 3 He/ 4 He ratio of air), but limited ranges of 87 Sr/ 86 Sr and 143 Nd/ 144 Nd. Here we report new trace element abundance data and Sr-Nd-Pb isotope data for mafic lavas previously analyzed for their 3 He/ 4 He and He contents from the two main islands of Robinson Crusoe and Alexander Selkirk. Lavas from these islands have been previously grouped based on geochemical and petrological classification into Group I and III basalts, and Group II basanites. In general, samples have overlapping Sr-Nd-Pb isotope compositions that suggest a common, albeit slightly heterogeneous mantle source. In detail, the Group I and III tholeiitic and alkalic basalts have nearly identical incompatible trace element patterns, whereas the Group II basanites show elevated incompatible trace element abundances. Major and incompatible trace element modeling indicates that Group III basalts ( 3 He/ 4 He = 7.8–9.5 R A ) from younger Alexander Selkirk Island were produced by the highest degree of partial melting (> 10%) of a common mantle source, followed by Group I basalts (13.6–18.0 R A ) and Group II basanites (11.2–12.5 R A ) from older Robinson Crusoe Island. The 206 Pb/ 204 Pb of Group I basalts and Group II basanites are slightly more radiogenic and limited in range (19.163 to 19.292) compared with those of Group III (18.939 to 19.221). The Group I and II lavas from Robinson Crusoe are consistent with an origin from the so-called focus zone (FOZO) mantle component, whereas the Alexander Selkirk basalts additionally contain contributions from a less-enriched or relatively depleted mantle component. Juan Fernandez lavas reveal limited ranges of Sr-Nd-Pb isotopes but variable 3 He/ 4 He as their parental magmas originated mainly from the FOZO component with high 3 He/ 4 He (> 9 R A ) and variably polluted with a depleted component with lower 3 He/ 4 He (ca. 8 R A ). Contributions from high- 3 He/ 4 He mantle sources to ocean island basalts can therefore vary both spatially and temporally, over meter to kilometer lengths and hundred to million-year time scales, and may not be strongly correlated to radiogenic lithophile isotope systematics. [ABSTRACT FROM AUTHOR]

We compared the geographic distribution of groups of chondrychthid fishes of two physically proximal, although geographically different, regions that include the Juan Fernández seamounts and the central Chilean continental slope, both sampled at mesopelagic and mesobenthonic depths. The ridge is in the Nazca Plate, while the slope region in on the South American Plate, and is closer to the South American continent. We found six species of Chondrichthyes for the seamounts (four orders, four families). The slope sampling produced ten species of Chondrichthyes, of which Torpedo tremens De Buen 1959, was the only species in common with the Juan Fernández area. There are clear differences between the Chondrichthyes of the two regions. These fisheries require adequate administrative modes. Rev. Biol. Trop. 56 (1): 181-190. Epub 2008 March 31.

Este trabajo tiene por finalidad analizar el juicio de residencia del fiscal Juan Fernández. La investigación la llevó adelante el Doctor Gregorio González de Cuenca, oidor del tribunal limeño, por pedido del mismo fiscal ante la solicitud de una licencia para retornar a Castilla. El análisis de este juicio de residencia temprano, nos dará indicios acerca del comportamiento de un personaje influyente y conocido en el Virreinato del Perú, revelándonos cómo fue su actuación pública, su vida privada y cuáles fueron las principales acusaciones que recayeron sobre el Licenciado Juan Fernández mientras ejerció el oficio de fiscal y aplicaba la tan valorada recta justicia.

A fern hybrid of the genus Pleopeltis was discovered on Robinson Crusoe Island in the Juan Fernández Archipelago, off the coast of Chile, and is described as P. xcerro-altoensis. Its putative parents are P. macrocarpa and P. masafuerae, two species present in the archipelago. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lobster fishing sustained the economy of Juan Fernández Islands over a century. [•] Access effectively regulated by informal tenure system: ownership of fishing spots. [•] Generic prescriptions for reducing harvest rates likely disruptive if implemented. [•] Sustainability due to productive stock, simple regulations, tenure, social capital. [•] Resiliency tested by recovery after tsunami of 2010. [ABSTRACT FROM AUTHOR]

Aspiciliopsis macrophthalma, Placopsis fusciduloides, P. gelidioides and P. tararuana are reported for the first time from southern South America. New records for 13 species of Placopsis in southern South America are reported, and a revised key to 22 species of Placopsis and A. macrophthalma in the region is given. [ABSTRACT FROM AUTHOR]

We compared the geographic distribution of groups of chondrychthid fishes of two physically proximal, although geographically different, regions that include the Juan Fernández seamounts and the central Chilean continental slope, both sampled at mesopelagic and mesobenthonic depths. The ridge is in the Nazca Plate, while the slope region in on the South American Plate, and is closer to the South American continent. We found six species of Chondrichthyes for the seamounts (four orders, four families). The slope sampling produced ten species of Chondrichthyes, of which Torpedo tremens De Buen 1959, was the only species in common with the Juan Fernández area. There are clear differences between the Chondrichthyes of the two regions. These fisheries require adequate administrative modes. [ABSTRACT FROM AUTHOR]

The new combination Lithographa skottsbergii (Zahlbr.) Fryday & Coppins is made for Enterostigma skottsbergii Zahlbr., described from the Juan Fernandez Islands off the coast of Chile. The species is known only from Chile but its geographical range is here extended to include maritime regions of south-west Chile. The distribution pattern of the Lithographa species with submuriform ascospores is also discussed. [ABSTRACT FROM AUTHOR]

Olivine crystals in basalt contain helium that can be extracted for isotopic analysis. Helium-bearing olivine phenocrysts in picritic tholeiites from the Juan Fernandez Islands, SE Pacific, crystallized from moderately differentiated liquids. None are xenocrysts of mantle peridotite. The helium occurs in cavities or bubbles in inclusions best seen at high magnification in the olivine. The olivine grew around spinel, sulfide, and bubbles that preferentially nucleated on crystal surfaces. Inclusions within these phases range from large cavities to tiny, faceted pits arranged in rows. Many crystals contain curving trains of inclusions along annealed features. The inclusions formed during mixing between cooler differentiated magma and hotter olivine-charged magma, which accelerated vesiculation. Bubbles nucleated on the olivine as they do on ice when stirred in carbonated water. Mixing also induced thermal stress fracturing, like the cracking of ice dropped into water. Cracking, irregular extinction, and subgrain formation occurred when faceted crystals collided with each other or with conduit walls. Boundary layer melts and bubbles were drawn quickly into the fractures. Thus few inclusions contain equilibrium proportions of minerals and vapor. Mantle-derived helium clearly permeated into shallow storage reservoirs, including rift zones where magmatic differentiation, mixing, and vapor exsolution were fairly extensive. [ABSTRACT FROM PUBLISHER]