Mantle Xenoliths from Huanul Volcano (Central-West Argentina): A Poorly Depleted Mantle Source under Southern Payenia

Huanul is a shield volcano with several lava flows hosting mantle xenoliths erupted during the Pleistocene (0.84 ± 0.05 Ma). It is located in the southern part of the Payenia Volcanic Province, which is among the largest Neogene-Quaternary volcanic provinces of South America. The vol-canism here has been ascribed as the northernmost expression of the back-arc volcanism of the Andean Southern Volcanic Zone. We present the first petrographic and mineral chemistry study of mantle xenoliths collected from Huanul lavas with the aim of reconstructing directly the mantle source of the Payenia Volcanic Province. Xenoliths are commonly small (<5 cm in radius) but scarcely crossed by basaltic veins. All xenoliths have a fertile lherzolitic modal composition and are equilibrated in the spinel-facies. Most of them exhibit an almost primitive-mantle geochemical affinity, characterized by slightly depleted clinopyroxene REE patterns reproducible by partial melting degrees between 0 and 4% of a PM source. Geothermobarometric P-T estimates of cli-nopyroxene-orthopyroxene couples form a linear trend between 10 and 24 kbar with constant increase of T from 814 to 1170 °C along a 50–60 mW/m2 geotherm. Evidences of interaction with the host basalts occur as spongy textures in clinopyroxene and reacted spinel, which tend to became more restitic in composition and show chromatographic or complete overprinting of the trace element compositions. The presence of plagioclase and calculated P-T values constrain this melt/rock reaction process between 6 and 14 kbar, during magma ascent, and fit the mantle ad-iabat model. Calculated melts in equilibrium with the primary clinopyroxenes do not fit the composition of the host basalt and, together with the geothermobarometric estimations, point to an asthenospheric mantle source for the magmatism in southern Payenia. The PM geochemical affinity of the xenoliths of Huanul is an extremely rare finding in the South America lithospheric mantle, which is commonly extensively refertilized by subduction-derived melts

Short-scale variability of the SCLM beneath the extra-Andean back-arc (Paso de Indios, Argentina): Evidence from spinel-facies mantle xenoliths

Cenozoic basalts carrying ultramafic mantle xenoliths occur in the Matilde, León and Chenque hills in the Paso de Indios region, Argentina. The mantle xenoliths from the Chenque and León hills mainly present porphyroclastic textures, whereas the Matilde hill xenoliths have coarse-grained to porphyroclastic textures. The equilibrium temperatures are in the range of 780 to 940°C, indicating a provenance from shallow sectors of the lithospheric mantle column that were subjected to a relatively low heat flux at Cenozoic Era. According to the modal compositions of xenoliths, the mantle beneath Matilde and León hills was affected by greater than 22% partial melting, while less depleted peridotites occur in the Chenque suite (starting from 10% partial melting). Such an observation is con rmed by the partial melting estimates based on Cr#Sp, which vary from 8 to 14% for the selected Chenque samples and from 14 to 18% for the Matilde ones. The common melting trend is overlapped by small-scale cross cutting local trends that may have been generated by open-system processes, such as open-system partial melting and/or post partial-melting metasomatic migration of exotic Na-Cr-rich melts. The two main mineralogical reaction schemes are: i) the dissolution of pyroxenes and the segregation of new olivine in olivine-rich peridotites, and ii) the replacement of primary olivine by orthopyroxene±clinopyroxene in orthopyroxene-rich peridotites. These were produced by channelled and/or pervasive melt extraction/ migration. Enhanced pyroxene dissolution is attributed to channelling of silica- undersaturated melts, whereas the replacement of primary olivine by orthopyroxene±clinopyroxene points to reaction with silica-saturated melts. Late disequilibrium reactions identified in the xenoliths comprise: the breakdown of orthopyroxene in contact with the host basalt, and (rarely) reaction coronae on orthopyroxene, clinopyroxene and spinel linked to glassy veins. Such features are apparently related to the injection of melt, likely during entrainment into the host basalts and ascent to the surface.Centro de Investigaciones Geológica

How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons

COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; p < 0.0001) and diagnostic evaluations (16.4% vs. 42.2%; p < 0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; p < 0.0001) or urgent (20.4% vs. 38.5%; p < 0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; p < 0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice

Lockdown dreams: dream content and emotions during the COVID-19 pandemic in an Italian sample

Introduction In the current study, following the continuity hypothesis and considering the adaptive function of dreaming, dreams were investigated from a quantitative and qualitative perspective, focusing on how the COVID-19 restrictions impacted dream frequency, content, and emotions during the lockdown in an Italian sample [N=598, aged 18-70 years (M = 30.9; SD = 10.9)]. Methods The participants were recruited through an online survey in which they were asked to report one or two dreams they had during the lockdown, and to provide socio-demographical information. Levels of anxiety, depression and rumination were assessed. Questions also explored participants perceived fear of contagion, dream recall frequency, and dream vividness. Dream reports were analyzed using thematic analysis, and quantitative analyses were conducted using chi-square tests, t-tests, ANOVA, and bivariate correlations. Results Several themes emerged from the content analysis, including relationships, the human and natural environment, and COVID-19. Higher levels of anxiety, depression, and rumination were found in young adults, compared to middle age and older participants. A positive correlation emerged between the frequency of dreams relating to COVID-19 and anxiety and fear of contagion. Moreover, in both male and female participants, higher fear of contagion corresponded to greater dream vividness during the lockdown. Results showed that women had greater dream recall than men and reported greater psychological distress and more dreams related to COVID-19. Concerning the emotional tone of participants' dreams, it was found a higher proportion of negative dream emotions relative to positive ones: fear/fright/terror and anxiety/anguish/worry were the most frequent emotions in the dream reports. Conclusions Results were discussed highlighting clinical implications. The current study suggests that a traumatic collective event such as the Covid-19 pandemic may have implications for dream life

Lockdown dreams: dream content and emotions during the COVID-19 pandemic in an Italian sample

Beginning in March 2020, the Italian population was subjected to a lockdown lasting approximately 3 months due to the Coronavirus disease (COVID-19) emergency. Drawing on a quantitative and qualitative analysis of dream data, the present study aimed at exploring the effects of social isolation and the lockdown on Italian people’s dreams, focusing on content and dominating emotions. An online survey was administered to 598 participants who aged 18–70 years (M = 30.9, SD = 10.9). In the survey, participants were asked to: (a) write down two dreams they had during the lockdown and (b) provide data on demographic and socioeconomic factors; sleep quality before and after lockdown; and levels of anxiety, depression, and rumination. Questions also explored participants’ perceived fear of contagion, dream recall frequency (DRF), and dream vividness. Participants’ dream transcripts revealed a majority of negative emotions—particularly fear/fright/terror and anxiety/anguish/preoccupation. Moreover, several themes emerged from the content analysis, including relationships, the human and natural environment, and COVID-19. The results deepen our understanding of the dominant dream emotions of people experiencing a collective stressful event, such as the social isolation necessitated by the COVID-19 pandemic. Further, the findings support the continuity hypothesis, which holds that dreams tend to reflect the emotional concerns of the dreamer and help to integrate intense or disruptive emotions experienced during waking life

Short-scale variability of the SCLM beneath the extra-Andean back-arc (Paso de Indios, Argentina): Evidence from spinel-facies mantle xenoliths

Cenozoic basalts carrying ultramafic mantle xenoliths occur in the Matilde, Leon and Chenque hills in the Paso de Indios region, Argentina. The mantle xenoliths from the Chenque and Leon hills mainly present porphyroclastic textures, whereas the Matilde hill xenoliths have coarse-grained to porphyroclastic textures. The equilibrium temperatures are in the range of 780 to 940 degrees C, indicating a provenance from shallow sectors of the lithospheric mantle column that were subjected to a relatively low heat flux at Cenozoic Era. According to the modal compositions of xenoliths, the mantle beneath Matilde and Leon hills was affected by greater than 22% partial melting, while less depleted peridotites occur in the Chenque suite (starting from 10% partial melting). Such an observation is con firmed by the partial melting estimates based on Cr#(Sp), which vary from 8 to 14% for the selected Chenque samples and from 14 to 18% for the Matilde ones. The common melting trend is overlapped by small-scale cross cutting local trends that may have been generated by open-system processes, such as open-system partial melting and/or post partial-melting metasomatic migration of exotic Na-Cr-rich melts. The two main mineralogical reaction schemes are: i) the dissolution of pyroxenes and the segregation of new olivine in olivine-rich peridotites, and ii) the replacement of primary olivine by orthopyroxene +/- clinopyroxene in orthopyroxene-rich peridotites. These were produced by channelled and/or pervasive melt extraction/migration. Enhanced pyroxene dissolution is attributed to channelling of silica-undersaturated melts, whereas the replacement of primary olivine by orthopyroxene +/- clinopyroxene points to reaction with silica-saturated melts. Late disequilibrium reactions identified in the xenoliths comprise: the breakdown of orthopyroxene in contact with the host basalt, and (rarely) reaction coronae on orthopyroxene, clinopyroxene and spinel linked to glassy veins. Such features are apparently related to the injection of melt, likely during entrainment into the host basalts and ascent to the surface

Multiple refertilisation of a strongly refractory mantle column in the extra-Andean back-arc (Paso de Indios, Argentina)

In the central part of the Chubut province, close to the village of Paso de Indios, there are several outcrops of Cenozoic basalts carrying spinel-facies mantle xenoliths. In this area, located in the extra-Andean back-arc, basaltic necks and dikes outcrop between 43° 36′ – 43° 50′ S and 68° 53′ – 69° 02′ W, along with remnants of lava flows, being divided in two groups of Paleocene and Eocene age. This volcanism was generated by extensional tectonic related to an episode of transform plate margin that affected the southern sector of South America western margin from the Paleocene to the Oligocene, as the Aluk plate detached and a slab window opened beneath the study area. In this contribution, the petrochemical processes experienced by mantle xenoliths hosted in Eocene basalts belonging to the Matilde lava flow, the Leon volcano and the Chenque dike, are presented and discussed. The studied samples are mainly spinel-facies harzburgites and clinopyroxene(Cpx)-poor lherzolites, with some dunites. The Chenque xenoliths mainly display porphyroclastic to equigranular texture, whereas those from Matilde and Leon volcanoes have coarse-granular to porphyroclastic textures. Estimated equilibrium temperatures based on pyroxenes solvus range from 800 to 940°C. The overall refractory character of the mineral assemblages is matched by the major element mineral compositions, which are mostly Al-poor and Mg-and-Cr-rich. Spinel composition is consistent with melt extraction from 8 to 14% for Chenque and Leon samples, and from 14 to 18% for the Matilde ones. The estimated degree of partial melting rises up to 24% considering the literature spinel data. However, the occurrence of melt related open-system processes is suggested by local trends of positive correlation between Na and Cr# in Cpx, being fully confirmed by the trace element compositions. In particular, the Matilde harzburgites ubiquitously show Cpx with transient U-shaped REE patterns. The LREE fractionation is very strong, with LaN up to 100 and REE patterns minimum in the M-HREE region between 0.1-1 xCI. The HREE level content (LuN down to 1 xCI) is consistent with 20-23% fractional melting of spinel DM. V-to-U-shaped REE patterns are also shown by Chenque lherzolites and harzburgites. Their M/HREE are significantly more fractionated than that expected in residue after spinel-facies basalt removal, thus suggesting an onset of the partial melting process at garnet facies conditions. Other Chenque lherzolites experienced a more pronounced refertilisation process led by LREE-enriched to LREE-depleted melts. The latter gave rise to peculiar, transient LREE-depleted sinusoidal patterns in Cpxs through reaction with the depleted ambient peridotite. A refertilised geochemical composition is also shown by the Leon samples, with harzburgite Cpxs resulting enriched in highly-incompatible elements such as U, Th, Sr and LREE. The data presented in this study, in combination with those from the literature, allow us to conclude that the shallow mantle column beneath Paso de Indios was strongly refractory in origin, being successively affected by multiple events of melt migration. These letter, however, were able to produce only an incomplete refertilisation of the depleted protoliths, which still record geochemical gradients developed during the interaction with both LREEenriched and LREE-depleted migrating melts. These petrochemical features make the Paso de Indios mantle column a unique study case in the Patagonian region, where the composition of the shallow mantle is usually completely overprinted by multiple stages of melt/fluid migration

Short-scale variability of the SCLM beneath the extra-Andeanback-arc (Paso de Indios, Argentina): Evidence from spinel-faciesmantle xenoliths

Cenozoic basalts carrying ultramafic mantlexenoliths occur in the Matilde, León and Chenque hillsin the Paso de Indios region, Argentina. The mantle xenolithsfrom the Chenque and León hills mainly presentporphyroclastic textures, whereas the Matilde hill xenolithshave coarse-grained to porphyroclastic textures. Theequilibrium temperatures are in the range of 780 to 940ºC,indicating a provenance from shallow sectors of the lithosphericmantle column that were subjected to a relativelylow heat ffiux at Cenozoic Era