Thermal evolution of Andean iron oxide-apatite (IOA) deposits as revealed by magnetite thermometry.

Magnetite is the main constituent of iron oxide-apatite (IOA) deposits, which are a globally important source of Fe and other elements such as P and REE, critical for modern technologies. Geochemical studies of magnetite from IOA deposits have provided key insights into the ore-forming processes and source of mineralizing fluids. However, to date, only qualitative estimations have been obtained for one of the key controlling physico-chemical parameters, i.e., the temperature of magnetite formation. Here we reconstruct the thermal evolution of Andean IOA deposits by using magnetite thermometry. Our study comprised a > 3000 point geochemical dataset of magnetite from several IOA deposits within the Early Cretaceous Chilean Iron Belt, as well as from the Pliocene El Laco IOA deposit in the Chilean Altiplano. Thermometry data reveal that the deposits formed under a wide range of temperatures, from purely magmatic (~ 1000 to 800 °C), to late magmatic or magmatic-hydrothermal (~ 800 to 600 °C), to purely hydrothermal (< 600 °C) conditions. Magnetite cooling trends are consistent with genetic models invoking a combined igneous and magmatic-hydrothermal origin that involve Fe-rich fluids sourced from intermediate silicate magmas. The data demonstrate the potential of magnetite thermometry to better constrain the thermal evolution of IOA systems worldwide, and help refine the geological models used to find new resources.

Formation of massive iron deposits linked to explosive volcanic eruptions.

The genetic link between magmas and ore deposit formation is well documented by studies of fossil hydrothermal systems associated with magmatic intrusions at depth. However, the role of explosive volcanic processes as active agents of mineralization remains unexplored owing to the fact that metals and volatiles are released into the atmosphere during the eruption of arc volcanoes. Here, we draw on observations of the uniquely preserved El Laco iron deposit in the Central Andes to shed new light on the metallogenic role of explosive volcanism that operates on a global scale. The massive magnetite (Fe3O4) ore bodies at El Laco have surface structures remarkably similar to basaltic lava flows, stimulating controversy about their origin. A long-standing debate has endured because all proposed models were constructed based exclusively on samples collected from surface outcrops representing the uppermost and most altered portion of the deposit. We overcome this sampling bias by studying samples retrieved from several drill cores and surface outcrops. Our results reveal complex lithological, textural and geochemical variations characterized by magmatic-like features and, most notably, a systematic increase in titanium concentration of magnetite with depth that account for an evolving system transitioning from purely magmatic to magmatic-hydrothermal conditions. We conclude that El Laco, and similar deposits worldwide, formed by a synergistic combination of common magmatic processes enhanced during the evolution of caldera-related explosive volcanic systems.

Factores que intervienen en la sobrecarga del cuidador primario del paciente con cáncer / Factors involved in the burden of the primary caregiver of cancer patients

Objetivo. Identificar los factores que intervienen en la sobrecarga y calidad de vida del cuidador primario del paciente con cáncer. Material y métodos. Se realizó un estudio transversal en un hospital de segundo nivel de atención que incluyó 100 cuidadores primarios de pacientes con cáncer. Se determinó el nivel de sobrecarga con la escala de Zarit, y la percepción de calidad de vida con el cuestionario World Health Organization Quality of Life. Se categorizó la calidad de vida como alta o baja y se comparó entre grupos según su nivel de sobrecarga. Se realizó estadística descriptiva para las variables de estudio y se analizaron las diferencias entre grupos según su nivel de sobrecarga. Resultados. Al evaluar la sobrecarga se encontró que el 31% de cuidadores presentó sobrecarga. El 76% de los cuidadores percibió una buena calidad de vida, mientras que el 24% restante la percibió como mala. Para identificar la asociación entre estas 2 variables se utilizó la Chi cuadrado, encontrando una asociación con una p≤0,05. Para identificar correlación entre calidad de vida y sobrecarga del cuidador primario se realizó una correlación de Spearman, obteniendo un valor r de 0,321 con una p≤0,05, encontrando una correlación levemente positiva. Conclusiones. Los factores que inciden en mayor medida para una buena calidad de vida a pesar de tener sobrecarga fueron: el ser casado, el dedicarse al hogar y el parentesco (ser familiar directo: cónyuge, padres e hijos). De manera contraria el tipo de cáncer, las horas de sueño y las horas de cuidado influyen en la percepción de una mala calidad de vida (AU)

Objective. The aim of the study was to identify the factors involved between burden in the primary caregiver of cancer patients and their quality of life. Material and methods. A cross-sectional study was conducted in a secondary level hospital on 100 primary caregivers of cancer patients. The level of burden was determined using the Zarit scale and the perception of quality of life using the World Health Organisation Quality of Life questionnaire. Quality of life was categorised as high or low and compared between groups according to their level of burden. Descriptive statistics were performed on the study variables, and differences between groups were analysed according to their level of burden. Results. In assessing the overload, it was found that 31% of caregivers had burden. A good quality of life was perceived by 76% of caregivers, while the remaining 24% perceived it as poor. To identify association between these two variables Chi squared (X2) was used to determine whether there was any association between quality of life and overloading of the primary caregiver, giving a P≤.05. A Spearman correlation was also performed, obtaining an r-value of .321 with a P≤.05, finding a slightly positive correlation. Conclusions. The factors that have a bearing on a good quality of life despite having burden were: being married, dedicated to the home, and kinship (to be immediate family: spouse, parents and children). Conversely, the type of cancer, sleep hours, and hours of care influence the perception of a poor quality of life (AU)

[Factors involved in the burden of the primary caregiver of cancer patients]. / Factores que intervienen en la sobrecarga del cuidador primario del paciente con cáncer.

OBJECTIVE: The aim of the study was to identify the factors involved between burden in the primary caregiver of cancer patients and their quality of life. MATERIAL AND METHODS: A cross-sectional study was conducted in a secondary level hospital on 100 primary caregivers of cancer patients. The level of burden was determined using the Zarit scale and the perception of quality of life using the World Health Organisation Quality of Life questionnaire. Quality of life was categorised as high or low and compared between groups according to their level of burden. Descriptive statistics were performed on the study variables, and differences between groups were analysed according to their level of burden. RESULTS: In assessing the overload, it was found that 31% of caregivers had burden. A good quality of life was perceived by 76% of caregivers, while the remaining 24% perceived it as poor. To identify association between these two variables Chi squared (X2) was used to determine whether there was any association between quality of life and overloading of the primary caregiver, giving a P≤.05. A Spearman correlation was also performed, obtaining an r-value of .321 with a P≤.05, finding a slightly positive correlation. CONCLUSIONS: The factors that have a bearing on a good quality of life despite having burden were: being married, dedicated to the home, and kinship (to be immediate family: spouse, parents and children). Conversely, the type of cancer, sleep hours, and hours of care influence the perception of a poor quality of life.

[Seroprevalence of Epstein Barr virus infection in a healthy population of Santiago de Chile]. / Seroprevalencia de infección por virus de Epstein Barr en población sana de Santiago de Chile.

To study the rate of infection by Epstein Barr virus (EBV) in Santiago, Chile, the prevalence of antibody to the viral capsid antigen (VCA-IgG) was determined in a group of 663 healthy individuals grouped by age and socioeconomic level (SEL). In addition, several risk factors for infection were studied. VCA-IgG was determined by ELISA. The total prevalence was 76.7%. When grouped by age and SEL, 50% of the children from low and medium SEL had been already infected by the age two, compared to 5.9% in the high SEL (p < 0.01). However, by age twenty, 90% of the total sample had already specific antibodies to EBV. Age and number of household members were positively associated with the infection. High socioeconomic level represented a delay factor in the acquisition of the virus, (p < 0.01). These results show that EBV infection is frequent in Santiago, occurring early in childhood among medium and low SEL. Hence, the classical infectious mononucleosis should be recognized more frequently among adolescents and young adults belonging to high SEL, while the clinical spectrum of associated manifestations different from the typical mononucleosis syndrome should be investigated among those exposed in early age.

Seroprevalence of Helicobacter pylori in Chile: vegetables may serve as one route of transmission.

Helicobacter pylori infection is very common in Chilean adults, but the age-related prevalence, risk factors for infection, and mode of transmission in Chilean children are unknown. An ELISA was used to test for H. pylori antibodies in 1815 Chileans < 35 years of age. Seropositivity was > 60% in lower socioeconomic groups. H. pylori seropositivity correlated with increased age, low socioeconomic status, and consumption of uncooked vegetables by use of a logistic regression analysis. Risk factors that reached marginal significance were consumption of uncooked shell-fish, female sex, and residence in Santiago. Although multiple modes of transmission for H. pylori undoubtedly exist, prior studies have suggested that contamination of irrigation water by raw sewage (and the subsequent contamination of vegetables that are eaten uncooked) is a key factor in the transmission of enteric pathogens in Chile; H. pylori may be transmitted by a similar route.