Composition and textures of chromite and platinum-group minerals in chromitites of the western ophiolitic belt from Pampean Ranges of Córdoba, Argentina

Chromitite bodies hosted in the Neoproterozoic western ophiolitic belt of Pampean Ranges of Córdoba (Argentina) were studied at Los Congos and Los Guanacos ultramafic bodies, with regard to the composition and textures of the chromite and platinum group minerals. Primary chromite composition is only preserved in some massive chromitites from the Los Guanacos ultramafic body, and is similar to Al-rich ophiolitic chromitites, suggesting that they crystallized from melts with back arc basin basalts (BABB) affinity in the suprasubduction mantle. Subsequently, these chromitites underwent a prograde metamorphism. Chromites from chromitites and associated metamorphosed ultramafic rocks show complex replacement and exsolution textures. Mineral chemistry and texture indicate that the chromite composition records two main metamorphic trends. A first trend defined by chromite from massive chromitite, in which there is an enrichment in Fe3+ and Fe2+, Cr remain relatively constant, and slightly depleted in Al, Mg. A second trend is defined by chromite from disseminated chromitite and metamorphosed dunite and harzburgite, in which a Fe-rich phase is replacing the Al-rich chromite. This alteration trend is characterized by enrichment in the total iron content (Fe3++Fe2+) and a strong depletion in Al and Mg. The chemical composition of all analyzed spinels from Los Guanacos and Los Congos, as plotted on the ternary Fe3+–Cr–Al diagram, correlates well with the Cr-spinels from the upper amphibolite to granulite-facies metamorphism. Platinum group minerals (PGM) identified include native osmium, laurite, erlichmanite, irarsite, platinum and a number of inadequately identified phases such as an oxide or hydroxide of Ru, Pt and Ir–Ru, Pt telluride, Ir–Ru–As–Se and Ir–Ru–Ti compounds. Native osmium was the only PGMwhich remained unaltered; other PGMunderwentmineralogical reworking duringmetamorphism.Although it is difficult to establish the extent of platinum group element mobilization based on mineralogical observation, our results suggest that the Ru–Os–Ir PGM in the Los Guanacos and Los Congos chromitites were modified in situ, producing re-distribution of these PGE on a small scale. The presence of rare Pt and PGE–As–Se minerals was possibly related to remobilization of Pt, As and Se by fluids during the alteration processes.Fil: Proenza, J.. Universidad de Barcelona; EspañaFil: Zaccarini, F.. University of Leoben; AustriaFil: Escayola, M.. University of Leoben; AustriaFil: Cábana, C.. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: Schalamuk, Bernardo Isidoro. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Garuti, G.. Università di Modena e Reggio Emilia; Itali

Paleomagnestism of the Santa Victoria Group in the Mojotoro Range, Salta: Contributions to the paleogeographic position of Pampia in Early Paleozoic

Sedimentologic magnetofabric paleomagnetic studies were carried out on the early Ordovician La Pedrera Formation (Santa Victoria Group) in the Mojotoro Range Salta province. These studies aim at contributing to a better knowledge on the paleogeographic position of the Pampia block in the Early Paleozoic in relation to the Gondwana supercontinent. Oriented samples were collected from 12 sites distributed in three localities. These outcrops consist of middle to proximal shelf deposits of mainly quarzitic composition. Studies on the anisotropy of magnetic susceptibility (AMS) suggest a depositional fabric in one of these localities meanwhile some tectonic influence cannot be ruled out in the magnetic fabric found in the other two. The paleomagnetic analysis permitted to determine a characteristic magnetic remanence carried by hematite at all twelve sites. From the virtual geomagnetic poles computed at each site a paleomagnetic pole was obtained for the Santa Victoria Group at these localities which is located at 340,4°E 38,3°N A95=8,8°. This pole position suggests that any of the three localities underwent significant tectonic rotations due to the Andean orogeny or pre-vious tectonic events. However, it presents a somewhat lower than expected paleolatitude in comparison to coeval reference poles for Gondwana. Studies of oriented isothermal remanent magnetization suggest that this difference should not be due to inclination errors. On the other hand, the paleomagnetic pole for the Santa Victoria Group disagrees with those previously obtained for the middle to upper Cambrian Mesón Group and the lowermost Ordovician Santa Rosita Formation, to the north of our study localities but still in the same region. These discrepancies can be explained either by the presence of Andean local tectonic rotations around vertical axes in the localities to the north of our study zone or by considering that the hypothetical displacement of Pampia along the Río de la Plata craton margin was already over, or nearly so, by the Early Ordovician

Descriptive review of current practices and prognostic factors in patients with ovarian cancer treated by pressurized intraperitoneal aerosol chemotherapy (PIPAC): a multicentric, retrospective, cohort of 234 patients.

Ovarian cancer (OC) is the primary cause of mortality in women diagnosed with gynecological cancer. Our study assessed pressurized intraperitoneal aerosol chemotherapy (PIPAC) as treatment for peritoneal surface metastases (PSM) from recurrent or progressive OC and conducted survival analyses to identify prognostic factors. This retrospective cohort study, conducted across 18 international centers, analyzed the clinical practices of patients receiving palliative treatment for PSM from OC who underwent PIPAC. All patients were initially treated appropriately outside any clinical trial setting. Feasibility, safety, and morbidity were evaluated along with objective endpoints of oncological response. Multivariate analysis identified prognostic factors for OS and PFS. From 2015-2020, 234 consecutive patients were studied, from which 192 patients were included and stratified by platinum sensitivity for analysis. Patients with early recurrence, within one postoperative month, were excluded. Baseline characteristics were similar between the groups regarding platinum sensitivity (platinum sensitive (PS) and resistant (PR)), but chemotherapy frequency differed, as did PCI before PIPAC. Median PCI decreased in both groups after three cycles of PIPAC (PS 16 vs. 12, p < 0.001; PR 24 vs. 20, p = 0.009). Overall morbidity was 22%, with few severe complications (4-8%) or mortality (0-3%). Higher pathological response and longer OS (22 vs. 11m, p = 0.012) and PFS (12 vs. 7m, p = 0.033) were observed in the PS group. Multivariate analysis (OS/PFS) identified ascites (HR 4.02, p < 0.001/5.22, p < 0.001), positive cytology at first PIPAC (HR 3.91, p = 0.002/1.96, p = 0.035), and ≥ 3 PIPACs (HR 0.30, p = 0.002/0.48, p = 0.017) as independent prognostic factors of overall survival/progression-free survival. With low morbidity and mortality rates, PIPAC is a safe option for palliative treatment of advanced ovarian cancer. Promising results were observed after 3 PIPAC, which did improve the peritoneal burden. However, further research is needed to evaluate the potential role of PIPAC as an independent prognostic factor

Axial Ligand Effects of Ru-BDA Complexes in the O-O Bond Formation via the I2M Bimolecular Mechanism in Water Oxidation Catalysis

A detailed computational investigation of the mechanistic aspects of the water oxidation catalysis (WOC) for ruthenium-based catalysts [Ru(bda)(isoq)(2)] (H(2)bda = 2,2 '-bipyridine-6,6 '-dicarboxylic acid; isoq = isoquinoline). Density functional theory (DFT) calculations describe the kinetics by means of the energy barrier that leads to the O-O coupling, the rate-limiting step for WOC. To test the effect of the axial ligand environment, we investigated bda complexes with para-substituted isoquinolines, phthalazines and pyridines. Since previous screening analyses of the potential energy surface revealed a face to face orientation of metal-oxo species to be best for facilitating the O-O bond formation, this paper probes the deeper role of the axial ligands that saturate the Ru(bda) based complexes from a computational point of view

Age and setting of Permian Slide Mountain terrane ophiolitic ultramafic-mafic complexes in the Yukon: Implications for late Paleozoic-early Mesozoic tectonic models in the northern Canadian Cordillera

The Yukon Tanana (YTT) and Slide Mountain terranes (SMT) of the Cordillera in Canada and Alaska were interpreted in terms of opening and closing of a Late Devonian-Permian Japan Sea-style backarc basin behind a continental arc built upon YTT, which rifted from Laurentia during the Famennian-early Mississippian. Formation of Famennian transitional oceanic lithosphere supports rifting, but a combination of existing and new data on the setting and age of SMT ophiolites do not support the Japan Sea model. The studied Clinton Creek and Midnight Dome complexes represent suprasubduction zone ophiolites formed at ca. 265 Ma, consistent with analyses of other SMT ophiolites. Ultramafic rocks dominate most ophiolites. They lack sheeted dikes and contain relatively minor volumes of mafic plutonic and volcanic rocks, suggesting they formed in oceanic core complexes characterised by slow spreading and low magma productivity. The Permian ophiolites formed during or immediately after eclogite formation in YTT, coeval with or immediately preceding emplacement of orogenic peridotites into YTT due to hyperextension. Several tectonic scenarios are discussed. We propose that YTT is a composite terrane comprising a continental block and an oceanic arc-backarc complex with the latter obducted onto the former during the middle Permian-early Triassic Klondike orogeny. Obduction may have come from the west or east, but east-directed obduction is most consistent with geological constraints. Obduction was followed by initiation of west-dipping subduction east of the composite YTT; slab roll back causing extension in the composite upper plate, leading to exhumation of orogenic peridotites. Tectonic relationships show many analogies to the collision between Australia and the New Britain arc, in which collision in the Huon Peninsula of New Guinea is contemporaneous with extension in Australian crust in the adjacent Woodlark basin. Syn-orogenic Permian Klondike calc-alkaline magmatism is attributed to extension in a Woodlark basin-like setting rather than a representing a continental arc.Fil: van Staal, Cees R.. Geological Survey Of Canada Vancouver; Canadá. University of Waterloo; CanadáFil: Zagorevski, Alexandre. Geological Survey Of Canada; CanadáFil: McClelland, William C.. University of Iowa; Estados UnidosFil: Escayola, Monica Patricia. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Ryan, James J.. Geological Survey Of Canada Vancouver; CanadáFil: Parsons, Andrew J.. University of Oxford; Reino Unido. Geological Survey Of Canada Vancouver; CanadáFil: Proenza, Joaquin. Universidad de Barcelona; Españ

Experimental demonstration of multi-band upstream in statistical OFDM-PONs and comparison with digital subcarrier assignment

A multiband subcarrier allocation scheme is demonstrated for the uplink in a statistical OFDM-PON. Performance achieved is similar to digital subcarrier allocation, with the significant advantage of a lower transmitter complexity.Peer ReviewedPostprint (published version

Varieties of representations of surface groups

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