Magmatic Sulfides from the Rincón-Portezuelo de las Ánimas Volcanic Complex, Northwest Argentina: Insights on Magma Fertility and Comparison with Mineralized Volcanic Systems

The composition and fate of magmatic sulfides are some of the most critical factors invoked to play a role in the chalcophile metal fertility of arc magmas. Examination of magmatic sulfide accessory minerals in non-mineralized volcanic systems may help to understand the behavior of chalcophile metals at sulfide saturation. This study presents compositional data on magmatic sulfides in lavas of the Late Miocene Rincón-Portezuelo de las Ánimas volcanic complex, NW Argentina. This is the easternmost magmatic occurrence in the back-arc of Southern Central Andes, at 27°S, about 75 km NE from the world-class Bajo de la Alumbrera porphyry Cu-Au deposit. At this latitude the Late Miocene volcanic activity migrated eastward as a consequence of the shallowing slab subduction. Both copper-rich and pyrrhotite magmatic sulfide inclusions have been identified in the Rincón-Portezuelo de las Ánimas volcanic suite, straddling the high-K calc-alkaline–shoshonite boundary. We discuss the sulfide composition in the framework of magmatic evolution and in comparison with the metal content of magmatic sulfides of the coeval Farallón Negro volcanic complex, associated with the Bajo de la Alumbrera porphyry Cu-Au, and other mineralized systems. The results show that sulfide liquid, exsolved from silicate melts of intermediate composition, stores Cu, Pb, Ag, Bi in crystal mushes, reducing the mineralizing potential of residual melts while fertilizing the middle-upper crust. Gold behavior seems to be controlled by additional mechanisms, linked to the magma source or to an early partitioning into a S-bearing fluid phase. The high Au/Cu ratio of sulfides formed as monosulfide solid solution may be associated with the potassic character of the magmas in this sector of the Central Andes

Structure, Energy, and Vibrational Frequencies of Oxygen Allotropes On (n ≤ 6) in the Covalently Bound and van der Waals Forms: Ab Initio Study at the CCSD(T) Level

Recent experiments on the UV and electron beam irradiation of solid O2 reveals a series of IR features near the valence antisymmetric vibration band of O3 which are frequently interpreted as the formation of unusual On allotropes in the forms of weak complexes or covalently bound molecules. In order to elucidate the question of the nature of the irradiation products, the structure, relative energies, and vibrational frequencies of various forms of On (n = 1−6) in the singlet, triplet, and, in some cases, quintet states were studied using the CCSD(T) method up to the CCSD(T,full)/cc-pCVTZ and CCSD(T,FC)/aug-cc-pVTZ levels. The results of calculations demonstrate the existence of stable highly symmetric structures O4(D3h), O4 (D2d), and O6 (D3d) as well as the intermolecular complexes O2·O2, O2·O3, and O3·O3 in different conformations. The calculations show that the local minimum corresponding to the O3···O complex is quite shallow and cannot explain the ν3 band features close to 1040 cm−1, as was proposed previously. For the ozone dimer, a new conformer was found which is more stable than the structure known to date. The effect of the ozone dimer on the registered IR spectra is discussed

Present clinical practice of breast cancer radiotherapy in Italy: a nationwide survey by the Italian Society of Radiotherapy and Clinical Oncology (AIRO) Breast Group

Aims: To investigate the present attitude of the Italian Radiation Oncologists in the management of breast cancer (BC) concerning hypofractionated radiotherapy (hRT), partial-breast irradiation (PBI), re-irradiation (rRT) and radiotherapy after neoadjuvant chemotherapy (post-NAC RT). Methods: A nationwide, 21-point questionnaire was distributed online via SurveyMonkey. Results: Seventy-four Italian Radiotherapy Centers answered to the survey. In most cases, the responding centers treated more than 100 BC patients/year between January 2016 and December 2017. Almost half of responding centers (49%) treated patients with hRT,out of these, 95% as routine practice for early-stage BC. Dose prescriptions ranged between 39 and 45 Gy indicating a high use of moderate hRT. The chest wall and regional lymph nodes were irradiated with hRT by 13% and 15% of the responding centers, respectively. PBI was used by 60% of responders, with different techniques. Only 0.6% of participants perform rRT after BC recurrence.Finally, only 11% of the interviewed centers responded to their attitude toward post-NAC RT, which, however, was indicated in 97% of patients after breast-conserving surgery. Conclusions: This survey shows a fairly good use of hRT and a moderate practice of PBI in Italy. Some practices like hRT to the chest wall and regional lymph nodes as well as rRT need further verification. Likewise, the management of post-NAC RT is very heterogeneous. Future national clinical collaborative studies are advocated in order to investigate these controversial topics about breast cancer radiotherapy