Mineralogical and Crystalochemical Characterization of the Sepiolite Deposit from Andrichi (Pranjani Basin, Serbia)

Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu

Plume-Induced Sinking of the Intracontinental Lithosphere as a Fundamentally New Mechanism of Subduction Initiation

Although many different mechanisms for subduction initiation have been proposed, few of them are viable in terms of agreement with observations and reproducibility in numerical experiments. In particular, it has recently been demonstrated that intra-oceanic subduction triggered by an upwelling mantle plume could contribute greatly to the onset and functioning of plate tectonics in the early Earth and, to a lesser extent, in the modern Earth. In contrast, the onset of intracontinental subduction is still underestimated. Here we review 1) observations demonstrating the upwelling of hot mantle material flanked by sinking proto-slabs of the continental mantle lithosphere, and 2) previously published and new numerical models of plume-induced subduction initiation. Numerical modelling shows that under the condition of a sufficiently thick (> 100 km) continental plate, incipient down thrusting at the level of the lowermost lithospheric mantle can be triggered by plume anomalies with moderate temperatures and without significant strain and/or melt-induced weakening of the overlying rocks. This finding is in contrast to the requirements for plume-induced subduction initiation in oceanic or thin continental lithosphere. Consequently, plume-lithosphere interactions in the continental interior of Paleozoic-Proterozoic (Archean) platforms are the least demanding (and therefore potentially very common) mechanism for triggering subduction-like foundering in Phanerozoic Earth. Our findings are supported by a growing body of new geophysical data collected in a variety of intracontinental settings. A better understanding of the role of intracontinental mantle downthrusting and foundering in global plate tectonics and, in particular, in triggering "classic" oceanic-continental subduction will benefit from further detailed follow-up studies

Mineralogical and Crystalochemical Characterization of the Sepiolite Deposit from Andrichi (Pranjani Basin, Serbia)

Comunicación del Congreso SEM 2014, XXXIV Reunión Científica de la Sociedad Española de Mineralogía, Granada 2-7 Julio de 2014.Peer reviewe

Mg-Phyllosilicates crystal cremistry of the Andrici sepiolite deposit (Serbia)

Trabajo presentado en la 2nd European Mineralogical Conference (EMC), celebrada en Rimini (Italia) del 11 al 15 de septiembre de 2016The sepiolite deposit Andri i is located in the Pranjani Basin, in the western part of Serbia. The studied section of Andri i deposit represents the sepiolite-bearing succession characterized by rhythmic alternation of clay-rich and dolomite-rich intervals. The section started with claystone dominated by detrital material derived from the surrounding paleorelief of ultramafic rocks. In this basal part smectites are inherited but smectites deposited from solution are also present. In dolomicrite marls, sepiolite occurs as interwoven fibres which coat and fill pores between dolomite crystals while, in the clay-rich layers, sepiolite consists of fibres forming planes. The texture in these layers indicates that sepiolite crystallized directly from solution. The chemical composition of individual particles was obtained using analytical electron microscope (AEM) with TEM, using a JEOL 3000 FX Field Emission Microscope at an acceleration voltage of 300 kV that incorporates an OXFORD ISIS EDX spectrometer. In these materials, different Mg-phyllosilicates have been found and it is remarkable that all these phyllosilicates are rich in Fe. In the basal detrital material, Fe-rich chrysotile and two types of smectites appear. From the structural formula obtained, the two smectites can be classified as Fe-rich saponite. In the rest of the section, sepiolite is the main mineral and it can occur with trioctahedral smectites, with dolomite, or almost pure. The crystal chemistry of these three groups is slightly different: i) in dolomitic marls sepiolite has the octahedral content close to the ideal, with very low amounts of VIAl and Fe3+ and also small amounts of tetrahedral substitutions. It is remarkable that Fe3+ appears as tetrahedral cation in the mean structural formulae in most samples, which is not very common in sepiolite. ii) The sepiolites that appear with smectites are characterized by the high amount of tetrahedral substitution, while the octahedral content is close to the ideal sepiolite. In these samples, as in the dolomitic levels Fe3+ is needed to fill the tetrahedral positions indicating the low availability of Al in the sedimentary ambience. iii) Finally, the purest sepiolite level presents a composition relatively close to the ideal sepiolite whit only small amounts of Al as tetrahedral and octahedral cation.Peer reviewe

Health-status outcomes with invasive or conservative care in coronary disease

BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline

Initial invasive or conservative strategy for stable coronary disease

BACKGROUND Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, 121.8 percentage points; 95% CI, 124.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used