Quadricuspid aortic valve associated with hypoplastic aortic annulus

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Carbonatites from the southern brazilian platform. A review. II. Isotopic evidences

Early and Late Cretaceous alkaline and alkaline– carbonatitic complexes from southern Brazil are located along the main tectonic lineaments of the South America Platform. Calcium-, magnesium-, and ferrocarbonatites are well represented and frequently associated even in the same complex. Primary carbonates present significant variations in C–O isotopic compositions, which are mainly due to isotope exchange with H2O–CO2-rich hydrothermal fluids, whereas fractional crystallization or liquid immiscibility probably affects the δ18O and δ13C values by no more than 2δ‰. Our isotope exchange model implies that the most significant isotopic variations took place in a hydrothermal environment, e.g., in the range 400–80°C, involving fluids with the CO2/H2O ratio ranging from 0.8 to 1. Sr–Nd–Pb isotope systematics highlight heterogeneous mixtures between HIMU and EMI mantle components, similar to the associated alkaline rocks and the flood tholeiites from southern Brazil. In spite of the strong variation shown by C–O isotopes, Sr-Nd–Pb–Os isotopic systematics could be related to an isotopically enriched source where the chemical heterogeneities reflect a depleted mantle “metasomatized” by small-volume melts and fluids rich in incompatible elements. These fluids are expected to have promoted crystallization of K-rich phases in the mantle, which produced a veined network variously enriched in LILE and LREE. The newly formed veins (enriched component) and peridotite matrix (depleted component) underwent a different isotopic evolution with time as reflected by the carbonatites. These conclusions may be extended to the whole Paraná–Etendeka system, where isotopically distinct parent magmas were generated following two main enrichment events of the subcontinental lithospheric mantle at 2.0–1.4 and 1.0–0.5 Ga, respectively, as also supported by Re–Os systematics. The mantle sources preserved the isotopic heterogeneities over a long time, suggesting a non convective lithospheric mantle beneath different cratons or intercratonic regions. Overall, the data indicate that the alkaline–carbonatitic magmatism originated from a locally heterogeneous subcontinental mantle

Carbonatites from the Southern Brazilian platform: I

We present a comprehensive overview of the geochemical characteristics and evolution of the carbo- natites from the southern Brazilian Platform (Paraná Basin). The carbonatites from dierent complexes dis- play large compositional variability in terms of abun- dances of incompatible and rare earth elements. This is in agreement with an origin from heterogeneous litho- spheric sources, as conrmed by isotopic data (see Speziale et al., this issue). The characteristic major and trace element abundances of these carbonatites present compelling evidence for invoking liquid unmixing as the main mechanism of their formation and evolution albeit few exceptions. We propose an evolutionary trend for the Brazilian carbonatites, which can be summarized as following: exsolution of the primary Ca- or Mg-carbona- titic liquids systematically takes place at the phonolite- peralkaline phonolite stage of magma dierentiation; this is followed by progressive Fe-enrichment and by nal emplacement of uorocarbonatites associated with hydrothermal uids

Co-composted biochar improves barley yield, manure use efficiency and offsets chemical fertilizer demand in organic agriculture under low rainfall conditions

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Innovazioni tecnologiche nel trattamento dei pazienti con patologia valvolare, ad alto rischio chirurgico: confronto tra procedure transcatetere e chirurgia convenzionale e mininvasiva nel trattamento della stenosi aortica severa sintomatica.

OBJECTIVES - Surgical aortic valve replacement (AVR) is still the treatment of choice for patients with severe symptomatic aortic valve stenosis (SSAVS). During few last years novel technologies, like transcatheter aortic valve replacement (TAVI) and sutureless bioprosthesis have shown early good results. The aim of this study was to compare early and mid-term outcomes of high-risk patients undergoing TAVI procedures versus patients undergoing minimally invasive aortic valve replacement with sutureless valves and versus patients undergoing conventional surgical AVR for SSAVS. METHODS - From January 2011 to December 2013, 69 patients with severe aortic stenosis underwent TAVI procedure at our centre. This prospective cohort of patients was matched by four categories of risk profile and three categories of age, to a prospective/retrospective cohort of patients undergoing conventional surgical AVR from May 2004 to December 2013 (CCH GROUP, n = 250 patients) and to a prospective cohort of patients undergoing minimally invasive AVR with a sutureless bioprosthesis from January 2011 and December 2013 (SUTURELESS GROUP, n = 73 patients) at our centre. Were created two groups of pairs: TAVI versus CCH, with 51 matched pairs with comparable preoperative risk profile and age, and TAVI and SUTURELESS, with 40 matched pairs with comparable preoperative risk profile and age. RESULTS - TAVI versus CCH: After matching 1:1 for the entire population, 51 patients undergoing TAVI procedure were matched to the CCH GROUP. Major/minor vascular complications were significantly more frequent in the TAVI group than in the CCH group (15.7% versus 0%, p=0.0058). Median mechanical ventilation time and Median ICU stay were significantly lower in TAVI Group compared with CCH Group. In CCH group the rate of new onset of AF was significantly higher respect to TAVI group (31.4% (n16) vs. 8.5% (n4) respectively, p=0.0058). At discharge mean transvalvular gradient was significantly lower in TAVI group, while the incidence of moderate to severe paravalvular leak was significantly higher in patients undergoing TAVI (P0.001). At discharge mortality rate was higher in TAVI group compared with CCH group (7.8% vs. 0%, P = 0.1176), but one-year mortality rate was 6.5% (n = 3) in the TAVI group and 12% (n = 6) in the CCH group (P= 0.4898), and one year cumulative mortality was not significantly different among two cohorts. TAVI versus SUTURELESS: After matching 1:1 for the entire population, 40 patients undergoing TAVI procedure were matched to the SUTURELESS group. Major/minor vascular complications were significantly more frequents in the TAVI group than in the SUTURELESS group (15.0% versus 0%, p=0.0255). Median mechanical ventilation time and Median ICU stay were significantly lower in TAVI group compared with SUTURELESS group. In SUTURELESS group the rate of new onset of AF was higher respect to TAVI group 38.5% ((n = 15) vs. 10.8% (n = 4) respectively) (P=0.0083). At discharge and at one-year FU mean transvalvular gradient was comparable among two groups, while paravalvular regurgitation was more frequent after TAVI (P0.001). At discharge mortality rate was higher in TAVI group compared with SUTURELESS group (7.5% vs. 2.5%) (P=0.6153), but one-year mortality rate was 5.6 % (n = 2) in the TAVI group and 13.2% (n = 5) in the SUTURELESS group (P= 0.4310), and the one year cumulative mortality was not significantly different among two cohorts. CONCLUSIONS - In high-risk patients with a severe symptomatic aortic valve stenosis, transcatheter and surgical procedures (both conventional and MIAVR with sutureless) for aortic-valve replacement are associated with similar rates of survival at one year, although there were some differences in periprocedural complications and mid-term outcomes. All these therapeutic alternatives must be offered to our patients population and the most appropriate technique could be tailored to each patient

Metabasites from Namibe Province, SW-Angola: An Archean komatiitic magmatism?

Metabasite intercalations in Precambrian metasedimentary sequences from Namibe Province, southwestern Angola, show strong geochemical affinity with komatiites and komatiitic basalts. Rb-Sr systematics, probably "perturbed" by polymetamorphic processes, as well as by crustal contamination and alteration, seem to indicate two main thermal events, at 2.0 Ga (initial 87Sr/86Sr = 0.70194) and 0.9 Ga (initial 87Sr/86Sr = 0.70614), respectively, roughly corresponding to the Early Proterozoic (Eburnean) cratonization, and to the beginning of the Pan-African event. However, Sm-Nd isotopic data display an errorchron of 3.1±0.1 Ga (initial 143Nd/144Nd = 0.50868) consistent with the values inferred by both DM (depleted mantle: 3.4±0.3 Ga) and CHUR (chondritic mantle: 3.2±0.4 Ga) model ages, suggesting an of Early middle Archean magmatism in SW-Angola

A review of carbonatitic magmatism in the Parana-Angola-Namibia (PAN) system

Mesozoic to Cenozoic alkaline-carbonatitic complexes from southern Brazil, Angola and Namibia occur along main tectonic lineaments. In general, the alkaline-carbonatite complexes show intrusive/subintrusive, subcircular or oval shaped structures and are indicative of high upwelling energy. Processes of liquid immiscibility from trachytic-phonolitic liquids, starting from parental alkaline mafic magmas are believed to have generated carbonatitic liquids, as suggested by field relationships and geochemical characteristics. Ca-, Mg- and Fe-carbonatites are widespread even in the same complex. The occurrences comprise three main chronogroups, i.e. 1) Early Cretaceous (Eastern Paraguay; Brazil, Ponta Grossa Arch and Anitapolis; Angola and Namibia); 2) Late Cretaceous (Brazil , Ponta Grossa Arch, Lages and Alto Paranaiba. Namibia); 3) Paleogene, Brazil and Namibia Two principal types of associated alkaline rocks are represented, i.e. plagioleucitites l.s. (Eastern Paraguay; Brazil: Ponta Grossa Arch- Angola and Namibia) and kamafugites l.s. (Brazil: alto Paranaiba and Lages; Namibia). Significant variations in O-C isotope compositions are found in primary carbonates , the variations being mainly due to isotope exchange between carbonates and H2O-CO2-rich hydrothermal fluids, whereas magmatic processes, i.e. fractional crystallization or liquid immiscibility, probably affect the delta O-18 and delta C-13 values by not more than 2 delta%.. The isotope exchange model implies that the most significant isotopic variations took place in a hydrothermal environment, e.g. in the range 400-80 degrees C, involving fluids with CO2/H2O ratio ranging from 0.8 to 1. Sr-Nd-Pb isotope systematics highlight heterogeneous mixtures between HIMU and EMI mantle components, similar to the associated alkaline rocks and the flood tholeiites of the Parana-Angola-Etendeka (Namibia) system. This is also consistent with Re-Os systematics on selected mafic samples from the Alto Paranaiba alkaline-carbonatite province. The data relative to the noble gases suggest that the source(s) are similar to other mantle derived magmas (e.g. HIMU and MORB) and that the carbon of carbonatites is unlikely to be subduction-related carbon, and support a C-O fractionation model starting from mantle-derived sources. In spite of the strong variation shown by C-O isotopes, Sr-Nd-Pb-Os isotopic systematics could be related to an isotopically enriched source where the chemical heterogeneities reflect a depleted mantle "metasomatized" by small-volume melts and fluids rich in incompatible elements. These fluids are expected to have promoted crystallization in the mantle of K-rich phases that gave rise to a veined network variously enriched in LILE and LREE (cf. Foley, 1992b). The newly formed veins (enriched component) and peridotite matrix (depleted component) underwent a different isotopic evolution with time as reflected by the carbonatitic rocks. These conclusions may be extended to the whole Parana-Angola-Etendeka system, where isotopically distinct parent magmas were generated following two main enrichment events of the subcontinental lithospheric mantle at 2.0-1.4 and 1.0-0.5 Ga, respectively, as also supported by Re-Os systematics. The mantle sources preserved the isotopic heterogeneities over a long time, suggesting a non-convective lithospheric mantle beneath different cratons or intercratonic regions. Overall the data indicate that the alkaline-carbonatitic magmatism originated from a significant, but small scale heterogeneous subcontinental mantle. In this scenario, the Tristan da Cunha, Walvis Ridge-Rio Grande Rise and Vitoria-Trindade hotspot tracks might reflect the accomodation of stresses in the lithosphere during rifting, rather than continuous magmatic activity induced by mantle plumes beneath the moving lithosphere

Geochemical characteristics of Cretaceous carbonatites from Angola

The Early Cretaceous (138-130 Ma) carbonatites and associated alkaline rocks of Angola belong to the Parana-Angola-Etendeka Province and occur as ring complexes and other central-type intrusions along northeast trending tectonic lineaments, parallel to the trend of coeval Namibian alkaline complexes. Most of the Angolan carbonatite-alkaline bodies are located along the apical part of the Mocamedes Arch, a structure representing the African counterpart of the Ponta Grossa Arch in southern Brazil, where several alkaline-carbonatite complexes were also emplaced in the Early Cretaceous. Geochemical and isotopic (C, O, Sr and Nd) characteristics determined for five carbonatitic occurrences indicate that: (1) the overall geochemical composition, including the O-C isotopes, is within the range of the Early and Late Cretaceous Brazilian occurrences from the Parana Basin; (2) the La versus La/Yb relationships are consistent with the exsolution of CO2-rich melts from trachyphonolitic magmas; and (3) the 143Nd/144Nd and 87Sr/86Sr initial ratios are similar to the initial isotopic ratios (129 Ma) of alkaline complexes in northwest Namibia. In contrast, the Lupongola carbonatites have a distinctly different 143Nd/144Nd initial ratio, suggesting a different source. The Angolan carbonatites have Sr-Nd isotopic compositions ranging from bulk earth to time-integrated depleted sources. Since those from eastern Paraguay (at the western fringe of the Parana-Angola-Etendeka Province) and Brazil appear to be related to mantle-derived melts with time-integrated enriched or B.E. isotopic characteristics, it is concluded that the carbonatites of the Parana-Angola-Etendeka Province have compositionally distinct mantle sources. Such mantle heterogeneity is attributed to 'metasomatic processes', which would have occurred at ca 0.6-0.7 Ga (Angola, northwest Namibia and Brazil) and ca 1.8 Ga (eastern Paraguay), as suggested by Nd-model ages. (C) 2000 Elsevier Science Limited. All rights reserved

A review of carbonatitic magmatism in the Parana-Angola-Namibia (PAN) system

Mesozoic to Cenozoic alkaline-carbonatitic complexes from southern Brazil, Angola and Namibia occur along main tectonic lineaments. In general, the alkaline-carbonatite complexes show intrusive/subintrusive, subcircular or oval shaped structures and are indicative of high upwelling energy. Processes of liquid immiscibility from trachytic-phonolitic liquids, starting from parental alkaline mafic magmas are believed to have generated carbonatitic liquids, as suggested by field relationships and geochemical characteristics. Ca-, Mg- and Fe-carbonatites are widespread even in the same complex. The occurrences comprise three main chronogroups, i.e. 1) Early Cretaceous (Eastern Paraguay; Brazil, Ponta Grossa Arch and Anitapolis; Angola and Namibia); 2) Late Cretaceous (Brazil , Ponta Grossa Arch, Lages and Alto Paranaiba. Namibia); 3) Paleogene, Brazil and Namibia Two principal types of associated alkaline rocks are represented, i.e. plagioleucitites l.s. (Eastern Paraguay; Brazil: Ponta Grossa Arch- Angola and Namibia) and kamafugites l.s. (Brazil: alto Paranaiba and Lages; Namibia). Significant variations in O-C isotope compositions are found in primary carbonates , the variations being mainly due to isotope exchange between carbonates and H2O-CO2-rich hydrothermal fluids, whereas magmatic processes, i.e. fractional crystallization or liquid immiscibility, probably affect the delta O-18 and delta C-13 values by not more than 2 delta%.. The isotope exchange model implies that the most significant isotopic variations took place in a hydrothermal environment, e.g. in the range 400-80 degrees C, involving fluids with CO2/H2O ratio ranging from 0.8 to 1. Sr-Nd-Pb isotope systematics highlight heterogeneous mixtures between HIMU and EMI mantle components, similar to the associated alkaline rocks and the flood tholeiites of the Parana-Angola-Etendeka (Namibia) system. This is also consistent with Re-Os systematics on selected mafic samples from the Alto Paranaiba alkaline-carbonatite province. The data relative to the noble gases suggest that the source(s) are similar to other mantle derived magmas (e.g. HIMU and MORB) and that the carbon of carbonatites is unlikely to be subduction-related carbon, and support a C-O fractionation model starting from mantle-derived sources. In spite of the strong variation shown by C-O isotopes, Sr-Nd-Pb-Os isotopic systematics could be related to an isotopically enriched source where the chemical heterogeneities reflect a depleted mantle "metasomatized" by small-volume melts and fluids rich in incompatible elements. These fluids are expected to have promoted crystallization in the mantle of K-rich phases that gave rise to a veined network variously enriched in LILE and LREE (cf. Foley, 1992b). The newly formed veins (enriched component) and peridotite matrix (depleted component) underwent a different isotopic evolution with time as reflected by the carbonatitic rocks. These conclusions may be extended to the whole Parana-Angola-Etendeka system, where isotopically distinct parent magmas were generated following two main enrichment events of the subcontinental lithospheric mantle at 2.0-1.4 and 1.0-0.5 Ga, respectively, as also supported by Re-Os systematics. The mantle sources preserved the isotopic heterogeneities over a long time, suggesting a non-convective lithospheric mantle beneath different cratons or intercratonic regions. Overall the data indicate that the alkaline-carbonatitic magmatism originated from a significant, but small scale heterogeneous subcontinental mantle. In this scenario, the Tristan da Cunha, Walvis Ridge-Rio Grande Rise and Vitoria-Trindade hotspot tracks might reflect the accomodation of stresses in the lithosphere during rifting, rather than continuous magmatic activity induced by mantle plumes beneath the moving lithosphere