213 research outputs found
Evidence of basaltic magma intrusions in a trachytic magma chamber at Pantelleria (Italy)
In the last 50 ka basalts have erupted outside the margin of the young caldera on the island
of Pantelleria. The inner portion of the caldera has instead been filled by trachyte lavas,
pantellerite lavas and pumice fall deposits. This paper focuses on a low-volume benmoreite
lava topping the trachyte lava pile in the middle of the young caldera.
The mineral chemistry, including trace elements in clinopyroxene (LA-ICP-MS), suggests
that benmoreite is a hybrid product resulting from mixing between a trachytic magma and a
basaltic end member even more primitive than those erupted during the past 50 ka. The
principal inference is that basaltic magmas intruded the trachytic magma chamber below the
caldera and were erupted in recent times within the caldera and not only beyond, as the
distribution of basaltic centers would suggest. Data are used to discuss the relationship
between felsic and mafic magmas at Pantelleria
Petrology of some amphibole-bearing volcanics of the pre-ellittico period (102-80 ka) Mt. Etna
We present here petrological and
geochemical data on volcanics cropping out in
southern and northeastern walls of the Valle del
Bove (Mt. Etna), belonging to the Rocche, Serra
Giannicola Grande and Canalone della Montagnola
Units. These units constitute the remnants of several
volcanoes that were active in the time span 102-80
ka, i.e. before the growth of the Ellittico-Mongibello
strato-volcano. Their products, range in composition
from hawaiites to benmoreites. Amphibole
(kaersutite) is present as phenocryst in all the studied
rocks, and commonly shows breakdown coronas
of rhönite ± clinopyroxene and plagioclase formed
during magma ascent. Nevertheless, in mafic rocks,
amphibole occurs as an early liquidus phase enclosed
in a Ca-rich plagioclase (up to An87). We propose that
early cotectic crystallization of amphibole and Caplagioclase
may reflect H2O-rich melts. Variations in
major and trace elements among lavas erupted from
coeval centres, suggest that fractional crystallization
was the principal evolutionary process but at the same
time magmas feeding the various volcanoes belonging
to the Rocche Unit were more heterogeneous with
respect to the younger Units studied here
Renal involvement in psychological eating disorders
Psychological eating disorders--anorexia nervosa (AN), bulimia nervosa (BN), binge eating disorder--are an increasing public health problem with severe clinical manifestations: hypothermia, hypotension, electrolyte imbalance, endocrine disorders and kidney failure; they are of interest to nephrologists, but pathophysiological mechanisms in determining the renal involvement are still unclear. We describe pathophysiology, histological features and clinical manifestations of the most frequent psychological eating disorders: AN and BN. Regarding AN, we analyze the recent literature, and identify 3 principal pathways towards renal involvement: chronic dehydration-hypokalemia, nephrocalcinosis and chronic rhabdomyolysis. Regarding BN, we describe the correlation between obesity and many proinflammatory cytokines, chemokines, growth factors and adipokines, having potential metabolic and hemodynamic effects on the kidney and an important role in the pathogenesis of obesity-related renal injury, independently of hypertension and diabetes
Cognate xenoliths in Mt. Etna lavas: witnesses of the high-velocity body beneath the volcano
Various xenoliths have been found in lavas of the
1763 (“La Montagnola”), 2001, and 2002–03 eruptions at Mt.
Etna whose petrographic evidence and mineral chemistry
exclude a mantle origin and clearly point to a cognate nature.
Consequently, cognate xenoliths might represent a proxy to
infer the nature of the high-velocity body (HVB) imaged
beneath the volcano by seismic tomography. Petrography
allows us to group the cognate xenoliths as follows: i) gabbros
with amphibole and amphibole-bearing mela-gabbros, ii)
olivine-bearing leuco-gabbros, iii) leuco-gabbros with amphibole,
and iv) Plg-rich leuco gabbros. Geobarometry estimates
the crystallization pressure of the cognate xenoliths between
1.9 and 4.1 kbar. The bulk density of the cognate xenoliths
varies from2.6 to 3.0 g/cm3. P wave velocities (VP), calculated
in relation to xenolith density, range from 4.9 to 6.1 km/s. The
integration of mineralogical, compositional, geobarometric data,
and density-dependent VP with recent literature data on 3D
VP seismic tomography enabled us to formulate the first
hypothesis about the nature of the HVB which, in the depth
range of 3–13 km b.s.l., is likely made of intrusive gabbroic
rocks. These are believed to have formed at the “solidification
front”, a marginal zone that encompasses a deep region (>5 km
b.s.l.) of Mt. Etna’s plumbing system, within which magma
crystallization takes place. The intrusive rocks were afterwards
fragmented and transported as cognate xenoliths by the
volatile-rich and fast-ascending magmas of the 1763 “La
Montagnola”, 2001 and 2002–03 eruptions
High-resolution 40Ar/39Ar chronostratigraphy of the post-caldera (<20 ka) volcanic activity at Pantelleria, Sicily Strait
The island of Pantelleria (Sicily Strait), the type locality for pantellerite, has been the locus of major calderaforming
eruptions that culminated, ca. 50 ka ago, in the formation of the Cinque Denti caldera produced by the
Green Tuff eruption. The post-caldera silicic activity since that time has been mostly confined inside the caldera
and consists of smaller-energy eruptions represented by more than twenty coalescing pantelleritic centers
structurally controlled by resurgence and trapdoor faulting of the caldera floor. A high-resolution 40Ar/39Ar
study was conducted on key units spanning the recent (post-20 ka) intracaldera activity to better characterize
the present-day status (and forecast the short-term behavior of) the system based on the temporal evolution of
the latest eruptions. The new 40Ar/39Ar data capture a long-term (N15 ka) decline in eruption frequency with a
shift in eruptive pace from 3.5 ka−1 to 0.8 ka−1 associated with a prominent paleosol horizon marking the only
recognizable volcanic stasis around 12–14 ka. This shift in extraction frequency occurswithoutmajor changes in
eruptive style, and is paralleled by a subtle trend of decreasingmelt differentiation index. We speculate that this
decline probably occurred (i) without short-term variations in melt production/differentiation rate in a steadystate
compositionally-zoned silicic reservoir progressively tapped deeper through the sequence, and (ii) that it
was possibly modulated by outboard eustatic forcing due to the 140 m sea level rise over the past 21 ka. The
intracaldera system is experiencing a protracted stasis since 7 ka. Coupled with recent geodetic evidence of
deflation and subsidence of the caldera floor, the system appears today to be on a wane with no temporal
evidence for a short-term silicic eruption
Diagnosis and treatment of asymptomatic left ventricular systolic dysfunction after myocardial infarction.
The increased survival after acute myocardial infarction induced an increase in heart failure with left ventricular systolic dysfunction. Early detection and treatment of asymptomatic left ventricular systolic dysfunction give the chance to improve outcomes and to reduce costs due to the management of patients with overt heart failure
A two-component mantle source feeding Mt. Etna magmatism; insights from the geochemistry of primitive magmas.
The major elements, trace elements and Sr and Nd isotopes of selected Etnean primitive rocks (b15 ky BP) were
studied in order to characterize their mantle source. The noble-gas geochemistry of fluid inclusions in minerals
fromthe same lavaswas also investigated. Themajor element compositions ofwhole rocks and minerals showed
that these products are among the most primitive atMt. Etna, comprising 6.3–17.5 wt.% MgO. The variable LREE
(Light Rare Earth Elements) enrichment relative to MORB (Mid-Ocean Ridge Basalt) (Lan/Ybn = 11–26), togetherwith
the patterns of certain trace-element ratios (i.e., Ce/Yb versus Zr/Nb and Th/Y versus La/Yb), can be attributed
to varying degrees of melting of a common mantle source. Numerical simulations performed with the
MELTS program allowed the melting percentages associated with each product to be estimated. This led us to recalculate
the hypothetical parental trace-element content of the Etneanmantle source, whichwas common to all
of the investigated rocks. The characteristics of the Sr, Nd and He isotopes confirmed the primitive nature of the
rocks,with themost-depleted and primitive lava being that ofMt. Spagnolo (SPA; 143Nd/144Nd = 0.512908 87Sr/
86Sr = 0.703317–0.703325 and 3He/4He = 7.6 Ra), and highlighted the similarity of the mantle sources feeding
the volcanic activity of Mt. Etna and the Hyblean Plateau (a region to the south of Mt. Etna and characterized by
oldermagmatismthan Mt. Etna). The coupling of noble gases and trace elements suggests an origin for the investigated
Etnean lavas from melting of a Hyblean-like mantle, consisting of a two-component source where a
peridotitic matrix is veined by 10% pyroxenite. A variable degree of mantle contamination by crustal-like fluids,
probably related to subduction, is proposed to explain the higher Sr-isotope and lowerNd-isotope values in some
rocks (143Nd/144Nd up to 0.512865 and 87Sr/86Sr up to 0.703707). This process probably occurred in the source
prior tomagma generation, refertilizing some portions of themantle. Accordingly, the estimated degree of melting
responsible for each magma appears to be related to its 87Sr/86Sr enrichment. In contrast, the decoupling
between 3He/4He and 87Sr/86Sr ratios requires the occurrence in the crustal reservoirs of further processes capable
of shifting the He isotope ratio towards slightly more radiogenic values, such as magma aging or a contribution
of shallow fluid. Therefore, different residence times in the Etnean reservoir and/or various rates of magma
ascent could be key parameters for preserving the original He isotope marker of the Etnean mantle source.
© 2013 Published by Elsevier
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