Late evolution of the inner Northern Apennines from the structure of the Monti del Chianti-Monte Cetona Ridge (Tuscany, Italy)

<p>The Neogene and Quaternary tectonic evolution of the inner Northern Apennines (i.e southern Tuscany and northern Tyrrhenian Sea), as well as its crustal features (i.e. low crustal thickness, Neogene-Quaternary magmatism, widespread geothermal anomalies, lateral segmentation of the stacked tectonic units, extensive deep sedimentary basins), are framed in different geodynamic scenarios: compressional, extensional or both, pulsing. Consequently, the basin and range structure that characterises the northern Tyrrhenian Sea and southern Tuscany is considered as a consequence of (i) out-of-sequence thrusts and related thrust-top-basins, (ii) polyphased normal faulting that formed horst and graben structures or (iii) a combination of both. This paper provides a new dataset from a sector of the eastern inner Northern Apennines (i.e. Monti del Chianti - Monte Cetona ridge) contributing to this scientific debate. New fieldwork and structural analysis carried out in selected areas along the ridge allowed to define the chronology of the main tectonic events on the basis of their influence on the marine and continental sedimentation. The dataset supports for early Miocene - (?) Serravallian in-sequence and out-of-sequence thrusting. Thrusting produced complex staking patterns of Tuscan and Ligurian Units. Extensional detachments developed since later middle Miocene and controlled the Neogene sedimentation in bowl-shaped structural depressions, later dissected by normal faults enhancing the accommodation space for Pliocene marine deposits in broad NNW-trending basins (Siena-Radicofani and Valdichiana Basins). In this perspective, no data supports for active, continuous or pulsing, compressional tectonics after late Serravalian. As a result, in the whole inland inner Northern Apennines the extensional tectonics was continuously active at least since middle Miocene and controlled the basins development, magmatism and structure of the crust and lithosphere.</p>

Phanerozoic radiation of ammonia oxidizing bacteria

The modern nitrogen cycle consists of a web of microbially mediated redox transformations. Among the most crucial reactions in this cycle is the oxidation of ammonia to nitrite, an obligately aerobic process performed by a limited number of lineages of bacteria (AOB) and archaea (AOA). As this process has an absolute requirement for O2, the timing of its evolution—especially as it relates to the Great Oxygenation Event ~ 2.3 billion years ago—remains contested and is pivotal to our understanding of nutrient cycles. To estimate the antiquity of bacterial ammonia oxidation, we performed phylogenetic and molecular clock analyses of AOB. Surprisingly, bacterial ammonia oxidation appears quite young, with crown group clades having originated during Neoproterozoic time (or later) with major radiations occurring during Paleozoic time. These results place the evolution of AOB broadly coincident with the pervasive oxygenation of the deep ocean. The late evolution AOB challenges earlier interpretations of the ancient nitrogen isotope record, predicts a more substantial role for AOA during Precambrian time, and may have implications for understanding of the size and structure of the biogeochemical nitrogen cycle through geologic time.

Rare isotope beams in astrophysics

Unstable isotopes govern the late evolution of stars and their explosive phenomena, such as novae, supernovae, x-ray bursters and neutron star mergers. Most of them are still out of reach of terrestrial experiments. Upcoming facilities will allow scientists to produce/observe them and shed light on fundamental questions about our universe.

Stability of hyperbolic and matter-dominated bounce cosmologies from F(R,𝒢)modified gravity at late evolution stages

The stability of two different bounce scenarios from [Formula: see text] modified gravity at later times is studied, namely a hyperbolic cosine bounce model and a matter-dominated one. After describing the main characteristics of [Formula: see text] modified gravity, the two different bounce scenarios stemming from this theory are reconstructed and their stability at late stages is discussed. The stability of the hyperbolic cosine model is proven, while the concrete matter-bounce model here chosen does not seem to accomplish the necessary conditions to be stable at later times.

Phanerozoic Radiation of Ammonia Oxidizing Bacteria

The modern nitrogen cycle consists of a web of microbially mediated redox transformations. Among the most crucial reactions in this cycle is the oxidation of ammonia to nitrite, an obligately aerobic process performed by a limited number of lineages of bacteria (AOB) and archaea (AOA). As this process has an absolute requirement for O2, the timing of its evolution – especially as it relates to the Great Oxygenation Event ~2.3 billion years ago – remains contested and is pivotal to our understanding of nutrient cycles. To estimate the antiquity of bacterial ammonia oxidation, we performed phylogenetic and molecular clock analyses of AOB. Surprisingly, bacterial ammonia oxidation appears quite young, with crown group clades having originated during Neoproterozoic time (or later) with major radiations occurring during Paleozoic time. These results place the evolution of AOB broadly coincident with the pervasive oxygenation of the deep ocean. The late evolution AOB challenges earlier interpretations of the ancient nitrogen isotope record, predicts a more substantial role for AOA during Precambrian time, and may have implications for understanding of the size and structure of the biogeochemical nitrogen cycle through geologic time.

The Galactic WC and WO stars

Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. Thus, the determination of the WC star parameters is of major importance for several astrophysical fields. With Gaia DR2, for the first time parallaxes for a large sample of Galactic WC stars are available, removing major uncertainties inherent to earlier studies. In this work, we re-examine a previously studied sample of WC stars to derive key properties of the Galactic WC population. All quantities depending on the distance are updated, while the underlying spectral analyzes remain untouched. Contrasting earlier assumptions, our study yields that WC stars of the same subtype can significantly vary in absolute magnitude. With Gaia DR2, the picture of the Galactic WC population becomes more complex: We obtain luminosities ranging from logL/L⊙ = 4.9–6.0 with one outlier (WR 119) having logL/L⊙ = 4.7. This indicates that the WC stars are likely formed from a broader initial mass range than previously assumed. We obtain mass-loss rates ranging between log Ṁ = −5.1 and −4.1, with Ṁ ∝ L0.68 and a linear scaling of the modified wind momentum with luminosity. We discuss the implications for stellar evolution, including unsolved issues regarding the need of envelope inflation to address the WR radius problem, and the open questions in regard to the connection of WR stars with Gamma-ray bursts. WC and WO stars are progenitors of massive black holes, collapsing either silently or in a supernova that most-likely has to be preceded by a WO stage.

The Gersdorffite-Bismuthinite-Native Gold Association and the Skarn-Porphyry Mineralization in the Kamariza Mining District, Lavrion, Greece

Vein-type Pb-Ni-Bi-Au-Ag mineralization at the Clemence deposit in the Kamariza and “km3” in the Lavrion area, was synchronous with the intrusion of a Miocene granodiorite body and related felsic and mafic dikes and sills within marbles and schists in the footwall of (and within) the Western Cycladic detachment system. In the Serpieri deposit (Kamariza area), a porphyry-style pyrrhotite-arsenopyrite mineralized microgranitic dike is genetically related to a garnet-wollastonite bearing skarn characterized by a similar base metal and Ni (up to 219 ppm) enrichment. The Ni–Bi–Au association in the Clemence deposit consists of initial deposition of pyrite and arsenopyrite followed by an intergrowth of native gold-bismuthinite and oscillatory zoned gersdorffite. The zoning is related to variable As, Ni, and Fe contents, indicating fluctuations of arsenic and sulfur fugacity in the hydrothermal fluid. A late evolution towards higher sulfur fugacity in the mineralization is evident by the deposition of chalcopyrite, tennantite, enargite, and galena rimming gersdorffite. At the “km3” locality, Ni sulfides and sulfarsenides, vaesite, millerite, ullmannite, and polydymite, are enclosed in gersdorffite and/or galena. The gersdorffite is homogenous and contains less Fe (up to 2 wt.%) than that from the Clemence deposit (up to 9 wt.%). Bulk ore analyses of the Clemence ore reveal Au and Ag grades both exceeding 100 g/t, Pb and Zn > 1 wt.%, Ni up to 9700 ppm, Co up to 118 ppm, Sn > 100 ppm, and Bi > 2000 ppm. The “km3” mineralization is enriched in Mo (up to 36 ppm), Ni (>1 wt.%), and Co (up to 1290 ppm). Our data further support a magmatic contribution to the ore-forming fluids, although remobilization and leaching of metals from previous mineralization and/or host rocks, through the late involvement of non-magmatic fluid in the ore system, cannot be excluded.