1,722,808 research outputs found
Tectonometamorphic discontinuities in the Greater Himalayan Sequence: a local or a regional feature?
Full text linkThe Greater Himalayan Sequence (GHS) is one of the major tectonic units of the Himalaya
running for more than 2400 km along-strike. It has been considered as a coherent tectonic unit
bound by the South Tibetan Detachment (STD) and the Main Central Thrust (MCT). However,
thrusts within it have been recognized in several places and have been mainly interpreted as
out-of-sequence thrusts being active after the main phase of exhumation of the crystalline unit
after the MCT activated. Recent integrated studies allow the recognition of several ductile shear
zones in the core of the GHS, with top-to-the-SW-sense of shear (Higher Himalayan Discontinuity
(HHD)). U–Th–Pb in situ monazite ages provide ages older than the MCT. Data on pressure and
temperature evolution testify that these shear zones affected the tectonometamorphic evolution of
the belt and different pressure and temperature conditions were recorded in the hanging wall and
footwall of the HHD. The correlation of the WNW–ESE-trending HHD with other discontinuities
recognized in the GHS led to the proposal that it is a tectonic feature running for several hundred
kilometres, documented at the regional scale dividing the GHS in two different portions
Relazioni tra pieghe e lineazioni di estensione nel Verrucano dei Monti Pisani (Appennino Settentrionale)
No full textLo studio dell'evoluzione strutturale della successione silico-clastica triassica del Verrucano dei Monti Pisani (Appennino Settentrionale) ha messo in evidenza la presenza di due principali eventi deformativi duttili: una prima fase deformativa (D1), attribuita alla collisione continentale, seguita da un'ulteriore fase D2 attribuita alla tettonica di collasso delle unità metamorfiche. L'analisi strutturale e la stima della deformazione finita ci consentono di discuterealcuni modelii che possono spiegare il marcato parallelismo tra assi di pieghe e lineazioni di estensione nei Monti Pisani e le loro possibili implicazioni nell'evoluzione della caten
The polyphase folding structure of S. Giuliano Terme (S. Maria del Giudice Unit, Pisani Mounts, Northern Apennines)
No full text
Generalized Graph k-Coloring Games
No full textWe investigate pure Nash equilibria in generalized graphk-coloring games where we are given an edge-weighted undirected graph together with a set of k colors. Nodes represent players and edges capture their mutual interests. The strategy set of each player consists of k colors. The utility of a player v in a given state or coloring is given by the sum of the weights of edges {v, u} incident to v such that the color chosen by v is different than the one chosen by u, plus the profit gained by using the chosen color. Such games form some of the basic payoff structures in game theory, model lots of real-world scenarios with selfish players and extend or are related to several fundamental class of games. We first show that generalized graph k-coloring games are potential games. In particular, they are convergent and thus Nash Equilibria always exist. We then evaluate their performance by means of the widely used notions of price of anarchy and price of stability and provide tight bounds for two natural and widely used social welfare, i.e., utilitarian and egalitarian social welfare
Strutture tardo-orogeniche e compressione parallela all'orogene in Appennino Settentrionale: la struttura di interferenza polifasica di S.Giuliano (Unità di Santa Maria del Giudice, Monti Pisani)
No full textII rilevamento geologico di dettaglio affiancato
dall’analisi meso e microstrutturale hanno messo in evidenza,
nell’Unità di Santa Maria del Giudice (Monti Pisani,
Appennino Settentrionale), la presenza di due sistemi di pie
ghe tardive che ripiegano una precedente sinclinale di prima
fase.
Entrambi i sistemi di pieghe tardive sono caratterizzati da
piani assiali molto inclinati e da assi circa ortogonali, con
orientazioni rispettivamente NW-SE e SW-NE. Mentre ii
primo sistema di pieghe ammette una direzione di raccorcia
mento orientata SW-NE, ii secondo sistema è compatibile
con una direzione di raccorciamento parallela al trend della
catena stessa. Le due direzioni di raccorciamento orizzontale
possono aver giocato un ruolo non secondario nella crescita
dei duomi metamorfici nell’Appennino Settenthonale
Relations between foldsand stretching lineation in the Verrucano of Pisani Mounts, Northern Apennines
No full textStructural analysis of the Triassic siliciclastic Verrucano sequence of the Pisani Mounts (northern Apennines) revealed the presence of two main ductile deformation pahses: an earlier deformation phase (D1), attributed to continental collision, followed by a second deformation phase (D2) related to the tectonic collapse of the tectonic units. The D1 phase is characterized by F1 folds, sometimes cleavage transected, by an S1 penetrative axial plane foliation and by a stretching lineation L1, that is parallel to F1 fold axes. Structural analysis and finite strain determinations allow the authors to discuss some models that could explain this parallelism in the Pisani Mount
Transpressional deformation in NW Sardinia (Italy): insights on the tectonic evolution of the Variscan Belt
No full textLate Oligocene high-temperature shear zones in the core of the Higher Himalayan Crystallines (Lower Dolpo, western Nepal)
Full text linkA high‐temperature shear zone, Toijem shear zone, with a top‐to‐the‐SW sense of shear affects the core of the Higher Himalayan Crystallines (HHC) in western Nepal. The shear zone developed during the decompression, in the sillimanite stability field, of rocks
that previously underwent relatively high‐pressure metamorphism deformed under the kyanite stability field. PT conditions indicate that the footwall experienced higher pressure (∼9 kbar) than the hanging wall (∼7 kbar) and similar temperatures (675°–700°C). Monazite growth constrains the initial activity of the shear zone at 25.8 ± 0.3 Ma, before the onset of the Main Central Thrust zone, whereas the late intrusion
of a crosscutting granitic dike at 17 ± 0.2 Ma limits its final activity. Monazites in kyanite‐bearing gneisses from the footwall record prograde metamorphism in the HHC from ∼43 to 33Ma. The new data confirm that exhumation of the HHC started earlier in western Nepal than in other portions of the belt and before the activity of both the South Tibetan Detachment System (STDS)
and Main Central Thrust (MCT) zones. As a consequence,
western Nepal represents a key area where the channel‐flow‐driven mechanism of exhumation, supposed to be active from Bhutan to central‐eastern Nepal, does terminate. In this area, exhumation of crystalline units occurred by foreland propagation of ductile and, subsequently, brittle deformation
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