Search results for "blue"
showing 10 items of 487 documents
How to resist subduction: evidence for large-scale out-of-sequence thrusting during Eocene collision in western Turkey
2001
Significant along-strike variations have locked large parts of the Alpine subduction complex in the Eastern Mediterranean in the Eocene, and defined the end of high-pressure accretion in western Turkey. Structural analysis reveals that the Anatolide belt in western Turkey formed under greenschist facies metamorphic conditions in the Eocene when a high-pressure metamorphic fragment of the Adriatic plate (the Cycladic blueschist unit) was thrust onto the imbricated mid-crustal units of the Anatolian microcontinent (the Menderes nappes). The contact between the Cycladic blueschist unit and the Menderes nappes, the Cyclades–Menderes thrust, represents an out-of-sequence ramp which cuts up-sect…
2001
The roles of volume loss, coaxial versus noncoaxial flow, and blueschist exhumation in subduction-related accretionary wedges are still poorly understood. In our study at Leech Lake Mountain in the Eastern belt of the Franciscan subduction complex, we focus on these subjects. In the specific example of the Franciscan, the tectonic significance of the boundary between the Eastern and Central belts remains controversial. The Leech Lake Mountain area in northern California is situated immediately above this boundary and, therefore, appears to be of crucial importance for understanding aspects of the tectonic evolution of the Franciscan. The structural development at Leech Lake Mountain is char…
Miocene high-pressure metamorphism in the Cyclades and Crete, Aegean Sea, Greece: Evidence for large-magnitude displacement on the Cretan detachment
2001
The Cyclades in the backarc region of the present Hellenic subduction zone are known for widespread Late Cretaceous to Eocene high-pressure metamorphism in the Cycladic blueschist unit. We report 40 Ar/ 39 Ar and Rb/Sr phengite ages of 24–21 Ma for high- pressure metamorphism (8–10 kbar, 350–400 °C) in the lowest tectonic unit in the Cyclades, the Basal unit, which structurally underlies the Cycladic blueschist unit. The Basal unit is correlated with the Tripolitza unit of the External Hellenides in the forearc region of the Hellenic subduction zone. The Tripolitza unit is unmetamorphosed on Crete, where it is separated from the underlying high-pressure (8–10 kbar, 300–400 °C) Plattenkalk a…
Horizontal contraction or horizontal extension? Heterogeneous Late Eocene and early Oligocene general shearing during blueschist and greenschist faci…
1995
Mylonitic structures related to two orogenic events are described from the upper and lower contacts of the Combin zone and the immediately overlying upper Austroalpine Dent Blanche nappe/Mont Mary klippe and the directly underlying lower Austroalpine Etirol-Levaz slice. The first event, Late Eocene in age, commenced during blueschist facies P-T conditions, but pre-dated the peak of subsequent greenschist facies overprint. The second event, Early Oligocene in age, took place during retrograde greenschist facies conditions. Most sense of shear indicators associated with the retrograde mylonites indicate top SE shearing, but subordinate top NW displacing shear sense indicators have also been m…
Origin of potassic postcollisional volcanic rocks in young, shallow, blueschist-rich lithosphere
2020
Unusually high Th/La in K-rich orogenic rocks may indicate shallow blueschist-rich sources in accretionary settings.
From intra-oceanic subduction to arc accretion and arc-continent collision: Insights from the structural evolution of the Río San Juan metamorphic co…
2013
The Río San Juan metamorphic complex exposes a segment of a high-pressure subduction-accretionary complex built during Caribbean island arc-North America continental margin convergence. It is composed of accreted arc- and oceanic-derived metaigneous rocks, serpentinized peridotites and minor metasediments forming a structural pile. Combined detailed mapping, structural and metamorphic analysis, and geochronology show that the deformation can be divided into five main events (D1eD5). An early subduction-related D1 deformation and M1 metamorphism produced greenschist (mafic rocks of the Gaspar Hernández peridotite-tectonite), blueschist and eclogite (metamafic blocks in the Jagua Clara mélang…
GEOLOGIA DE LAS MARGENES DE LA PLACA DEL CARIBE: GENERALIDADES EN GUATEMALA, COSTA RICA, LA ESPAÑOLA Y RESULTADOS PRELIMINARES DEL ANALISIS DE UNA TR…
2011
The Caribbean Plate margins are constituted by deformed belts built up since the Cretaceous in acompressional and strike-slip stress field, which allowed overthrusting of the Caribbean crust onto the Pacific,North and South American Plates.The Caribbean borders include Jurassic-Cretaceous ophiolitic units (Great Antilles, Venezuela, Costa Rica,Guatemala, etc.), composed by mantle peridotites, gabbros, volcanic and sedimentary covers, which have beendeformed in at least two ductile penetrative phases and were often metamorphosed in the prehnite-pumpelleyite,green and blue schist, amphibolite, and in places eclogite facies. These units may present part of a subductioncomplex or are an accreti…
Structural analysis of a complex nappe sequence and late-orogenic basins from the Aegean Island of Samos, Greece
1999
The island of Samos in the Aegean Sea exposes high-pressure metamorphic rocks of the Cycladic blueschist unit which are sandwiched between the mildly blueschist-facies Kerketas nappe below and the overlying non-metamorphic Kallithea nappe. Structural and metamorphic analysis shows that deformation can generally be divided into four main stages: (1) Eocene and earliest Oligocene 0ESE‐WNW-oriented nappe stacking (D1 and D2) associated with blueschist- and transitional blueschist‐ greenschist-facies metamorphism (M1 and M2). D2 caused emplacement of the blueschist unit onto the Kerketas nappe indicating that thrusting occurred during decompression. (2) A subsequent history of Oligocene and Mio…
On the design of pervasive computing applications based on Bluetooth and a P2P concept
2006
As an example of implementing the pervasive computing, we developed an application framework to deploy an easy, spontaneous, and infrastructureless network. We selected the Bluetooth technology with the peer-to-peer (P2P) concept to develop an experimental application which enables peers to exchange their resources. Overall network architecture and the prototype application are presented. We selected a small test-bed and simulation to evaluate the overall performance and system behaviour. We measured and present our findings in term of the duration of inquiry procedure and the throughput, according to various experimental parameters such as physical distance between nodes and their speeds.
Mobile Telephony in Sub-Saharan Africa
2007
A mobile telephone is a telecommunications device that connects its user to a network using a wireless radio wave transmission technology. In some parts of the world, mobile phones are known as cellular phones. Mobile telephones were first introduced in the mid-1980s (Marcussen, 2002; Sadeh & Sadeh, 2002; Sarker & Wells, 2003). Mobile telephony is diffusing globally due to a variety of reasons, including cost advantages in setting up the system compared to landlines, its small-sized nature, portability, and its ability to foster and enhance social relationships, among others (Plant, n.d.; Marcussen, 2002; Sadeh & Sadeh, 2002; Sarker & Wells, 2003; ITU, 2004; Anonymous, 2006)…