Search results for "Phyllite"

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…

Quantitative phase petrology of cordierite-orthoamphibole gneisses and related rocks

2008

Cordierite-orthoamphibole gneisses and rocks of similar composition commonly contain low-variance mineral assemblages that can provide useful information about the metamorphic evolution of a terrane. New calculated petrogenetic grids and pseudosections are presented in the FeO-MgO-Al2O3-SiO2-H2O (FMASH), Na2O-CaO-K2O-FeO-MgO-Al2 O3- SiO2-H2O (NCKFMASH) and Na2O-CaO-K2O-FeO-MgO-Al2O3- SiO2-H2O-TiO2-Fe2 O3 (NCKFMASHTO) chemical systems to investigate quantitatively the phase relations in these rocks. Although the bulk compositions of cordierite-orthoamphibole gneisses are close to FMASH, calculations in this system do not adequately account for the observed range of mineral assemblages. Calcu…

Bader's topologycal analysis of the electron density and the laplacian in TOT Phyllosilicates: the case of pyrophyllite and talc

2009

Repeated Load Triaxial Testing of Recycled Excavation Materials Blended with Recycled Phyllite Materials

2022

Recycled Excavation Materials (REM) are becoming viable alternative construction resources due to their economic benefits. However, REM may be composed of weak rocks, e.g., phyllites, limiting the use in a base layer. The present paper attempts to further the knowledge of the mechanical performance of REM by performing Repeated Load Triaxial Tests (RLTT). REM are mixed with Recycled Phyllite Materials (RPM) in systematic blends of 0%, 25%, 50%, and 100%. The batches’ resilient modulus (MR) and permanent deformation (PD) characteristics were assessed to establish the maximum RPM allowed into REM while maintaining the required performance. Hicks and Monismith’s and Uzan’s mo…

Recycled aggregates derived from excavation materials — mechanical performance and identification of weak minerals

2022

AbstractThe present study investigates the mechanical performance of recycled aggregates derived from excavation materials (REM). REM is blended with different quantities of recycled phyllite materials (RPM) and is investigated by Los Angeles (LA) and micro-Deval (MD) tests. X-ray diffraction (XRD) and acid solubility test are performed on the pulverized fractions < 1.6 mm obtained from the LA and MD tests to assess the respective degree of fragmentation and wear of mineral components. The results of the materials in unblended conditions showed considerable difference between MD performance while similar performance was found for LA. Furthermore, about 40% of RPM was sufficient to blend …

Constraints on the Cretaceous thermal event in the Transantarctic Mountains from alteration processes in Ferrar flood basalts

1999

Abstract K–Ar and 40 Ar/ 39 Ar incremental-heating analyses on apophyllite formed during hydrothermal alteration of volcanic rocks from the Ferrar Supergroup in North Victoria Land, Antarctica, provide strong evidence for hydrothermal events during mid-Cretaceous time. A last event has been dated at 96.7±0.6 Ma. Variable older ages between 112 and 125 Ma are interpreted as mixed ages of hydrothermal events or may be caused by disturbances of the Ar–Ar system. The Rb–Sr isotope system of the apophyllites is not applicable to dating because a large portion of the Sr is radiogenic and because of Rb-mobility in the crystal structure. Secondary mineralogy suggests a temperature for alteration be…

Acid-Base Properties of 2:1 Clays. I. Modeling the Role of Electrostatics

2010

We present a theoretical investigation of the titratable charge of clays with various structural charge (sigma(b)): pyrophyllite (sigma(b) = 0 e x nm(-2)), montmorillonite (sigma(b) = -0.7 e x nm(-2)) and illite (sigma(b) = -1.2 e x nm(-2)). The calculations were carried out using a Monte Carlo method in the Grand Canonical ensemble and in the framework of the primitive model. The clay particle was modeled as a perfect hexagonal platelet, with an "ideal" crystal structure. The only fitting parameters used are the intrinsic equilibrium constants (pK(0)) for the protonation/deprotonation reactions of the broken-bond sites on the lateral faces of the clay particles, silanol, =SiO(-) + H(+) --=…

Eine Subfaziesfolge der Grünschieferfazies in den Mittleren Cévennen (Dép. Ardèche) mit Pyrophyllit aufweisenden Mineralparagenesen

1969

In the middle part of the Cevennes, situated at the south-eastern border of the Massif Central, there are outcrops of micaschists, gneisses and granites in which the increase of metamorphic grade was investigated along the river Beaume. This paper presents the results of the petrographic-geochemical analysis of the micaschists of the greenschist facies. Chemical analyses of the micaschist-samples examined petrographically show their nearly constant composition, a fact which e.g., is expressed by similar CaO/Na2O- and MgO/FeO-proportions. As the average values of the determined oxides approach the respective average values of analyses of graywackes recorded by Pettijohn (1957) the original s…

The geochemistry of Tl and its isotopes during magmatic and hydrothermal processes: The peralkaline Ilimaussaq complex, southwest Greenland

2014

Abstract We use thallium (Tl) concentrations, K/Rb, K/Tl and Rb/Tl ratios and Tl isotopes in minerals from the alkaline to peralkaline Ilimaussaq complex (South Greenland) to trace magmatic differentiation, crustal assimilation, magmatic degassing, ore precipitation and hydrothermal metasomatism. Closed-system magmatic differentiation is marked by a coherent decrease of K/Tl- and K/Rb-ratios, whereas crustal assimilation results in a strong Tl-enrichment, causing low K/Tl-ratios compared to K/Rb-ratios. Thallium isotopes show only slight changes during orthomagmatic differentiation and the assimilation of crustal material cannot be traced, since the isotopic composition of the average crust…