Search results for " petrology"
showing 10 items of 1353 documents
Assessing vermetid reefs as indicators of past sea levels in the Mediterranean
2020
Abstract The endemic Mediterranean reef building vermetid gastropods Dendropoma petraeum complex (Dendropoma spp) and Vermetus triquetrus develop bio-constructions (rims) on rocky shorelines at about Mean Sea Level (MSL) and are therefore commonly used as relative sea-level (RSL) markers. In this study, we use elevations and age data of vermetid reefs to (1) re-assess the vertical uncertainties of these biological RSL indicators, and (2) evaluate the vertical growth rates along a Mediterranean east-west transect, in attempt to explain the differences found in both growth rates and uncertainties. In Israel, Differential Global Positioning System (DGPS) and laser measurements relative to the …
The use and beauty of ultra-high-resolution seismic reflection imaging in Late Quaternary marine volcaniclastic settings, Napoli Bay, Italy
2019
A Nápolyi-öbölben felvett ultra nagy felbontású egycsatornás (IKB-Seistec™) reflexiós szeizmikus szelvények korábbi geológiai és geofizikai vizsgálatok eredményeivel együtt kivételes, eddig soha nem látott felbontású szeizmikus leképezését nyújtják a Flegrei-mezők és a Somma-Vezúv felszín alá süllyedt késő-pleisztocén–holocén rétegtani felépí - tésének. A szeizmikus szelvényeken látott geometria és gravitációs magvevővel nyert üledékek adatainak összevetéséből Campania partközeli kontinentális talapzatán számos olyan üledékes és vulkáni szerkezet, valamint hidrotermális jelenség került leképezésre, melyek a legutolsó glaciális maximum (kb. 18 000 év) óta keletkeztek. A Pozzuoli-öbölben mért…
Synthetic and natural chromium bearing spinels: an optical spectroscopy study
2014
Four samples of synthetic chromium-bearing spinels of (Mg, Fe2+)(Cr, Fe3+)2O4 composition and four samples of natural spinels of predominantly (Mg, Fe2+)(Al, Cr)2O4 composition were studied at ambient conditions by means of optical absorption spectroscopy. Synthetic end-member MgCr2O4 spinel was also studied at pressures up to ca. 10 GPa. In both synthetic and natural samples, chromium is present predominantly as octahedral Cr3+ seen in the spectra as two broad intense absorption bands in the visible range caused by the electronic spin-allowed 4A2g → 4T2g and 4A2g → 4T1g transitions (U- and Y-band, respectively). A distinct doublet structure of the Y-band in both synthetic and natural spine…
Experimental constraints on pre-eruptive conditions of a chemically-zoned peralkaline ignimbrite: the Green Tuff eruption at Pantelleria Island (Ital…
2015
Pantelleria island is the type locality for pantellerite, an iron and alkali-rich rhyolite. The eruptive products outcropping in the island fall in a mafic end member (mildly alkaline basalt) and a felsic end member (metaluminous trachytes and pantellerites). A key event in the volcanological history of the island is the Green Tuff eruption the sole ignimbrite at Pantelleria compositionally zoned from crystal-poor pantellerite at the base to crystal-rich trachyte at the top. We experimentally investigated the phase relations of the pantelleritic end member AI = 1.8 (agpaitic index = molar ratio Na2O+K2O/Al2O3) and trachyte end member AI = 1.05 of the Green Tuff eruption. The intensive varia…
Pre-Eruptive Conditions of La Sommata Basalt (Vulcano, Aeolian Islands): Constraints from Experimental Petrology.
2011
One of the most primitive magma of Aeolian Arc is the basalt erupted (about 50 ka B.P.) by the La Sommata scoria cone at Vulcano; this is a silica-undersaturated (ne-normative) low-phyric (10-20 wt. %), Ca-rich (CaO = 13 wt. %) shoshonitic basalt (K2O = 2.28 wt.%) in which olivine phenocrysts host melt inclusions more primitive than whole rock composition and with an ultra-calcic character: CaO/Al2O3 > 1.4 [Métrich and Clocchiatti, 1996; Gioncada et al., 1998; Schiano et al., 2000]. Phenocrysts mainly include olivines (Fo92) and clinopyroxenes (Fs5). Plagioclase microlites (from An79 to An67) are the most abundant groundmass phase (45 wt. %), together with clinopyroxene (Fs11) and olivine (…
Just another drip: Re-analysis of a proposed Mesoarchean suture from the Barberton Mountain Land, South Africa
2014
Abstract Structural analysis of a proposed Mesoarchean suture located immediately to the southwest of the Barberton Greenstone Belt, South Africa – known as the Inyoni Shear Zone (ISZ) – reveals that the main, steeply dipping, NNE-striking fabric is distributed across only 1 km width, is late (D3), and clearly overprints two earlier sets of fabric elements (D1, D2) that were originally oriented at right angles to the direction of proposed collision. Dating of a S2 foliated meta-trondhjemite is interpreted to indicate that D2 deformation was at, or younger than, 3238.2 ± 0.9 Ma. The D3 high strain fabric of the ISZ is localised around tightly folded, kilometre-scale supracrustal rafts, but d…
Contrasting metamorphic evolution of metasedimentary rocks from the Çine and Selimiye nappes in the Anatolide belt, western Turkey
2003
P-T conditions, mineral isograds, the relation of the latter to foliation planes and kinematic indicators are used to elucidate the tectonic nature and evolution of a shear zone in an orogen exhumed from mid- crustal depths in western Turkey. Furthermore, we discuss whether simple monometamorphic fabrics of rock units from different nappes result from one single orogeny or are related to different orogenies. Metasedimentary rocks from the Cine and Selimiye nappes at the southern rim of the Anatolide belt of western Turkey record different metamorphic evolutions. The Eocene Selimiye shear zone separates both nappes. Metasedimentary rocks from the Cine nappe underneath the Selimiye shear zone…
The genesis of actively growing siliceous stromatolites: Evidence from Lake Specchio di Venere, Pantelleria Island, Italy
2010
This study documents the attributes of siliceous stromatolites growing in the Lake Specchio di Venere, on the volcanic island of Pantelleria, Italy, in a setting characterized by very shallow cold waters and pools and by scattered hydrothermal activity, which exhales mainly CO2, at emission point temperatures of 34 to 58 °C. The saturation indexes indicate that the lake waters are saturated with respect to tridymite, cristobalite, chalcedony and quartz, and slightly undersaturated with respect to amorphous silica. Common roughly laminated and poorly lithified stromatolites show scanning electron microscope (SEM) evidence for silicified microbial mat structures, including biofilms, filamento…
Structural and dynamical properties of sodium silicate melts: An investigation by molecular dynamics computer simulation
2001
We present the results of large scale computer simulations in which we investigate the static and dynamic properties of sodium disilicate and sodium trisilicate melts. We study in detail the static properties of these systems, namely the coordination numbers, the temperature dependence of the Q^(n) species and the static structure factor, and compare them with experiments. We show that the structure is described by a partially destroyed tetrahedral SiO_4 network and the homogeneously distributed sodium atoms which are surrounded on average by 16 silicon and other sodium atoms as nearest neighbors. We compare the diffusion of the ions in the sodium silicate systems with that in pure silica a…
Bentonites with grafted aminogroups: Synthesis, protolytic properties and assessing Cu(II), Cd(II) and Pb(II) adsorption capacity
2019
Abstract Bentonites with grafted methylaminopropyl (NHCH3-Bent), aminopropyl (NH2-Bent), ethylenediaminopropyl (En-Bent) and diethylenetriaminopropyl (Dien-Bent) groups were synthesized by silylation procedure. The successful covalent grafting of silylating agents on the bentonite was confirmed by 29Si NMR, FTIR and thermal analysis. The effects of polar (ethanol) and non-polar (dioxane) solvents on grafting process were compared. The samples prepared in ethanol showed the increase of d001 value from initial 1.44 nm to 1.63–2.05 nm proportionally to the loading amount of grafted silane. However, an almost constant value of d001 (1.96–2.10 nm) was observed for all samples obtained in dioxane…