Search results for "rock"
showing 10 items of 1160 documents
Proterozoic Tectonostratigraphy and Paleogeography of Central Madagascar Derived from Detrital Zircon U‐Pb Age Populations
2004
Abstract Detrital zircon U‐Pb ages determined by SHRIMP distinguish two clastic sequences among Proterozoic metasedimentary rocks from central Madagascar. The Itremo Group is older: zircon data, stromatolite characteristics, and carbon isotope data all point to a depositional age around 1500–1700 Ma. The Molo Group is younger, deposited between ∼620 Ma (the age of the youngest zircon) and ∼560 Ma (the age of metamorphic overgrowths on detrital cores). Geochronologic provenance analysis of the Itremo Group points to sources in East Africa as well as local sources in central and southern Madagascar but provides no evidence for a detrital contribution from northern and eastern Madagascar nor f…
Geochemistry, provenance and stratigraphic age of metasedimentary rocks from the eastern Vardar suture zone, northern Greece
2009
Abstract Uppermost Palaeozoic and Mesozoic sediments from the Vardar suture zone in northern Greece record a cycle of Neotethyan oceanic basin opening and closure and their analysis places tight constraints on the geotectonic evolution of the area. The oldest post-Carboniferous sedimentary unit in the study area is the Examili Formation, which comprises mainly metaarkoses and metaquartzites, and was deposited in an intracontinental rift-related sedimentary basin in proximity to the Vertiskos Terrane during the Permian–Triassic. The Melissochori Formation (former Svoula flysch) comprises predominantly metasandstones with significant carbonate content and was deposited in front of a Carbonife…
Diffuse degassing of carbon dioxide at Somma-Vesuvius volcanic complex (Southern Italy) and its relation with regional tectonics
2004
Abstract A systematic survey of soil CO 2 concentrations was carried out on the flanks of Somma–Vesuvius volcano in order to constrain possible pathways responsible of carbon dioxide diffuse degassing taking place during the present state of quiescence. Measurements were performed at 1162 sites in late winter–spring 2000, highlighting that soil CO 2 concentrations range from 50 to 10500 ppmV. A statistical analysis was developed in order to define the threshold value of anomaly and separate the biogenic CO 2 component, produced by soil respiration, from the inorganic component of deep provenance. A computer routine was also elaborated to interpret the grid of CO 2 anomalous concentration va…
Revision of "Leptite-gneisses" in the Menderes Massif: a supracrustal metasedimentary origin
2001
The Pan-African basement of the Menderes Massif comprises a regular lithological succession that reaches a thickness of 8 km, the oldest units of which are, in ascending order, so-called leptite-gneisses, a quartzite-sequence transition zone and mica schists. New findings suggest that the protoliths for the leptite-gneisses, proposed to be of volcanic origin in previous studies, were predominantly elastic sediments of litharenitic composition, Geochemical data indicate that the protoliths for the leptite-gneisses were of cratonic provenance. Because they have undergone Pan-African polymetamorphism and are intruded by approximately 550 Ma gneisses of granitic origin, it is believed that the …
LA-ICP-MS U–Pb dating of detrital rutile and zircon from the Reynolds Range: A window into the Palaeoproterozoic tectonosedimentary evolution of the …
2014
Abstract The Palaeoproterozoic Reynolds Range of the Arunta Region, central Australia, comprises a series of shallow marine clastic sediments (Reynolds Range Group) which overlies deeper water sequences of turbidites (Lander Rock Formation) and minor sandstones (“unnamed sandstone”). U–Pb age data collected from detrital rutile and zircon in these rocks indicates these sequences contain very similar age spectra, although with a notable and important shift to younger ages within the stratigraphically younger Reynolds Range Group. Detrital zircons from the “unnamed sandstone” directly underlying the unconformity with the Reynolds Range Group contain a major age component at ca. 1860 Ma, toget…
Querns and mills during Roman times at the northern frontier of the Roman Empire (Belgium, Northern France, Southern Netherlands, Western Germany): U…
2016
International audience; This paper presents the results of a multi-disciplinary provenance study of querns and millstones during the Roman period (1st-4th century CE) in the northern part of the Roman Empire (provinces of Gallia Belgica and Germania Inferior). Comparative petrographical, mineralogical and geochemical analysis allowed an international team of archaeologists and geologists to identify the different raw materials used for the manufacturing of querns and millstones. As a result, (litho-) stratigraphic assignments as well as geological-geographical provenances are suggested or corroborated for the broad spectrum of these natural geo-materials. We give evidence for the exploitati…
Computer Simulation to Optimize the VFA Alpha Prototype with a Hydraulic Piston Compressor and an Integrated Booster
2020
The research has been supported by the European Regional Development Fund project "Competence Centre of Mechanical Engineering", contract No.1.2.1.1/18/A/008 signed between the Competence Centre of Mechanical Engineering and the Central Finance and Contracting Agency, Research No. 3.1 "Additional research and integra tion of the technology of hydraulic piston, aiming to develop and demonstrate economically efficient compressed natural gas smart commercial vehicle fuelling appliance". Our special gratitude to Gaspard Bouteau, PhD, Research Engineer, who conducted research in Engie Lab CRIGEN. Scientific co-authorship of the Laboratory of Materials for Energy Harvesting and Storage, ISSP UL h…
Ciclos pelíticos de bahía Interdistributaria del nivel intramareal inferior del grupo Roda-Oroel (sector occidental del paleodelta de Ager, Lérida)
1984
The deposits of the ancient Ager deltaic system (Lérida, Spain) are characterized in some way by the existence of cycles constituted, in a large scale, by alternances of pelites and sandstone bodies. According to geological literature these deposits represent bay marls and stream-mouth-bars, in the eastern-most counterpart. In this area sorne pelitic sections show a pronounced cyclical pattern devoid to repetitions of two terms: A marly bioturbated one, and the other one, constituted by undisturbed delicately laminated clays. Part of the deposits of the "Intramarea1 Inferior" level (''Tramo Superior" of the Roda-Oroel depositional system) in the area comprised between La Régola cementery an…
VolcDeGas: A program for modelling hydrogen isotope fractionation during degassing of rhyolitic melts
2020
Magma degassing mechanisms are key determinants of explosive and effusive eruption styles. Paired measurements of H2O content and hydrogen isotopic ratios (e.g., dD) in pyroclastic and effusive products can elucidate end-member degassing mechanisms (e.g. closed and open system) during eruption. Here we present VolcDeGas, a MatLab program that models dD-H2O degassing trajectories of rhyolitic magma. Operating within an intuitive GUI, VolcDeGas calculates degassing paths based on: initial dD (in ‰), the H2O content of the melt (wt.%), degassing step size, and temperature. VolcDeGas also calculates hydrous speciation based on either empirical models or analytical data, and incorporates this…
Highly stable Zerodur based optical benches for microgravity applications and other adverse environments
2019
A number of cold atom experiments are restrained by the impeding effects of gravity. While efforts have been made to overcome these limitations in a gravitational environment, another approach is placing the experiment in a microgravity environment, as can be found aboard sounding rockets, satellites or a space station. The cornerstone of such experiments is a robust laser system. The adverse conditions during a rocket launch impose stringent requirements on thermal stability and resilience against mechanical stress on this part of the experimental setup. Furthermore, the very limited space found on any of the aforementioned microgravity platforms necessitates maximal miniaturization. In or…