Search results for " ROC"

The evolution of the southern Menderes Massif in SW Turkey as revealed by zircon dating

1999

This geochronological study concentrates on the evolution of the southern part of the Menderes Massif, a metamorphic core complex in W Turkey, by dating single zircons with the Pb–Pb evaporation and the U–Pb methods. We have analysed zircons from granitic augen gneisses of the core as well as from quartzites of the metasedimentary envelope. Zircons from the granitic core gneisses are euhedral with typical igneous morphologies. The single zircon ages of these gneisses indicate a time span for magmatic activity from 520 to 570 Ma with a major event at about 550 Ma. Some gneisses contain older zircons of c. 660 Ma which are interpreted as inherited grains. Zircons from the quartzites are detri…

Jeroglíficos, símbolos, alegorías y diosas en la biblioa ilustrada de Klauber

2000

Modélisation d'images agronomiques - application a la reconnaissance d'adventices par imagerie pour une pulvérisation localisée

2009

Plant (crop and weed) identification is a very active field of research in agriculture since the reinforcement of European laws about pesticide applications for a site-specific management of spraying practices. A new crop/weed simulation model was developed to allow the evaluation of crop/weed spatial identification methods from imaging. Considering multiples agronomic parameters – crop location, weed infestation rate, weed spatial distribution – the first step of this model allows the simulation of an infested crop field. Then, in a second step, a world to camera transformation is applied to allow every kind of picture (with or without perspective effect). The validation of this model was …

In situ Laser Induced Breakdown Spectroscopy as a tool to discriminate volcanic rocks and magmatic series, Iceland.

2015

7 pages; International audience; This study evaluates the potentialities of a lab-made pLIBS (portable Laser-Induced Breakdown Spectroscopy) to sort volcanic rocks belonging to various magmatic series. An in-situ chemical analysis of 19 atomic lines, including Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Na, Si, Sr and Ti, from 21 sampled rocks was performed during a field exploration in Iceland. Iceland was chosen both for the various typologies of volcanic rocks and the rugged conditions in the field in order to test the sturdiness of the pLIPS. Elemental compositions were also measured using laboratory ICP-AES measurements on the same samples. Based on these latter results, which can be used to ident…

Regime shifts and alternative stable states in intertidal rocky habitats: State of the art and new trends of research

2018

Abstract The existence of regime shifts and alternative stable states in ecosystems is well known and has very large effects on their structure and dynamics. Since shifts between alternative stable states have significant implications for the ecosystems conservation, their prevention should be an aim of primary interest, and for this reason a particular attention has been paid to their study. Regarding marine ecosystems, rocky intertidal habitats, in particular, represent an ideal system for the study of alternative stable states because of their characteristics: they exhibit strong environmental gradients, are easy to manipulate, and most of the inhabiting species grow rapidly. Given the s…

U-Pb data on zircons for the thermal peak of metamorphism in the Variscan Odenwald, Germany

1995

U-Pb data are presented for zircons from metamorphic rocks of the crystalline Odenwald that comprises part of the Mid-German Crystalline Rise. The Odenwald can be divided into four principal domains with different magmatic and metamorphic histories on the basis of published structural and petrological data and the presented ages. In the eastern (Boll-stein) Odenwald the metasedimentary rocks contain zircons derived from basement rocks that exceed 2.2 Ga in age. The intrusion of granitic magmas into these metasedimentary rocks took place before or close to the end of the thermal peak of metamorphism at 375 ± 5 Ma ago. Rapid uplift of the Bollstein Odenwald occurred at about 320 Ma bp, later …

Phosphogenesis in the Bonarelli Level from northwestern Sicily, Italy: petrographic evidence of microbial mediation and related REE behaviour

2010

Phosphogenesis at the base of the Bonarelli Level from the Calabianca stratigraphic section (northwestern Sicily) was investigated using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, and stable-isotope mass spectrometry. The anoxic event onset is marked by high P(2)O(5tot) concentrations related to the presence of authigenic carbonate-fluorapatite. This mineral is poorly crystallized and occurs in three different forms: (i) fish debris locally showing evidence of re-crystallization, (ii) phosphatically cemented layers, and (iii) dense aggregates of microcrystals. Petrographic features are indicative of a microbial genesis for the carbonate-fluorapatite. Conversely, th…

Sapphire-bearing magmatic rocks trace the boundary between paleo-continents: A case study of Ilmenogorsky alkaline complex, Uralian collision zone of…

2021

Abstract Metamorphic gem corundum (mainly ruby) deposits are robust indicators of continent-continent collision processes. However, a systematic link of primary magmatic blue sapphire occurrences to orogenic belts is less understood. An example is the Ilmenogorsky alkaline complex, within the Ilmen Mountains region and part of the Uralian orogenic belt. The mobile belt is a product of the collision among Kazakhstania, Laurussia, and Siberia continents prior to the closure of the Paleo-Uralian ocean and formation of the Laurasia supercontinent (330–250 Ma). It is believed that the alkaline complex became inсluded into the separate Sysertsk-Ilmenogorsk microcontinent with unconstrained border…

Young ages from old garnet in the polyphase metamorphic terrane of the Limpopo Belt, South Africa

2020

Abstract The P–T–t path of high-grade metamorphic rocks is significant for understanding vertical motions and heating of the crust. In general, garnet is used to constrain P–T paths and metamorphic zircon is used to obtain t for different metamorphic stages. However, this approach may be complicated by polyphase tectonothermal events. The Central Zone of the Limpopo Belt in South Africa is a complex Precambrian metamorphic terrane that has experienced three distinct high-grade metamorphic events at 3.22 Ga (M1), 2.62 Ga (M2), and 2.02 Ga (M3), based on zircon dating. A previous investigation of a metapelite enclave in the Bulai pluton in the Central Zone showed that metamorphic zircon in th…

Evolution of Pan-African island arc assemblages in the southern Red Sea Hills, Sudan, and in southwestern Arabia as exemplified by geochemistry and g…

1991

Kr6ner, A., Linnebacher, P., Stern, R.J., Reischmann, T., Manton, W. and Hussein, I.M., 1991. Evolution of Pan-African island arc assemblages in the southern Red Sea Hills, Sudan, and in southwestern Arabia as exemplified by geochemistry and geochronology. In: R.J. Stern and W.R. van Schmus (Editors), Proterozoic Crustal Evolution in the Late Proterozoic. Precambrian Res., 53:99-117. We report Rb-Sr whole-rock and zircon ages for metavolcanic and plutonic associations in the southeastern part of the Red Sea Hills, Sudan, and show that these rocks constitute one of the earliest Pan-African arc assemblages within the Arabian-Nubian shield. The remarkable similarity in geochemistry and age bet…