Maria Ovtcharova

Maria Ovtcharova
University of Geneva | UNIGE · Department of Earth Sciences

About

119
Publications
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4,290
Citations
Citations since 2017
34 Research Items
2402 Citations
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20172018201920202021202220230100200300400
20172018201920202021202220230100200300400

Publications

Publications (119)
Conference Paper
Full-text available
The Paleoproterozoic is characterized by major changes in Earth’s surficial environments, which are currently preserved in multiple sedimentary sequences around the world (e.g. occurrence of widespread glaciations, the Great Oxidation Event, milestones in the evolution of life, etc.). Precise absolute time constraints are of paramount importance fo...
Article
The long-term history of the Earth–Moon system as reconstructed from the geological record remains unclear when based on fossil growth bands and tidal laminations. A possibly more robust method is provided by the sedimentary record of Milankovitch cycles (climatic precession, obliquity, and orbital eccentricity), whose relative ratios in periodicit...
Conference Paper
Full-text available
The Precambrian comprises the vast majority of Earth’s history. Preserved archives contain essential information about the first few billion years for planetary evolution of our planet. Despite covering a large part of the history of our planet, these outcrops are not so abundant due to erosion and frequently occur in disparate areas. In this study...
Article
Full-text available
In the Cadomian orogenic belt a package of glacigenic sedimentary deposits have been recently described in the Armorican Massif (Normandy, France). The Granville Tillite Member, the middle part of the upper Granville Formation, is late Ediacaran in age. Maximum depositional ages of the pre- and syn-glacial sedimentary deposits obtained by LA-ICP-MS...
Article
Full-text available
Four voluminous ignimbrites (150–500 km ³ ) erupted in rapid succession at 27 Ma in the central San Juan caldera cluster, Colorado. To reconstruct the timescales and thermal evolution of these magma reservoirs, we used zircon ID-TIMS U–Pb geochronology, zircon LA-ICP-MS geochemistry, thermal modeling, and zircon age and crystallization modeling. Zi...
Article
Full-text available
Age determination of minerals using the U-Pb technique is widely used to quantify time in Earth's history. A number of geochronology laboratories produce the highest precision U-Pb dates employing the EARTHTIME 202Pb-205Pb-233U-235U tracer solution for isotope dilution, and the EARTHTIME ET100 and ET2000 solutions for system calibration and laborat...
Article
Full-text available
Latest advances in laser ablation inductively coupled plasma mass spectrometer (LA-ICPMS) allow for accurate in situ U−Pb dating of carbonate material, with final age uncertainties usually >3 % 2σ. Cross-laboratory reference materials (RMs) used for sample-bracketing are currently limited to WC1 calcite with an age of 254.4±6.5 (2σ). The minimum un...
Article
Full-text available
The Bolnisi district is a distinct tectonic zone of the Lesser Caucasus, which is considered to represent the eastern extremity of the Turkish Eastern Pontides. Late Cretaceous, low-K, calc-alkaline to high-K rhyolite of the Mashavera and Gasandami Suites is the predominant rock type of the district, and is accompanied by subsidiary dacite, and rar...
Article
The Cerro de Pasco district in central Peru hosts one of the world largest porphyry-related epithermal polymetallic deposits. The district is centered onto a large diatreme-dome complex crosscut by numerous dacite to rhyodacite bodies showing domal structures and quartz-monzonite dykes. Three temporally distinct high-temperature porphyry-type miner...
Article
Precise U–Pb zircon dating using the chemical abrasion – isotope dilution – thermal ionization mass spectrometry (CA-ID-TIMS) method constrains the age of the Central Sudetic Ophiolite (CSO) in the Variscan Belt of Europe. A felsic gabbro from the Ślęża Massif contains zircon xenocrysts dated at 404.8 ± 0.3 Ma and younger crystals dated at 402.6 ±...
Preprint
Full-text available
Latest advances in laser ablation inductively coupled plasma mass spectrometer (LA-ICPMS) allow for accurate in-situ U-Pb dating of carbonate material, with final age uncertainties usually > 3 % 2σ. Cross-laboratory reference materials (RMs) used for sample-bracketing are currently limited to WC1 calcite with an age of 254.4 ± 6.5 (2σ). The minimum...
Conference Paper
High Precision U-Pb CA-ID-TIMS dates from the type Livian Substage (Mississippian) of Belgium
Article
Full-text available
The Neoproterozoic Era was characterized by rapidly changing paleogeography, global climate changes and especially by the rise and fall of the Ediacaran macro-biota. The correlation between disparate Ediacaran fossil-bearing localities and the tentative reconstruction of their paleoenvironmental and paleogeographic contexts are usually complicated...
Data
Appendix S2. Measurement results from EPMA (n = 84 for each of the two zircon samples) at Universität Göttingen, Germany.
Data
Appendix S3. Documentation of locations of EPMA (Universität Göttingen, Germany) linescans, and plots and histograms of mass fractions of HfO2, ThO2 and UO2.
Data
Appendix S1. Details for ID‐TIMS analytical procedures in the laboratories.
Data
Appendix S4. Measurement results from SHRIMP analyses (Curtin University, Perth, Australia) including additional Concordia plots and Th/U histograms.
Article
Full-text available
Here we document a detailed characterization of two zircon gemstones, GZ7 and GZ8. Both stones had the same mass at 19.2 carats (3.84 g) each; both came from placer deposits in the Ratnapura district, Sri Lanka. The U–Pb data are in both cases concordant within the uncertainties of decay constants and yield weighted mean ²⁰⁶Pb/²³⁸U ages (95% confid...
Article
Quantitative reconstruction of thermal histories can be a powerful tool to study numerous natural processes such as tectonic plate interaction, cratonic stability and extra-terrestrial phenomena such as asteroid ejection. A majority of thermochronological studies have focused on temperatures lower than 300°C. Few previous studies have demonstrated...
Article
The Kleivan and Sjelset granitic complexes are two composite plutons, containing both orthopyroxene and biotite (± hornblende) facies, emplaced in the Sveconorwegian (Grenvillian) high-grade basement of SW Norway. A structural study of these two plutons, based on the anisotropy of magnetic susceptibility (AMS) technique and combined with high-preci...
Article
The Variscan orogen in southeast Europe is exposed in isolated remnants, affected by a subsequent Alpine tectono-magmatic overprint. Unlike the central European Variscides, in SE Europe the juxtaposition and correlation of the events and products are impeded by the scarcity of Variscan domains with preserved magmatic, metamorphic, sedimentological...
Article
Full-text available
The presence of Paleoproterozoic glacial diamictites deposited at low latitudes on different continents indicates that three or four worldwide glaciations occurred between 2.45 and 2.22 Ga. During that time period, the first atmospheric oxygen rise, known as the Great Oxidation Event (GOE), occurred, implying a potential connection between these ev...
Article
The Magaliesberg Formation quartzite of the upper Transvaal Supergroup in north-central South Africa represents the biggest Paleoproterozoic arenite deposit on Earth, with a present-day lateral extent of more than 600 km. It therefore has a great potential to provide detailed information about Archean to early Paleoproterozoic crust–mantle evolutio...
Article
Full-text available
Determining the primary compositions of arc magmas is fundamental in retracing the chemical differentiation processes responsible for the formation of juvenile arc crust and the thermal structure of the mantle wedge. We have investigated a series of post-plutonic dykes that intruded the gabbroic to tonalitic southern part of the Tertiary Adamello B...
Article
Full-text available
The potential petrogenetic link between a crystal-poor rhyolite (the Rhyolite Canyon Tuff) and its associated subvolcanic intrusion and crystal-rich post-caldera lavas from Turkey Creek, Arizona (USA), is examined using zircon chemical abrasion–thermal ionization mass spectrometry U-Pb geochronology and inductively coupled plasma mass spectrometry...
Article
Full-text available
The composite Meghri–Ordubad and Bargushat plutons of the Zangezur–Ordubad region in the southernmost Lesser Caucasus consist of successive Eocene to Pliocene magmatic pulses, and host two stages of porphyry Cu–Mo deposits. New high-precision TIMS U–Pb zircon ages confirm the magmatic sequence recognized by previous Rb–Sr isochron and whole-rock K–...
Article
Full-text available
The Morococha district in central Peru is characterised by economically important Cordilleran polymetallic (Zn-Pb-Ag-Cu) vein and replacement bodies and the large Toromocho porphyry Cu-Mo deposit in its centre. U-Pb, Re-Os, and 40Ar/39Ar geochronology data for various porphyry-related hydrothermal mineralisation styles record a 3.5-Ma multi-stage h...
Article
Precise and accurate determination of the timing and duration of ore-forming processes in porphyry systems is a fundamental step in understanding their genesis and placing them in a regional context. Here, we take advantage of the considerable improvements in the field of geochronology over the last decade to provide a robust geochronologic framewo...
Article
Full-text available
Trace element, Hf, and O isotopic composition and U-Pb geochronological data are reported for zircon megacrysts found in miaskitic (zircon, biotite, plagioclase-bearing) nepheline syenite pegmatites from the Finero complex in the Northeastern part of the Ivrea-Verbano Zone, southern Alps. Zircon from these pegmatites was reported to reach up to 9 c...
Article
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We present four new (CA-ID-TIMS) U–Pb ages from ammonite-bearing rocks in Peru.•We present new U–Pb zircon and baddeleyite data from the K-LIP in South Africa.•The age of the falciferum CIE is between and .•The falciferum CIE correlates with Karoo sill emplacement at .
Article
Three new U–Pb zircon chemical abrasion isotope dilution thermal ionization mass spectrometry dates obtained from late Viséan Belgian bentonites are reported and are used to estimate the periodicity of early Warnantian shallowing-upwards carbonate parasequences that are interbedded with the dated bentonites. Early Warnantian parasequences exhibit m...
Article
Resolving time differences between successive magmatic pulses in composite granitoid plutons is often a difficult task. High-precision CA-ID-TIMS zircon ages obtained from such a pluton, the Variscan Karkonosze Granite (NE part of the Bohemian Massif), provide evidence that the crystallization of the two main granite facies, porphyritic and equigra...
Article
Full-text available
We present zircon geochronologic (LA-ICPMS and ID-TIMS), trace element and Hf isotopic evidence for a complex evolution of the plutonic roots of the Eocene Coroccohuayco porphyry system, southern Peru. LA-ICPMS U–Pb dating has initially been carried out to optimize grain selection for subsequent high-precision ID-TIMS dating and to characterize cru...
Article
Precise determinations of the isotopic compositions of a variety of elements is a widely applied tool in Earth sciences. Isotope ratios are used to quantify rates of geological processes that occurred during the previous 4.5 billion years, and also at the present time. An outstanding application is geochronology, which utilizes the production of ra...
Conference Paper
Full-text available
The importance of the Early-Middle Triassic boundary (EMTB) lays in the fact that this boundary marks the end of the time interval characterized by the biotic recovery after the end-Permian mass extinction. Therefore, to gain highest possible time accuracy and precision for quantification of biotic processes, we undertook a detailed calibration of...
Article
Full-text available
Post-collisional (56.0-40.4 Ma) adakitic magmatism in the Rhodope Massif and the Kraishte region, including W. Srednogorie, in South Bulgaria followed the collision of the Rhodope and Pelagonian Massifs. It forms a 250 km NW trending belt which continues into the 1000 km long belt of Eocene magmatism in northern Turkey and Iran. The rocks are repre...
Article
Full-text available
Determining the absolute duration of magmatic-hydrothermal events leading to the formation of porphyry systems (i.e., including porphyry copper, skarn, and epithermal deposits) is one of the key questions in ore geology. This is so because the duration of magmatic-hydrothermal events in porphyry systems is instrumental to the development of genetic...
Article
The late Alpine evolution of the Rhodope Massif in southern Bulgaria and northern Greece involved postcollisional extension, which generated detachment faults, syndeformational sedimentary basins, and exhumation of a large metamorphic core complex composed of gneisses and marbles: the Central Rhodopian dome. Closely associated with this complex, su...
Article
The lifetimes and thermal histories of upper crustal plutons are increasingly determined using geochronology, but complex growth of datable minerals in magmas impedes simple age interpretations. Careful field observation helps constrain zircon U–Pb dates in terms of timing of magma injection, for example because relative ages of successive magma pu...
Article
Full-text available
Field, geochemical, and geochronologic data of high-grade basement metamafic and evolved rocks are used to identify the nature and timing of pre-Alpine crustal growth of the Rhodope Massif. These rocks occur intrusive into clastic-carbonate metasedimentary succession. Petrography and mineral chemistry show compositions consistent with Alpine amphib...
Article
Full-text available
We present three new high-precision U-Pb zircon chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) dates from western European Carboniferous diagenetically altered volcanic ash layers (bentonites and tonsteins) that occur interbedded with cyclic siliciclastic sedimentary rocks. The dates constrain the average perio...
Article
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We report new high-precision U/Pb ages and geochemical data from the Chaltén Plutonic Complex to better understand the link between magmatism and tectonics in Southern Patagonia. This small intrusion located in the back-arc region east of the Patagonian Batholith provides important insights on the role of arc migration and subduction erosion. The C...
Article
The Canavese Line in the Western Alps represents the position in the Alpine chain, where alkaline and calc-alkaline magmatism occur in close spatial and temporal association. In addition to available data on the alkaline Valle del Cervo Pluton, we present petrological and geochemical data on the Miagliano tonalite. The latter is of special interest...
Article
The high-pressure metamorphic rocks of the Sesia–Lanzo zone are partly covered by a volcano-sedimentary unit, the Biella Volcanic Suite. Calc-alkaline and shoshonitic lavas extruded sub-aerially on the Oligocene surface. Uranium–Lead zircon dating yields 32.44–32.89 Ma for the eruption of the calc-alkaline lavas and therefore fixes a minimum age fo...
Article
Full-text available
Granitic and mafic magma pulses were sequentially accreted in the spectacularly exposed shallow crustal Torres del Paine laccolith, in southern Patagonia. This 12.5 Ma pluton forms a composite intrusion with a subvertical feeding system in the west and a laccolith in the east. A key unknown in the formation of sill complexes is how individual magma...
Article
High-precision U-Pb zircon geochronology has become an invaluable tool for calibrating the tempo of eruptive and intrusive igneous processes, quantifying volumes and rates of magma flux, degrees of liquid-crystal separation, and of magma mixing and crustal assimilation during fractionation. Age scatter of individual zircon and titanite grains sugge...
Conference Paper
Refined U-Pb dating techniques, applying an empirical chemical abrasion treatment prior to analysis [1], and using a precisely calibrated double isotope Pb, U EARTHTIME tracer solution, have led to an unprecedented <0.1% precision and accuracy of obtained 206Pb/238U dates of single zircon crystals or fragments. Results very often range over 10e4 to...
Conference Paper
The spectacularly exposed Torres del Paine laccolith (Southern Patagonia) has been constructed by successive injections of mafic and granitic melt batches. The sill complex is connected, at its western border, to a dike complex, interpreted as the laccolith feeder zone. A key unknown in sill complexes is the mechanism by which individual mafic and...
Article
Full-text available
Two age groups were determined for the Cenozoic granitoids in the Dinarides of southern Serbia by high-precision single grain U–Pb dating of thermally annealed and chemically abraded zircons: (1) Oligocene ages (Kopaonik, Drenje, Željin) ranging from 31.7 to 30.6Ma (2) Miocene ages (Golija and Polumir) at 20.58–20.17 and 18.06–17.74Ma, respectively...
Article
High-precision isotope dilution - thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon and baddeleyite ages from the PX1 vertically layered mafic intrusion Fuerteventura, Canary Islands, indicate initiation of magma crystallization at 22.10 ± 0.07 Ma. The magmatic activity lasted a minimum of 0.52 Ma. 40Ar/39Ar amphibole dating yielded ages f...