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Bucharest, Romania

Harris C.R.,ETH Zurich | Pettke T.,ETH Zurich | Pettke T.,University of Bern | Heinrich C.A.,ETH Zurich | And 4 more authors.
Earth and Planetary Science Letters | Year: 2013

The history of processes that have affected the lithospheric mantle can be reflected in the chemical characteristics of magmas that are emplaced millions of years later during crustal extension. As a result, ore deposits normally associated with subduction can form in environments where they are not conventionally expected. Calc-alkaline magmatism in the Apuseni Mountains, Romania, occurred in response to Miocene extension and formed rich Au-Ag-Te epithermal and Cu-Au porphyry deposits. We present major, trace element and Sr-Nd-Pb isotopic data from a comprehensive suite of unaltered Apuseni samples. This dataset indicates that the Apuseni magmas were derived from partial melting of a lithospheric mantle source enriched in volatiles and incompatible elements. Mantle-like Sr and Nd isotopic signatures, combined with large ion lithophile element enrichments, Nb-Ta depletions, and Pb enrichments, are best explained by mantle refertilization during subduction. Subduction metasomatism of the Apuseni source region occurred at least 50. Ma prior to extensional magma generation in the Miocene, most likely during NE-dipping subduction associated with closure of the Neotethys Ocean in the Mesozoic.We suggest that the different types of mineralization in the region are generally related to the degree of Miocene extension and consequent partial melting of the mantle source. Initial extension is correlated with the largest Au deposits in the Apuseni Mountains. The magmatic rocks associated with these deposits contain the most isotopically enriched Pb-Sr-Nd ratios, higher SiO2 and lower Mg-number, consistent with significant lower crustal influence during the initiation of extension and associated crustal anatexis. As extension progressed, increased mantle input resulted in magmas with more isotopically depleted Pb-Sr-Nd ratios, lower SiO2 and higher Mg-numbers. Uniquely rich Te-rich Au-Ag epithermal deposits are associated with these magmas, and are followed by porphyry Cu-Au deposits. Exceptional endowment in Te-rich epithermal deposits is common to other provinces associated with extensional magmatism preceded by much older mantle metasomatism, and we suggest that these deposits are ultimately linked to this metasomatism. © 2013 Elsevier B.V.. Source

Sabau G.,Geological Institute of Romania
Geochronometria | Year: 2012

In a single decaying system, the age determined from the exponential decay law is directly related to its linear Maclaurin approximation. This relationship can be additively extended to several decaying systems resulting in the same daughter element, by using proportionality functions, thus al-lowing an explicit formulation of the age as a function of element concentrations. The values of the binary proportionality function for the 238U- 235U-Pb system and the ternary proportionality function for the 232Th- 238U- 235U-Pb system were determined by iterations of the exponential decay formula up to 4 Ga, with a step of 10 Ma, for a set of 24 different U/Th ratios. From the iteration data, the expres-sions of the two functions and the associated coefficients were determined by polynomial regression and mathematical programing on conveniently separated time and compositional intervals. Additional time- and composition-dependent age corrections optimized by mathematical program-ming of the residuals lead to an accuracy of 0.005 Ma of the resulting age. The error propagation can be traced through all the operations defined by explicit formulas according to simple error propaga-tion rules, finally allowing the calculation of the standard error of the result. The formulas and param-eters derived can be used in a calculation spreadsheet. © 2012 Silesian University of Technology, Gliwice, Poland. Source

Nimirciag R.,Polytechnic University of Bucharest | Nimirciag R.,Geological Institute of Romania
Environmental Engineering and Management Journal | Year: 2012

The present study was carried out to highlight the areas where heavy metal content in the soils from Rodna mining perimeter exceeds normal limits and to attempt to reduce the concentration of free heavy metal ions by using natural Zeolite from the Dej tuff. In order to emphasize the heavy metal content and their accumulation in soil in Rodna region, 35 soil samples were collected from the upper and deeper layer (about 0-10 and 10-20 cm depth) and analyzed to determine total and free Cu, Pb and Zn concentrations. These investigations showed a heavy metal accumulation area downstream of Izvoru Rosu brook and Valea Vinului locality, where there is a large number of galleries. The aqueous solutions of soils collected from the previously mentioned area were treated with natural zeolite, with results emphasizing not only the efficiency of zeolites for heavy metal retention, but also their selectivity and behaviour, as the immobilization potential depends on initial concentration of the contaminants. Zinc sorption was much lower than lead retention, while copper was affected by the opposite process, of desorption. Source

Asimopolos N.S.,Geological Institute of Romania
8th Congress of the Balkan Geophysical Society, BGS 2015 | Year: 2015

The paper objective is to contribute to the clarification of the deep structure of the curvature Carpathians Vrancea by gravimetric and geodetic data interpretation in plate tectonics concept, conceptual models of the lithosphere, able to explain the increased seismicity in this area. Developing models that help explain the lithosphere geological structure of the upper crust, helping to elucidate the causes which contribute to the production of intermediate earthquakes in the Vrancea area. Source

Radan S.-C.,Geological Institute of Romania
Geo-Eco-Marina | Year: 2012

This tentative synopsis mainly focusses on the aspects of dating the loess - palaeosol sequences in the Romanian Plain and Dobrogea. The approach - placed in a historical framework - is defined by two characteristics. The first part is a short review of important achievements concerning the estimation or evaluation of the loess age, starting ca 120 years ago and ending in 1961. The second part continues with the loess dating history in a comprehensive table systematizing significant contributions of the last half-century. Actually, this article has been generated by another paper (under review), dedicated to a conceptual sedimentary model of the loess in the Lower Danube Basin (Jipa, submitted). The table emphasizes the interest for the loess dating during the last 50 years, and follows the chronological order of contributions. Implicitly, it is remarked the way passed through time in order to know the loess age, i.e. from the classic stratigraphy/pedostratigraphy to magnetostratigraphy, astronomically tuned ciclostratigraphy, magnetoclimatology, and up to the multi-proxy approach and optical/luminescence dating. In most of the sections, ages up to 781 ka are determined (the loess - palaeosol horizons are assigned to the Brunhes Chron of the ATNTS20004/ATNTS2012), but the synopsis includes a section from Dobrogea (analysed by the Infrared Stimulated Luminescence/IRSL dating method; Bǎlescu et al., 2003), wherefore the "estimated geological age" of 800 ka and the Marine Isotope Stage 20 are mentioned. Moreover, a recent result (Rǎdan, 2000, updated in 2012 - references therein) for a loess - palaeosol borehole profile (ca 30m thick) from the Romanian Plain points out, according to the palaeomagnetic investigation of the basal part and to the magnetic susceptibility vertical variation along the sampled borehole (40m depth), the possible identification of the Matuyama/Brunhes boundary (0.781 Ma), located at the base of the MIS 19. This subject has generated a dispute in the scientific literature on both the Chinese and the European loess. A tentative discussion on the "observed MBB" (within the loess horizon L8) and the "corrected/true MBB" (placed within the palaeosol S7) is done, by comparing our results from the Romanian Plain with data from the Chinese Loess Plateau. Source

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