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671.
Ricardo Arevalo Jr Jeremy Bellucci William F. McDonough 《Geostandards and Geoanalytical Research》2010,34(4):327-341
Recent developments from 2008 to 2009 in ICP-MS engineering, methods and applications are reviewed here. Of particular emphasis are advances in: (a) maximising sensitivity and reducing elemental/isotopic fractionation during laser ablation processing; (b) developing new analytical techniques to measure major, minor and trace element abundances without depending on matrix-matched calibrating materials, pre-determined internal standard concentrations and/or multiple analytical methods; (c) applying in situ and solution-based ICP-MS techniques to the analysis of forensic materials for criminal and/or nuclear investigations; and (d) improving precision and limits of detection of laser ablation multi-collector ICP-MS measurements of (ultra) trace elemental and isotopic abundances. 相似文献
672.
Natalia Hauser Massimo Matteini Ricardo H. Omarini Márcio M. Pimentel 《Mineralogy and Petrology》2010,100(3-4):153-184
In the Río Grande Valley, NW Argentina, several porphyritic panidiomorphic, ocelli-bearing dykes and sills intrude the Neoproterozoic to lower Paleozoic basement of the Eastern Cordillera. New petrographical and geochemical data permit us to classify these rocks as ocellar-analcime monchiquites, a feldspar-free variety of alkaline lamprophyre composed of Ti-rich-diopside/augite, Ti-rich biotite/phlogopite, forsteritic olivine, titanian-pargasite and analcime, with abundant ocelli filled with analcime/carbonate. In terms of geochemical compositions they are characterized by LILE and LREE enrichment and lack of Nb-Ta and Eu anomalies. The 87Sr/86Sr and 143Nd/144Nd initial ratios range between 0.70377 to 0.70781 and 0.512506 and 0.512716 respectively, and TDM model ages vary between 0.25–0.64 Ga. A K-Ar age of 163?±?9 Ma suggests that these rocks are related to the pre-rifting stage of the Mesozoic-Cenozoic continental Salta Rift in NW Argentina. Partial melting of a heterogeneous enriched metasomatized lithospheric mantle, magma mixing and fractionation are envisaged to explain the petrographic, geochemical and isotope characteristics of these magmas. 相似文献
673.
Jürgen Titschack Daniel Baum Ricardo De Pol‐Holz Matthias López Correa Nina Forster Sascha Flögel Dierk Hebbeln André Freiwald 《Sedimentology》2015,62(7):1873-1898
Cold‐water coral ecosystems present common carbonate factories along the Atlantic continental margins, where they can form large reef structures. There is increasing knowledge on their ecology, molecular genetics, environmental controls and threats available. However, information on their carbo‐nate production and accumulation is still very limited, even though this information is essential for their evaluation as carbonate sinks. The aim of this study is to provide high‐resolution reef aggradation and carbonate accumulation rates for Norwegian cold‐water coral reefs from various settings (sunds, inner shelf and shelf margin). Furthermore, it introduces a new approach for the evaluation of the cold‐water coral preservation within cold‐water coral deposits by computed tomography analysis. This approach allows the differentiation of various kinds of cold‐water coral deposits by their macrofossil clast size and orientation signature. The obtained results suggest that preservation of cold‐water coral frameworks in living position is favoured by high reef aggradation rates, while preservation of coral rubble prevails by moderate aggradation rates. A high degree of macrofossil fragmentation indicates condensed intervals or unconformities. The observed aggradation rates with up to 1500 cm kyr?1 exhibit the highest rates from cold‐water coral reefs so far. Reef aggradation within the studied cores was restricted to the Early and Late Holocene. Available datings of Norwegian cold‐water corals support this age pattern for other fjords while, on the shelf, cold‐water coral ages are reported additionally from the early Middle Holocene. The obtained mean carbonate accumulation rates of up to 103 g cm?2 kyr?1 exceed previous estimates of cold‐water coral reefs by a factor of two to three and by almost one order of magnitude to adjacent sedimentary environments (shelf, slope and deep sea). Only fjord basins locally exhibit carbonate accumulation rates in the range of the cold‐water coral reefs. Furthermore, cold‐water coral reef carbonate accumulation rates are in the range of tropical reef carbonate accumulation rates. These results clearly suggest the importance of cold‐water coral reefs as local, maybe regional to global, carbonate sinks. 相似文献
674.
F. A. Temporim Ricardo Ivan Ferreirae da Trindade Marcos Egydio-Silva Tiago Valim Angelo Eric Tohver Caroline Cibele Soares Lucas Pequeno Gouvêa Julio Cesar Mendes Silvia Regina Medeiros Antônio Carlos Pedrosa-Soares Gabriel Gomes Silva 《地学学报》2023,35(1):23-31
Featuring 3 000-km-long large and hot orogen, the Mantiqueira Province provides a rare opportunity to study the process of gravitational collapse at mid to deep crustal levels. Distinct but contemporary (~500 Ma) post-collisional intrusions show structures and anisotropy of magnetic susceptibility (AMS) fabrics related to their emplacements, recording different flow patterns. In southern deep-seated intrusions, ellipsoidal-shaped roots with gabbroic-to-hybrid cores surrounded by granitic rocks show concentric patterns of AMS fabrics that cut across the NE-trending regional foliation. In contrast, northern intrusions, exposed as the upper sections of batholith-size bodies of coarse-grained granite emplaced at the shallow to mid-crust, show general NS-trending magnetic fabrics roughly parallel to strike of the orogen and the regional foliation of host rocks. These contrasting magnetic patterns from shallow to deeper crust suggest vertical magma migration from the overthickened orogenic core to be emplaced across its thinner stretched flanks during the gravitational collapse of the orogenic edifice. 相似文献