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Wyszukujesz frazę "deep-sea" wg kryterium: Temat


Wyświetlanie 1-3 z 3
Tytuł:
Geochemistry of surface sediments from the northwestern Gulf of Mexico : implications for provenance and heavy metal contamination
Autorzy:
Armstrong-Altrin, John S.
Botello, Alfonso V.
Villanueva, Susana F.
Soto, Luis A.
Powiązania:
https://bibliotekanauki.pl/articles/2058576.pdf
Data publikacji:
2019
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Tamaulipas
deep-sea sediments
enrichment factor
contamination
principle component analysis
Opis:
Thirty-five near-surface sediment samples were recovered from the continental shelf and upper slope regions of the north-western (NW) Gulf of Mexico. The geochemical data of the sediments recovered were examined to investigate the weathering intensity, provenance, palaeo-oxygenation condition, and level of heavy metal contamination. The sediments analysed showed a moderate to high intensity of chemical weathering. Major and trace element concentrations indicated a terrigenous origin, closely related to the weathering of rocks rich in aluminosilicates. The results of this study further revealed that major rivers, the Bravo and Soto La Marina, played an important role in delivering sediments to the study area. The concentration of transition trace elements such as Cr, Cu, Ni, and V revealed that the sediments were derived from intermediate rocks such as andesite. The V/Cr, Ni/Co, and Cu/Zn ratios in the sediments were <2, <5, and <1, respectively, suggesting a depositional process occurred under well-oxygenated conditions. Principle Component Analysis (PCA) did not show a significant difference in sediment texture between the continental shelf and slope areas. The enrichment factor (EF) and Geo-accumulation index (lgeo) values were <2 and <1, respectively, suggesting the absence of an anthropogenic input.
Źródło:
Geological Quarterly; 2019, 63, 3; 522--538
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chemical and morphological characterization of polymetallic (Mn-Fe) nodules from the Clarion-Clipperton Zone in the Pacific Ocean
Autorzy:
Kozłowska-Roman, Agata
Mikulski, Stanisław
Powiązania:
https://bibliotekanauki.pl/articles/2058694.pdf
Data publikacji:
2021
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
polymetallic nodules
critical elements
rare earth elements
deep-sea mining
Clarion-Clipperton Fracture Zone
Pacific
Opis:
Geochemical studies (WD-XRF, ICP-MS, and GF-AAS) have shown that polymetallic nodules from the eastern Clarion-Clipperton Zone (CCZ) in the Pacific Ocean are enriched in several metals such as Cu (mean 1.16%), Ni (1.15%), Co (0.15%), and Zn (0.14%), as well as remarkable contents of Mo (0.059%), V (0.04%), Ce (0.019%), Nd (0.011%), Li (0.015), and Pt (43 ppb). The average content of REE, together with Y and Sc, is 620 ppm. In nodules from the CCZ metal concentrations are often much higher than those reported in nodules from other ocean basins in the world. The bulk-nodule mean value of the Mn/Fe ratio is 5.3, which is characteristic for a mixed (hydrogenetic and diagenetic) origin of the nodules. Microprobe investigation revealed two different chemical compositions of the layers, and ascertained their general metal content. The nodules analyzed are composed mainly of concentric-collomorphic laminae of Mn and Fe (oxy)hydroxides which crystallized around mineral nuclei (e.g., quartz, clay minerals), bioclasts or rock fragments. They are from 3.3 to 7.6 cm in diameter. The chemical and physical properties of the laminae allowed distinction of two genetic types: hydrogenetic and diagenetic. Those formed as a result of hydrogenesis had increased values of Co, Si, Cl and S, while formed diagenetically showed increased levels of Cu, Ni, Mg, Zn and K. These lamina types are characterized by different growth structures, reflectivity, density and Mn/Fe ratios. The ratio of the diagenetic layers to hydrogenetic layers (192/53) in representative polymetallic nodules shows that the nodules of this study are of mixed hydrogenetic-diagenetic type. A mixed genesis was also shown by discriminant diagrams, with these CCZ samples being located at the transition between typical hydrogenetic and diagenetic fields.
Źródło:
Geological Quarterly; 2021, 65, 4; 177--194
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Eco-biostratigraphic advances in late Quaternary geochronology and palaeoclimate : the marginal Gulf of Mexico analogue
Autorzy:
Antonarakou, Assimina
Kontakiotis, George
Karageorgis, Aristomenis P.
Besiou, Eva
Zarkogiannis, Stergios
Drinia, Hara
Mortyn, Graham P.
Tripsanas, Efthymis
Powiązania:
https://bibliotekanauki.pl/articles/2058605.pdf
Data publikacji:
2019
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
integrated stratigraphy
Late Glacial-Holocene transition
planktonic foraminiferal eco-bioevents
deep-sea sedimentary correlations
climate variability
palaeoceanography
Opis:
This study combines high-resolution planktonic foraminiferal eco-biostratigraphy and palaeoclimatic data from the high-sedimentation-rate core J PC-26 from the northwestern margin of the Gulf of Mexico (GoM). The eco-biozones recognized (GOMPFE1-12) being correlated with published Mg/Ca-based sea surface temperatures. This updated palaeoclimatic and stratigraphic reference record facilitates correlations with the Greenland ice core events and their climatic relationships, and also provides a solid stratigraphic framework for correlations with other palaeoclimatic and palaeoceanographic records in the circum-GOM/Caribbean region. This multidisciplinary approach underlines the utility of supporting conventional dating methodologies with different constraints, and further reveals a powerful tool for reliably correlating marine records between comparable deep-sea marginal settings and coeval sequences of this region.
Źródło:
Geological Quarterly; 2019, 63, 1; 178--191
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
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