Distribución de As en granitoides del centro-oeste de España y sus relaciones metalogenéticas (Sn, W)

[Resumen] La distribución de As en los granitos estudiados es lag-normal polimodal. La mayoría de las muestras analizadas presentan valores de As inferiores a lO ppm y sin relación clara con otros caracteres mineralógicos y/o geoquímicos mayoritarios. Algunas muestras con contenidos de hasta 200 ppm corresponden a granitos con algún grado de alteración deutérica, o a muestras cercanas a filones de cuarzo mineralizados (W, As.). Esto puede utilizarse en prospección litogeoquímica a nivel táctico. Los contenidos de As en apófisis graníticas mineralizadas son muy variables, con anomalía positiva muy clara en solo dos de ellas[Abstract] The distribution of As in the studied granites is lognormal polymodal. The main group of analized samples contains values of As lower than lO ppm, and there are not relation with other mayor mineralogical and geochemical characteristics. Sorne samples with As contents up to 200 ppm correspond with granites with deuteric alteration or as well with sam¿12s near from mineralized quartz veins (W, As). This knowledge can be useful in tactical litoge chemical prospection. The As contents in mineralized apogranites are widely varied, with positive anomaly in only two apogranite

Geoquímica del W en el área circundante al yacimiento de cheelita de Barruecopardo (Salamanca)

La microclinización, proceso ácido débil, implica una corrosión de plagioclasas y una transformación biotita-clorita, con paso del W de dicha biotita a la fase volátil, bajo forma compleja. El descenso de presión en las fisuras (filones) hace precipitar a los wolframatos. Este mecanismo explica el empobrecimiento en W en las inmediaciones del yacimiento, y justifica una explicación geoquímica y mineralógica expuesta precedentemente

Geoquímica del W en el área circundante al yacimiento de cheelita de Barruecopardo (Salamanca)

La microclinización, proceso ácido débil, implica una corrosión de plagioclasas y una transformación biotita-clorita, con paso del W de dicha biotita a la fase volátil, bajo forma compleja. El descenso de presión en las fisuras (filones) hace precipitar a los wolframatos. Este mecanismo explica el empobrecimiento en W en las inmediaciones del yacimiento, y justifica una explicación geoquímica y mineralógica expuesta precedentemente

Quantitative reconstruction of primary productivity in low latitudes during the last glacial maximum and the mid-to-late Holocene from a global Florisphaera profunda calibration dataset

[EN]Ocean net primary productivity (Npp) is a key component of the marine carbon cycle. Multi-model Npp projections based on a few decades of satellite data show large uncertainties, in particular at low latitudes (30°N−30°S). Calibration of sedimentary proxies with satellite-based Npp estimates allows for the quantitative reconstruction of this variable at longer time-scales. Relative abundance of deep-photic zone coccolithophore species Florisphaera profunda in the fossil record can potentially be used as a quantitative proxy for Npp. However, the robustness of this proxy calibration has been tested in very specific oceanographic settings using surface sediment samples. Here, we use a global dataset of surface sediment (n = 1258) and sediment trap (n = 26) samples with relative abundance data of F. profunda (%) to test the robustness of this proxy as a quantitative indicator of Npp. We study the modern and paleo-ecology of this species and the main factors affecting its latitudinal distribution. Results show that F. profunda % is a strong indicator of Npp at latitudes between 30°N and 30°S, while at higher latitudes temperature-related variables are more important. We develop a global calibration model between satellite Npp estimates and F. profunda for the latitudinal range between 30°N and 30°S, and we apply it to several low-latitude sediment cores with available F. profunda counts covering the Late Glacial Maximum (LGM; 24–19 ka) and the Mid-to-Late Holocene period (MLH; <6 ka). Reconstructed Npp during the LGM is 15% higher than during the MLHdue to the intensification of trade winds that enhanced oceanic upwelling at low latitudes

Strong glacial-interglacial variability in upper ocean hydrodynamics, biogeochemistry, and productivity in the southern Indian Ocean

This work used samples and data provided by the IODP. We are thankful for the support from the crew of the R/V JOIDES Resolution and IODP staff. This work is funded through the Universidad de Salamanca Postdoctoral Contract supported by the Ministerio de Ciencia, Innovacion y Universidades Grant RTI2018-099489-B-I00 and the German Science Foundation (DFG) Research Center/Cluster of Excellence 'The Ocean in the Earth System' (MARUM; Grant No. 49926684). We acknowledge financial support from the National Science Foundation of the US under Award No. 1737218 (M.A.B), the European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska Curie Grant Agreement No. 799531 (M.S.P.), and the Spanish Ministry of Science and Innovation Grant CTM2017-89711-C2-1-P, co-funded by the European Union through FEDER funds (F.J.J.E.).In the southern Indian Ocean, the position of the subtropical front – the boundary between colder, fresher waters to the south and warmer, saltier waters to the north – has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the subtropical front and use alkenones and coccolith assemblages to reconstruct oceanographic conditions over the past 300,000 years. We identify a strong glacial-interglacial variability in sea surface temperature and productivity associated with subtropical front migration over the Agulhas Plateau, as well as shorter-term high frequency variability aligned with variations in high latitude insolation. Alkenone and coccolith abundances, in combination with diatom and organic carbon records indicate high glacial export productivity. We conclude that the biological pump was more efficient and strengthened during glacial periods, which could partly account for the reported reduction in atmospheric carbon dioxide concentrations.Universidad de Salamanca - Ministerio de Ciencia, Innovacion y Universidades Grant RTI2018-099489-B-I00German Research Foundation (DFG) 49926684National Science Foundation (NSF) 1737218European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska Curie Grant 799531Spanish Government CTM2017-89711-C2-1-PEuropean Union through FEDER fund

Temperature Modulates Coccolithophorid Sensitivity of Growth, Photosynthesis and Calcification to Increasing Seawater pCO2

Increasing atmospheric CO2 concentrations are expected to impact pelagic ecosystem functioning in the near future by driving ocean warming and acidification. While numerous studies have investigated impacts of rising temperature and seawater acidification on planktonic organisms separately, little is presently known on their combined effects. To test for possible synergistic effects we exposed two coccolithophore species, Emiliania huxleyi and Gephyrocapsa oceanica, to a CO2 gradient ranging from ,0.5–250 mmol kg21 (i.e. ,20–6000 matm pCO2) at three different temperatures (i.e. 10, 15, 20uC for E. huxleyi and 15, 20, 25uC for G. oceanica). Both species showed CO2-dependent optimum-curve responses for growth, photosynthesis and calcification rates at all temperatures. Increased temperature generally enhanced growth and production rates and modified sensitivities of metabolic processes to increasing CO2. CO2 optimum concentrations for growth, calcification, and organic carbon fixation rates were only marginally influenced from low to intermediate temperatures. However, there was a clear optimum shift towards higher CO2 concentrations from intermediate to high temperatures in both species. Our results demonstrate that the CO2 concentration where optimum growth, calcification and carbon fixation rates occur is modulated by temperature. Thus, the response of a coccolithophore strain to ocean acidification at a given temperature can be negative, neutral or positive depending on that strain’s temperature optimum. This emphasizes that the cellular responses of coccolithophores to ocean acidification can only be judged accurately when interpreted in the proper eco-physiological context of a given strain or species. Addressing the synergistic effects of changing carbonate chemistry and temperature is an essential step when assessing the success of coccolithophores in the future ocean

Coccolithophores as proxy of seawater changes at orbital-to-millennial scale during middle Pleistocene Marine Isotope Stages 14-9 in North Atlantic core MD01-2446

midlatitude North Atlantic, to reconstruct climatically induced sea surface water conditions throughout Marine Isotope Stages (MIS) 14–9. The data are compared to new and available paleoenvironmental proxies from the same site as well as other nearby North Atlantic records that support the coccolithophore signature at glacial‐interglacial to millennial climate scale. Total coccolithophore absolute abundance increases during interglacials but abruptly drops during the colder glacial phases and deglaciations. Coccolithophore warm water taxa (wwt) indicate that MIS11c and MIS9e experienced warmer and more stable conditions throughout the whole photic zone compared to MIS13. MIS11 was a long‐lasting warmer and stable interglacial characterized by a climate optimum during MIS11c when a more prominent influence of the subtropical front at the site is inferred. The wwt pattern also suggests distinct interstadial and stadial events lasting about 4–10 kyr. The glacial increases of Gephyrocapsa margereli‐G. muellerae 3–4 µm along with higher values of Corg, additionally supported by the total alkenone abundance at Site U1313, indicate more productive surface waters, likely reflecting the migration of the polar front into the midlatitude North Atlantic. Distinctive peaks of G. margereli‐muellerae (>4 µm), C. pelagicus pelagicus , Neogloboquadrina pachyderma left coiling, and reworked nannofossils, combined with minima in total nannofossil accumulation rate, are tracers of Heinrich‐type events during MIS12 and MIS10. Additional Heinrich‐type events are suggested during MIS12 and MIS14 based on biotic proxies, and we discuss possible iceberg sources at these times. Our results improve the understanding of mid‐Brunhes paleoclimate and the impact on phytoplankton diversity in the midlatitude North Atlantic region.Provided by PTCRIS: 58282, C2007-FCT/319/2006info:eu-repo/semantics/publishedVersio

Reconstrucción de las características ambientales de las masas de agua superficiales del Pacífico y Atlántico del último ciclo climático mediante el desarrollo de una función de análogos con cocolitos

[EN] In this PhD thesis, we contribute to a more detailed knowledge of the biogeography of coccolithophores in one of the most productive marine ecosystem on earth: the Peru-Chile Current realm, which extends along the west coast of South America.[ES] En esta tesis se contribuye a un mayor conocimiento de la biogeografía de los Cocolitóforos en uno de los ecosistemas marinos más productivos de nuestro planeta: el sistema de corrientes de Perú- Chile, que se extiende a lo largo de la costa oeste de Suramérica