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| PIMENTEL,MÁRCIO M.; BOTELHO,NILSON F.. |
| Supracrustal rocks of the Araí Group, together with coeval A-type granites represent a ca. 1.77-1.58 Ga old continental rift in Brazil. Two granite families are identified: the older (1.77 Ga) group forms small undeformed plutons, and the younger granites (ca. 1.58 Ga) constitute larger, deformed plutons. Sr-Nd isotopic data for these rocks indicate that the magmatism is mostly product of re-melting of Paleoproterozoic sialic crust. Initial Sr ratios for both granite families are ca 0.726 and 0.720. Most TDM model ages are between 2.58 and 1.80 Ga. epsilonND(T) values are between +3.6 and -11.9. Araí volcanics are bimodal, with basalts and dacites/rhyolites interlayered with continental sediments. The felsic volcanics show Nd isotopic characteristics which... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Sr-Nd isotopes; Paleoproterozoic; Tin granites; Transamazonian. |
| Ano: 2001 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652001000200010 |
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| Awasthi, Neeraj; Ray, Jyotiranjan S. |
| Terrestrial and marine sediments preserved on the Indian sub-continent and in seas/oceans around it are excellent archives for studying and reconstructing past variations in monsoonal climate. Based on the multiproxy studies on the sediment cores, a coherent relationship between the intensities of the monsoon and glacial–interglacial conditions and a strong atmospheric teleconnection between the Asian and North Atlantic climates has been suggested. Terrestrial sediment cores clearly established that the variations in the monsoonal climate and/or change in glacial extant played an important role in varying weathering/erosion in source regions and relative supply of sediments. Marine sediment studies presented a more complicated picture because their... |
| Tipo: Text |
Palavras-chave: Climate; Himalaya; Indian monsoon; Sediment cores; Sr-Nd isotopes; Weathering-erosion. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75467/76290.pdf |
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| Meyer, Inka; Davies, Gareth R.; Stuut, Jan-berend W.. |
| Five sediment cores from offshore NW Africa were analyzed for strontium and neodymium isotope ratios to reconstruct temporal variations in continental weathering regimes. Sediments were taken from three time slices with well-known and distinctive environmental conditions: present-day (dry and warm), similar to 6 ka (wet and warm), and similar to 12 ka (dry and cold). Terrigenous sediment samples were split into two size fractions to distinguish between the two dominant transport mechanisms offshore NW Africa: fluvial (0-10 mu m) and aeolian (10-40 mu m). Sr isotope data record evidence of marked grain size control with higher isotopic ratios in the fine fraction. In contrast, epsilon(Nd) values are largely unaffected by grain size. Minor variability in Nd... |
| Tipo: Text |
Palavras-chave: Holocene; Sr-Nd isotopes; Provenance; Grain size effect. |
| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00227/33870/32263.pdf |
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