caa a22 4500 475825942 CHVBK 20180406123828.0 cr unu---uuuuu 170329e20000101xx s 000 0 eng 10.1007/PL00008912 doi (NATIONALLICENCE)springer-10.1007/PL00008912 The 1996 and 1998 subglacial eruptions beneath the Vatnajökull ice sheet in Iceland: contrasting geochemical and geophysical inferences on magma migration [Elektronische Daten] [O. Sigmarsson, H. R. Karlsson, G. Larsen] 87: Sr/86Sr (0.70322) and δ 18O ( ∼2.9‰), whereas significantly lower and higher values, respectively, are found in samples from the Bárdarbunga volcanic system (0.70307 and 3.8‰). These results strongly indicate that the Gjálp magma originated from the Grímsvötn magma system. The 1996 magma is of an intermediate composition, representing a basaltic icelandite formed by 50% fractional crystallization of a tholeiite magma similar in composition to that expelled by the 1998 Grímsvötn eruption. The differentiation that produced the Gjálp magma may have taken place in a subsidiary magma chamber that last erupted in 1938 and would be located directly beneath the 1996 eruption site. This chamber was ruptured when a tectonic fracture propagated southward from Bárdarbunga central volcano, as indicated by the seismicity that preceded the eruption. Our geochemical results are therefore not in agreement with lateral magma migration feeding the 1996 Gjálp eruption. Moreover, the results clearly demonstrate that isotope ratios are excellent tracers for deciphering pathways of magma migration and permit a clear delineation of the volcanic systems beneath Vatnajökull ice sheet. Springer-Verlag Berlin Heidelberg, 2000 Bárdarbunga nationallicence Grímsvötn nationallicence Gjálp nationallicence Magma migration nationallicence Lateral intrusion nationallicence Sigmarsson O. CNRS, Université Blaise Pascal, 5 rue Kessler, F-63038 Clermont-Ferrand, France e-mail: olgeir@opgc.univ-bpclermont.fr, FR aut Karlsson H. R. Department of Geosciences and Department of Chemistry and Biochemistry, Texas Tech University, Box 41053, Lubbock, TX 79409, USA, US aut Larsen G. Science Institute, University of Iceland, 101 Reykjavik, Iceland, IS aut https://doi.org/10.1007/PL00008912 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/PL00008912 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sigmarsson O. CNRS, Université Blaise Pascal, 5 rue Kessler, F-63038 Clermont-Ferrand, France e-mail: olgeir@opgc.univ-bpclermont.fr, FR aut NATIONALLICENCE 700 1- Karlsson H. R. Department of Geosciences and Department of Chemistry and Biochemistry, Texas Tech University, Box 41053, Lubbock, TX 79409, USA, US aut NATIONALLICENCE 700 1- Larsen G. Science Institute, University of Iceland, 101 Reykjavik, Iceland, IS aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer