References of "Geology"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailMagma chamber-scale liquid immiscibility in the siberian traps represented by melt pools in native iron
Kamenetsky, V. S.; Charlier, Bernard ULg; Zhitova, L. et al

in Geology (2013), 41(10), 1091-1094

Magma unmixing (i.e., separation of a homogeneous silicate melt into two or more liquids) is responsible for sudden changes in the evolution of common melts, element fractionation, and potential formation ... [more ▼]

Magma unmixing (i.e., separation of a homogeneous silicate melt into two or more liquids) is responsible for sudden changes in the evolution of common melts, element fractionation, and potential formation of orthomagmatic ore deposits. Although immiscible phases are a common phenomenon in the mesostasis of many tholeiitic basalts, evidence of unmixing in intrusive rocks is more difficult to record because of the transient nature of immiscibility during decompression, cooling, and crystallization. In this paper, we document a clear case of liquid immiscibility in an intrusive body of tholeiitic gabbro in the Siberian large igneous province, using textures and compositions of millimeter-sized silicate melt pools in native iron. The native iron crystallized from a metallic iron liquid, which originated as disseminated globules during reduction of the basaltic magma upon interaction with coal-bearing sedimentary rocks in the Siberian craton. The silicate melts entrapped and armored by the native iron are composed of two types of globules that represent the aluminosilicate (60-77 wt% SiO2) and silica-poor, Fe-Ti-Ca-P-rich (in wt%: SiO2, 15-46; FeO, 15-22; TiO2, 2-7; CaO, 11-27; P2O5, 5-30) conjugate liquids. Different proportions and the correlated compositions of these globules in individual melt pools suggest a continuously evolving environment of magmatic immiscibility during magma cooling. These natural immiscible melts correspond extremely well to the conjugate liquids experimentally produced in common basaltic compositions at <1025 °C. Our results show that immiscibility can occur at large scale in magma chambers and can be instrumental in generating felsic magmas and Fe-Ti-Ca-P-rich melts in the continental igneous provinces. © 2013 Geological Society of America. [less ▲]

Detailed reference viewed: 8 (0 ULg)
Full Text
Peer Reviewed
See detailVolcano- and climate-driven changes in atmospheric dust sources and fluxes since the Late Glacial in Central Europe
Le Roux, Gael; Fagel, Nathalie ULg; De Vleeschouwer, François et al

in Geology (2012)

Atmospheric dusts are an important part of the global climate system, and play an important role in the marine and terrestrial bio- geochemical cycles of major and trace nutrient elements. A peat bog ... [more ▼]

Atmospheric dusts are an important part of the global climate system, and play an important role in the marine and terrestrial bio- geochemical cycles of major and trace nutrient elements. A peat bog record of atmospheric deposition shows considerable variation in dust deposition during the past 15 k.y., with abrupt changes in fl uxes at 12, 9.2, 8.4, 7.2, and 6 cal. kyr B.P. Using Nd isotopes and rare earth ele- ments, it is possible to clearly distinguish between volcanic inputs and those driven by climate change, such as the long-term aridifi cation of the Sahara and regional erosion due to forest clearing and soil cultiva- tion activities. Our results indicate that a major dust event in North Africa and Europe preceded the 8.2 kyr B.P. cold event by 200 yr. This dust event may have played an active role in the following climate cooling of the 8.2 kyr B.P. event. Nd isotope evidence also indicates a relatively slow change in dust regime over Europe from 7 to 5 kyr B.P. due to Sahara expansion. These fi ndings show that the inorganic frac- tion in high-resolution peat records can provide remarkably sensitive indicators of dust load and sources. Our study supports the priority to better identify the impact of dust loading during the Holocene in terms of direct and indirect impacts on environmental and climate changes. [less ▲]

Detailed reference viewed: 39 (7 ULg)
Full Text
Peer Reviewed
See detailGrowth of subtropical forests in Miocene Europe: The roles of carbon dioxide and Antarctic ice volume
Hamon, N.; Sepulchre, P.; Donnadieu, Y. et al

in Geology (2012), 40

The middle Miocene is a crucial period for the evolution of apes, and it corresponds to their <br />appearance in Europe. The dispersion of apes was made possible by tectonic changes and the <br ... [more ▼]

The middle Miocene is a crucial period for the evolution of apes, and it corresponds to their <br />appearance in Europe. The dispersion of apes was made possible by tectonic changes and the <br />expansion of their habitat, (sub-) tropical forest, in Europe. The context in which the middle <br />Miocene climatic optimum occurred still lacks constraints in terms of atmospheric pCO2 and <br />ice-sheet volume and extent. Using a coupled atmosphere-ocean general circulation model <br />(GCM) and dynamic vegetation model, we investigated the sensitivity of Miocene climate and <br />vegetation to pCO2 levels and Antarctic ice-sheet confi gurations. Our results indicate that <br />higher than present pCO2 is necessary to simulate subtropical forest in Western and Central <br />Europe during the middle Miocene, but that a threshold at high pCO2 makes subtropical <br />forest partly collapse. Moreover, removing ice over Antarctica modifi es oceanic circulation <br />and induces warmer and slightly wetter conditions in Europe, which are consistent with the <br />expansion of subtropical forest. These results suggest that a small East Antarctic Ice Sheet <br />(25% of present-day ice volume) together with higher than present pCO2 values are in better <br />agreement with available European middle Miocene data. [less ▲]

Detailed reference viewed: 73 (11 ULg)
Full Text
Peer Reviewed
See detailFirst paleoseismological constraints on the strongest earthquake in France (Provence) in the twentieth century
Chardon, D.; Hermitte, D.; Nguyen, Frédéric ULg et al

in Geology (2005)

Detailed reference viewed: 31 (6 ULg)
Full Text
Peer Reviewed
See detailQuest for palladium: Application of the Groves hypothesis to Precambrian terranes of northeast North America
Gauthier, Michel; Gardoll, S.; Duchesne, Jean-Clair ULg

in Geology (2004), 32(7), 593-596

A compilation of all types of magmatic deposits in Precambrian terranes of northeast North America revealed a continental-scale metallic zonation. Nickel is homogeneously distributed. Palladium and ... [more ▼]

A compilation of all types of magmatic deposits in Precambrian terranes of northeast North America revealed a continental-scale metallic zonation. Nickel is homogeneously distributed. Palladium and chromite are centered on the Archean craton, as predicted by the Groves hypothesis, whereas low-Ti Cu-U-rare earth element iron oxide deposits occur just south and east of the Archean and Paleoproterozoic margin, within the Grenville province. Ti is concentrated along this margin in association with anorthosite. Nickel is still abundant there, but palladium and chromite are remarkably absent. This Grenvillian Ni-Pd-Cr paradox suggests that the fractionation process invoked in the classical plume model is inadequate to explain the geochemical characteristics of the anorthosite parental magmas. The crustal-tongue melting model seems to better explain the metallic zonation observed at the margin of the Archean and Proterozoic terranes. [less ▲]

Detailed reference viewed: 28 (1 ULg)
Full Text
Peer Reviewed
See detailWestward propagation of the North Anatolian fault into the northern Aegean: Timing and kinematics
Armijo, R.; Meyer, B.; Hubert, Aurelia ULg et al

in Geology (1999), 27

We present new evidence for the propagation processes of the North Anatolian fault. Fold- ing in the Dardanelles Straits region allows us to document the timing of the deformation pre- ceding, and the ... [more ▼]

We present new evidence for the propagation processes of the North Anatolian fault. Fold- ing in the Dardanelles Straits region allows us to document the timing of the deformation pre- ceding, and the finite displacement after, the passage of the propagating tip of the fault. The accuracy of the observations is due to interplay between deformation and the sea-level changes in the Mediterranean (the well-known Messinian regression followed by the Pliocene transgres- sion). The long-term kinematics around the Sea of Marmara pull-apart (total displacement of about 85 km over the past 5 m.y.) is similar to the present-day kinematics deduced from space geodesy. At a larger scale, westward propagation of the North Anatolian fault over nearly 2000 km in the past 10 m.y. appears to be associated with strain recovery, suggesting that the continental lithosphere retains long-term elasticity. [less ▲]

Detailed reference viewed: 19 (0 ULg)