Rare Earth Geochemistry of Iceland Basalts: Spatial and Temporal Variations
11
Citation
50
Reference
10
Related Paper
Citation Trend
Keywords:
Mantle plume
Rift zone
Newly available, 2D Bouguer gravity anomaly data from the Baikal Rift zone, Siberia, indicate that this discrete, intracontinental rift system is regionally compensated by an elastic plate ∼50 km thick. However, spectral and spatial domain analyses and isostatic anomaly calculations show that simple elastic plate theory does not offer an adequate explanation for compensation in the rift zone, probably because of significant lateral variations in plate strength and the presence of subsurface loads. Our results and other geophysical observations support the interpretation that the Baikal Rift zone is colder than either the East African or Rio Grande rift.
Rift zone
Anomaly (physics)
Cite
Citations (36)
Rift zone
Rift valley
Cite
Citations (26)
Rift zone
Shield volcano
East African Rift
Rift valley
Cite
Citations (129)
Abstract Previous seismological results and geodynamic modeling showed that mantle plumes have thin tails. However, the latest geophysical observations reveal the presence of broad and bifurcate plumes in the lower and upper mantle, providing a new challenge to further understand the evolution of plume morphology. Here, developing 3‐D numerical models, we demonstrate that a plume shaped like a tree, derived from the mantle transition zone, branches up to surface volcanoes due to the combined influence of weak layers in the asthenosphere and the mantle transition zone. Clusters of mantle plumes likely explain the simultaneous occurrence of multiple subparallel hot spot tracks in the Pacific and Atlantic Oceans. Meanwhile, the mantle plume wandering at a rate of ~1.5 cm/year in the upper mantle without a strong mantle wind provides a new mechanism for hot spot motions. Thus, our model represents a significant advance for linking plume studies in seismology, geochemistry, and plate reconstruction.
Mantle plume
Hotspot (geology)
Asthenosphere
Cite
Citations (21)
Abstract Large volcanic edifices are often shaped by the coalescence of adjacent volcanoes as well as intrusive rift zones and gravitational spreading. To better understand the structure of such volcanoes we designed analogue experiments simulating gravitational spreading of an edifice made by overlapping cones of different age, and examined the formation of rift zones. The results allow distinction of two main rift geometries. (i) Spreading edifices of similar age that partly overlap, tend to develop a rift zone approximately perpendicular to the boundary of both volcanoes. Such a rift zone causes two volcanoes to grow together and form an elongated topographic ridge. (ii) Partly overlapping volcanoes of different age are spreading at different rates and thus form a rift zone parallel to the boundary of both volcanoes. Such a rift zone causes two volcanoes to structurally separate. The results are widely applicable for large volcanoes subject to rifting and flank spreading, which we demonstrate for Réunion Island and for southern Hawaii.
Rift zone
Rift valley
Shield volcano
Cite
Citations (39)
Mantle plume
Hotspot (geology)
Cite
Citations (0)
Abstract The Midcontinent Rift of North America is a ca. 1.1 Ga, 3000-km-long failed rift that nearly split the Precambrian continent of Laurentia. Unlike most continental rifts, which are filled with a mixture of volcanic rocks and sediments, the Midcontinent Rift contains a large volume of flood basalts that were emplaced during both syn- and post-rift stages. Consequently, the Midcontinent Rift, which comprises the Keweenaw large igneous province, is the most significant positive anomaly on gravity maps of central North America. We investigated the mantle conditions required to produce this large volume of flood basalt and the observed two main stages of emplacement. To explore whether these magma volumes required a plume or, instead, could have resulted from the increased ambient mantle temperatures expected for the Neoproterozoic, we used a geodynamic model for a range of ambient mantle and plume temperatures under different scenarios of lithospheric extension. The most favorable scenario for the generation of both syn-rift and post-rift lavas combines a plume with excess temperatures between 175 and 225 °C introduced during the syn-rift phase and ambient mantle potential temperatures between 1393 and 1443 °C, with an initial lithospheric thickness not exceeding 150 km for 3 mm/yr extension rates.
Flood basalt
Mantle plume
Rift zone
Shield volcano
Laurentia
Magma chamber
Cite
Citations (6)