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Incompatible element
About: Incompatible element is a research topic. Over the lifetime, 2420 publications have been published within this topic receiving 154052 citations.
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TL;DR: The most frequent and voluminous eruptive products at Mount St. Helens are dacitic in composition, although a wide variety of magma types (basalt to rhyodacite) is represented as discussed by the authors.
Abstract: The most frequent and voluminous eruptive products at Mount St. Helens are dacitic in composition, although a wide variety of magma types (basalt to rhyodacite) is represented. To address the petrogenesis of the dacites, we present major and trace element analyses of samples of pumice clasts and dome or flow lavas erupted during the past ∼40,000 years. The dacites have similar (in some cases even lower) contents of many incompatible elements (e.g., Zr, Hf, REE, U, Be, Ta, Nb) compared with those in associated basalts and andesites, whereas Ba, Rb, K, Cs, and Sr are relatively enriched. The unusual depleted nature of the dacites and generally low bulk distribution coefficients (estimated from glass/whole-rock pairs) for numerous trace elements preclude an origin of these magmas principally by crystal fractionation of associated mafic magmas. A more plausible model for their origin involves melting of metabasaltic crustal rocks that have been enriched in Ba, Rb, Cs, and Sr by either intercalation of sediments with depleted basalt or selective metasomatic enrichment of the source region. Melting at crustal levels presumably is related to intrusion of mantle-derived basaltic magmas. Compositional diversity among the erupted dacites can be attributed to spatial or temporal heterogeneity of the magma sources or, in some specific cases, to such processes as crystal fractionation, assimilation, and magma mixing.
142 citations
TL;DR: The deformed peridotites experienced a complex evolution, i.e., they were formed initially as high-degree melt extraction residues and later were subjected to three main stages of metasomatic modification as discussed by the authors.
142 citations
TL;DR: In this article, the authors presented results from four of these sites, 1136, 1138, 1141 and 1142, showing that basalt from these two sites have ocean-island-like incompatible element ratios and age-corrected isotopic characteristics similar (but not identical) to those proposed for the post-30 Ma Kerguelen plume.
Abstract: Ocean Drilling Program (ODP) Leg 183 was designed to investigate the origin and evolution of the large igneous province composed of the Kerguelen Plateau and Broken Ridge. Of the eight sites drilled, basalt was recovered from seven, five on the plateau and two on Broken Ridge. We present results from four of these sites, 1136, 1138, 1141 and 1142. Although this large igneous province is interpreted as being derived from the Kerguelen mantle plume, the geochemical characteristics of basalt from some parts of the province indicate a role for continental lithosphere. The 118–119 Ma basalt flows recovered in the Southern Kerguelen Plateau (Site 1136) have a more subtle continental signature than shown by basalt at Leg 119 Site 738. A continental signature is absent in the 100–101 Ma tholeiitic basalts at Site 1138 in the Central Kerguelen Plateau (CKP); their age-corrected Nd–Sr–Pb isotopic values and incompatible element ratios are similar to those estimated for primitive mantle. These flows may represent a major mantle source in the Kerguelen starting-plume head. The 20 basalt units identified are a product of magma chamber replenishment, fractional crystallization, and resorption of crystallizing phases. The topmost unit, Unit 1, is a dacite that evolved from a basalt magma similar to those represented by Units 3–22; unlike the basalts the dacite magma was probably influenced by continental material. Middle Cretaceous (∼95 Ma) lavas of Sites 1141 and 1142 on Broken Ridge (originally part of the CKP) are alkalic, with one exception (a tholeiite at the base of Site 1142). The alkalic lavas may represent a late-stage cap or carapace of relatively low-degree partial melts that overlies a thick tholeiitic lava pile. The tholeiite and pebbles from the top of a probable talus deposit (Unit 2) at Site 1142 have geochemical signatures consistent with a minor contribution from continental material. This signature is absent in the other units from these two sites, which have ocean-island-like incompatible element ratios and age-corrected isotopic characteristics similar (but not identical) to those proposed for the post-30 Ma Kerguelen plume. These alkalic basalts may be the purest representatives of the Cretaceous plume tail composition yet found.
142 citations
TL;DR: In this paper, the partitioning of an extensive suite of trace elements between garnet, clinopyroxene, and hydrous tonalitic melts has been studied experimentally at 1.8 GPa and 1000-1040 C. The partition coefficients (D's) are independent of the trace element concentration over the concentration ranges used.
142 citations
TL;DR: In this article, a detailed study of a peridotite from the Ronda massif, Spain, and five xenoliths from the East African Rift, Ethiopia has revealed that this layer is dominantly composed of titanium oxides and phlogopite, hardly detectable by optical methods.
142 citations