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Partial melting
About: Partial melting is a research topic. Over the lifetime, 8934 publications have been published within this topic receiving 435919 citations.
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TL;DR: In this article, the compositions of melts formed by partial melting of two relatively fertile spinel lherzolites were determined at pressures between 10 and 30 kbar under dry conditions using a layer of diamond aggregates sandwiched between peridotite layers.
880 citations
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TL;DR: A comparative study of Archean and post-Archengitic granitic rocks shows significant changes with time as mentioned in this paper, which is a direct consequence of the cooling of Earth, and the high rare-earth element fractionation and the low Yb content of the Archean granitoids indicate the major role of garnet and hornblende, whereas these two minerals do not play a prominent part in the genesis of modern granitic rock.
Abstract: The comparative study of Archean and post-Archean granitic rocks shows significant changes with time. The high rare-earth element fractionation and the low Yb content of the Archean granitoids indicate the major role of garnet and hornblende, whereas these two minerals do not play a prominent part in the genesis of modern granitic rocks. This difference is a direct consequence of the cooling of Earth. In Archean time the subducted oceanic crust was young and warm, so it reached the conditions of melting before dehydration had occurred, leaving a garnet- and hornblende-bearing residue. In contrast, the modern subducted oceanic slab is generally old and cold, so it is dehydrated before it reaches the melting conditions of hydrous tholeiite; therefore, in the absence of a hydrous phase, it cannot melt at shallow depth. The fluids produced by dehydration reactions of modern crust rehydrate the overlying mantle wedge, which, in consequence, can undergo partial melting and give rise to calc-alkaline magmas; in this case, olivine and pyroxene are the most important residual phases. The location of calc-alkaline magma genesis in subduction-zone environments has migrated over time from the subducted Archean oceanic crust to the mantle wedge, a migration attributed to the progressive cooling of Earth.
870 citations
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TL;DR: In this article, the authors classified ultramafic inclusions from San Carlos, Arizona into two groups: Group I inclusions are dominated by magnesian (Mg/Mg + ΣFe= 0.86-0.91), olivine-rich peridotites containing Cr-rich clinopyroxene and spinel.
863 citations
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TL;DR: The low niobium/tantalum ratio seen in subduction-zone igneous rocks of all ages is evidence that the melting of rutile-eclogite has never been a volumetrically important process.
Abstract: It is thought that the first continental crust formed by melting of either eclogite or amphibolite, either at subduction zones or on the underside of thick oceanic crust. However, the observed compositions of early crustal rocks and experimental studies have been unable to distinguish between these possibilities. Here we show a clear contrast in trace-element ratios of melts derived from amphibolites and those from eclogites. Partial melting of low-magnesium amphibolite can explain the low niobium/tantalum and high zirconium/samarium ratios in melts, as required for the early continental crust, whereas the melting of eclogite cannot. This indicates that the earliest continental crust formed by melting of amphibolites in subduction-zone environments and not by the melting of eclogite or magnesium-rich amphibolites in the lower part of thick oceanic crust. Moreover, the low niobium/tantalum ratio seen in subduction-zone igneous rocks of all ages is evidence that the melting of rutile-eclogite has never been a volumetrically important process.
862 citations
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TL;DR: In this article, the authors consider that continental collision is followed by crustal thickening, to accommodate further plate convergence, with ensuing partial melting of the lower crust, resulting in a dry refractory lower crust consisting of pyroxene granulites and anor-thosites.
Abstract: Extensive terranes of basement reactivation are interpreted as resulting from crustal thickening following continental collision. It is suggested that terranes, such as the Grenville Province and much of the Variscan orogenic belt in Europe, have their modern analog in the Tibetan Plateau. The Tibetan Plateau is underlain by a continental crust between 60 and 80 km thick and is characterized by extensive high-potash Neogene vulcanism. Following T. H. Green's arguments that partial melting of a dioritic lower crust may yield potassic granitic liquids and refractory anorthositic residues, we consider that continental collision is followed by crustal thickening, to accommodate further plate convergence, with ensuing partial melting of the lower crust. At high structural levels, silicic-potassic ignimbrites are extruded in intermontane basin-horst terranes, with subjacent granite plutons. At deeper levels, a dry refractory lower crust consisting of pyroxene granulites and anor-thosites is generated.
848 citations