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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 Cima D'Asta Complex (CDC) is a composite intrusive body of Permian age, outcropping in the eastern sector of the Southern Alps (Italy), close to the Valsugana Line.
10 citations
TL;DR: In this article, the authors report petrographic, geochemical and chronostratigraphic characteristics of Eocene calc-alkaline igneous activity in the Southern Alps, which was probably developed through a NE-SW oriented magmatic arc during Eocene and an E-W-oriented arc during Oligocene.
Abstract: In the Southern Alps (NE Italy), within the Giudicarie fault zone, Middle to Upper Eocene deep-water foredeep succession includes volcanic layers, pebbles from porphyric dykes and volcaniclastic sandstones, testifying the occurrence of Eocene volcanic activity from unknown volcanic centres. In this paper, we report petrographic, geochemical and chronostratigraphic characteristics.Both the volcanic layers and the pebbles share their petrographic and geochemical characteristics with calc-alkaline igneous activity of the nearby Eocene Adamello batholith, as well as with dykes from the Eastern Lombardian Alps and the Southern Alps basement, in the proximity of the Giudicarie fault zone. All of these rocks have incompatible element ratios typical of orogenic magmas (e.g., high Th/Yb and La/Nb, and low Ta/Yb, Nb/U) in contrast to that observed for the coeval anorogenic Veneto volcanic rocks. In addition, the studied Eocene calc-alkaline rocks also differ in part from the Oligocene calc-alkaline ones distributed along the E-W oriented Periadriatic fault system in terms of trace element distribution and incompatible element ratios. The Oligocene rocks are generally more enriched in incompatible elements than the Eocene ones and show higher Zr/Y but lower Nb/Y ratios. The set of data presented in this paper allows us to advance new insights on the evolution of Tertiary magmatism in the Alps, which was probably developed through a NE-SW-oriented magmatic arc during Eocene and an E-W-oriented magmatic arc during Oligocene. The two events are marked by different geochemical features of the magmatic products.
10 citations
TL;DR: In this paper, the authors presented geochemical, Sr, Nd and Pb isotopic data for the youngest back-arc tholeiitic and alkali basalts in the southern tip of Goto Islands along the Taiwan-Shinji Folded Belt in northwestern Kyushu, SW Japan.
10 citations
Journal Article•
TL;DR: In this article, the authors show that the Ongarbira volcanics of middle Proterozoic age occur with the Sahedba sedimentaries in the south of Singhbhum shear zone.
Abstract: The Ongarbira volcanics of middle Proterozoic age occur with the Sahedba sedimentaries in the south of Singhbhum shear zone. The volcanics are of tholeiitic composition with high content of MgO (> 8%) and high MgO/Al 2 O 3 , ratio (> 0.6). In terms of REE data these rocks show LREE depleted patterns which resemble those of basaltic rocks from Dalma volcanic belt and basaltic komatiite of Kolar schist belt. MORB- normalized incompatible element patterns of these rocks display distinct enrichment of LILE including Th and depletion of HFSE and marked trough at Nb and Ta. These features suggest a subduction zone component in the source of Ongarbira volcanics. Nb-normalized ratio spidergrams and incompatible element ratio plots Ce/Yb- Ta/Yb-, Th/Yb- Ta/Yb and Th- Hf- Ta are consistent with their eruption in a subduction related environment. REE modelling spggests that they were generated through 14 to 18 percent partial melting of a LREE depleted source. The source was probably selectively enriched in LILE by materials derived from the subducting slab. Geochemical-Geological evidences indicate that Ongarbira volcanics were probably erupted on a thin continental crust or even on oceanic crust as a result of a southward plate convergence below the Singhbhum craton.
10 citations
TL;DR: Spinel pyroxenites occur locally as clasts in polygenic breccias from the Late Cretaceous sedimentary melanges of the Northern Apennine (Italy) as discussed by the authors.
Abstract: Spinel pyroxenites occur locally as clasts in polygenic breccias from the Late Cretaceous sedimentary melanges of the Northern Apennine (Italy) They are of cumulus origin and formed in the deep crust by early precipitation of clinopyroxene and minor olivine and late crystallisation of orthopyroxene, spinel, Ti-pargasite and sulphides Pyroxenites underwent high-temperature (~850°C) subsolidus re-equilibration and ductile deformation with development of mylonitic bands made of clinopyroxene, orthopyroxene, Ti-pargasite and spinel U–Pb geochronology on zircons revealed the occurrence of inherited grains of Early Proterozoic to Late Devonian age The inherited zircons are locally rimmed by recrystallised zircon domains The oldest rims yield a mean concordia U–Pb age at 306 ± 8 Ma, which is considered to date the emplacement of the pyroxenites, in the framework of the post-Variscan lithospheric extension The incompatible element compositions of calculated melts in equilibrium with clinopyroxenes from the pyroxenites are characterised by Ba, Nb, LREE and Sr enrichment relative to N-MORB The depleted Nd isotopic signature of the pyroxenites (initial eNd values of +53 to +61) may be thus linked to primary magmas produced by low degrees of melting of asthenospheric mantle In addition, the pyroxenites locally record the infiltration of plagioclase-saturated hydrous melts, most likely evolved through fractional crystallisation and enriched in highly incompatible elements, within the clinopyroxene-dominated crystal mush A thermal event in Late Permian–Middle Triassic caused the partial resetting of zircon U–Pb system
10 citations