A lower crust origin of some flood basalts of the Emeishan large igneous province, SW China. (1st September 2015)

• Record Type: Journal Article
• Authors: Shellnutt, J. Gregory; Usuki, Tadashi; Kennedy, Allen K.; Chiu, Han-Yi
• Is Part Of: Journal of Asian earth sciences. Volume 109(2015)
• Page Start: 74
• Page End: 85
• Publication Date: 2015-09-01
• Subjects: Emeishan large igneous province -- Ultramafic rocks -- Late Permian -- Partial melting -- Lower crust -- Kangdian basalt; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2015.04.037
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: Neoproterozoic zircons are found within ELIP-related mafic and silicic intrusions. Partial melting of Neoproterozoic basalt can generate Emeishan flood basalts. Some Emeishan basalts may be the product of lower crustal recycling. Abstract: High seismic velocity layers within the lower crust (i.e. ∼40 km) of the Yangtze Block are interpreted as mafic underplated rocks derived from the Late Permian Emeishan mantle plume. However, the region experienced a previous magmatic event during the Neoproterozoic (∼800 Ma) that produced the Kangdian basalts and associated mafic intrusions and therefore the lower crust seismic velocity layers may represent a mixture of two different magmatic episodes. The identification of inherited Neoproterozoic (i.e. ∼750 to ∼850 Ma) zircons within Emeishan magmatic rocks indicates either assimilation of older material during emplacement or that the rocks could be derived from a mafic Neoproterozoic precursor. Equilibrium partial melt modeling of Neoproterozoic Kangdian basalts can produce compositions similar to Emeishan basalt at a pressure of 1.2 GPa (i.e. ≈40 km depth). It is suggested that the injection of high temperature picritic magmas into the lower crust of the Yangtze Block could be sufficient to induce high degrees of melting of the lower crust and produce magmas that are similar in composition to some Emeishan mafic rocks and/or produce melts that could contaminate 'pristine' Emieshan magmas.