ISBN:

0024-4937

Keywords:

A-type granites, absolute age, alkaline earth metals, Asia, China, complexes, dates, electron probe data, Emeishan Basalts, Far East, fayalite, granites, igneous rocks, ion probe data, isotope ratios, Isotopes, large igneous provinces, magmatism, major elements, mass spectra, metals, mineral composition, Nd-144/Nd-143, neodymium, nesosilicates, olivine group, orthosilicates, Paleozoic, Panxi Rift, Permian, petrography, plate tectonics, plutonic rocks, rare earths, rifting, SHRIMP data, Sichuan China, silicates, spectra, Sr-87/Sr-86, Stable isotopes, strontium, syenites, Trace elements, U/Pb, Upper Permian, whole rock, zircon, zircon group

Abstract:

Within the Panxi rift of the Permian Emeishan large igneous province (ELIP), SW China, a 20 km (super 2) quartz-bearing fayalite syenitic pluton intrudes the 260 Ma Baima igneous complex (BIC). The fayalite syenite is dated using SHRIMP zircon U-Pb techniques at 252+ or -2.5 Ma. The Panxi fayalite syenite is mainly composed of alkali feldspar, ferroan augite, fayalite, quartz and Fe-Ti oxides and contains 61.8-63.7 wt.% SiO (sub 2) , 5.0-7.3 wt.% Fe (sub 2) O (sub 3) t and 9.9-12.1 wt.% total alkalis, belonging to an A-type variety of ferroan alkalic metaluminous granitoids. The fayalite syenite displays positive Eu anomalies (Eu/Eu (super *) = 0.9-8.9) and is enriched in LREE [(La/Yb) (sub N) = 6.6-11.5]. The epsilon Nd values and ( (super 87) Sr/ (super 86) Sr) (sub initial) ratios of the fayalite syenite range from +1.3 to +1.9 and from 0.7035 to 0.7068, respectively. The fayalite syenite and the BIC had the same mantle source; however the 8 myr age gap between them suggests the fayalite syenite formed by remelting of underplated mafic magmas injected into the crust during ELIP magmatism. The ages of the fayalite syenite and BIC are coincident with two Permian mass extinction events and suggest that ELIP may have influenced both. Abstract Copyright (2008) Elsevier, B.V.

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2008-076191<br/>Baima Complex<br/>southwestern China