The Lithospheric Thickness Control on the Compositional Variation of Continental Intraplate Basalts: A Demonstration Using the Cenozoic Basalts and Clinopyroxene Megacrysts From Eastern China

Abstract

AbstractStudies on intraplate ocean island basalts have demonstrated the control of lithosphere thickness on the extent of melting and pressure of melt extraction (i.e., the lid effect). However, whether lithosphere thickness also controls the composition of within‐continent basalts remains unclear. Here, we test this hypothesis by studying the Cenozoic basalts contaitning clinopyroxene megacrysts from 10 localities throughout eastern continental China with a north‐south spatial coverage in excess of 2,500 km. Indeed, the geochemical parameters (e.g., abundances and ratios of major and trace elements) correlate well with the depth of the lithosphere‐asthenosphere boundary (LAB) calculated using the clinopyroxene barometry, showing significant lithospheric thickness control on basalt compositions. These observations offer further evidence for melt pooling (a melt rich layer) close beneath the LAB as a “stable magma reservoir” for crystallizing compositionally uniform clinopyroxene megacrysts to be carried by subsequent pulses of melt transport and eruption.