Growing magma chambers control the distribution of small-scale flood basalts.

Xun Yu,Li-Hui Chen,Gang Zeng

doi:10.1038/srep16824

Abstract

Small-scale continental flood basalts are a global phenomenon characterized by regular spatio-temporal distributions. However, no genetic mechanism has been proposed to explain the visible but overlooked distribution patterns of these continental basaltic volcanism. Here we present a case study from eastern China, combining major and trace element analyses with Ar–Ar and K–Ar dating to show that the spatio-temporal distribution of small-scale flood basalts is controlled by the growth of long-lived magma chambers. Evolved basalts (SiO2 > 47.5 wt.%) from Xinchang–Shengzhou, a small-scale Cenozoic flood basalt field in Zhejiang province, eastern China, show a northward younging trend over the period 9.4–3.0 Ma. With northward migration, the magmas evolved only slightly ((Na2O + K2O)/MgO = 0.40–0.66; TiO2/MgO = 0.23–0.35) during about 6 Myr (9.4–3.3 Ma). When the flood basalts reached the northern end of the province, the magmas evolved rapidly (3.3–3.0 Ma) through a broad range of compositions ((Na2O + K2O)/MgO = 0.60–1.28; TiO2/MgO = 0.30–0.57). The distribution and two-stage compositional evolution of the migrating flood basalts record continuous magma replenishment that buffered against magmatic evolution and induced magma chamber growth. Our results demonstrate that the magma replenishment–magma chamber growth model explains the spatio-temporal distribution of small-scale flood basalts.

Highlights

Russia Korea (a) field from eastern China to determine the role of the magma chamber in the formation and distribution of eruptive centers within small-scale continental flood basalts
Eastern China hosts widely distributed late Cenozoic basalts (Fig. 1a) that occur in dozens of small-scale flood basaltic fields as well as a few monogenic basaltic fields, have trace element signatures consistent with ocean island basalt (OIB), and are identified as typical intraplate basalts derived from the asthenosphere in a continental setting[7,14]
This study is the first to document the relationship between the temporal-spatial distribution of small-scale flood basalts and the evolution of long-lived basaltic magma chambers, illustrating the importance of magma replenishment in the growth of basaltic magma chambers

Summary

Introduction

Russia Korea (a) field from eastern China to determine the role of the magma chamber in the formation and distribution of eruptive centers within small-scale continental flood basalts. The high-SiO2 alkaline/tholeiitic basalts show lower Ce/Pb (13.8–22.1), Nb/U (36.4–49.3) and higher Sm/Nd (0.24–0.29) ratios than the low-SiO2 alkaline basalts (Ce/Pb = 20.7–33.1; Nb/U = 50.6–57.2; Sm/Nd = 0 .22–0.25; Fig. 3B). The OIB-like primitive-mantle-normalized trace element patterns (Fig. S3) and high Ce/Pb ratios suggest an asthenospheric source for the low-SiO2 alkaline basalts (Fig. 3B).

Results

Conclusion