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

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.

SUBMITTER: Yu X 

PROVIDER: S-EPMC4652174 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature