Petrogenesis and Geodynamic Implications of a Newly Discovered Basanite Dike in Zaolin, Jingdezhen City, South China

Xiaofei Pan,Xuejing Gong,Yanshen Yang,Yongpeng Ouyang,Yufeng Ren,Qiuyun Li,Zengqian Hou,Christoph Hauzenberger

doi:10.2113/2021/9732167

Abstract

Abstract A recently discovered basanite dike in the Zaolin area of Jingdezhen, South China, contains mantle xenocrysts such as kink-banded olivines, olivines + orthopyroxenes assemblage, and chromites. In addition, polymorphic carbonates of the MgCO3–FeCO3 series occur as augens, either independently or interspersed with diopside and spinel in the matrix. The rock is characterized by high Cr and Ni contents, high whole-rock Mg# values (0.66–0.72), and high Ca/Al (0.72–1.03) and TFeO/MgO (1.1–1.3) ratios and is alkali-rich with Na2O &gt; K2O. The trace-element partition patterns are similar to those of other basanites in eastern China as well as ocean island basalts. Whole-rock geochemical analyses show depleted Sr and Nd isotopic compositions (86Sr/87Sr=0.70358–0.703853, εNd=2.52–6.73). These data indicate that the rock has experienced negligible crustal contamination, should be derived from asthenospheric mantle, or mixed by the MORB with EMI/EMII mantle and have been carbonated. The calculated T–P conditions of the melt in equilibrium with xeno-olivine are 1160–1320°C at the mantle depth. The high Cr# values of the spinel xenocrysts indicate that the lithospheric mantle under the Jingdezhen area was probably relict Proterozoic mantle. The Ar–Ar plateau age and the isochron and inverse isochron ages for the matrix of the basanite are all 44 Ma. The basanite, as well as other alkaline basalt or lamprophyre dikes in southeastern China, formed in a rifting regime during the Eocene.

Highlights

Cenozoic alkaline basalt provinces occur in every continent and are commonly associated with active lithospheric extension in localized continental rifts or over broader continental regions ([1])
Representative microprobe data for minerals in the Zaolin basanite are listed in Supplementary Data Tables 1–6
(2) The Zaolin basanite contains mantle xenocrysts, i.e., kink-banded olivines, olivines + orthopyroxenes, and chromites, and shows high Cr and Ni contents and depleted Sr and Nd isotopes. These features indicate an origin from low-degree partial melting of asthenosphere mantle and enriched mantle, which was subsequently metasomatized by carbonate melt

Summary

Introduction

Cenozoic alkaline basalt provinces occur in every continent and are commonly associated with active lithospheric extension in localized continental rifts or over broader continental regions ([1]). Large volumes of Cenozoic alkaline basalts are widespread in the eastern Asian continental margin (Figure 1(a)) These basalts outcrop along coastal areas and adjacent offshore shelf regions from north of Heilongjiang province to south of Hainan Island, as well as in the South China Sea along the eastern margin of China, together constituting the eastern China volcanic belt ([2]; Figure 1(b)). They were erupted mainly during the Miocene and Pleistocene (20.7-0.38 Ma, [3]). Cong et al [8] proposed that during the Oligocene, eastern China entered a stage of continental-margin rifting based on the occurrence of Paleocene tholeiitic basalts (58.7– 59.7 Ma) and Oligocene alkaline basalts (22.7–28.8 Ma) in the Subei Basin

Methods

Results

Discussion

Conclusion