Journal Article

W-Fe isotopes argue against OIB-like basalts in Inner Mongolia originating from primordial peridotite mantle

Kikuchi, Junko, Xu, Jifeng, Lei, Ming, Guo, Zhengfu, Suzuki, Katsuhiko, Kurisu, Minako, Kashiwabara, Teruhiko, Watakabe, Ayako, Chen, Jianlin

2024

Overview

Whether Inner Mongolia OIB-like basalts originate from the modern upper mantle [e.g. depleted MORB mantle (DMM)] with recycled oceanic crust in the form of pyroxenite or ancient primordial mantle (lower mantle) dominated by peridotite remains unclear. This study presents high-precision W-Fe isotopic data for Late Cenozoic Chifeng basalts (CBs) in Inner Mongolia, NE China, along with their olivine compositions, to better constrain their petrogenesis. The modern mantle-like μ 182 W values (μ 182 W =  − 3.2 ± 3.8 to + 2.5 ± 2.4 ppm) of the CBs indicate that they most likely originated from DMM rather than ancient primordial mantle. The CBs exhibit elevated fractional crystallization-corrected δ 56 Fe values ranging from 0.09 to 0.16‰, compared to those of primitive normal mid-ocean ridge basalts (N-MORBs; δ 56 Fe = 0.03–0.07‰). This argues against the notion that the CBs could be generated solely by the melting of DMM peridotite. The high δ 56 Fe values of the CBs, coupled with their elevated olivine Fe/Mn ratios, suggest the involvement of pyroxenite in their mantle source. The absence of correlation between the Fe isotopes of CBs and Sr-Nd-Hf isotopes, along with their previously reported low δ 98/95 Mo values and existing geophysical evidence, supports the idea that pyroxenite in the mantle source of the CBs was most likely generated by the reaction between DMM peridotite and recycled Pacific oceanic crust originating from the mantle transition zone beneath NE China. Therefore, we propose that the mantle source of Inner Mongolia basalts (e.g. CBs) is DMM with some recycled oceanic crust in the form of pyroxenite, without the involvement of ancient primordial mantle. Our study highlights that W-Fe isotopes of basalts can help to identify the nature of mantle source (especially the ancient primordial mantle) and offer valuable insights into mantle lithology and the causes of mantle heterogeneity both locally and globally.

• Publisher: Springer Berlin Heidelberg,Springer,Springer Nature B.V
• Subject: Basalt / Cenozoic / Crystallization / Earth / Earth and Environmental Science / Earth science / Earth Sciences / Fractional crystallization / Geochemistry / Geology / Heterogeneity / Homogenization / Iron / Iron isotopes / Isotopes / Laboratories / Lithofacies / Lithology / Lower mantle / Mantle / Mid-ocean ridges / Mineral Resources / Mineralogy / Oceanic crust / Olivine / Original Paper / Peridotite / Petrogenesis / Petrology / Transition zone / Upper mantle