Publication detail

Transition from tholeiitic to alkali basalts via interaction between decarbonated eclogite-derived melts and peridotite

XIE, Q. ZHANG, Z. FOLEY, S.F. CHEN, C. CHENG, Z. WANG, Y. KONG, W. LV, Y. SANTOSH, M. JIN, Q. KRMÍČEK, L. ZHU, X.

Original Title

Transition from tholeiitic to alkali basalts via interaction between decarbonated eclogite-derived melts and peridotite

Type

journal article in Web of Science

Language

English

Original Abstract

Intraplate basalts generally show a geochemical continuum from alkali to tholeiitic basalts. However, the genetic link between these two types of rocks has remained controversial. The Early Jurassic Karamay basalts in the West Junggar terrane, southern Central Asian Orogenic Belt (CAOB), erupted to form a small-volume outcrop in the stable continental intraplate region. The basalts are characterized by aphyric textures without any visible phenocrysts. Thus, they are different from the ubiquitous porphyritic-textured intraplate basalts and have a composition close to that of the mantle-derived primary melt. In contrast to chemically and petrographically well-defined alkali and tholeiitic basalts, the Karamay basalts exhibit transitional compositions spanning from alkali (with normative olivine+nepheline and normative olivine+hypersthene) to tholeiitic (with normative quartz+hypersthene), providing an important case to address the geochemical continuum of intraplate basalts. Similar to the alkali basalts in eastern China, the Karamay basalts have isotopic imprints of sedimentary carbonates, i.e., significantly lighter Mg (δ26Mg = −0.54‰ to −0.34‰) and heavier Zn (δ66Zn = 0.36–0.46‰) isotopes than the normal mantle. However, they display initial ((87Sr/86Sr)t ratios of 0.7047–0.7051, positive εNd(t) values (3.3–4.2) and positive anomalies of Nb-Ta-Ti-Zr-Hf, which are not expected in the case of incorporation of recycled carbonates. This contradiction can be reconciled by considering a decarbonation reaction between carbonates (i.e., dolomite and magnesite) and co-existing eclogite in the subducted oceanic slab at pressure >5 GPa, leaving light Mg and heavy Zn isotope signatures in the stagnant eclogite residue in the deep mantle. Combining the geochemical compositions of our samples with the geologic evidence, and considering the previous results of melt-peridotite reaction experiments, we conclude that the Karamay basalts might have originated from the interaction of silica-rich tholeiitic melt derived from the recycled decarbonated eclogite with fertile peridotite during its ascent. Our study highlights that intraplate alkali basalts, especially silica-rich ones (e.g., with SiO2>45 wt.%), can be transformed from tholeiitic melts through reaction with peridotite mantle, and demonstrates that deeply recycled oceanic crust stagnated in mantle can serve as a main source for alkaline lavas.

Keywords

Intraplate basalts; Geochemical continuum; Decarbonation reaction; Melt-peridotite interaction; Mg-Zn isotopes

Authors

XIE, Q.; ZHANG, Z.; FOLEY, S.F.; CHEN, C.; CHENG, Z.; WANG, Y.; KONG, W.; LV, Y.; SANTOSH, M.; JIN, Q.; KRMÍČEK, L.; ZHU, X.

Released

29. 3. 2023

Publisher

ELSEVIER

Location

NETHERLANDS

ISBN

0009-2541

Periodical

CHEMICAL GEOLOGY

Year of study

621

Number

3

State

Kingdom of the Netherlands

Pages count

20

URL

https://www.sciencedirect.com/science/article/abs/pii/S0009254123000542

BibTex

@article{BUT183209,
  author="Qiuhong {Xie} and Zhaochong {Zhang} and Stephen F. {Foley} and Chunfei {Chen} and Zhiguo {Cheng} and Yu {Wang} and Weiliang {Kong} and Yiwen {Lv} and Ma {Santosh} and Qizhen {Jin} and Lukáš {Krmíček} and Xiangkun {Zhu}",
  title="Transition from tholeiitic to alkali basalts via interaction between decarbonated eclogite-derived melts and peridotite",
  journal="CHEMICAL GEOLOGY",
  year="2023",
  volume="621",
  number="3",
  pages="20",
  doi="10.1016/j.chemgeo.2023.121354",
  issn="0009-2541",
  url="https://www.sciencedirect.com/science/article/abs/pii/S0009254123000542"
}