Magnesium isotope behavior during titanomagnetite fractionation in basaltic lavas

Sun，Yang1; Teng，Fang Zhen2; Rooney，Tyrone O.3; Pang，Kwan Nang4; Wang，Ze Zhou2,5

2024-06-20

10.1016/j.chemgeo.2024.122088

Chemical Geology   影响因子和分区

0009-2541

Knowledge of the behavior of magnesium (Mg) isotopes during magmatic differentiation is a prerequisite for applying Mg isotopes as a tracer of crustal recycling and mantle heterogeneity. Crystal fractionation of mafic silicate minerals leads to limited Mg isotope fractionation; hence, Mg isotopic variations in basalts largely result from contributions of subducted crustal materials into their mantle sources. However, recent studies have revealed that the segregation of iron oxides, such as chromite during early-stage basaltic differentiation and titanomagnetite and ilmenite during late-stage differentiation, can potentially modify Mg isotopic compositions of mantle-derived lavas. Titanomagnetite is much more commonly observed in terrestrial basaltic lavas than chromite and ilmenite, and can also form during early-stage basaltic differentiation. To constrain the effects of titanomagnetite crystallization on Mg isotopic systematics of basaltic magma, we report Mg isotopic data for a suite of well-characterized alkaline basaltic lavas (MgO wt% = 4.99 to 6.52) from Gerba Guracha, western Ethiopian Plateau, which have undergone extensive titanomagnetite fractionation. Their δMg values range from −0.29‰ to −0.17‰ and do not correlate with indicators of titanomagnetite fractionation such as TiO and V. These observations suggest that the segregation of titanomagnetite produced limited Mg isotope fractionation, possibly because of its composition-dependent, highly variable ΔMg (ΔMg = δMg − δMg) values. Considering that most iron oxides occur as complex solid solutions that are controlled by the oxygen fugacity of magmas, the effects of oxide segregation on Mg isotopic systematics of basalts require further evaluation.

Alkaline basaltic lavas Ethiopian Plateau Magnesium isotopes Oxygen fugacity Titanomagnetite fractionation

SCI ; EI

英语

第一 ; 通讯

GEOSCIENCES

2-s2.0-85189860155

Scopus

1.Department of Earth and Space Sciences,Southern University of Science and Technology,Shenzhen,518055,China
2.Isotope Laboratory,Department of Earth and Space Sciences,University of Washington,Seattle,98195-1310,United States
3.Department of Earth and Environmental Sciences,Michigan State University,East Lansing,48824,United States
4.Institute of Earth Sciences,Academia Sinica,Taipei,11529,China
5.State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Beijing,100083,China

Sun，Yang,Teng，Fang Zhen,Rooney，Tyrone O.,et al. Magnesium isotope behavior during titanomagnetite fractionation in basaltic lavas[J]. Chemical Geology,2024,655.

Sun，Yang,Teng，Fang Zhen,Rooney，Tyrone O.,Pang，Kwan Nang,&Wang，Ze Zhou.(2024).Magnesium isotope behavior during titanomagnetite fractionation in basaltic lavas.Chemical Geology,655.

Sun，Yang,et al."Magnesium isotope behavior during titanomagnetite fractionation in basaltic lavas".Chemical Geology 655(2024).