DOI: 10.1016/j.epsl.2018.01.036
Scopus记录号: 2-s2.0-85044353398
论文题名: Magnesium isotopic evidence for chemical disequilibrium among cumulus minerals in layered mafic intrusion
作者: Chen L.-M. ; Teng F.-Z. ; Song X.-Y. ; Hu R.-Z. ; Yu S.-Y. ; Zhu D. ; Kang J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 487 起始页码: 74
结束页码: 83
语种: 英语
英文关键词: Baima mafic intrusion
; chemical diffusion
; compositional zoning
; kinetic isotope fractionation
; magnesium isotopes
Scopus关键词: Clouds
; Fractionation
; Ilmenite
; Kinetics
; Light sources
; Magnesia
; Olivine
; Silicate minerals
; Titanium oxides
; Zoning
; Chemical diffusion
; Compositional zoning
; Kinetic isotope fractionation
; Mafic intrusion
; Magnesium isotopes
; Isotopes
; cumulate
; diffusion
; disequilibrium
; isotopic composition
; isotopic fractionation
; layered intrusion
; mafic rock
; magnesium
; zoning
; China
英文摘要: Magnesium isotopic compositions of olivine, clinopyroxene, and ilmenite from the Baima intrusion, SW China, for the first time, are investigated to constrain the magnitude and mechanisms of Mg isotope fractionation among cumulus minerals in layered mafic intrusions and to evaluate their geological implications. Olivine and clinopyroxene have limited Mg isotope variations, with δ26Mg ranging from −0.33 to +0.05‰ and from −0.29 to −0.13‰ respectively, similar to those of mantle xenolithic peridotites. By contrast, ilmenites display extremely large Mg isotopic variation, with δ26Mg ranging from −0.50 to +1.90‰. The large inter-mineral fractionations of Mg isotopes between ilmenite and silicates may reflect both equilibrium and kinetic processes. A few ilmenites have lighter Mg isotopic compositions than coexisting silicates and contain high MgO contents without compositional zoning, indicating equilibrium fractionation. The implication is that the light Mg isotopic compositions of lunar high-Ti basalts may result from an isotopically light source enriched in cumulate ilmenites. On the other hand, most ilmenites have heavy Mg isotopic compositions, coupled with high MgO concentration and chemical zoning, which can be quantitatively modeled by kinetic Mg isotope fractionations induced by subsolidus Mg–Fe exchange between ilmenite and ferromagnesian silicates during the cooling of the Baima intrusion. The extensive occurrence of kinetic Mg isotope fractionation in ilmenites implies the possibility of widespread compositional disequilibrium among igneous minerals in magma chambers. Consequently, disequilibrium effects need to be considered in studies of basaltic magma evolution, magma chamber processes, and magmatic Fe–Ti oxide ore genesis. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/110005
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China; Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, United States; University of Chinese Academy of Sciences, Beijing, 100049, China
Recommended Citation:
Chen L.-M.,Teng F.-Z.,Song X.-Y.,et al. Magnesium isotopic evidence for chemical disequilibrium among cumulus minerals in layered mafic intrusion[J]. Earth and Planetary Science Letters,2018-01-01,487