Iron, magnesium, and titanium isotopic fractionations between garnet, ilmenite, fayalite, biotite, and tourmaline: Results from NRIXS, ab initio, and study of mineral separates from the Moosilauke metapelite

Nie, N. X.; Dauphas, N.; Esen, E.; Zeng, Hao; Sio, Corliss Kin I; Hu, Jingshi; Chen, Xi; Aarons, Sarah M.; Zhang, Zhe; Tian, Heng‐Ci; Wang, Da; Prissel, Kelsey B.; Greer, Jennika; Bi, Wenli; Hu, Michael Y.; Zhao, Jiyong; Shahar, Anat; Roskosz, Mathieu; Teng, Fang‐Zhen; Krawczynski, M. J.; Heck, Philipp R.; Spear, Frank S.

doi:10.1016/j.gca.2021.03.014

Cited by 42 publications

(32 citation statements)

References 121 publications

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“…Force constants were obtained for barium orthotitanate, fresnoite, potassium titanate, Ti-diopside, geikielite, karrooite, titanite, anatase, pseudobrookite, and Ti 3+ titanium oxide, respectively (force constants listed in Table ). The relationship between the force constants calculated in this study and the inverse of the cube of the bond length (the ionic bond model predicts a linear relationship between F and 1/ r 3 ) , together with reported literature values is shown in Figure . A correlation between the two variables and the coordination environment of Ti (with the exception of one outlier) is observed.…”

Section: Results and Discussionsupporting

confidence: 77%

Clues from Ab Initio Calculations on Titanium Isotopic Fractionation in Tholeiitic and Calc-Alkaline Magma Series

Aarons

Dauphas

Blanchard

et al. 2021

ACS Earth Space Chem.

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Magmatic differentiation produces positive correlations between  49 Ti and SiO2. The equilibrium Ti isotope fractionation factors of Ti-bearing minerals are essential for understanding the mechanisms driving this isotopic fractionation. We present ab initio derived mean force constants of Ti-bearing minerals (barium orthotitanate, potassium titanium oxide, fresnoite, diopside, geikielite, karooite, titanite, pseudobrookite, anatase, and titanium oxide) based on density functional theory (DFT) to calculate equilibrium isotopic fractionation factors. We find that the main driver for Ti isotopic fractionation is its coordination, with 4-, 5-, and 6-fold coordinated Ti characterized by mean force constants of 547, 462, and 310 N/m respectively. The coordination number of Ti in silicate melts is thought to be lower than in minerals, driving magmas towards higher  49 Ti values by fractional crystallization. The mineral-melt fractionation factors allow modeling of the observed Ti isotope trends in tholeiitic and calc-alkaline rocks. Our model results indicate that to first order, the steeper  49 Ti trend observed in tholeiitic vs. calc-alkaline magmas is most likely due to enhanced removal of Ti into sequestered minerals at low SiO2 concentration in tholeiitic series compared to calc-alkaline series. The  49 Ti-SiO2 differentiation trends however depend on Ti coordination in the melt and the strengths of Ti bonds in diverse Fe,Ti-oxides, which are still uncertain. Our resultsshow that Ti isotopes can be used to reconstruct the crystallization history and identify the magmatic series parentage of magmas that otherwise lack context, but further work is needed to identify the drivers behind Ti isotopic fractionation in igneous rocks.

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Section: Results and Discussionsupporting

confidence: 77%

Clues from Ab Initio Calculations on Titanium Isotopic Fractionation in Tholeiitic and Calc-Alkaline Magma Series

Aarons

Dauphas

Blanchard

et al. 2021

ACS Earth Space Chem.

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“…The Fe isotopic fractionation factor between biotite and tourmaline has not been well‐calibrated yet. Since Fe 2+ occupies the octahedral site in both biotite and tourmaline (Hawthorne & Dirlam, 2011), they should have comparable Fe isotopic composition at the same Fe 3+ /ΣFe ratio which is supported by the ab initio calculations (Nie et al., 2021). Tourmaline in the Himalayan leucogranite yields δ 56 Fe slightly lower than biotite, with a ∆ 56 Fe biotite‐tourmaline of 0.08 ± 0.04‰.…”

Section: Discussionmentioning

confidence: 82%

“…Tourmaline in the Himalayan leucogranite yields δ 56 Fe slightly lower than biotite, with a ∆ 56 Fe biotite‐tourmaline of 0.08 ± 0.04‰. However, the ∆ 56 Fe biotite‐tourmaline constrained from Moosilauke metapelite is about −0.06 ± 0.03‰ at 700°C (Nie et al., 2021). This discrepancy may result from their different Fe 3+ /ΣFe ratios and/or compositional variations in biotite and tourmaline (Nie et al., 2021; H. Wu et al., 2017).…”

Section: Discussionmentioning

confidence: 99%

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Petrogenesis of Himalayan Leucogranites: Perspective From a Combined Elemental and Fe‐Sr‐Nd Isotope Study

et al. 2021

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The petrogenesis of Himalayan leucogranites remains crucial for understanding the thermal and tectonic evolution of the Himalayan orogen. To understand whether they are largely pristine melts of crustal anatexis or have experienced a high degree of fractional crystallization (FC), we present Fe isotopic data of 30 representative Himalayan leucogranites and 9 local metasedimentary rocks. Excepting three garnet leucogranites with low δ 56 Fe (−0.04‰-0.06‰) that are likely affected by garnet accumulation, tourmaline, and two-mica leucogranites have largely homogeneous δ 56 Fe from 0.13‰ to 0.24‰ irrespective of their highly variable SiO 2 , MgO, and FeOt contents. Combined with observed mineral assemblages and available fractionation factors, this does not support a high degree of FC (with or without assimilation) in their petrogenesis. The elevated δ 56 Fe relative to the supposed source rocks, represented by metasedimentary rocks and/or metabasite with a δ 56 Fe value of 0.10‰, by ∼0.07‰, may reflect Fe isotope fractionation during crustal anatexis. This study indicates most leucogranites can provide robust constraints on the conditions of crustal anatexis and thus the thermal and tectonic evolution of the Himalayan orogen.Plain Language Summary The Himalayas have been formed from the collision between two tectonic plates. During their formation, the rocks of the continental crust have melted to form leucogranites which potentially provide important information on how the collision process evolves. Several recent studies of rare-element mineralization associated with these granites have argued that the magmas result from extensive removal of early formed minerals during the cooling of the magma (fractional crystallization [FC]) which, if true, would undermine their usefulness as monitors of the collisional process. In this study, we address this issue through a geochemical approach that combines isotopic data from iron, strontium, and neodymium. Whereas Sr and Nd give information on the source of the magmas, the isotopes of Fe will remain largely unfractionated if the granites result simply from melting the crust but fractionate significantly during FC. Our results reveal very limited fractionation of Fe isotopic compositions for two types of leucogranites, which is inconsistent with the model requiring a high degree of FC but supports the interpretation that they represent largely unfractionated crustal melts. Our study therefore confirms that Himalayan leucogranites can provide reliable probes for the thermal and tectonic evolution of the Himalayan crust. SHI ET AL.

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“…4d), which are within errors of the published SN-MC-ICP-MS value of d 56 Fe ¼ À0.172 AE 0.019& (95% conf., n ¼ 2) (Table 2). 34 Consistent results of ilmenite directly calibrated against the new IRMM-524A and the conventional IRMM-014 isotopic reference materials prove the analytical feasibility of using IRMM-524A as the RM for in situ Fe isotopic analysis by fs LA-MC-ICP-MS.…”

Section: The Analytical Feasibility Of Irmm-524a As the Rm For Fe Iso...mentioning

confidence: 73%

Analytical feasibility of a new reference material (IRMM-524A Fe metal) for the in situ Fe isotopic analysis of pyrite and ilmenite without matrix effects by femtosecond LA-MC-ICP-MS

Yang

Wang

et al. 2022

J. Anal. At. Spectrom.

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Iron, magnesium, and titanium isotopic fractionations between garnet, ilmenite, fayalite, biotite, and tourmaline: Results from NRIXS, ab initio, and study of mineral separates from the Moosilauke metapelite

Cited by 42 publications

References 121 publications

Clues from Ab Initio Calculations on Titanium Isotopic Fractionation in Tholeiitic and Calc-Alkaline Magma Series

Clues from Ab Initio Calculations on Titanium Isotopic Fractionation in Tholeiitic and Calc-Alkaline Magma Series

Petrogenesis of Himalayan Leucogranites: Perspective From a Combined Elemental and Fe‐Sr‐Nd Isotope Study

Analytical feasibility of a new reference material (IRMM-524A Fe metal) for the in situ Fe isotopic analysis of pyrite and ilmenite without matrix effects by femtosecond LA-MC-ICP-MS

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