Application of multi-collector inductively coupled plasma mass spectrometry（MC-ICP-MS） has led to big breakthrough of analytical methods for metal stable isotopes, resulting in rapid progresses in non-traditional st...Application of multi-collector inductively coupled plasma mass spectrometry（MC-ICP-MS） has led to big breakthrough of analytical methods for metal stable isotopes, resulting in rapid progresses in non-traditional stable isotope geochemistry. As a new geological tracer, Mg isotopes have been widely applied in studies of almost all important disciplines of geochemistry. High precision Mg isotope data measured by MC-ICP-MS are now available with precision about 0.05‰ amu-1（2SD） or better. Because mass bias caused by chemical procedure and instrument can easily cause significant analytical error, it is still a challenge to obtain accurate Mg isotope data for natural samples. In this paper, we systematically review the development of analytical technique of Mg isotopes, with a detailed description of a series of important techniques used in the measurement process, including calibration of instrumental mass-bias, chemical purification process, matrix effect, and pitfalls for high precision isotope analyses. We compare standard data from different labs and establish a guideline for Mg isotope analysis procedure. Additionally, we briefly discuss the behaviors of Mg isotopes during geological processes including equilibrium and kinetic Mg isotope fractionations, such as magma differentiation, chemical and thermal diffusion, and continental weathering. Finally, we propose some future prospects for Mg isotope geochemistry in both high and low temperature geological processes.展开更多
The biomineralization of CaCO_(3)often involves the transformation of amorphous precursors into crystalline phases,which is regulated by various proteins and inorganic ions such as Mg^(2+)ions.While the effects of Mg^...The biomineralization of CaCO_(3)often involves the transformation of amorphous precursors into crystalline phases,which is regulated by various proteins and inorganic ions such as Mg^(2+)ions.While the effects of Mg^(2+)ions on the polymorph and shape of the crystalline CaCO_(3)have been observed and studied,the interplay between Mg^(2+)ions and CaCO_(3)during the mineralization remains unclear.This work focuses on the mechanism of Mg^(2+)ion-regulated mineralization of CaCO_(3).By tracing the Mg isotope fractionation,the different mineralization pathways of CaCO_(3)under different Mg^(2+)ion concentrations had been clarified.Detailed regulatory role of Mg^(2+)ions at the different stages of mineralization had been proposed through combining the fractionation data with the analyses of the CaCO_(3)polymorph and shape evolution.These results provide a clear view of the Mg-mediated crystallization process of amorphous CaCO_(3),which can be used to finely control the phase of the crystalline products according to different needs.展开更多
Experiments of boron incorporated into Mg(OH)2 from magnesium-free synthetic seawater were carried out at various pH values, in order to investigate the adsorption species and the variation of isotopic fractionation o...Experiments of boron incorporated into Mg(OH)2 from magnesium-free synthetic seawater were carried out at various pH values, in order to investigate the adsorption species and the variation of isotopic fractionation of boron on Mg(OH)2. The results showed that the incorporation of boron into Mg(OH)2 was very rapid and reached the equilibrium after 4 h. The [B]s and the partition coefficient Kd between Mg(OH)2 and final solution decreased with the increasing pH. The maximum values of [B]s and Kd were much higher than that of boron adsorbed on metal oxide or clay minerals, indicating that the incorporation capability of boron into Mg(OH)2 was very strong. When the adsorption reached the equilibrium, the δ 11Bfsw was lower than δ 11Bisw. The boron isotopic fractionation αs-fsw was between 1.0186 and 1.0220 with an average of 1.0203. All these indicated that 11B incorporated into Mg(OH)2 preferentially due to B(OH)3 incorporation into Mg(OH)2 preferentially. The deposition reaction of B(OH)3 with Mg(OH)2 was the direct reason for B(OH)3 incorporation into Mg(OH)2. During the boron incorporation into Mg(OH)2, the isotopic fractionation characteristic of boron was decided by the simultaneous existence of adsorption of boron on Mg(OH)2 and the deposition reaction of H3BO3 with Mg(OH)2. Different from the fact that only B(OH)4-species incorporated into bio-carbonate, B(OH)3 and B(OH)4 incorporated into Mg(OH)2 simultaneously, and B(OH)3 incorporated into it preferentially. The lower pH is, the more incorporated fraction of B(OH)3 will be. Mg(OH)2 exists widely in madrepore, which influences the quantitative correspondence of the boron isotopic composition δ 11Bcarb of corals on the pH of the seawater badly, and brings serious uncertainty to the δ 11Bcarb as the indicator of the ancient seawater pH.展开更多
基金supported by the National Natural Science Foundation of China (No. 41173031)
文摘Application of multi-collector inductively coupled plasma mass spectrometry（MC-ICP-MS） has led to big breakthrough of analytical methods for metal stable isotopes, resulting in rapid progresses in non-traditional stable isotope geochemistry. As a new geological tracer, Mg isotopes have been widely applied in studies of almost all important disciplines of geochemistry. High precision Mg isotope data measured by MC-ICP-MS are now available with precision about 0.05‰ amu-1（2SD） or better. Because mass bias caused by chemical procedure and instrument can easily cause significant analytical error, it is still a challenge to obtain accurate Mg isotope data for natural samples. In this paper, we systematically review the development of analytical technique of Mg isotopes, with a detailed description of a series of important techniques used in the measurement process, including calibration of instrumental mass-bias, chemical purification process, matrix effect, and pitfalls for high precision isotope analyses. We compare standard data from different labs and establish a guideline for Mg isotope analysis procedure. Additionally, we briefly discuss the behaviors of Mg isotopes during geological processes including equilibrium and kinetic Mg isotope fractionations, such as magma differentiation, chemical and thermal diffusion, and continental weathering. Finally, we propose some future prospects for Mg isotope geochemistry in both high and low temperature geological processes.
基金the National Natural Science Foundation of China(Nos.U1932213,51732011,and 21701161)the National Key Research and Development Program of China(Nos.2018YFE0202201 and 2021YFA0715700)+1 种基金Science and Technology Major Project of Anhui Province(No.201903a05020003)the University Synergy Innovation Program of Anhui Province(No.GXXT-2019-028).
文摘The biomineralization of CaCO_(3)often involves the transformation of amorphous precursors into crystalline phases,which is regulated by various proteins and inorganic ions such as Mg^(2+)ions.While the effects of Mg^(2+)ions on the polymorph and shape of the crystalline CaCO_(3)have been observed and studied,the interplay between Mg^(2+)ions and CaCO_(3)during the mineralization remains unclear.This work focuses on the mechanism of Mg^(2+)ion-regulated mineralization of CaCO_(3).By tracing the Mg isotope fractionation,the different mineralization pathways of CaCO_(3)under different Mg^(2+)ion concentrations had been clarified.Detailed regulatory role of Mg^(2+)ions at the different stages of mineralization had been proposed through combining the fractionation data with the analyses of the CaCO_(3)polymorph and shape evolution.These results provide a clear view of the Mg-mediated crystallization process of amorphous CaCO_(3),which can be used to finely control the phase of the crystalline products according to different needs.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40573013 and 40776071) International Partnership Project of Chinese Academy of Sciences
文摘Experiments of boron incorporated into Mg(OH)2 from magnesium-free synthetic seawater were carried out at various pH values, in order to investigate the adsorption species and the variation of isotopic fractionation of boron on Mg(OH)2. The results showed that the incorporation of boron into Mg(OH)2 was very rapid and reached the equilibrium after 4 h. The [B]s and the partition coefficient Kd between Mg(OH)2 and final solution decreased with the increasing pH. The maximum values of [B]s and Kd were much higher than that of boron adsorbed on metal oxide or clay minerals, indicating that the incorporation capability of boron into Mg(OH)2 was very strong. When the adsorption reached the equilibrium, the δ 11Bfsw was lower than δ 11Bisw. The boron isotopic fractionation αs-fsw was between 1.0186 and 1.0220 with an average of 1.0203. All these indicated that 11B incorporated into Mg(OH)2 preferentially due to B(OH)3 incorporation into Mg(OH)2 preferentially. The deposition reaction of B(OH)3 with Mg(OH)2 was the direct reason for B(OH)3 incorporation into Mg(OH)2. During the boron incorporation into Mg(OH)2, the isotopic fractionation characteristic of boron was decided by the simultaneous existence of adsorption of boron on Mg(OH)2 and the deposition reaction of H3BO3 with Mg(OH)2. Different from the fact that only B(OH)4-species incorporated into bio-carbonate, B(OH)3 and B(OH)4 incorporated into Mg(OH)2 simultaneously, and B(OH)3 incorporated into it preferentially. The lower pH is, the more incorporated fraction of B(OH)3 will be. Mg(OH)2 exists widely in madrepore, which influences the quantitative correspondence of the boron isotopic composition δ 11Bcarb of corals on the pH of the seawater badly, and brings serious uncertainty to the δ 11Bcarb as the indicator of the ancient seawater pH.
