Magnesium Isotope Geochemistry
Magnesium Isotope Geochemistry
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DOI：
10.2138/rmg.2017.82.7
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发表时间：
2017
影响因子：
--
通讯作者：
F. Teng
中科院分区：
文献类型：
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作者：
F. Teng
镁（Mg）的原子序数为12，属于元素周期表的碱土元素（第II族）。纯镁是一种银白色金属，在 1 个标准大气压下熔点为 650 °C，沸点为 1090 °C（Lide 1993-1994）。 Mg的电子构型为[Ne]3s2，具有低电离能，这使得Mg具有离子性，常见价态为2+，典型离子半径为0.72 A (Shannon 1976)。镁是一种主要元素，广泛分布于硅酸盐地球、水圈和生物圈中（图1a）。它是地球上第四丰富的元素（仅次于 O、Fe 和 Si，MgO = 25.5 wt%）（McDonough 和 Sun 1995），是大陆地壳中第五丰富的元素（MgO = 4.66 wt%）（Rudnick 和 Gau 2003），也是海水中第二丰富的阳离子（仅次于 Na，Mg = 0.128 wt%）（Pilson） 2013）。尽管如此，由于其高 MgO 含量（37.8 wt%，McDonough 和 Sun 1995）和质量分数，地幔中的 Mg 占地球的 99.9% 以上。硅酸盐地球中镁的丰度很高，使其成为火成岩、变质岩和沉积岩中矿物（例如橄榄石、辉石、石榴石、角闪石、云母、尖晶石、碳酸盐、硫酸盐和粘土矿物）的主要成分。镁具有三种稳定同位素，质量数分别为24、25和26，典型丰度分别为78.99%、10.00%和11.01%（Berglund和Wieser 2011）（图1b），标准原子量为24.305（CIAAW 2015）。由于质谱分析的局限性，许多以前的镁同位素研究都集中在质量无关的同位素异常上，以寻找由短命 26Al 衰变产生的放射性 26Mg（Gray 和 Compston 1974；Lee 和……
Magnesium (Mg) has an atomic number of 12 and belongs to the alkaline earth element (Group II) of the Periodic Table. The pure Mg is a silvery white metal and has a melting point of 650 °C and boiling point of 1090 °C at 1 standard atmosphere (Lide 1993–1994). The electronic configuration of Mg is [Ne]3s2, with low ionization energies, which makes Mg ionic in character with a common valance state of 2+ and a typical ionic radius of 0.72 A (Shannon 1976). Magnesium is a major element and widely distributed in the silicate Earth, hydrosphere and biosphere (Fig. 1a). It is the fourth most abundant element in the Earth (after O, Fe and Si, MgO = 25.5 wt%) (McDonough and Sun 1995), the fifth most abundant element in the bulk continental crust (MgO = 4.66 wt%) (Rudnick and Gao 2003) and the second most abundant cation in seawater (after Na, Mg = 0.128 wt%) (Pilson 2013). Nonetheless, the mantle has > 99.9% of Mg in the Earth because of its high MgO content (37.8 wt%, McDonough and Sun 1995) and mass fraction. The high abundance of Mg in the silicate Earth makes it a major constituent of minerals (e.g., olivine, pyroxene, garnet, amphibole, mica, spinel, carbonate, sulfate, and clay minerals) in igneous, metamorphic and sedimentary rocks. Magnesium has three stable isotopes, with mass numbers of 24, 25 and 26, and typical abundances of 78.99%, 10.00% and 11.01%, respectively (Berglund and Wieser 2011) (Fig. 1b), and a standard atomic weight of 24.305 (CIAAW 2015). Because of the limitations in the mass spectrometry, many previous Mg isotopic studies have concentrated on either mass independent isotope anomalies to look for the radiogenic 26Mg produced by the decay of short-lived 26Al (Gray and Compston 1974; Lee and …