Origin of life from apatite dating?
Origin of life from apatite dating?
复制标题
生命起源从磷灰石测年？
作者：
Y. Sano;K. Terada;Y. Takahashi;A. Nutman
Mojzsis等人，报告了来自格陵兰西南部Akilia岛沉积序列的磷灰石颗粒中碳质内含物的碳同位素组成，这些磷灰石颗粒的年龄超过38.5亿年。Mojzsis等人测量的δ 13 C值使他们得出结论，这些碳质物质是38.5亿年前早期生命的证据。但如果使用其他同位素（U-Pb和Pb-Pb），磷灰石的年龄估计仅为1，504 ±336（2σ）和1，459 ±160（2σ）百万年。这一数值与该地区Amitsog片麻岩中黑云母上Rb-Sr矿物等时线的1600 - 1700百万年和K-Ar白云母的1,670百万年的测量值一致。我们的结论是，大约15亿年前，Akilia岛的磷灰石经历了一次约600 °C的变质事件（根据U-Pb系统的闭合温度估计）。
Mojzsis et al., reported the carbon-isotope composition of carbonaceous inclusions in grains of apatite from sediment sequences of Akilia island, southwest Greenland, that are more than 3,850 million years (Myr) old. The δ13C values measured by Mojzsis et al. led them to conclude that these carbonaceous materials are evidence of early life 3,850 Myr ago. But if other isotopes (U-Pb and Pb-Pb) are used, the apatites are estimated at just 1,504±336 (2σ) and 1,459±160 (2σ) Myr old. This value is consistent with measurements of 1,600-1,700 Myr for Rb-Sr mineral isochrons on biotites and 1,670 Myr for K-Ar muscovite from Amitsog gneiss in the region. We conclude that, about 1,500 Myr ago, these apatites in Akilia island experienced a metamorphic event of about 600 °C (estimated by the closure temperature of the U-Pb system,).