Abstract Diamonds are unrivalled in their ability to record the mantle carbon cycle and mantle fO2 over a vast portion of Earth’s history. Diamonds’ inertness and antiquity means their carbon isotopic characteristics directly reflect their growth environment within the mantle as far back as ∼3.5 Ga. This paper reports the results of a thorough secondary ion mass spectrometry (SIMS) carbon isotope and nitrogen concentration study, carried out on fragments of 144 diamond samples from various locations, from ∼3.5 to 1.4 Ga for P [peridotitic]-type diamonds and 3.0 to 1.0 Ga for E [eclogitic]-type diamonds. The majority of the studied samples were from diamonds used to establish formation ages and thus provide a direct connection between the carbon isotope values, nitrogen contents and the formation ages. In total, 908 carbon isotope and nitrogen concentration measurements were obtained. The total δ13C data range from −17.1 to −1.9 ‰ (P = −8.4 to −1.9 ‰; E = −17.1 to −2.1‰) and N contents range from 0 to 3073 at. ppm (P = 0 to 3073 at. ppm; E = 1 to 2661 at. ppm). In general, there is no systematic variation with time in the mantle carbon isotope record since > 3 Ga. The mode in δ13C of peridotitic diamonds has been at −5 (±2) ‰ since the earliest diamond growth ∼3.5 Ga, and this mode is also observed in the eclogitic diamond record since ∼3 Ga. The skewness of eclogitic diamonds’ δ13C distributions to more negative values, which the data establishes began around 3 Ga, is also consistent through time, with no global trends apparent. No isotopic and concentration trends were recorded within individual samples, indicating that, firstly, closed system fractionation trends are rare. This implies that diamonds typically grow in systems with high excess of carbon in the fluid (i.e. relative to the mass of the growing diamond). Any minerals included into diamond during the growth process are more likely to be isotopically reset at the time of diamond formation, meaning inclusion ages would be representative of the diamond growth event irrespective of whether they are syngenetic or protogenetic. Secondly, the lack of significant variation seen in the peridotitic diamonds studied is in keeping with modeling of Rayleigh isotopic fractionation in multicomponent systems (RIFMS) during isochemical diamond precipitation in harzburgitic mantle. The RIFMS model not only showed that in water-maximum fluids at constant depths along a geotherm, fractionation can only account for variations of

中文翻译：

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穿越时空的深层碳：地球的钻石记录及其对地幔中碳循环和流体物种形成的影响

摘要 在地球历史的大部分时间里，钻石在记录地幔碳循环和地幔 fO2 方面的能力是无与伦比的。钻石的惰性和古老性意味着它们的碳同位素特征直接反映了它们在地幔内的生长环境，最早可以追溯到 3.5 Ga。本文报告了彻底的二次离子质谱 (SIMS) 碳同位素和氮浓度研究的结果，进行了来自不同位置的 144 个钻石样品的碎片，P [橄榄岩] 型钻石为 3.5 至 1.4 Ga，E [榴辉岩] 型钻石为 3.0 至 1.0 Ga。大多数研究样本来自用于确定地层年龄的钻石，因此提供了碳同位素值、氮含量和地层年龄之间的直接联系。总共，获得了 908 个碳同位素和氮浓度测量值。总 δ13C 数据范围从 -17.1 到 -1.9 ‰（P = -8.4 到 -1.9 ‰；E = -17.1 到 -2.1‰），N 含量范围从 0 到 3073 at。ppm（P = 0 到 3073 at. ppm；E = 1 到 2661 at. ppm）。一般来说，自 > 3 Ga 以来，地幔碳同位素记录没有随时间的系统变化。自最早的金刚石生长 ∼3.5 Ga 以来，橄榄岩钻石的 δ13C 模式一直处于 -5 (±2) ‰，而这种模式自 3 Ga 以来，在榴辉岩钻石记录中也观察到了。 榴辉岩钻石的 δ13C 分布向更负值的偏度，数据建立在 3 Ga 左右，随着时间的推移也是一致的，没有明显的全球趋势。在单个样品中没有记录到同位素和浓度趋势，这表明，首先，封闭系统分馏趋势很少见。这意味着钻石通常在流体中碳含量高的系统中生长（即相对于生长的钻石的质量）。在生长过程中包含在钻石中的任何矿物更有可能在钻石形成时进行同位素重置，这意味着内含物年龄将代表钻石生长事件，无论它们是同生的还是原生的。其次，在所研究的橄榄岩钻石中没有发现显着变化，这与在哈茨伯岩地幔中等化学钻石沉淀过程中多组分系统 (RIFMS) 中的瑞利同位素分馏模型一致。RIFMS 模型不仅表明，在沿地温恒定深度的含水量最大的流体中，分馏只能解释