Koornneef Janne M, Gress Michael U, Chinn Ingrid L, Jelsma Hielke A, Harris Jeff W, Davies Gareth R
Vrije Universiteit Amsterdam, Faculty of Earth and Life Sciences, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands.
De Beers Exploration, Private Bag X01, Southdale, 2135, South Africa.
Nat Commun. 2017 Sep 21;8(1):648. doi: 10.1038/s41467-017-00564-x.
Precise dating of diamond growth is required to understand the interior workings of the early Earth and the deep carbon cycle. Here we report Sm-Nd isotope data from 26 individual garnet inclusions from 26 harzburgitic diamonds from Venetia, South Africa. Garnet inclusions and host diamonds comprise two compositional suites formed under markedly different conditions and define two isochrons, one Archaean (2.95 Ga) and one Proterozoic (1.15 Ga). The Archaean diamond suite formed from relatively cool fluid-dominated metasomatism during rifting of the southern shelf of the Zimbabwe Craton. The 1.8 billion years younger Proterozoic diamond suite formed by melt-dominated metasomatism related to the 1.1 Ga Umkondo Large Igneous Province. The results demonstrate that resolving the time of diamond growth events requires dating of individual inclusions, and that there was a major change in the magmatic processes responsible for harzburgitic diamond formation beneath Venetia from the Archaean to the Proterozoic.Dating of inclusions within diamonds is used to reconstruct Earth's geodynamic history. Here, the authors report isotope data on individual garnet inclusions within diamonds from Venetia, South Africa, showing that two suites of diamonds define two isochrons, showing the importance of dating individual inclusions.
要了解早期地球的内部运作和深部碳循环，需要精确测定钻石的生长年代。在此，我们报告了来自南非威尼斯26颗方辉橄榄岩型钻石中26个单个石榴石包裹体的钐-钕同位素数据。石榴石包裹体和寄主钻石包含在明显不同条件下形成的两个成分组，并确定了两条等时线，一条是太古代（29.5亿年）的，另一条是元古代（11.5亿年）的。太古代钻石组是在津巴布韦克拉通南陆架裂谷作用期间由相对低温的流体主导交代作用形成的。年轻18亿年的元古代钻石组是由与11亿年翁孔多大火成岩省相关的熔体主导交代作用形成的。结果表明，确定钻石生长事件的时间需要对单个包裹体进行年代测定，并且从太古代到元古代，威尼斯下方负责方辉橄榄岩型钻石形成的岩浆过程发生了重大变化。对钻石内部包裹体进行年代测定可用于重建地球的地球动力学历史。在此，作者报告了南非威尼斯钻石中单个石榴石包裹体的同位素数据，表明两组钻石确定了两条等时线，显示了对单个包裹体进行年代测定的重要性。
