Integrated models of diamond formation and craton evolution
Integrated models of diamond formation and craton evolution
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金刚石形成和克拉通演化的综合模型
DOI：
10.1016/j.lithos.2004.04.018
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发表时间：
2004
期刊：
影响因子：
3.5
通讯作者：
J. Harris
中科院分区：
文献类型：
--
作者：
S. Shirey;S. H. Richardson;J. Harris
在非洲南部进行了20年的钻石研究，使人们能够在克拉通范围内综合研究钻石的年龄、平均氮含量和碳组成，以及它们的同生硅酸盐和硫化物包裹体的主要共生作用，并建立了克拉通形成模型。金伯利地区金伯利岩、Koffiefontein、Orapa和Jwaneng的钻石中个别的辉生岩硫化物包裹体的Re-Os同位素年龄从大约2.9 Ga到中元古代不等，与地幔岩石圈在钻石稳定场深度（150-225 km）显示的纵波速度（±1%）的显著变化几乎没有对应关系。上述金伯利岩、Finsch、Jagersfontein、Roberts Victor、Premier、Venetia和Letlhakane的钻石中的硅酸盐包裹体及其主钻石成分与岩石圈地震速度具有区域关系。相对于克拉通平均值，p波速度较慢的地幔岩石圈与钻石中榴辉岩和橄榄岩硅酸盐包裹体的比例较大，更年轻的Sm-Nd年龄的硅酸盐包裹体的发生率更高，碳同位素组成较轻的钻石比例更高，低氮钻石的比例更低。钻石最古老的形成年龄支持一种模型，即地幔最初成为克拉通核大陆龙骨的一部分，是由中太古宙（3.2-3.3 Ga或更早）具有高度熔融和早期辉石形成的地幔枯竭事件形成的。2.9 Ga年龄群中榴辉岩硫化物包裹体的优势将晚太古宙（2.9 Ga）俯冲-增生事件与克拉通稳定联系起来。这些事件导致了在合并克拉通中广泛分布的太古宙晚期榴辉岩钻石。随后的元古代构造和岩浆事件改变了大陆岩石圈的组成，并在已经很广泛的太古宙钻石套件中添加了新的黑玄武岩和榴辉岩钻石。类似的年龄/共生系统在奴隶和西伯利亚克拉通的更有限的数据集中可以看到。
Two decades of diamond research in southern Africa allow the age, average N content and carbon composition of diamonds, and the dominant paragenesis of their syngenetic silicate and sulfide inclusions to be integrated on a cratonwide scale with a model of craton formation. Individual eclogitic sulfide inclusions in diamonds from the Kimberley area kimberlites, Koffiefontein, Orapa and Jwaneng have Re–Os isotopic ages that range from circa 2.9 Ga to the mid-Proterozoic and display little correspondence with the prominent variations in the P-wave velocity (±1%) that the mantle lithosphere shows at depths within the diamond stability field (150–225 km). Silicate inclusions in diamonds and their host diamond compositions for the above kimberlites, Finsch, Jagersfontein, Roberts Victor, Premier, Venetia, and Letlhakane show a regional relationship to the seismic velocity of the lithosphere. Mantle lithosphere with slower P-wave velocity relative to the craton average correlates with a greater proportion of eclogitic vs. peridotitic silicate inclusions in diamond, a greater incidence of younger Sm–Nd ages of silicate inclusions, a greater proportion of diamonds with lighter C isotopic composition, and a lower percentage of low-N diamonds. The oldest formation ages of diamonds support a model whereby mantle that became part of the continental keel of cratonic nuclei first was created by middle Archean (3.2–3.3 Ga or older) mantle depletion events with high degrees of melting and early harzburgite formation. The predominance of eclogitic sulfide inclusions in the 2.9 Ga age population links late Archean (2.9 Ga) subduction–accretion events to craton stabilization. These events resulted in a widely distributed, late Archean generation of eclogitic diamonds in an amalgamated craton. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the already extensive Archean diamond suite. Similar age/paragenesis systematics are seen for the more limited data sets from the Slave and Siberian cratons.