Composition of trapped fluids in cuboid fibrous diamonds from the Udachnaya kimberlite: LAM-ICPMS analysis
Composition of trapped fluids in cuboid fibrous diamonds from the Udachnaya kimberlite: LAM-ICPMS analysis
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Udachnaya 金伯利岩长方体纤维钻石中截留流体的成分：LAM-ICPMS 分析
DOI：
10.1016/j.chemgeo.2007.02.003
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发表时间：
2007
期刊：
影响因子：
3.9
通讯作者：
V. Shatsky
中科院分区：
文献类型：
--
作者：
D. Zedgenizov;S. Rege;W. Griffin;H. Kagi;V. Shatsky
采用激光烧蚀电感耦合等离子体质谱（LAM-ICPMS）对俄罗斯西伯利亚Udachnaya金伯利岩管中24颗长方体金刚石中的微包裹体进行了主量元素和微量元素的定量分析。在所研究的金刚石中的微包裹体代表了金刚石结晶的流体的大量样品;它们在相对恒定的Fe含量（Ca/（Ca+Mg）=0.31-0.68; Mg/（Mg+Fe）=0.66-0.78）下定义了富镁和富碳酸钙组合物之间的连续范围。一般来说，Udachnaya长方体钻石中捕获流体的主要和微量元素模式与金伯利岩和碳酸岩相似。与金伯利岩相比，金刚石中的流体富集K、Na、Fe，亏损Al;稀土元素配分模式比金伯利岩中的更陡; Ti、Zr、Y在许多流体中表现出强烈亏损。所观察到的地球化学特征是一致的钻石形成流体和短暂的碳酸岩流体/熔体，这可能是主机金伯利岩的前体之间的遗传联系。这些流体/熔体可能来自碳酸化剂的交代和流入，或来自先前碳酸化的榴辉岩和橄榄岩的部分熔融。一些元素的变化可以通过这种流体/熔体的分级结晶或具有不同成分的流体之间的混合来解释。
The bulk major- and trace-element compositions of micro-inclusions in 24 cuboid diamonds from the Udachnaya kimberlite pipe (Siberia, Russia) have been quantitatively analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LAM-ICPMS). Micro-inclusions in the studied diamonds represent a bulk sample of the fluids from which the diamonds crystallized; they define a continuous range between magnesian and calcic carbonate-rich compositions at relatively constant Fe contents (Ca/(Ca+Mg)=0.31–0.68; Mg/(Mg+Fe)=0.66–0.78). In general the major- and trace-element patterns of the trapped fluids in Udachnaya cuboid diamonds are similar to those of kimberlites and carbonatites. However, some important differences are observed: (1) the fluids in diamonds are enriched in K, Na, Fe and depleted in Al relative to the host kimberlite; (2) the REE patterns of the fluids are steeper than those of kimberlites; (3) many of the fluids show strong depletion in Ti, Zr and Y. The observed geochemical features are consistent with a genetic link between the diamond-forming fluids and ephemeral carbonatitic fluids/melts which may be precursors of the host kimberlite. These fluids/melts may originate either from the metasomatic and influx of carbonatitic agents or from partial melting of previously carbonated eclogites and peridotites. Some elemental variations may be explained by fractional crystallization of such fluid/melts, or mixing between fluids with different compositions.