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首页> 外文期刊>Contributions to Mineralogy and Petrology >Zircon Hf isotope evidence for an enriched mantle source for the Bushveld Igneous Complex
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Zircon Hf isotope evidence for an enriched mantle source for the Bushveld Igneous Complex

机译：锆石Hf同位素证据表明布什维尔德火成岩复合体富含地幔源

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摘要

We use the Hf isotope composition of zircon from the Bushveld Complex to better understand the source of its parent magmas. The data set, which consists of 141 individual LA-ICP-MS analyses from 11 samples encompassing the entire cumulate stratigraphy, shows that the parent magmas had a Hf isotope composition unlike that of the depleted mantle at 2.06 Ga. Specifically, sample average ~εHf(present) values range from -55.3 to -52.5 (~εHf(2.06 Ga) =-9.0 to-6.8) and are surprisingly homogeneous. This homogeneity is difficult to reconcile with direct assimilation of crustal material by Bushveld parent magmas because it would require that each batch of magma had assimilated just the right amount of material to all acquire the same Hf isotopic composition. Also, calculations suggest that simple mixing of regional crust into a primitive, mantle-derived liquid cannot account for both the presumed Hf and major elemental concentrations and the ~(176)Hf/~(177)Hf ratio of the Bushveld magmas. Rather, the Hf data are consistent with generation of these magmas by partial melting in a sub-continental mantle lithospheric source withan unradiogenic Hf isotopic composition equal to that of the Bushveld parent magmas. Several possibilities for the development of such a source are explored using the new Hf isotope data.
机译：我们使用Bushveld复杂体中锆石的Hf同位素组成来更好地了解其母岩浆的来源。该数据集由来自11个样品的141个单独LA-ICP-MS分析组成，涵盖了整个累积地层，显示母岩浆的had同位素组成与贫化地幔在2.06 Ga时的同位素组成不同。具体地说，样品平均〜εHf （当前）值的范围是-55.3至-52.5（〜εHf（2.06 Ga）= -9.0至-6.8），并且令人惊讶地均匀。布什维尔德母岩浆与地壳物质的直接同化很难统一，因为这将要求每批岩浆仅吸收了适量的物质才能全部获得相同的H同位素组成。此外，计算表明，将地壳简单混合到地幔衍生的原始液体中，既不能解释推测的Hf和主要元素浓度，也不能解释Bushveld岩浆的〜（176）Hf /〜（177）Hf比。相反，Hf数据与在次大陆幔岩石圈源中部分融化而产生的这些岩浆一致，其非放射性的Hf同位素组成与Bushveld母岩浆相同。使用新的H同位素数据探索了开发这种源的几种可能性。

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