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首页> 外文期刊>Contributions to Mineralogy and Petrology >Olivine in ultramafic lamprophyres: chemistry, crystallisation, and melt sources of Siberian Pre- and post-trap aillikites
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Olivine in ultramafic lamprophyres: chemistry, crystallisation, and melt sources of Siberian Pre- and post-trap aillikites

机译：橄榄石在超巨乳林百罗朗斯：化学，结晶和西伯利亚前后塔里克斯后的熔融来源

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摘要

We studied olivines from the Devonian pre-trap (the Ilbokich occurrence) and the Triassic post-trap (the Chadobets occurrence) carbonate-rich ultramafic lamprophyres (UMLs) in the southwestern portion of the Siberian craton. On the basis of detailed investigations of major, minor, and trace-element distributions, we have reconstructed the main processes that control the origins of these olivines. These include fractional crystallisation from melt, assimilation, and fractional crystallisation processes with orthopyroxene assimilation, melt-reaction diffusive re-equilibration, alkali enrichment, and CO2 degassing of the melt. Furthermore, we inferred the composition of the sources of the primary UML melt and their possible correlations with proto-kimberlitic melts, as well as the influence of the Triassic Siberian plume on the composition of the lithospheric mantle. The main differences between olivines from the Ilbokich and the Chadobets aillikites were that the olivines from the former had more magnesium-rich cores (Mg# = 89.2 +/- 0.2), had Mg- and Cr-rich transition zones (Mg# = 89.7 +/- 0.2 and 300-500 ppm Cr), had lower Ni (up to 3100 ppm) and Li (1.4-1.5 ppm), and had higher B (0.8-2.6 ppm) contents, all at higher Fo values (90-86), relative to the olivines from the latter (Mg# = 88-75; 200-300 ppm Cr; up to 3400 ppm Ni; 1.4-2.4 ppm Li; 0.4-2.2 ppm B). The Siberian aillikite sources contained a significant amount of metasomatic material. Phlogopite-rich MARID-type veins provided the likely metasomatic component in the pre-trap Devonian Ilbokich aillikite source, whereas the Triassic Chadobets aillikitic post-trap melts were derived from a source with a significant carbonate component. A comparison of UML olivines with olivines from the pre-trap and post-trap Siberian kimberlites shows a striking similarity. This suggests that the carbonate component in the aillikitic source could have been produced by evolved kimberlite melts. The differences in the lithospheric metasomatic component that contributed to pre-trap and post-trap aillikitic melts can be interpreted as reflections of the thermal impact of the Siberian Traps, which reduced phlogopite-bearing metasomes within the southwestern Siberian sub-continental lithospheric mantle.
机译：我们研究了从西伯利亚Craton的西南部的德国捕获前（ILBOKICH发生）和富含钙质捕集（Chadobets血液）碳酸盐的替代（Chadobets血液）碳酸盐的后捕集（Chadobets）的橄榄石。在重大，次要和微量元素分布的详细调查的基础上，我们重建了控制这些橄榄石起源的主要过程。这些包括来自熔融，同化和分馏的分数结晶，具有正交同化的晶体同化，熔融反应扩散重新平衡，碱富集和熔体的CO 2脱气。此外，我们推断初级UML熔体的来源的组成及其与原型 - 金伯利丝熔体的可能相关性，以及三叠系西伯利线羽流对岩石罩的组成的影响。来自Ilbokich和Chadobets Aillikites的橄榄石之间的主要差异是前者的橄榄石具有更多的富含富含镁的核心（Mg＃= 89.2 +/- 0.2），具有Mg-和Cr的过渡区（Mg＃= 89.7 +/- 0.2和300-500ppm Cr），含有较低的Ni（高达3100ppm）和Li（1.4-1.5 ppm），并且具有较高的B（0.8-2.6ppm）内容物，均处于较高的值（90- 86），相对于来自后者的橄榄石（Mg＃= 88-75; 200-300 ppm Cr;高达3400 ppm Ni; 1.4-2.4 ppm; 0.4-2.2 ppm b）。西伯利亚二十颗粒含量含有大量的代偏石材料。富含植物富含植物的絮凝物型在Pre-Trap Devonian Ilbokich Aillikite来源中提供了可能的态化组分，而七十次陷阱矿泉疏水阀熔化源于具有显着碳酸盐组分的源极。从陷阱前和陷阱后橄榄石的UML橄榄石的比较和陷阱西伯利亚金伯利特的相似性。这表明可以通过演进的金伯利钛矿熔体制造氧化钛源中的碳酸盐组分。导致陷阱前和陷阱后的岩石态偏离熔体的差异可以被解释为西伯利亚陷阱的热撞击的反射，这减少了西南西南部亚欧式岩石地幔内的磷石岩含量。

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