Institut für Mineralogie, Westfälische Wilhelms-Universität Münster, Corrensstraße 24, 48149, Münster, Germany.
Nat Commun. 2022 May 24;13(1):2892. doi: 10.1038/s41467-022-30500-7.
Carbonatites are rare but worldwide occurring igneous rocks and their genesis remains enigmatic. Field studies show a close spatial but controversially debated genetic relationship with alkaline silicate rocks, and petrological and experimental studies indicate liquid immiscibility from mantle-derived magmas being one viable model for the generation of carbonatites. However, unaltered carbonatitic melts are rare and the composition of primary carbonate liquids and their silicate conjugates is poorly constrained. Here we show an example of primary Ca-carbonatitic melt formed by liquid immiscibility from a phonolitic magma of the Laacher See volcano (Eifel, Germany). The conjugate blebs of carbonate-silicate liquids are found in hauyne-hosted melt inclusions. The Ca-carbonatite melts are moderately alkali-rich and contain high F and Cl at elevated SiO and AlO concentrations. Such carbonatite liquids are viable parental magmas to the globally dominating intrusive Ca-carbonatite complexes and may provide the missing link to extrusive Na-carbonatitic magmas.
碳酸岩是一种罕见但在全球范围内存在的火成岩，其成因仍然是一个谜。野外研究表明，碳酸岩与碱性硅酸盐岩具有密切的空间关系，但在成因上存在争议，岩石学和实验研究表明，幔源岩浆的不混溶性是碳酸岩形成的一种可行模式。然而，未蚀变的碳酸岩熔体很少见，原始碳酸盐熔体及其硅酸盐共轭物的组成也没有得到很好的限制。在这里，我们展示了一个由拉赫湖火山（德国埃菲尔地区）的响岩熔体通过不混溶作用形成的原始 Ca 碳酸熔体的例子。共生的碳酸盐-硅酸盐熔体囊泡存在于钙霞石寄主熔体包裹体中。Ca 碳酸熔体具有中等程度的富碱度，在高 SiO 和 AlO 浓度下含有高 F 和 Cl。这种碳酸熔体是全球占主导地位的侵入性 Ca 碳酸岩杂岩体的可行母岩浆，可能为喷出的 Na 碳酸岩浆提供了缺失的联系。
