Carbonatitic tear-drop lapillistone

Carbonatitic tear-drop lapilli-stone are extrusive carbonatite which is composed almost exclusively by carbonatitic spherical and tear-drop lapilli (from 0.5 to 15 mm). The lapilli-stone form a hard bank, in part due to agglutination, in part due to secondary cementation by sparrite calcite. The lapilli are pyroclastic-fall droplets of calcite carbonatite melt erupted explosively by a lava-spray to lava-fountain mechanism. The lapilli are built of micro-phenocrysts and sparse phenocrysts of calcite, which, in some case, exhibit a trachytic texture, and in some examples are vesicular. Calcite comprises > 95% of the rock, with magnetite and apatite 1-2%. Accessories include melanite, pyroxene, amphibole, biotite and titanite. The chemical composition of the Henkenberg lapilli-stone is very similar to that of alvikitic dikes and the extrusive carbonatite activity in the Kaiserstuhl is considered the surface expression of the numerous alvikitic dikes.

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Calciocarbonatite lapillistone (extrusive calciocarbonatite). From James St. John



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Calciocarbonatite lapillistone (extrusive calciocarbonatite). From Tony Peterson



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Calciocarbonatite lapillistone (extrusive calciocarbonatite). From Tony Peterson






Bibliography



• Ulianov, A., Müntener, O., Ulmer, P., & Pettke, T. (2007). Entrained macrocryst minerals as a key to the source region of olivine nephelinites: Humberg, Kaiserstuhl, Germany. Journal of Petrology, 48(6), 1079-1118.
• Walter, B. F., Marks, M. A. W., & Markl, G. (2016). The Kaiserstuhl natural laboratory-an introduction and first results. Abstract Malawi Expert Council.
• Weisenberger, T. B., Spürgin, S., & Lahaye, Y. (2014). Hydrothermal alteration and zeolitization of the Fohberg phonolite, Kaiserstuhl Volcanic Complex, Germany. International Journal of Earth Sciences, 103(8), 2273-2300.
• Weisenberger, T., & Spuergin, S. (2009). Zeolites in alkaline rocks of the Kaiserstuhl Volcanic Complex, SW Germany–new microprobe investigation and the relationship of zeolite mineralogy to the host rock. Geologica Belgica

Photo
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. XPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. XPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. XPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. XPL image, 2x (Field of view = 7mm)
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Tear-drop carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Tear-drop carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. XPL image, 2x (Field of view = 7mm)
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Tear-drop carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Tear-drop carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. XPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. XPL image, 2x (Field of view = 7mm)
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Rounded carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Tear-drop carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)
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Tear-drop carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. XPL image, 2x (Field of view = 7mm)
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Tear-drop carbonatitic lapilli (with calcite and magnetite phenocrysts) set in a secondary calcite groundmass. Lapillistone from Henkenberg. PPL image, 2x (Field of view = 7mm)