Melilitolite

Melilitolite: An ultramafic plutonic rock consisting essentially of melilite, pyroxene and olivine.

The melilitolites are classified according to their mineral content. Those with melilite < feldspathoid and with feldspathoid > 10% are classified as melilite foidolites. In a recent paper on the classification of melilitic rocks, Dunworth & Bell (1998) suggested that melilitolites with melilite > 65% be termed ultramelilitolites.

Besides melilite, other principal mineral components include perovskite, olivine, hauyne, nepheline and pyroxene. If these minerals comprise > 10% of the rock and melilite is < 65% then the following names may be used:

1) if perovskite > 10% then it is an afrikandite.
2) if olivine > 10% then it is a kugdite.
3) if hauyne > 10% and melitite > hauyne then it is an okaite.
4) if nepheline > 10% and melitite > nepheline then it is a turjaite.
5) if pyroxene > 10% then it is an uncompahgrite.

If a third mineral is present in amounts greater than 10% then it can be applied as a modifier, e.g. magnetite-pyroxene Melilitolite.


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Melilitolite classification.



San Venanzo melilitolite

The calcite-leucite-melilitolite of Pian di Celle (San Venanzo) has been famous for over a century, and was previously called pegmatoid venanzite (Gallo et al., 1984). It contains tabular melilite up to 5 cm long, nepheline intergrowths associated with coarse-grained, intergranular, twinned leucite, nepheline and kalsilite as essential minerals. The interstices between these phases are filled with a fine-grained groundmass composed of Apatite, F-phlogopite, clinopyroxene, Zr-cuspidine, gotzenite, khibinskite, pyrrhotite, Co-Ni-westerveldite, bartonite, wollastonite and brown or green glass. Olivine and monticellite also occur. The interstitial material commonly contains carbonate ocelli with high Sr, B a and REE (Stoppa and Woolley, 1997).

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Panoramic view of coarse-grained pegmatitic Venanzinte thin section. Image by Andy Tindle (Virtual Microscope). PPL image, field of view = 2.5cm.




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Panoramic view of coarse-grained pegmatitic Venanzinte thin section. Image by Andy Tindle (Virtual Microscope). XPL image, field of view = 2.5cm.




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Coarse-grained Melilitolite at Pian di Celle. The honey-orange crystals are Phlogopite.



For more information about the San Venanzo volcanic complex, see page: "San Venanzo"



Bibliography



• Stoppa, F., & Sforna, S. (1995). Geological map of the San Venanzo volcano (Central Italy): explanatory notes. Acta Vulcanologica, 7(1), 85-91.
• Stoppa, F. (1996). The San Venanzo maar and tuff ring, Umbria, Italy: eruptive behaviour of a carbonatite-melilitite volcano. Bulletin of Volcanology, 57(7), 563-577.
• Stoppa, F., & Cundari, A. (1998). Origin and multiple crystallization of the kamafugite-carbonatite association: The San Venanzo-Pian di Celle occurrence (Umbria, Italy). Mineralogical Magazine, 62(2), 273-289.
• Peccerillo.A (2005): Plio-Quaternary Volcanism in Italy.


Foto
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Melilite (with anomalous, berlin blue colors) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Phlogopite, Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (beige), Leucite and olivine (colorless) and Phlogopite (brown) in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Phlogopite, Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (beige), Leucite and olivine (colorless) and Phlogopite (brown) in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 2x (Field of view = 7mm)
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Melilite (beige), Leucite and olivine (colorless) and Phlogopite (brown) in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Phlogopite, Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (beige), Leucite and olivine (colorless) and Phlogopite (brown) in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (beige), Leucite and olivine (colorless), pyroxene (green) and Phlogopite (brown) in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned), pyroxene and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark) and Kalsilite (gray). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark) and Kalsilite (gray). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors) and Leucite (dark). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors) and Leucite (dark). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors) and Leucite (dark). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (beige), Leucite and olivine (colorless), pyroxene (green) and Phlogopite (brown) in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned), pyroxene and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned), pyroxene and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, violet-yellow and berlin blue colors) and Leucite (dark and twinned) in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned) and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Leucite (dark and twinned), Phlogopite, and olivine in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors) and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors) and Leucite (dark and twinned) in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Phlogopite, Kalsilite (gray) in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors) and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Phlogopite, Kalsilite (gray) in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors) in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors) in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 10x (Field of view = 2mm)
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Melilite (beige) and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors) in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors) and Leucite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors) and Leucite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 10x (Field of view = 2mm)
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Melilite (beige) and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 10x (Field of view = 2mm)
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Melilite (with anomalous, berlin blue colors) in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 10x (Field of view = 2mm)
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Melilite (beige), Magnetite and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 10x (Field of view = 2mm)
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Melilite (beige-white), Magnetite, green pyroxene and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 2x (Field of view = 7mm)
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Melilite (beige-white), Magnetite, green pyroxene and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). PPL image , 2x (Field of view = 7mm)
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Melilite, Magnetite, pyroxene and Phlogopite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Phlogopite and Leucite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Olivine, Phlogopite and Leucite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Melilite (with anomalous, berlin blue colors), Phlogopite and Calcite in a Melilitite, San Venanzo (Umbria, Italy). XPL image , 2x (Field of view = 7mm)
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Pyroxene and Kalsilite (gray). XPL image , 10x (Field of view = 2mm)
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Pyroxene and Kalsilite (colorless, rectangular crystals). PPL image , 10x (Field of view = 2mm)
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Pyroxene and Kalsilite (gray). XPL image , 10x (Field of view = 2mm)
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Phlogopite and Kalsilite (gray). XPL image , 10x (Field of view = 2mm)
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Phlogopite and Kalsilite (gray). XPL image , 10x (Field of view = 2mm)
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Pyroxene and Kalsilite (gray). XPL image , 10x (Field of view = 2mm)
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Leucite, Phlogopite and Kalsilite (gray) and Calcite. XPL image , 10x (Field of view = 2mm)
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Phlogopite and Calcite. XPL image , 10x (Field of view = 2mm)
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Green glass between Phlogopite crystals. PPL image , 10x (Field of view = 2mm)
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Green glass between Phlogopite crystals. The small, fibrous colorless crystals are Cuspidine. PPL image , 10x (Field of view = 2mm)
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Green glass between Phlogopite and Kalsilite (square) crystals. The small, fibrous colorless crystals are Cuspidine. PPL image , 10x (Field of view = 2mm)
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Green glass between Phlogopite crystals. The small, fibrous colorless crystals are Cuspidine. PPL image , 10x (Field of view = 2mm)
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Green glass between Phlogopite and Kalsilite (square) crystals. The small, fibrous colorless crystals are Cuspidine. PPL image , 10x (Field of view = 2mm)