Vulsini District


vulsini1.jpg

Schematic geological map of Vulsini. Simplified after Vezzoli et al. (1987).



Monti Vulsini is a large district formed by various multi-center volcanic complexes, which developed in the northern sector of the Roman Province. Rocks consist of prevailing pyroclastic products and minor lava flows with a potassic to ultrapotassic composition, which cover an area of about 2200 km2. Eruption occurred at over 100 different centres, including three calderas and the large volcano-tectonic depression of the Bolsena Lake. The volcanism developed along a Tortonian to Pleistocene horst and graben system (Siena-Radicofani and Paglia-Tevere grabens, Cetona and Razzano horsts), from about 0.6 to 0.15 Ma. The pre-volcanic rocks include Liguride, Tuscan and Umbria sequences and the underlying metamorphic basement. Most of these rocks are found as xenoliths in several pyroclastic units, especially at Montefiascone and Latera.

The Vulsini district consists of four distinct volcanic complexes: Paleo-Bolsena, Bolsena, Montefiascone and Latera.

The Paleo-Bolsena (about 0.6 to 0.45 Ma) is formed by latite, trachyte, tephriphonolite and phonolite lava flows, strombolian scoriae, plinian fallout and ignimbrites, which only outcrop at the margins of the Vulsini district, directly overlying the sedimentary bedrocks.

The Bolsena volcanic complex (about 0.49 to 0.32 Ma) consists of lava flows, strombolian scoriae, several plinian deposits, thick ignimbrite sheets, and hydrovolcanic products mostly displaying a leucite tephrite to trachyte and phonolite composition, with minor latite and shoshonite. These were mostly erupted from the Bolsena Lake depression and crop out extensively in the eastern sectors of the Vulsini district. Well known outcrops of pyroclastic rocks occur in the Orvieto and Bagnoregio areas where a thick ignimbrite layer forms small plateaux, bounded by steep cliffs, on which the towns of Orvieto and Civita di Bagnoregio are located.

The Montefiascone volcano (about 0.3 to 0.2 Ma) is formed by several coalescing eruptive centres developed around a 2.5 km wide caldera, and erupting lava flows, ignimbrites, hydrovolcanic products and strombolian scoriae, mostly with a leucite-tephrite and basanite composition. Melilite-bearing lavas and kalsilite-melilitolite ejecta have been also found. The southern Vulsini complex consists of prevailing phonotephritic and phonolitic products with an age of 0.4 to 0.1 Ma.

The Latera volcano (about 0.38 to 0.15 Ma; Turbeville 1992a) consists of several pyroclastic units and some lava flows, cropping out around an 8 km wide polyphasic caldera. Compositions of the Latera rocks range from trachybasalt and phonotephrite to trachyte and phonolite.

The volcanic rocks from the Vulsini exhibit a wide range of compositions, from mafic to felsic, for rocks that are nearly saturated to undersaturated in silica. Although there is a continuum in potassium enrichments, two main series of rocks have been distinguished. One consists of moderately potassic and nearly saturated trachybasalts to trachytes, and is known as the Potassic Series (KS) or Saturated Series. Another rock series is ultrapotassic in composition and consists of leucitites, leucite tephrites, leucite basanites to leucite phonolites, and is known as the High Potassium Series (HKS). KS and HKS have been erupted through the entire evolution history of Vulsini districts; however, KS rocks appear to prevail during the latest stages of activity at Latera. A third minor group is formed by melilite-bearing rocks from Montefia scone; these have major element compositions resembling ultrapotassic kamafugites and fall in the tephrite or in the foidite field on the TAS.

Mafic KS rocks contain phenocrysts of clinopyroxene, olivine, and plagioclase set in a groundmass containing the same phases plus Fe-Ti oxides, some alkali-feldspar, and brown mica. Evolved KS rocks contain phenocrysts of sanidine, plagioclase, clinopyroxene and biotite set in a groundmass containing the same phases and Fe-Ti oxides. Leucite occurs as phenocrysts, xenocrysts and in the groundmass of several KS rocks. The most mafic HKS rocks contain olivine and clinopyroxene phenocrysts; leucite and some plagioclase phenocrysts appear in the more evolved samples. The groundmass consists of clinopyroxene, plagioclase, leucite, some alkali-feldspar, and brown mica.

Felsic rocks contain phenocrysts of clinopyroxene, leucite, plagioclase, sanidine and biotite, set in groundmass consisting of the same phases plus Fe-Ti oxides, sporadic haŁyne, nepheline, amphibole, garnet, apatite, and sphene. Melilite-bearing lavas from Montefiascone have a poorly porphyritic texture with phenocrysts of leucite, clinopyroxene and melilite, and a groundmass of clinopyroxene, olivine, Fe-Ti oxides, pale brown mica, and carbonates.



Bibliography



• Peccerillo. A. Plio-Quaternary Volcanism in Italy. (2005)

Leucitite
leucititevulsini(2).jpg

Leucite crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini(3).jpg

Leucite crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini(4).jpg

Leucite crystals in a Leucitite from Vulsini. XPL image, 2x (Field of view = 7mm)
leucititevulsini(5).jpg

Leucite crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini(6).jpg

Leucite crystals in a Leucitite from Vulsini. XPL image, 2x (Field of view = 7mm)
leucititevulsini(7).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini23(2).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini23(3).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. XPL image, 2x (Field of view = 7mm)
leucititevulsini23(4).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini23(5).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini23(6).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini23(7).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)
leucititevulsini23(9).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. XPL image, 2x (Field of view = 7mm)
leucititevulsini23(8).jpg

Leucite and pyroxene crystals in a Leucitite from Vulsini. PPL image, 2x (Field of view = 7mm)


Tephrite
tefritevulsini(2).jpg

Leucite crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
tefritevulsini(3).jpg

Leucite and olivine crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
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Leucite and olivine crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
tefritevulsini(5).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
tefritevulsini(8).jpg

Skeletal Leucite in a Tephrite from Vulsini. PPL image, 10x (Field of view = 2mm)
tefritevulsini(7).jpg

Skeletal Leucite in a Tephrite from Vulsini. PPL image, 20x (Field of view = 1mm)
foiditeleucitevulsini(3).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(2).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(3).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(7).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(8).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. XPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(9).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(10).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(11).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. XPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(12).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(12).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(13).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. XPL image, 2x (Field of view = 7mm)
foiditeleucitevulsini(14).jpg

Leucite and pyroxene crystals in a Tephrite from Vulsini. PPL image, 2x (Field of view = 7mm)


Trachybasalt
olivinaeiddingsite(2).jpg

Olivine (altered by Iddingsite) and clinopyroxene (pale green). Latera. PPL image, 2x (Field of view = 7mm)
olivinaeiddingsite(3).jpg

Olivine (altered by Iddingsite) and clinopyroxene (pale green). Latera. PPL image, 2x (Field of view = 7mm)
olivinaeiddingsite(4).jpg

Olivine (altered by Iddingsite) and clinopyroxene (pale green). Latera. PPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(2).jpg

Olivine (altered by Iddingsite) and clinopyroxene (pale green). Latera. PPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(3).jpg

Olivine (altered by Iddingsite) and clinopyroxene. Latera. XPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(4).jpg

Olivine (altered by Iddingsite) and clinopyroxene (pale green). Latera. PPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(5).jpg

Olivine (altered by Iddingsite) and clinopyroxene. Latera. XPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(6).jpg

Olivine (altered by Iddingsite) and clinopyroxene (pale green). Latera. PPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(7).jpg

Olivine (altered by Iddingsite) and clinopyroxene (pale green). Latera. PPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(8).jpg

Olivine (altered by Iddingsite) and clinopyroxene. Latera. XPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(10).jpg

Olivine (altered by Iddingsite) and clinopyroxene (pale green). Latera. PPL image, 2x (Field of view = 7mm)
trachibasaltovulsini(9).jpg

Olivine (altered by Iddingsite) and clinopyroxene. Latera. XPL image, 2x (Field of view = 7mm)


Ignimbrite
ignimbritevulsini(2).jpg

Biotite and Pyroxene embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)
ignimbritevulsini(3).jpg

Biotite and Pyroxene embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)
ignimbritevulsini(4).jpg

Biotite crystals embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)
ignimbritevulsini(5).jpg

Biotite and Pyroxene embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)
ignimbritevulsini(6).jpg

Biotite and Pyroxene embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)
ignimbritevulsini(7).jpg

Biotite crystals embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)
ignimbritevulsini(8).jpg

Biotite and Plagioclase crystals embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)
ignimbritevulsini(9).jpg

Biotite and Plagioclase crystals embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)
ignimbritevulsini(10).jpg

Biotite and Plagioclase crystals embedded in Eutaxitic groudmass. PPL image, 2x (Field of view = 7mm)


foid-trachytes
hauyna.jpg

Hauyne crystal in a foid-trachyte. PPL image, 10x (Field of view = 2mm)
hauyna(2).jpg

Hauyne crystal in a foid-trachyte. PPL image, 10x (Field of view = 2mm)
trachiteleucitehauyna(2).jpg

Leucite crystal in a foid-trachyte. PPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(3).jpg

Leucite crystal in a foid-trachyte. XPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(4).jpg

Leucite crystal in a foid-trachyte. PPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(5).jpg

Pyroxene crystal in a foid-trachyte. PPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(11).jpg

Pyroxene crystal in a foid-trachyte. PPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(13).jpg

Pyroxene crystal in a foid-trachyte. PPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(6).jpg

Leucite crystal with pyroxene-plagioclase inclusions in a foid-trachyte. XPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(9).jpg

Leucite crystal in a foid-trachyte. XPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(10).jpg

Leucite crystal in a foid-trachyte. XPL image, 2x (Field of view = 7mm)
trachiteleucitehauyna(12).jpg

Leucite crystal in a foid-trachyte. XPL image, 2x (Field of view = 7mm)


Latite
latitebolsena(2).jpg

Sanidine, plagioclase, pyroxene (green) and olivine altered by Iddingsite in a Latite from Bolsena. PPL image, 2x (Field of view = 7mm)
latitebolsena(3).jpg

Sanidine, plagioclase, pyroxene (green) and olivine altered by Iddingsite in a Latite from Bolsena. PPL image, 2x (Field of view = 7mm)
latitebolsena(4).jpg

Sanidine, plagioclase, pyroxene and olivine altered by Iddingsite in a Latite from Bolsena. XPL image, 2x (Field of view = 7mm)
latitebolsena(5).jpg

Sanidine, plagioclase, pyroxene and olivine altered by Iddingsite in a Latite from Bolsena. XPL image, 2x (Field of view = 7mm)
latitebolsena(6).jpg

Biotite, Plagioclase, sanidine and green pyroxene in a Latite from Bolsena. PPL image, 2x (Field of view = 7mm)
latitebolsena(7).jpg

Biotite, Plagioclase, sanidine and pyroxene in a Latite from Bolsena. PPL image, 2x (Field of view = 7mm)
latitebolsena(8).jpg

Sanidine and pyroxene in a Latite from Bolsena. XPL image, 2x (Field of view = 7mm)
latitebolsena(9).jpg

Sanidine and pyroxene in a Latite from Bolsena. XPL image, 2x (Field of view = 7mm)
latitebolsena(10).jpg

Sanidine and pyroxene in a Latite from Bolsena. XPL image, 2x (Field of view = 7mm)
latitebolsena(11).jpg

Biotite, Plagioclase and Pyroxene-plagioclase Glomerocrysts in a Latite from Bolsena. PPL image, 2x (Field of view = 7mm)
latitebolsena(12).jpg

Biotite, Plagioclase and Pyroxene-plagioclase Glomerocrysts in a Latite from Bolsena. XPL image, 2x (Field of view = 7mm)
latitebolsena(13).jpg

Biotite, Plagioclase and Pyroxene-plagioclase Glomerocrysts in a Latite from Bolsena. PPL image, 2x (Field of view = 7mm)
latitebolsena(14).jpg

Pyroxene-plagioclase Glomerocrysts in a Latite from Bolsena. PPL image, 2x (Field of view = 7mm)
latitebolsena(12).jpg

Biotite, Plagioclase and Pyroxene-plagioclase Glomerocrysts in a Latite from Bolsena. XPL image, 2x (Field of view = 7mm)
latitebolsena(18).jpg

Pyroxene-plagioclase Glomerocrysts in a Latite from Bolsena. XPL image, 2x (Field of view = 7mm)


Xenolith and Xenocrystals
pirossenitevulsini(2).jpg

Pyroxenite Xenolith with interstitial Biotite. PPL image, 2x (Field of view = 7mm)
pirossenitevulsini(3).jpg

Pyroxenite Xenolith. PPL image, 2x (Field of view = 7mm)
pirossenitevulsini(4).jpg

Pyroxenite Xenolith. XPL image, 2x (Field of view = 7mm)
pirossenitevulsini(5).jpg

Pyroxenite Xenolith with interstitial Biotite. XPL image, 2x (Field of view = 7mm)
pirossenitevulsini(6).jpg

Pyroxenite Xenolith. PPL image, 2x (Field of view = 7mm)
pirossenitevulsini(7).jpg

Pyroxenite Xenolith. XPL image, 2x (Field of view = 7mm)
pirossenitevulsini(8).jpg

Pyroxenite Xenolith with interstitial Biotite. PPL image, 2x (Field of view = 7mm)
pirossenitevulsini(9).jpg

Pyroxenite Xenolith with interstitial Biotite. XPL image, 2x (Field of view = 7mm)
pirossenitevulsini(10).jpg

Pyroxenite Xenolith with interstitial Biotite. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(2).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(3).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(4).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(5).jpg

Pyroxenite Xenolith with big Apatite (gray) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(6).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(7).jpg

Pyroxenite Xenolith with big Apatite (gray) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(8).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(9).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(10).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(11).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(12).jpg

Pyroxenite Xenolith with big Apatite (gray) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(13).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(17).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(19).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(20).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(21).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenolitepirosseniticovulsini(22).jpg

Pyroxenite Xenolith with big Apatite (colorless) crystals. PPL image, 2x (Field of view = 7mm)
xenovulsini(3).jpg

Quartz xenocrystals with pyroxene reaction corona in a Basalt from Vulsini. XPL, 2x (Field of view = 7mm)
xenovulsini(11).jpg

Quartz xenocrystals with pyroxene reaction corona in a Basalt from Vulsini. XPL, 2x (Field of view = 7mm)
xenovulsini(8).jpg

Quartz xenocrystals with pyroxene reaction corona in a Basalt from Vulsini. XPL, 2x (Field of view = 7mm)
xenovulsini(10).jpg

Quartz xenocrystals with pyroxene reaction corona in a Basalt from Vulsini. XPL, 2x (Field of view = 7mm)
xenovulsini(21).jpg

Quartz xenocrystals with pyroxene reaction corona in a Basalt from Vulsini. XPL, 2x (Field of view = 7mm)
xenovulsini(14).jpg

Quartz xenocrystals with pyroxene reaction corona in a Basalt from Vulsini. XPL, 2x (Field of view = 7mm)
xenovulsini(19).jpg

Quartz xenocrystals with pyroxene reaction corona in a Basalt from Vulsini. XPL, 2x (Field of view = 7mm)
xenovulsini(6).jpg

Quartz xenocrystal with pyroxene reaction corona in a Basalt from Vulsini. XPL, 10x (Field of view = 2mm)
xenovulsini(4).jpg

Quartz xenocrystal with pyroxene reaction corona in a Basalt from Vulsini. XPL, 10x (Field of view = 2mm)
xenovulsini(5).jpg

Quartz xenocrystal with pyroxene reaction corona in a Basalt from Vulsini. XPL, 10x (Field of view = 2mm)
xenovulsini(16).jpg

Quartz xenocrystal with pyroxene reaction corona in a Basalt from Vulsini. XPL, 10x (Field of view = 2mm)
xenovulsini(17).jpg

Quartz xenocrystal with pyroxene reaction corona in a Basalt from Vulsini. XPL, 10x (Field of view = 2mm)