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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #Actualités volcaniques, #Eruptions historiques

The Carpathian - Pannonian Basin / CPR region is located in the northeastern part of the Alpes-Méditerrannée region; it is characterized by the Pannonian basin, surrounded by an orogenic arc, constituted by the alpine massif, the Carpathians and the Dinarides Mountains.

Location of the Carpathians and the Pannonian basin within the framework of Europe.

Location of the Carpathians and the Pannonian basin within the framework of Europe.

Volcanism of CPRCarpathes - Pannonian Basin - Neogene volcanic rocks in the Quaternary - Doc.Sz. Harangi

Volcanism of CPRCarpathes - Pannonian Basin - Neogene volcanic rocks in the Quaternary - Doc.Sz. Harangi

It is highlighted by a fine lithosphere, 50 to 80 km, and thin crust, 22-30 km, coupled with a significant heat flow, of more than 80 mW / m².

The Pannonian basin is considered a special type of back-arc basin formed by the heterogeneous stretching of the lithosphere. The extension of the lithosphere began in the early Miocene and the syn-rift phase ended in the late Miocene. The significant thinning of the lithosphere was accompanied by asthenospheric updoming. As a result, the Pannonian Basin is one of the hottest basins in continental Europe.

The results of numerical modeling (Burov et al., 2007, Burov & Cloetingh, 2009) and the interpretation of isotopic geochemistry of basaltic alkaline magmas (Embey-Isztin et al., 2001, Seghedi et al., 2004a) have leads to the proposition that a mantle plume plays a role in the evolution of this region.

Model suggested for the origin of alkaline basalt volcanism in the CPR. The melting occurred as a result of mantle flow from the alpine region with a thick lithospheric root. This flow has a subvertical component at the west-northwest boundary of the Pannonian basin, resulting in the fusion of the heterolithospheric heterogeneous mantle. - Doc. Sz.Harangi

Model suggested for the origin of alkaline basalt volcanism in the CPR. The melting occurred as a result of mantle flow from the alpine region with a thick lithospheric root. This flow has a subvertical component at the west-northwest boundary of the Pannonian basin, resulting in the fusion of the heterolithospheric heterogeneous mantle. - Doc. Sz.Harangi

The oldest eruptive centers are in Slovakia and Hungary, north of the belt, the youngest in Romania, to the south.

The activity ranges between the Miocene and the end of the Quaternary, from 21 Ma to 11 Ma-0.2 Ma.

The nature of the upper mantle under the CPR is deduced from seismic tomographic models. These show a high-velocity body in the transition zone (400-670 km) interpreted as an accumulation of subducted plate material (Wortel and Spakman, 2000, Piromallo and Morelli, 2003, Hetényi et al., 2009), a near-vertical elevation of high velocity plate below the southeastern margin of the CPR (Vrancea zone), considered as a trace of the final stage of subduction (Sperner et al., 2001, 2004) and velocity materials relatively low between the transition zone and the base of the lithosphere.

The complex of Ciomadul domes and lava flows, with craters Szent Ana and Mohos - Doc.Science direct
The complex of Ciomadul domes and lava flows, with craters Szent Ana and Mohos - Doc.Science direct

The complex of Ciomadul domes and lava flows, with craters Szent Ana and Mohos - Doc.Science direct

Recent studies also suggest that a mantle plume under the Pannonian basin is highly unlikely, and instead offers another possible mechanism for the origin of alkaline mafic volcanism. The extension of the lithosphere played a major role in the production of the fusion, directly and indirectly. The shallow sublithospheric mantle may still be close to its solidus as a result of a previous lithospheric extension event.

This, with its heterogeneous nature, implies that the mantle may still be able to produce fusion. Thus, other volcanic eruptions can not be excluded, even in this seemingly quiet part of Europe !

Ciomadul - crater crater Szent Ana - photo Istvan Fodor / via Szabolcs Harangi

Ciomadul - crater crater Szent Ana - photo Istvan Fodor / via Szabolcs Harangi

Dating of the youngest eruptions:

The discovery of charcoal fragments, datable by the C14 method in the pumiceous pyroclastic deposits of two localities around the Ciomadul volcano, allowed a precise dating of these eruptions.

The last eruption, based on the dating of Bixad samples, is dated at 29,500 +/- 260 years BC. The unusual behavior of the Ciomadul volcano is characterized by two major explosive volcanic eruptions (Plinian) at the Szent Ana crater, interrupted by a rest period of more than 10,000 years, which is confirmed by the geochemical data of the pumice and the main phase.

The magmatic chamber of the most recent eruption, according to Bixad deposits, is located at a depth of between 5 and 12 km.

Although it is a low production volcano, it has a long eruptive history. The K / Ar dating indicates that the Mohos crater may have been active about 220,000 years ago, while the dome-building phase is dated to 650,000 - 500,000 years ago.

So distrust of a dormant volcano ... Ciomadul can not be considered an inactive volcano.

The Ciomadul volcano - photo Keele Petrology

The Ciomadul volcano - photo Keele Petrology

Sources:

- Volcanism of the Carpathian-Pannonian region, Europe: The role of subduction, extension and mantle feathers - Szabolcs Harangi - link

- Radiocarbon dating of the last volcanic eruptions of Ciomadul volcano, se carpathians, eastern-central Europe - Sz. Harangi & al - link

- Early to Mid-Miocene massive syn-extensional silicic volcanism in the Pannonian Basin (East-Central Europe): Eruption chronology, correlation potential and geodynamic implications - R.Lulacs, Sz. Harangi & al.- link

- Amphibole perspective to unravel pre-eruptive processes and conditions in volcanic plumbing systems beneath intermediate arc volcanoes: a case study from Ciomadul volcano (SE Carpathians) - K.Balazs, Sz.Harangi & al -link

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