50 research outputs found
Dome-building volcanic activity in the Oas-Gutai Neogene Volcanic Area, Eastern Carpathians, Romania
A complex dome-building volcanic activity
developed during a 5 Myr time interval (13.2-
8.0 Ma) in OaĆ-GutĂąi Mts., associated to the
intermediate volcanism of the OaĆ-GutĂąi Neogene
volcanic area (OG). Numerous domes were built
up in the entire volcanic region also triggering
both non-explosive and explosive fragmentation
volcanic processes. The volcanic forms consist
of extrusive domes, lava domes and dome-
flows/coulées and cryptodomes predominantly
as solitary domes, or compound domes and dome
complexes. The domes are comprised of andesites,
dacites and rhyolites (acid andesites and dacites
are prevalent). The volcanic rocks show a calc-
alkaline and medium to high-K character and
typical subduction-zone geochemical signatures.
Overall, either subaerial or subaqueous, the dome
growth and collapse associated with fragmental
explosive or non-explosive processes, was
dominantly responsible for most of the volcanic
products. Dome emplacement in submarine setting
is commonly associated with marginal auto-
brecciation, much subordinated explosive events
and subsequent resedimentation. Overall, the
dome-building volcanic activity in OG is recorded
to a monogenetic-type of volcanism. The series
of dome-building events which were triggered
and controlled by magma-mixing and -mingling
processes developed from time to time in different
locations of O
Time-space evolution and volcanological features of the Late Miocene-Quaternary Calimani-Gurghiu-Harghita Volcanic Range, East Carpathians, Romania. A Review.
The Carpathian-Pannonian Region (CPR) hosts
one of the major Cainozoic volcanic provinces of
Europe extending in space over 6 eastern European
countries.The lithospheric evolution of this large
area governed by large-scale asthenospheric
processes is recorded by products of volcanic
activity occurred during a time interval of more
than 21 million years. According to their surface
occurrence areas, ages and composition the
Neogene volcanics of CPR were systematized in
three main groups: 1) mostly explosive products
of felsic magmas generated at the beginning of
volcanism in the whole CPR and in their particular
occurrence areas (21-12 Ma) developed in the
actual intra-Carpathian Pannonian Basin, 2) mostly
intermediate calc-alkaline rocks emplaced in both
the intra-Carpathian areas and along the arcuate
Carpathian fold-and-thrust belt, and 3) Na- and K-
alkaline and ultra-alkaline products clustered in a
number of monogenetic volcanic fields across the
whole intra-Carpathian realm developed in the final
stages of volcanic activity of the CPR as a whole
and of their particular occurrence areas. The ca.
160 km long CÄlimani-Gurghiu-Harghita volcanic
range (CGH) developed as part of the intermediate
calc-alkaline volcanism closely related in space
with the fold-and-thrust belt of the Carpathians,
representing the south-eastern segment of the CPR.
Although its map view and general petrochemical
and volcanological characteristics are quite similar
with those of other segments of the orogene belt-
tied calc-alkaline volcanic segments, at a closer
look CGH displays a number of unique features.
The time-space evolution of CGH is particular
not only in that it is the youngest (10.5 to < 0.05
Ma) dominantly calc-alkaline segment in CPR
but also it shows a transient character. Unlike
other segments along which volcanism occurred
simultaneously forming true subduction-related
400 to 800 km long volcanic fronts which were
stable in time for millions of year, in CGH
volcanic activity migrated continuously along the
range from NW to SE. So, during any given 1 Ma
time interval active volcanism was restricted to
very limited areas and to just a few active volcanic
centers. The along-range shift of volcanic foci
was concurrent with progressively lower volumes
of magma erupted and decreasing magma output
rates. As a result, gradually lower-volume and
less complex volcanic edifices were built up.
Moreover, at the range-ending and youngest South
Harghita sub-segment, magma compositions
gradually changed from normal calc-alkaline to
high-K calc-alkaline and shoshonitic, and adakitic
features emerged at the end of volcanic activity,
after a time gap of 0.5 Ma. This marks a major
geodynamic event in the development of the East
Carpathians themselves. During the transient
volcanism of CGH, edifices of varying volume and
complexity were built up forming a row of tightly-
packed adjoining stratovolcanoes/composite
volcanoes whose peripheral volcaniclastic aprons
complexly juxtaposed, overlapped and merged
with each other. The largest ones (CÄlimani
caldera, and FĂąncel-LÄpuĆna) developed until
caldera stage. Some of them (Rusca-Tihu in the
CÄlimani Mts., VĂąrghiĆ in the North Harghita
Mts.) became unstable during their growth and
collapsed, generating widespread large-volume
debris avalanche deposits. Edifice instability was
solved by volcano-basement interaction processes,
such as volcano spreading, at some large-volume
volcanoes (in particular those in the Gurghiu Mts.).
Volcano typology changed at the smaller-volume
constructs toward the southeastern terminus of the
range in the South Harghita Mts. from typical large
stratovolcanoes to smaller composite volcanoes,
dome clusters and isolated domes and simpler
internal structures. As a whole, CGH displays an
extremely particular evolutionary pattern strongly
suggesting a transient character and decreasing to
extinguishing volcanic activity along its length
from NW to SE
Complex geoarcheological investigation at the Székelyudvarhely-Kadicsfalva/Cãdiseni site (Romania)
Noble gas and carbon isotope systematics at the seemingly inactive Ciomadul volcano (EasternâCentral Europe, Romania): evidence for volcanic degassing
Ciomadul is the youngest volcano in the Carpathian-Pannonian Region, Eastern-Central Europe, which last erupted 30 ka. This volcano is considered to be inactive, however, combined evidence from petrologic and magnetotelluric data, as well as seismic tomography studies suggest the existence of a subvolcanic crystal mush with variable melt content. The volcanic area is characterized by high CO2 gas output rate, with a minimum of 8.7 Ă 103 t yr-1. We investigated 31 gas emissions at Ciomadul to constrain the origin of the volatiles. The ÎŽ13C-CO2 and 3He/4He compositions suggest the outgassing of a significant component of mantle-derived fluids. The He isotope signature in the outgassing fluids (up to 3.10 Ra) is lower than the values in the peridotite xenoliths of the nearby alkaline basalt volcanic field (R/Ra 5.95Ra±0.01) which are representative of a continental lithospheric mantle and significantly lower than MORB values. Considering the chemical characteristics of the Ciomadul dacite, including trace element and Sr- Nd and O isotope compositions, an upper crustal contamination is less probable, whereas the primary magmas could have been derived from an enriched mantle source. The low He isotopic ratios could indicate a strongly metasomatized mantle lithosphere. This could be due to infiltration of subduction-related fluids and postmetasomatic ingrowth of radiogenic He. The metasomatic fluids are inferred to have contained subducted carbonate material resulting in a heavier carbon isotope composition (13C is in the range of -1.4 to -4.6 â°) and an increase of CO2/3He ratio. Our study shows the magmatic contribution to the emitted gases
Neogene calc-alkaline intrusive magmatism of post-collisional origin along the Outer Carpathians: a comparative study of the Pieniny Mountains and adjacent areas
A petrographical and geochemical analysis was carried out on intrusive rocks from the Pieniny and Moravian areas, with special attention to boron content and K-Ar radiometric ages.
The intrusions form medium- to high-potassium calc-alkaline andesitic suites, which are compositionally slightly different from each other and from the other calc-alkaline sequences in the Carpathian-Pannonian Region. No significant geochemical differences were observed within the different phase intrusions in the Pieniny areas. However, there is a slight difference in major and trace element composition between the Moravian and Pieniny intrusions. The andesitic rocks in the Pieniny and Moravian area are enriched in large ion lithophile elements and light rare earth elements and depleted in high field strength elements, indicating a metasomatized mantle source of the parent magmas. The low boron concentration of the andesitic rocks in the Pieniny area is in the range measured in back-arc, intraplate basalts of the Bakony-Balaton Highland volcanic field, whereas the higher boron content of the Moravian rocks overlaps with that of the Western Carpathian andesites. This may indicates the heterogeneity of the mantle lithosphere below the areas, or indicates different magma evolution histories.
On the basis of the systematic geochronological study, the intrusive rocks along the Outer Carpathians can be divided on three groups, which overlap with each other temporally. The oldest magmatism occurred from 14.8 Ma to 11.0 Ma in the Uhersky Brod area, Moravia, which was followed by the emplacement of andesitic dikes and sills in the Pieniny Mts., south Poland (13.5â10.8 Ma). In the Pieniny area, two intrusive phases were distinguished. Partly overlapping with this area, but generally younger than this magmatism, the emplacement of the youngest intrusions is referable to the Poiana Botizei-ĆąibleĆ-Toroiaga-Rodna-BĂąrgĂąu intrusive area, Romania, where magmatic activity started at ~11.8 Ma and terminated at 8.0 Ma