Magmatický a vulkanický vývoj vulkanického komplexu Doupovských hor

Magmatický a vulkanický vývoj vulkanického komplexu Doupovských hor Abstrakt Vulkanický komplex Doupovských hor (DHVC) se nachází v západní části oherského riftu. Ten probíhá ve směru severovýchod-jihozápad severozápadní částí českého masivu. Oherský rift sleduje variskou suturu mezi saxothuringikem a tepelsko-barrandienskou oblastí. DHVC tvoří alkalické horniny složením a pozicí podobné dalším komplexům kenozoického vnitrodeskového vulkanizmu střední a západní Evropy (CIMACi). Vulkanická aktivita komplexu Doupovských hor začala v nejspodnějším oligocénu a trvala až do spodního miocénu. Vulkanická aktivita byla opakovaně přerušována periodami rozpadu sopečného horstva. Magmatická aktivita trvala zhruba 14 milionů let a vytvořila vulkanický komplex o mocnosti 600-1000 m. Erupční sty rané explozivní aktivita DHVC je klasifikován jako strombolský až subpliniovský a freatomagmatický. Erupce uložily asi 80 m vulkanoklastik. Stáří této počáteční aktivity je datováno paleontologicky do nejspodnějšího oligocénu. Následná vulkanická aktivita byla mnohem klidnější a převažovaly výlevy láv nad pyroklastiky. Růst raného sopečného masivu kulminovala intruzí doupovského intruzivního komplexu před 30-29 miliony let. Intruzi tvoří essexit, foidový mikrosyenit, melteigit, ijolit, urtit a další podobné horniny. Tento raný...The Doupovské hory Volcanic Complex (DHVC) occupies the western part of the northeast- southwest trending Eger Graben in northwestern part of the Bohemian Massif. The Graben follows the older Variscan suture between the Saxothuringian and Teplá-Barrandian Domains. The rocks of the DHVC are alkaline with setting and composition similar to other Cenozoic intraplate volcanic complexes of the Central and Western Europe (CIMACi). The Doupovské hory Volcanic Complex started the activity in the Lowermost Oligocene and lasted until Lower Miocene. The volcanic activity resulting in accumulation of the Doupovské hory Volcanic Complex was several times interrupted by periods of volcanic edifice decay and sector collapses. The magmatic activity lasted for ca. 14 M.y. and built a volcanic complex of total thickness 600-1000 m. The earliest volcanic activity was explosive in style and the eruptions could be classified as Strombolian to Sub-plinian and phreatomagmatic. The eruptions deposited about 80 m of volcaniclastics. This initial activity was dated by paleontology to the Lowermost Oligocene. The volcanic activity subsequently became calmer and lava flows dominated over explosive events. The growth of the early DHVC edifice culminated with intrusions of the Flurbühl intrusive complex by about 30-29 Ma. The...Ústav petrologie a strukturní geologieInstitute of Petrology and Structural GeologyPřírodovědecká fakultaFaculty of Scienc

Crandallite-rich beds of the Libkovice Member, Most Basin, Czech Republic : climatic extremes or paleogeographic changes at the onset of the Miocene Climatic Optimum?

We describe the occurrence and possible origin of rare beds 1-10cm thick and containing 20-70% of crandallite, a Ca-Al phosphate enriched in Sr and Ba, found within otherwise monotonous clay-rich lacustrine sediments of the Most Basin in the Central-European Neogene Ohře Rift system. The beds were formed at ca. 17.31, 17.06, and 16.88Ma, while the entire suite of monotonous clays of the Libkovice Member was deposited between 17.46 and 16.65Ma. Trace-element and organic geochemistry, Ar-Ar geochronology and C-O-Sr isotope systematics are used to infer their source and processes leading to their formation. The most enigmatic aspect of the formation of the crandallite beds is the removal of a huge amount of phosphorus from its biogenic cycle in the lacustrine system, which was otherwise stable for ca. 0.8My. Formation of detritus-poor crandallite beds could result from some exceptional environmental disruptions that hindered transport of fine clastic material to the basin floor. Silicic volcanic activity in the area of the Pannonian Basin could have triggered this disruption. Crandallite could provide evidence of long-lasting droughts and acidification of the exogenic environment, as they are roughly coeval with the onset of the Miocene Climatic Optimum at ca. 17.0Ma

Geologische Untersuchungen an der Neubaustrecke Dresden-Prag: Geologische Untersuchungen an der Eisenbahn-Neubaustrecke Dresden-Prag (2011 - 2020)

In der Schriftenreihe werden alle Ergebnisse der geologischen Untersuchungen vorgestellt, die seit 2011 im Umfeld der geplanten Eisenbahnneubaustrecke Dresden-Prag durchgeführt worden sind. Der geplante mindestens 25 km lange, grenzüberschreitende Erzgebirgsbasistunnel durchquert verschiedene Gesteine und komplexe Störungszonen. Untersuchungsschwerpunkt waren die geologischen, tektonischen und hydrogeologischen Verhältnisse im grenznahen Raum des geplanten Trassenkorridos. Die Veröffentlichung richtet sich an Behörden, Institutionen, Ingenieur- und Planungsbüros, die sich mit der Umsetzung der Neubaustrecke beschäftigen sowie an die geologisch interessierte Fachwelt und Öffentlichkeit. Redaktionsschluss: 28.08.202

Magmatic and Volcanic Evolution of the Doupovské hory Volcanic Complex

The Doupovské hory Volcanic Complex (DHVC) occupies the western part of the northeast- southwest trending Eger Graben in northwestern part of the Bohemian Massif. The Graben follows the older Variscan suture between the Saxothuringian and Teplá-Barrandian Domains. The rocks of the DHVC are alkaline with setting and composition similar to other Cenozoic intraplate volcanic complexes of the Central and Western Europe (CIMACi). The Doupovské hory Volcanic Complex started the activity in the Lowermost Oligocene and lasted until Lower Miocene. The volcanic activity resulting in accumulation of the Doupovské hory Volcanic Complex was several times interrupted by periods of volcanic edifice decay and sector collapses. The magmatic activity lasted for ca. 14 M.y. and built a volcanic complex of total thickness 600-1000 m. The earliest volcanic activity was explosive in style and the eruptions could be classified as Strombolian to Sub-plinian and phreatomagmatic. The eruptions deposited about 80 m of volcaniclastics. This initial activity was dated by paleontology to the Lowermost Oligocene. The volcanic activity subsequently became calmer and lava flows dominated over explosive events. The growth of the early DHVC edifice culminated with intrusions of the Flurbühl intrusive complex by about 30-29 Ma. The..

Magmatic and Volcanic Evolution of the Doupovské hory Volcanic Complex

The Doupovské hory Volcanic Complex (DHVC) occupies the western part of the northeast- southwest trending Eger Graben in northwestern part of the Bohemian Massif. The Graben follows the older Variscan suture between the Saxothuringian and Teplá-Barrandian Domains. The rocks of the DHVC are alkaline with setting and composition similar to other Cenozoic intraplate volcanic complexes of the Central and Western Europe (CIMACi). The Doupovské hory Volcanic Complex started the activity in the Lowermost Oligocene and lasted until Lower Miocene. The volcanic activity resulting in accumulation of the Doupovské hory Volcanic Complex was several times interrupted by periods of volcanic edifice decay and sector collapses. The magmatic activity lasted for ca. 14 M.y. and built a volcanic complex of total thickness 600-1000 m. The earliest volcanic activity was explosive in style and the eruptions could be classified as Strombolian to Sub-plinian and phreatomagmatic. The eruptions deposited about 80 m of volcaniclastics. This initial activity was dated by paleontology to the Lowermost Oligocene. The volcanic activity subsequently became calmer and lava flows dominated over explosive events. The growth of the early DHVC edifice culminated with intrusions of the Flurbühl intrusive complex by about 30-29 Ma. The..

Geology of the Metapán volcanic field NW El Salvador

Metapán volcanic field occupies the eastern margin of the Ipala Graben and represents one of several 'Behind volcanic front' type fields in El Salvador. It was subdivided into four zones in regard to the distinct age and location of each of them. The duration of the volcanic activity in the Metapán area has been from Pliocene to Quaternary. The volcanism started with the formation of the El Cóbano shield-volcano in the SE part of the study area, which is preserved as a relict of a sequence of basaltic lavas, approximately 300 m thick. Later volcanic activity represented by Strombolian cones, Hawaiian fissure vents and lava fields took place in three separated areas: El Shiste to the northwest, Ostúa to the west and San Diego to the south of the Metapán town. All studied volcanic events in this area are older than the last Plinian eruption of Ilopango caldera, which produced tephra of Tierra Blanca Joven (TBJ: 430 AD)

Supplemental Material: Gravitational collapse of a volcano edifice as a trigger for explosive carbonatite eruption?

Mineral chemistry data of analyzed carbonates from studied carbonatite pyroclastic deposits </p

On the Chemical Composition and Possible Origin of Na–Cr-Rich Clinopyroxene in Silicocarbonatites from Samalpatti, Tamil Nadu, South India

Mineralogical and chemical data are presented for a suite of Na&ndash;Cr-rich clinopyroxenes associated with chromite, winchite (sodium-calcium amphibole), titanite and calcite in Mg-Cr-rich silicocarbonatites from the Samalpatti carbonatite complex, Tamil Nadu, South India. The Mg-Cr-rich silicocarbonatites occur as 10&ndash;30 cm large enclaves in pyroxenites. The chemical composition of the pyroxenes differs among individual enclaves, with variable proportions of diopside, kosmochlor and jadeite-aegirine end-members. These compositions fill a previously unoccupied space in the kosmochlor-diopside-jadeite+aegirine ternary plot, indicating a distinct origin of kosmochlor-rich pyroxene compared with previous findings from diverse settings. The Na&ndash;Cr-rich clinopyroxene has low &Sigma;REE = 9.2 ppm, with slight enrichment in LREE (LaN = 7), coupled with low HREE (YbN = 0.6), and flat HREE, paralleled by a significant fractionation of Nb/Ta (2408) and Th/U (26.5). Sodic metasomatism (fenitization) associated with either carbonatite emplacement at shallow levels or during carbonatite ascent through the upper mantle most likely was the major process operating in the area. We suggest two scenarios of the formation of Na&ndash;Cr-rich pyroxene: (1) from mantle-derived chromian mineral phases (spinel and/or garnet) through fenitization, with subsequent corrosion by growing winchite due to volatile influx; (2) via metasomatic reaction of Cr-rich garnet in mantle peridotite due to reaction with Na-rich carbonatite melt. Collectively, the appearance of kosmochlor may play an important role in deconvolving metasomatic processes, and fenitization in particular. If combined with petrologic experiments, it could improve our understanding of the origin and subsequent history of chemical signatures of carbonate-rich materials in the mantle