Geology Fichtel Mountains

1 geology

1.1 mountain building
1.2 variscan orogeny: mountains depths of sea
1.3 alpine orogeny creates new pressures
1.4 predominant rock types

geology
early mountain building

geologically fichtel massif consists of granite. history of orogeny begins in precambrian eon 750–800 million years ago. time truncated uplands of once-towering mountain chain left.

subsequently area covered sea, , rivers transported sediments old eroding mountains on coast. these sediments deposited layers of clay, sand , limestone.

at beginning of cambrian period, 570 million years ago, these beds folded , raised form new mountains. high temperatures , pressure during mountain folding process, lasted upper carboniferous period, created metamorphic rock. shale layers transformed phyllites , schists, sandstones metamorphosed quartzite , limestone produced wunsiedel marble. these mountains, may have been several kilometres high, eroded sea level again.

typical granite rocks in fichtel mountains: rudolfstein near weißenstadt)


variscan orogeny: mountains depths of sea

in next phase, great, deep-sea sediments laid down under present-day fichtel mountains , franconian forest silurian, devonian , lower carboniferous periods; these recorded in franconian forest, rocks subject low-grade metamorphism (associated volcanism , ore formation) , contain dated fossils. finally, in upper carboniferous period 285 million years ago, hercynian mountain building phase began , raised fichtel mountains, franconian forest , münchberg gneiss plateau high mountains – fold mountains formed during hercynian period. mountain building episode variscan orogeny, named after hof s latin name (and tribe of varisci) of curia variscorum. @ same time, magma intruded in several phases folds, solidified under earth s surface present-day granites. granite formed, secondary rocks affected slight contact metamorphism. rest of molten rock ore-containing fluids formed pegmatite, veins of ore , minerals – basis of medieval mining industry , industrialisation of region.

during upper carboniferous , lower permian (rotliegendes) large quantities of rock debris deposited in intramontane basins , onto foreland of mountain range. these basins formed extensional tectonics accompanied intermediate acidic volcanism. sediments of rotliegendes exposed in few places, have been confirmed across wide area drilling beneath platform southwest of franconian line. late variscan volcanic rocks occur in fichtel mountains layers of rhyolite.

alpine orogeny creates new pressures

in neogene (upper tertiary beginning 26 million years ago) period, tectonic activity increased again – alpine orogeny (alps, carpathians etc.) came end. in time, parts of , other older massifs (such bohemian-moravian highlands or bohemian massif in alpine foothills) ended underneath younger rock. in upper miocene (10 million years ago), molten basalt broke through in northern upper palatinate eger graben being formed. through erosion, remains of former diatremes have been uncovered , may seen e.g. on rauher kulm or @ parkstein near weiden. basaltic surface layers, i.e. extensive flows of low-viscosity lava, visible e. g. on teichelberg near pechbrunn. these basaltic nappes should not confusd formation of tectonic layers.

the formation of present landscape took place in younger pliocene 5 million years ago: earlier-formed franconian fault line came under pressure again , fichtel mountains, franconian forest, münchberg gneiss massif , northern upper palatine forest uplifted along it. last uplift gave forces of erosion more again , rivers cut already, levelled, mountain range. present day structure created plateau: low mountain range being gnawed away @ on sides, long , varied history. although difficult interpret, eldorado geologists wide range of specialisms.

predominant rock types

granite (latin: granum grain) , derivatives make 40% of area – impact being more striking because hard, yet hydrous, rock forms highest peaks in area. stark appearance , emergency of industry here have made mark on landscape , people.

in detail there is:

porphyritic granite of weißenstadt/liebenstein massif (including towns of marktleuthen/röslau) , extending czech republic far haslau. porphyry contains biotite (dark mica) , phenocrysts of feldspar 8 cm across.
reut granite near gefrees is, contrast, finer bluish-grey hue. selb granite (found northeast of upper massif near schwarzenhammer , running through selb forest , czech republic saxony/ elster mountains) fine-grained, grey again.
holzmühl granite occurs in 2 small outcrops near holzmühl, 3 km southeast of marktleuthen , near längenau on wartberg, east-northeast of selb; medium-grained higher biotite content, unevenly grained microstructure.
redwitzite called syenite granite , occurs in marktredwitz/arzberg/thiersheim triangle; medium- , fine-grained, variable mineral composition produces colourations light grey, dark grey , dark green-grey black.
rand granite (dach granite) occurs in prominent massifs of fichtel mountains (the ochsenkopf, southern part of schneeberg , haberstein, platte hohe matze, kösseine , großer kornberg); groundmass small-grained phenocrysts of feldspar, quartz , biotite, sprinkled muscovite well;
kösseine-rand granite occurs on kösseine, including burgstein, haberstein , schauerberg, , southern part of großer kornberg massif; small- medium-grained, porphyritic structure weak or missing; low in phenocrysts.
kern granite found in central fichtelberg/ochsenkopf/nußhardt block , on eastern perimeter of schneeberg; forms outcrops of in shape of numerous rock formations; medium- coarse-grained.
kösseine , wolfsgarten kern granite. there numerous pockets of kösseine granite containing hornfels, cm-large biotite-rich shreds , nodules of host rock, rounded or round quartz-feldspar rich pockets on kösseine massif: narrow band on north, east , southern edge, small labyrinth, kleinwendern quarry, hirschensprung rock formation, wolfstein, hohenstein, ochsenkopf, hundslohe , gregnitz valley; on kornberg: wolfsgarten forest , south-southwestern part of großer kornberg; relatively coarse, has unusual appearance due blue feldspar, black biotite , richly sprinkled dark foreign bodies; wolfsgarten granite lighter blue.
zinn granite restricted central massif , occurs on rudolfstein, on drei brüder summit of schneeberg, western slope of seehügel, between seehügel , platte, fuchsbau , zufurt west of leupoldsdorf; even, medium grain; little biotite, lot of muscovite; lighter, brighter hue.
rand granite of steinwald massif: in western part of steinwald, e. g. on dachsfelsen, , northwestern part of grandfelsen; small-grained.
steinwald granite occurs in centre, including weißenstein, platte, katzentrögel, reiseneggerfelsen , hackelstein; coarse-grained.
friedenfels granite transitional facies between steinwald granite , falkenberg porphyritic granite; forms basement of pechbrunn basalt region , surfaces there @ various places between basalt nappes; porphyritic structure, rich in feldspar phenocrysts.