Sedimentpetrographische, mineralchemische und geochronologische Untersuchungen am Detritus neoproterozoischer und devonischer Siliziklastika im westlichen Südural

Studies of Detritus in the SW Urals (light and heavy mineral spectrum, mineralchemistry, age of detritic minerals) of three different siliciclastic sedimentic sequences (Riphean, Upper Vendian, Upper Devonian) deliver provenance signals of two orogenic events in the Neoproterozoic and in the Upper Devonian.The characteristics of the detritus are very similar in various formations of the Riphean and Lower Vendian on one side and of the Upper Vendian on the other. Riphean and Lower Vendian detritus with a “continental platform provenance” is in accordance with sediment transport from westerly directions from the eroded East European craton. On the other hand, the source for the detritus of the Upper Vendian abruptly changed to a „recycled orogenic provenance“. The Upper Vendian detritus can be interpret as erosion product of recycle collision orogen. The composition of phengites in Vendian rocks contrasts strongly with those of detrital white mica in the Riphean rocks. The composition of tourmalines derived from a metapsammopelitic source indicates a mainly Al-poor metasediment provenance, whereas Riphean tormalines were derived from mainly Al-rich metapsammopelites. Zircon morphology, tourmaline zoning and a reduced heavy mineral spectrum provide evidence for polycyclic sedimentation during Riphean and Vendian.Polycyclic zircons in the Riphean and Upper Vendian detritus have age signatories compatible with crystallisation in interval 1,8 - 2,3 Ga. This reflects the derivation from pre-Riphean Basement of the East European platform. The data of the euhedral zircons from the Upper Vendian sandstones would reflect a source age between 643 and 512 Ma. This age signature is compatible with a local magmatic event concomitant with exhumation and emplacement of the allochthonous Beloretzk Terrane after 620 Ma. It can be considered a potential provenance area of Upper Vendian detritus. Two contrasting provenance areas can be distinguished in the SW Urals by studies of the Neoproterozoic sandstones. This reflect a dramatic change of geotectonic conditions at the eastern border of the Baltica protocontinent in the Upper Vendian.During collision of the East European Craton continental margin with the Magnitogorsk island arc highly immature sandstones of the Zilair Formation (Upper Devonian) were deposited on both sides of the Main Uralian fault. The detritus of the Zilair sediments was derived from divers source rock assemblages. The metamorphic source consisted of low to medium metamorphic grade rocks and high pressure rocks as evidenced by phengites and glaucophane. Other sources are obducted ophiolites of the Main Uralian fault zone and metamorphic complexes at the rear of the collisional accretionary complex as well as volcanosedimentary series of the Magnitogorsk arc. Light and heavy mineral distribution as well as the variation of the chemical composition of minerals did not reveal any significant difference during the period of deposition of the Zilair formation. This time represents surface uplift of an axial rise between the collisional accretionary prism and the forearc basin during exhumation of high pressure rocks.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2006

Author dc:creator

• Ermolaeva, Tatiana

Contributors dc:contributor

• Kramm, Ulrich

• info:eu-repo/classification/ddc/550
• Geowissenschaften
• Südlicher Ural
• Riphäikum
• Vendium
• Devon
• Turmalin
• Zirkon
• Provenanzanalyse
• Phengit
• Provenance analysis
• SW Urals
• Riphean
• Vendian
• Devonian

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123806%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62225