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A giant late Precambrian chert-bearing olistostrome discovered in the Bohemian Massif: A record of Ocean Plate Stratigraphy (OPS) disrupted by mass-wasting along an outer trench slope
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SYSNO ASEP 0509408 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title A giant late Precambrian chert-bearing olistostrome discovered in the Bohemian Massif: A record of Ocean Plate Stratigraphy (OPS) disrupted by mass-wasting along an outer trench slope Author(s) Hajná, J. (CZ)
Žák, J. (CZ)
Ackerman, Lukáš (GLU-S) RID, SAI, ORCID
Svojtka, Martin (GLU-S) SAI, RID, ORCID
Pašava, J. (CZ)Source Title Gondwana Research. - : Elsevier - ISSN 1342-937X
Roč. 74, October (2019), s. 173-188Number of pages 16 s. Publication form Print - P Language eng - English Country NL - Netherlands Keywords Accretionary wedge ; Chert ; Mass-wasting deposits ; Ocean Plate Stratigraphy (OPS) ; Olistostrome Subject RIV DB - Geology ; Mineralogy OECD category Geology R&D Projects GA17-15700S GA ČR - Czech Science Foundation (CSF) Method of publishing Limited access Institutional support GLU-S - RVO:67985831 UT WOS 000493797200010 EID SCOPUS 85058372001 DOI 10.1016/j.gr.2018.10.010 Annotation An intriguing example of chert–graywacke olistostrome is exceptionally well preserved within the late Neoproterozoic to early Cambrian Blovice accretionary wedge, Bohemian Massif. The olistostrome exhibits a block-in-matrix fabric defined by chert blocks isolated within the graywacke matrix. The major and trace element composition indicates two distinct types of cherts that formed either in a hydrothermal pelagic or hemipelagic environment supplied with a distal terrigenous material. The former is documented by elevated contents of Fe, Co, Zn, Ni, and Ti whereas the latter by high Al2O3 contents, relatively lower LaN/CeN ratios, and higher Eu/Eu* and Ce/Ce* values. Based on these geochemical data integrated with field observations and detrital zircon U–Pb ages of the host graywackes (determined using laser ablation ICP-MS), a new model for the origin of chert–graywacke association is proposed. The cherts are interpreted as representing pelagic and hemipelagic members of the Ocean Plate Stratigraphy (OPS) that formed in a sedimentary basin, carried on top of a subducting plate towards the trench. While moving over the outer swell (rise), the chert basin was intensely fractured and disrupted into large blocks or slabs. Subsequent motion of the plate brought the blocks onto an outer trench slope where they became gravitationally unstable to slide down and mix in the trench with distal, ca. 580–570 Ma turbidites derived from the overriding plate. Finally, this chert–graywacke olistostrome was covered by younger, ca. 560–547 Ma trench-fill turbidites (devoid of chert blocks) and accreted to the accretionary wedge toe, deformed, buried, and exhumed back to the wedge surface. We propose that such an olistostrome composed of pelagic/hemipelagic chert blocks and terrigenous, arc-derived graywacke matrix represents a rarely documented case of submarine, outer trench slope mass-wasting deposits and may be considered a new type of subduction-related mélanges. We coin the term outer-trench-slope mélange. Workplace Institute of Geology Contact Jana Popelková, popelkova@gli.cas.cz, Sabina Janíčková, Tel.: 233 087 272 Year of Publishing 2020 Electronic address https://www.sciencedirect.com/science/article/pii/S1342937X18302776?via%3Dihub
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