Elemental and isotopic compositions of trench-slope black shales, Bohemian Massif, with implications for oceanic and atmospheric oxygenation in early Cambrian

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F21%3A00000046" target="_blank" >RIV/00025798:_____/21:00000046 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/67985831:_____/21:00538188 RIV/00216208:11310/21:10438946

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S003101822030643X?casa_token=ZGFI_kZ_xz0AAAAA:CldCOHCPfLd4A1ZqxV-mJ4-xaNS4sLGlMml6LbfTDkI-h2SOOTucIJq5JuToiuA9JkrJv9KAiA" target="_blank" >https://www.sciencedirect.com/science/article/pii/S003101822030643X?casa_token=ZGFI_kZ_xz0AAAAA:CldCOHCPfLd4A1ZqxV-mJ4-xaNS4sLGlMml6LbfTDkI-h2SOOTucIJq5JuToiuA9JkrJv9KAiA</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.palaeo.2020.110195" target="_blank" >10.1016/j.palaeo.2020.110195</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Elemental and isotopic compositions of trench-slope black shales, Bohemian Massif, with implications for oceanic and atmospheric oxygenation in early Cambrian

Popis výsledku v původním jazyce

This study examines a lower Cambrian pyrite-bearing black shale–graywacke succession in the Czech Republic interpreted as infill of a deep-marine, extensional trench-slope basin on top of an accretionary wedge that developed during subduction of an oceanic plate beneath the northern margin of Gondwana. The new U–Pb detrital zircon geochronology of the graywacke constrains the maximum age of deposition to 533 +5/−6 Ma, whereas the Re–Os dating of pyrite yielded a younger age of 7 ± 16 Ma. Distribution of major and trace elements and calculated enrichment factors (EF) indicate that this succession was deposited under changing redox conditions over a short time span and that the basin was presumably controlled by tectonic subsidence and varying supply of terrigenous arc-derived material. This depositional setting is reflected by largely variable EFs and delta98Mo and delta53Cr values. Euxinic conditions detected at the base of the sampled black shale interval are documented by the highest values of EFs of redox-sensitive metals (e.g., Mo, U, V, Ni, Co, As) and also the Corg/P (>;1000) and DOPT (>;0.7) values. Black shales show lower delta56Fe values due to the excess of authigenic pyrite-Fe with a mean delta56Fe value of −0.02per mille over detrital Fe in graywacke with a mean delta56Fe value of +0.25per mille. However, the Fe isotopic signatures of the black shales are not consistent with iron shuttling, mixing of authigenic and detrital sources, or hydrothermal metal enrichment. Instead, they most likely resulted from partial oxidation of pyrite through the syndepositional oxidizing hydrothermal fluids (Si–Ba enrichment), which resulted in precipitation of isotopically heavy Fe-oxyhydroxides. We propose that our maximal recorded delta98Mo value (+ 0.98per mille) might represent the best estimate for the ancient local seawater Mo composition at around 533 Ma and argues against deep-ocean oxygenation in the early Cambrian. On the other hand, the Se/Co ratios of synsedimentary pyrite indicate a mean atmosphere O2 value of ~27percent.

Název v anglickém jazyce

Elemental and isotopic compositions of trench-slope black shales, Bohemian Massif, with implications for oceanic and atmospheric oxygenation in early Cambrian

Popis výsledku anglicky

This study examines a lower Cambrian pyrite-bearing black shale–graywacke succession in the Czech Republic interpreted as infill of a deep-marine, extensional trench-slope basin on top of an accretionary wedge that developed during subduction of an oceanic plate beneath the northern margin of Gondwana. The new U–Pb detrital zircon geochronology of the graywacke constrains the maximum age of deposition to 533 +5/−6 Ma, whereas the Re–Os dating of pyrite yielded a younger age of 7 ± 16 Ma. Distribution of major and trace elements and calculated enrichment factors (EF) indicate that this succession was deposited under changing redox conditions over a short time span and that the basin was presumably controlled by tectonic subsidence and varying supply of terrigenous arc-derived material. This depositional setting is reflected by largely variable EFs and delta98Mo and delta53Cr values. Euxinic conditions detected at the base of the sampled black shale interval are documented by the highest values of EFs of redox-sensitive metals (e.g., Mo, U, V, Ni, Co, As) and also the Corg/P (>;1000) and DOPT (>;0.7) values. Black shales show lower delta56Fe values due to the excess of authigenic pyrite-Fe with a mean delta56Fe value of −0.02per mille over detrital Fe in graywacke with a mean delta56Fe value of +0.25per mille. However, the Fe isotopic signatures of the black shales are not consistent with iron shuttling, mixing of authigenic and detrital sources, or hydrothermal metal enrichment. Instead, they most likely resulted from partial oxidation of pyrite through the syndepositional oxidizing hydrothermal fluids (Si–Ba enrichment), which resulted in precipitation of isotopically heavy Fe-oxyhydroxides. We propose that our maximal recorded delta98Mo value (+ 0.98per mille) might represent the best estimate for the ancient local seawater Mo composition at around 533 Ma and argues against deep-ocean oxygenation in the early Cambrian. On the other hand, the Se/Co ratios of synsedimentary pyrite indicate a mean atmosphere O2 value of ~27percent.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

<a href="/cs/project/GA20-13644S" target="_blank" >GA20-13644S: Silicity a karbonáty jako geochemické indikátory vzniku stratigrafie oceánských desek a paleoenvironmentálních změn</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2021

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Palaeogeography, Palaeoclimatology, Palaeoecology

ISSN

0031-0182

e-ISSN

—

Svazek periodika

564

Číslo periodika v rámci svazku

February : 110195

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

21

Strana od-do

nestránkováno

Kód UT WoS článku

000636756800021

EID výsledku v databázi Scopus

2-s2.0-85100186796