Seawater silica cycling and chert formation at the Neoproterozoic–Cambrian transition: Insights from δ30Si and Ge/Si systematics of hydrothermal cherts from the Bohemian Massif

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985831%3A_____%2F23%3A00573253" target="_blank" >RIV/67985831:_____/23:00573253 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00025798:_____/23:10168789

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S000925412300298X" target="_blank" >https://www.sciencedirect.com/science/article/pii/S000925412300298X</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.chemgeo.2023.121598" target="_blank" >10.1016/j.chemgeo.2023.121598</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Seawater silica cycling and chert formation at the Neoproterozoic–Cambrian transition: Insights from δ30Si and Ge/Si systematics of hydrothermal cherts from the Bohemian Massif

Popis výsledku v původním jazyce

The genesis of cherts, rocks with >90 wt% SiO2, is suggested to be linked with dissolved seawater silica and its elevated precipitation in the Phanerozoic due to massive biological activity in the Earth’s oceans compared to the Precambrian where hydrothermal fluids played a more dominant role. Because cherts may record a history of global seawater Si cycle, their Si isotope systematics may serve as a proxy for their origin and depositional environment. In this study, Si isotope compositions, combined with Ge/Si ratios, were determined for a suite of shallow-water, deep-water and stromatolitic cherts from the Blovice accretionary complex (Bohemian Massif, Czech Republic), representative of deep marine and subduction settings, to establish the nature of cherts and processes of their formation, identify the sources of Si and Ge, and discuss the possible effect of the Neoproterozoic–Cambrian transition. The predominantly high δ30Si values > +0.23‰, associated with low Ge/Si, in deep-water cherts suggest their precipitation from seawater-derived low-temperature fluids at the seawater–sediment interface with subordinate admixture of terrigenous material. Moreover, the tight relationship between δ30Si and organic matter contents in these deep-water cherts is indicative of either equilibrium precipitation of isotopically lighter Si as the organic content of the medium increases or global decrease of δ30Si values of seawater during the Meso–Neoproterozoic related to coupled Si and C cycles. On the other hand, a δ30Si variation of ~2.5‰ (–0.94‰ to +1.60‰) in shallow-water cherts argues for precipitation from seawater interacting with hydrothermal fluids of variable temperature. Organic matter, Fe-(oxy)-hydroxides and clays represent important sinks for Ge (and Si in case of organic matter) and thus play a determining role in global marine Si–Ge cycling. This, together with the presence of abundant cherts at the Neoproterozoic–Cambrian transition, appears to be associated with redox-controlled Fe cycle which itself is related to microbial reduction and the increasing presence of organic matter towards the Phanerozoic.

Název v anglickém jazyce

Seawater silica cycling and chert formation at the Neoproterozoic–Cambrian transition: Insights from δ30Si and Ge/Si systematics of hydrothermal cherts from the Bohemian Massif

Popis výsledku anglicky

The genesis of cherts, rocks with >90 wt% SiO2, is suggested to be linked with dissolved seawater silica and its elevated precipitation in the Phanerozoic due to massive biological activity in the Earth’s oceans compared to the Precambrian where hydrothermal fluids played a more dominant role. Because cherts may record a history of global seawater Si cycle, their Si isotope systematics may serve as a proxy for their origin and depositional environment. In this study, Si isotope compositions, combined with Ge/Si ratios, were determined for a suite of shallow-water, deep-water and stromatolitic cherts from the Blovice accretionary complex (Bohemian Massif, Czech Republic), representative of deep marine and subduction settings, to establish the nature of cherts and processes of their formation, identify the sources of Si and Ge, and discuss the possible effect of the Neoproterozoic–Cambrian transition. The predominantly high δ30Si values > +0.23‰, associated with low Ge/Si, in deep-water cherts suggest their precipitation from seawater-derived low-temperature fluids at the seawater–sediment interface with subordinate admixture of terrigenous material. Moreover, the tight relationship between δ30Si and organic matter contents in these deep-water cherts is indicative of either equilibrium precipitation of isotopically lighter Si as the organic content of the medium increases or global decrease of δ30Si values of seawater during the Meso–Neoproterozoic related to coupled Si and C cycles. On the other hand, a δ30Si variation of ~2.5‰ (–0.94‰ to +1.60‰) in shallow-water cherts argues for precipitation from seawater interacting with hydrothermal fluids of variable temperature. Organic matter, Fe-(oxy)-hydroxides and clays represent important sinks for Ge (and Si in case of organic matter) and thus play a determining role in global marine Si–Ge cycling. This, together with the presence of abundant cherts at the Neoproterozoic–Cambrian transition, appears to be associated with redox-controlled Fe cycle which itself is related to microbial reduction and the increasing presence of organic matter towards the Phanerozoic.

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

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2023

Kód důvěrnosti údajů

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

Název periodika

Chemical Geology

ISSN

0009-2541

e-ISSN

1872-6836

Svazek periodika

634

Číslo periodika v rámci svazku

September

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

14

Strana od-do

121598

Kód UT WoS článku

001027862000001

EID výsledku v databázi Scopus

2-s2.0-85162258628