Sr-Nd-Pb isotopic systematics of Australasian tektites: Implications for the nature and composition of target materials and possible volatile loss of Pb

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F20%3A00000021" target="_blank" >RIV/00025798:_____/20:00000021 - isvavai.cz</a>

Výsledek na webu

<a href="https://doi.org/10.1016/j.gca.2020.02.025" target="_blank" >https://doi.org/10.1016/j.gca.2020.02.025</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.gca.2020.02.025" target="_blank" >10.1016/j.gca.2020.02.025</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Sr-Nd-Pb isotopic systematics of Australasian tektites: Implications for the nature and composition of target materials and possible volatile loss of Pb

Popis výsledku v původním jazyce

The Australasian tektite (AAT) strewn field is the largest strewn field on the Earth with about ~10–30percent coverage, both land and ocean, but a clearly identified source impact crater is absent despite a young age of AAT at ca. 790 ka. A genetic link between the Australasian tektites and their unequivocal parental materials is therefore largely impossible to establish. Nevertheless, the nature of the parental materials and the extent of volatilization can be constrained using the splash form tektites, carrying the chemical signatures of high-temperature processes, and the layered (so-called Muong Nong-type) tektites, which are less chemically homogenized and exceptionally abundant in the AAT field. The new high-precision Sr, Nd and Pb isotopic measurements have been obtained for a chemically and petrographically well-characterized suite of AAT, which included Muong Nong-type (MN-AAT) with precisely known field locations in Laos and splash forms (SF-AAT) from different parts of the strewn field. In addition, optically dark and light zones of the MN-AAT have also been analyzed. Homogeneous eNd values from &#8722;11.8 to &#8722;11.2, combined with a narrow range of two-stage Nd model ages from 1.67 to 1.72 Ga for the entire AAT suite, point to a well-mixed source of the crustal segment in terms of REE from which the sedimentary material for tektites was ultimately derived. The Sr isotopic data largely overlap for SF-AAT and MN-AAT (87Sr/86Sr = 0.71636–0.72021) and indicate Paleozoic to Mesozoic sedimentary parentage. However, late Neogene to early Quaternary re-deposition and formation of a thick silt-sized sedimentary section with vertical stratification is required to comply with 10Be data. Lead isotopic systematics document at least three different components which can perhaps be represented by different mineral phases, such as feldspar, zircon, organic matter adsorbed on young sediments etc., sorted during riverine transport and final deposition. In addition, the SF-AAT lost considerably more Pb than the MN-AAT, and generally have isotopically heavier Pb isotopic ratios. This is theoretically consistent with preferential volatilization of lighter Pb isotopes during evaporation, but experimental work would be necessary to unambiguously distinguish kinetic fractionation from source mixing.

Název v anglickém jazyce

Sr-Nd-Pb isotopic systematics of Australasian tektites: Implications for the nature and composition of target materials and possible volatile loss of Pb

Popis výsledku anglicky

The Australasian tektite (AAT) strewn field is the largest strewn field on the Earth with about ~10–30percent coverage, both land and ocean, but a clearly identified source impact crater is absent despite a young age of AAT at ca. 790 ka. A genetic link between the Australasian tektites and their unequivocal parental materials is therefore largely impossible to establish. Nevertheless, the nature of the parental materials and the extent of volatilization can be constrained using the splash form tektites, carrying the chemical signatures of high-temperature processes, and the layered (so-called Muong Nong-type) tektites, which are less chemically homogenized and exceptionally abundant in the AAT field. The new high-precision Sr, Nd and Pb isotopic measurements have been obtained for a chemically and petrographically well-characterized suite of AAT, which included Muong Nong-type (MN-AAT) with precisely known field locations in Laos and splash forms (SF-AAT) from different parts of the strewn field. In addition, optically dark and light zones of the MN-AAT have also been analyzed. Homogeneous eNd values from &#8722;11.8 to &#8722;11.2, combined with a narrow range of two-stage Nd model ages from 1.67 to 1.72 Ga for the entire AAT suite, point to a well-mixed source of the crustal segment in terms of REE from which the sedimentary material for tektites was ultimately derived. The Sr isotopic data largely overlap for SF-AAT and MN-AAT (87Sr/86Sr = 0.71636–0.72021) and indicate Paleozoic to Mesozoic sedimentary parentage. However, late Neogene to early Quaternary re-deposition and formation of a thick silt-sized sedimentary section with vertical stratification is required to comply with 10Be data. Lead isotopic systematics document at least three different components which can perhaps be represented by different mineral phases, such as feldspar, zircon, organic matter adsorbed on young sediments etc., sorted during riverine transport and final deposition. In addition, the SF-AAT lost considerably more Pb than the MN-AAT, and generally have isotopically heavier Pb isotopic ratios. This is theoretically consistent with preferential volatilization of lighter Pb isotopes during evaporation, but experimental work would be necessary to unambiguously distinguish kinetic fractionation from source mixing.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2020

Kód důvěrnosti údajů

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

Název periodika

Geochimica et Cosmochimica Acta

ISSN

0016-7037

e-ISSN

—

Svazek periodika

276

Číslo periodika v rámci svazku

May 1

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

16

Strana od-do

135-150

Kód UT WoS článku

000525416100009

EID výsledku v databázi Scopus

2-s2.0-85081350967