Carbon-Strontium Isotope Decoupling in Carbonatites from Caotan (Qinling, China): Implications for the Origin of Calcite Carbonatite in Orogenic Settings

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216305%3A26620%2F20%3APU143730" target="_blank" >RIV/00216305:26620/20:PU143730 - isvavai.cz</a>

Výsledek na webu

<a href="https://academic.oup.com/petrology/article/61/2/egaa024/5739450" target="_blank" >https://academic.oup.com/petrology/article/61/2/egaa024/5739450</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1093/petrology/egaa024" target="_blank" >10.1093/petrology/egaa024</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Carbon-Strontium Isotope Decoupling in Carbonatites from Caotan (Qinling, China): Implications for the Origin of Calcite Carbonatite in Orogenic Settings

Popis výsledku v původním jazyce

Mantle-derived carbonatites emplaced in orogenic belts and some extensional settings are hypothesized to contain recycled crustal material. However, these carbonatites are typically composed of calcite showing a typical mantle range of C-O isotopic values devoid of recognizable sedimentary fingerprints. Here, we report the first known instance of C-Sr isotope decoupling between intimately associated dolomite carbonatites and magnetite-forsterite-calcite carbonatites from the northern Qinling orogen, central China. The calcite-dominant variety is developed at the contact between the dolomite carbonatite and metasomatized wall-rock gneiss. The two types of carbonatites have similar delta O-18(vsmow) (6.98 parts per thousand to 9.96 parts per thousand), epsilon Nd-(i) (-3.01 to -6.47) and Pb ((206)pb/(204)pb((i)) 17.369-17.584, (207)pb/(204)pb((i)) 15.443-15.466) isotopic compositions, but significantly different C and Sr isotopic signatures (delta C-13(VPDB) = -3.09 to -3.58 parts per thousand and -6.11 to -7.19 parts per thousand; Sr-87/Sr-86((ii)) = 0.70373 to 0.70565 vs 0.70565 to 0.70624 for the dolomite and calcite rocks, respectively). The relative enrichment of the early-crystallizing dolomite carbonatite in C-13 and its depletion in Sr-87 are primary isotopic characteristics inherited from its mantle source. The observed field relations, petrographic and geochemical characteristics of the Caotan dolomite and calcite carbonatites imply that the strong C-Sr isotopic decoupling between them could not result from mixing of different mantle reservoirs (e.g. HIMU and EMI), or from magma fractionation processes. We propose that the calcite carbonatites were a by-product of metasomatic reactions between primary dolomitic melts and felsic wall-rock. These reactions involved the loss of Mg and CO2 from the magma, leading to depletion of the evolved calcite-saturated liquid in C-13 and its enrichment in radiogenic Sr. We conclude that calcite carbonatites in plate-collis

Název v anglickém jazyce

Carbon-Strontium Isotope Decoupling in Carbonatites from Caotan (Qinling, China): Implications for the Origin of Calcite Carbonatite in Orogenic Settings

Popis výsledku anglicky

Mantle-derived carbonatites emplaced in orogenic belts and some extensional settings are hypothesized to contain recycled crustal material. However, these carbonatites are typically composed of calcite showing a typical mantle range of C-O isotopic values devoid of recognizable sedimentary fingerprints. Here, we report the first known instance of C-Sr isotope decoupling between intimately associated dolomite carbonatites and magnetite-forsterite-calcite carbonatites from the northern Qinling orogen, central China. The calcite-dominant variety is developed at the contact between the dolomite carbonatite and metasomatized wall-rock gneiss. The two types of carbonatites have similar delta O-18(vsmow) (6.98 parts per thousand to 9.96 parts per thousand), epsilon Nd-(i) (-3.01 to -6.47) and Pb ((206)pb/(204)pb((i)) 17.369-17.584, (207)pb/(204)pb((i)) 15.443-15.466) isotopic compositions, but significantly different C and Sr isotopic signatures (delta C-13(VPDB) = -3.09 to -3.58 parts per thousand and -6.11 to -7.19 parts per thousand; Sr-87/Sr-86((ii)) = 0.70373 to 0.70565 vs 0.70565 to 0.70624 for the dolomite and calcite rocks, respectively). The relative enrichment of the early-crystallizing dolomite carbonatite in C-13 and its depletion in Sr-87 are primary isotopic characteristics inherited from its mantle source. The observed field relations, petrographic and geochemical characteristics of the Caotan dolomite and calcite carbonatites imply that the strong C-Sr isotopic decoupling between them could not result from mixing of different mantle reservoirs (e.g. HIMU and EMI), or from magma fractionation processes. We propose that the calcite carbonatites were a by-product of metasomatic reactions between primary dolomitic melts and felsic wall-rock. These reactions involved the loss of Mg and CO2 from the magma, leading to depletion of the evolved calcite-saturated liquid in C-13 and its enrichment in radiogenic Sr. We conclude that calcite carbonatites in plate-collis

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10511 - Environmental sciences (social aspects to be 5.7)

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

Journal of Petrology

ISSN

0022-3530

e-ISSN

1460-2415

Svazek periodika

61

Číslo periodika v rámci svazku

2

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

26

Strana od-do

„egaa024-1“-„egaa024-26“

Kód UT WoS článku

000593094800001

EID výsledku v databázi Scopus

2-s2.0-85096461247