Origin of cordierite-bearing monzogranites from the southern Central Iberian Zone - inferences from the zoned Sierra Bermeja Pluton (Extremadura, Spain)

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F19%3A00000027" target="_blank" >RIV/00025798:_____/19:00000027 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11310/19:10404570

Výsledek na webu

<a href="https://doi.org/10.1016/j.lithos.2019.05.028" target="_blank" >https://doi.org/10.1016/j.lithos.2019.05.028</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.lithos.2019.06.009" target="_blank" >10.1016/j.lithos.2019.06.009</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Origin of cordierite-bearing monzogranites from the southern Central Iberian Zone - inferences from the zoned Sierra Bermeja Pluton (Extremadura, Spain)

Popis výsledku v původním jazyce

Voluminous peraluminous (biotite, biotite-cordierite and cordierite-muscovite-bearing) granitic plutons were emplaced in the southern part of the Central Iberian Zone (Iberian Massif) during the waning stages of the Variscan Orogeny. The role of the mantle and the nature of the crustal sources involved in the generation of these remarkable granites are still a matter of discussion. To address these issues, a detailed study of the Sierra Bermeja Pluton, a ~60 km2 cordierite-bearing monzogranite intrusion representative of the regional Nisa-Alburquerque-Los Pedroches Magmatic Alignment, has been carried out. This pluton was formed by an inward sequence of three distinct but near contemporaneous magma pulses: Outer Unit (OU), Middle Unit (MU) and Inner Unit (IU). The nested pluton is cut by a number of syn-plutonic vaugneritic dykes, while lamprophyres were distinctly later. The age of the Pluton has been established at ca. 306 Ma (309 ± 3 to 304 ± 3 Ma) by LA-ICP-MS U-Pb dating of zircon and monazite. The peraluminosity (A/CNK = 1.01-1.33) and P2O5 contents (0.19-0.35 wtpercent) of the monzogranitic units increase inwards (OU -> MU -> IU). This is accompanied by an overall decrease in TiO2, MgO, CaO, and FeOt, and most trace-elements, including REE. The three units display similarly low 87Sr/86Sr306Ma ratios (0.7033-0.7046) but decreasing EpsNd306Ma (OU: ~ -2.7, MU: ~ -3.8, IU: -7.5 to -4.7). Vaugneritic rocks have homogeneous composition with similar 87Sr/86Sr306Ma ratios (~0.7043) to those of the monzogranites but higher EpsNd306Ma (~ +1.1) values. Whole-rock geochemical data imply a partial melting of mainly Cambro-Ordovician felsic metaigneous rocks (OU) with increasing proportion of Neoproterozoic-Lower Cambrian metasediments of the Schist-Greywacke Complex (MU) that formed, almost exclusively, the source of the IU. Thermobarometric data suggest that melting processes progressed upward through the geological record and magma emplacement took place at <3 kbar, with crystallization temperatures of 710-810 oC. Geochemical modelling implies that each monzogranitic unit could have evolved independently at the emplacement level by a 20-26percent fractional crystallization of a mineral assemblage constituted by Kfs + Pl > Bt > > Ap + Mnz + Xtm. The present results could be extensible to other cordierite-bearing granites of the southern Central Iberian Zone although forthcoming experimental work and detailed comparisons are required to confirm such extrapolation.

Název v anglickém jazyce

Origin of cordierite-bearing monzogranites from the southern Central Iberian Zone - inferences from the zoned Sierra Bermeja Pluton (Extremadura, Spain)

Popis výsledku anglicky

Voluminous peraluminous (biotite, biotite-cordierite and cordierite-muscovite-bearing) granitic plutons were emplaced in the southern part of the Central Iberian Zone (Iberian Massif) during the waning stages of the Variscan Orogeny. The role of the mantle and the nature of the crustal sources involved in the generation of these remarkable granites are still a matter of discussion. To address these issues, a detailed study of the Sierra Bermeja Pluton, a ~60 km2 cordierite-bearing monzogranite intrusion representative of the regional Nisa-Alburquerque-Los Pedroches Magmatic Alignment, has been carried out. This pluton was formed by an inward sequence of three distinct but near contemporaneous magma pulses: Outer Unit (OU), Middle Unit (MU) and Inner Unit (IU). The nested pluton is cut by a number of syn-plutonic vaugneritic dykes, while lamprophyres were distinctly later. The age of the Pluton has been established at ca. 306 Ma (309 ± 3 to 304 ± 3 Ma) by LA-ICP-MS U-Pb dating of zircon and monazite. The peraluminosity (A/CNK = 1.01-1.33) and P2O5 contents (0.19-0.35 wtpercent) of the monzogranitic units increase inwards (OU -> MU -> IU). This is accompanied by an overall decrease in TiO2, MgO, CaO, and FeOt, and most trace-elements, including REE. The three units display similarly low 87Sr/86Sr306Ma ratios (0.7033-0.7046) but decreasing EpsNd306Ma (OU: ~ -2.7, MU: ~ -3.8, IU: -7.5 to -4.7). Vaugneritic rocks have homogeneous composition with similar 87Sr/86Sr306Ma ratios (~0.7043) to those of the monzogranites but higher EpsNd306Ma (~ +1.1) values. Whole-rock geochemical data imply a partial melting of mainly Cambro-Ordovician felsic metaigneous rocks (OU) with increasing proportion of Neoproterozoic-Lower Cambrian metasediments of the Schist-Greywacke Complex (MU) that formed, almost exclusively, the source of the IU. Thermobarometric data suggest that melting processes progressed upward through the geological record and magma emplacement took place at <3 kbar, with crystallization temperatures of 710-810 oC. Geochemical modelling implies that each monzogranitic unit could have evolved independently at the emplacement level by a 20-26percent fractional crystallization of a mineral assemblage constituted by Kfs + Pl > Bt > > Ap + Mnz + Xtm. The present results could be extensible to other cordierite-bearing granites of the southern Central Iberian Zone although forthcoming experimental work and detailed comparisons are required to confirm such extrapolation.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

<a href="/cs/project/GA18-24378S" target="_blank" >GA18-24378S: Petrogeneze (ultra-)draselných magmat evropských Variscid – implikace pro vývoj kolizních orogenů a modely krustálního růstu</a><br>

Návaznosti

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

Rok uplatnění

2019

Kód důvěrnosti údajů

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

Název periodika

Lithos

ISSN

0024-4937

e-ISSN

—

Svazek periodika

342-343

Číslo periodika v rámci svazku

October

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

23

Strana od-do

440-462

Kód UT WoS článku

000477091500028

EID výsledku v databázi Scopus

2-s2.0-85067468564