Petrogenesis of early syn-tectonic monzonite-granodiorite complexes - Crustal reprocessing versus crustal growth
Identifikátory výsledku
Kód výsledku v IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F26722445%3A90120%2F20%3AN0000106" target="_blank" >RIV/26722445:90120/20:N0000106 - isvavai.cz</a>
Výsledek na webu
<a href="https://www.sciencedirect.com/science/article/abs/pii/S0301926820305465" target="_blank" >https://www.sciencedirect.com/science/article/abs/pii/S0301926820305465</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1016/j.precamres.2020.105957" target="_blank" >10.1016/j.precamres.2020.105957</a>
Alternativní jazyky
Jazyk výsledku
angličtina
Název v původním jazyce
Petrogenesis of early syn-tectonic monzonite-granodiorite complexes - Crustal reprocessing versus crustal growth
Popis výsledku v původním jazyce
The 563.7 +/- 6.1 Ma old, early-syntectonic Mon Repos complex is a predominantly metaluminous, magnesian, calc-alkalic granodioritic to granitic intrusion. Major and trace element variations imply that the rocks evolved through fractional crystallization processes involving amphibole, biotite, Fe-Ti oxides, zircon, and apatite. Rocks less evolved than granodiorite show evidence of hornblende accumulation. Initial Sr (Sr-87/Sr-86: 0.7090-0.7111) and Nd (epsilon Nd: -5.3 to -12.3) isotopic compositions of the granodiorites and granites are highly heterogeneous and vary with SiO2 contents indicating that assimilation of older crustal components occurred. Initial Pb-206/Pb-204 (16.65-17.65) and Pb-207/Pb-204 ratios (15.52-15.60) are similar to other mafic-intermediate com plexes from the Damara belt. One monzodiorite and two quartz monzonites are K2O-, LILE-, and HFSE enriched and have similar SiO2 contents as the granodiorites. These samples are similar to post-collisional mafic magmas from elsewhere in the world. Their epsilon Nd values (-3.8 to -4.3), Sr-87/Sr-86 ratios (0.7051-0.7073) and trace-element characteristics imply that their unexposed parental melts are derived from a lithospheric mantle source that was contaminated and metasomatized by crustal material during ancient subduction processes. The data are explained by assuming a "flat" subduction model where melting predominantly involves ancient continental mantle lithosphere and crust with limited, if any, melting of the underlying asthenospheric mantle. During flat subduction, a sliver consisting of buoyant oceanic lithosphere was amalgamated with the base of the ancient continental lithosphere of the overriding plate. The oceanic mantle lithosphere and the oceanic crust dehydrated (but did not melt) and these fluids lowered the solidus of the overlying continental mantle lithosphere and crust. This scenario can explain the occurrence of rare K2O- and LILE-enriched monzodiorites and quartz monzonites with crustal-like isotopic compositions observed in this study as well as some more alkaline rocks in the belt. Because the metasomatized continental lithospheric mantle has lower solidus temperatures than peridotitic mantle, it is very likely that such metasomatized rocks may melt early during flat subduction. Thus, K2O-enriched monzodiorites to monzogranites are not restricted to late stages of the evolution of an orogen but may already form at the onset of an orogeny.
Název v anglickém jazyce
Petrogenesis of early syn-tectonic monzonite-granodiorite complexes - Crustal reprocessing versus crustal growth
Popis výsledku anglicky
The 563.7 +/- 6.1 Ma old, early-syntectonic Mon Repos complex is a predominantly metaluminous, magnesian, calc-alkalic granodioritic to granitic intrusion. Major and trace element variations imply that the rocks evolved through fractional crystallization processes involving amphibole, biotite, Fe-Ti oxides, zircon, and apatite. Rocks less evolved than granodiorite show evidence of hornblende accumulation. Initial Sr (Sr-87/Sr-86: 0.7090-0.7111) and Nd (epsilon Nd: -5.3 to -12.3) isotopic compositions of the granodiorites and granites are highly heterogeneous and vary with SiO2 contents indicating that assimilation of older crustal components occurred. Initial Pb-206/Pb-204 (16.65-17.65) and Pb-207/Pb-204 ratios (15.52-15.60) are similar to other mafic-intermediate com plexes from the Damara belt. One monzodiorite and two quartz monzonites are K2O-, LILE-, and HFSE enriched and have similar SiO2 contents as the granodiorites. These samples are similar to post-collisional mafic magmas from elsewhere in the world. Their epsilon Nd values (-3.8 to -4.3), Sr-87/Sr-86 ratios (0.7051-0.7073) and trace-element characteristics imply that their unexposed parental melts are derived from a lithospheric mantle source that was contaminated and metasomatized by crustal material during ancient subduction processes. The data are explained by assuming a "flat" subduction model where melting predominantly involves ancient continental mantle lithosphere and crust with limited, if any, melting of the underlying asthenospheric mantle. During flat subduction, a sliver consisting of buoyant oceanic lithosphere was amalgamated with the base of the ancient continental lithosphere of the overriding plate. The oceanic mantle lithosphere and the oceanic crust dehydrated (but did not melt) and these fluids lowered the solidus of the overlying continental mantle lithosphere and crust. This scenario can explain the occurrence of rare K2O- and LILE-enriched monzodiorites and quartz monzonites with crustal-like isotopic compositions observed in this study as well as some more alkaline rocks in the belt. Because the metasomatized continental lithospheric mantle has lower solidus temperatures than peridotitic mantle, it is very likely that such metasomatized rocks may melt early during flat subduction. Thus, K2O-enriched monzodiorites to monzogranites are not restricted to late stages of the evolution of an orogen but may already form at the onset of an orogeny.
Klasifikace
Druh
J<sub>imp</sub> - Článek v periodiku v databázi Web of Science
CEP obor
—
OECD FORD obor
10505 - Geology
Návaznosti výsledku
Projekt
—
Návaznosti
—
Ostatní
Rok uplatnění
2020
Kód důvěrnosti údajů
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Údaje specifické pro druh výsledku
Název periodika
Precambrian research
ISSN
0301-9268
e-ISSN
1872-7433
Svazek periodika
351
Číslo periodika v rámci svazku
December
Stát vydavatele periodika
NL - Nizozemsko
Počet stran výsledku
21
Strana od-do
1-21
Kód UT WoS článku
000595149400013
EID výsledku v databázi Scopus
2-s2.0-85094124341