RT Journal Article
T1 The Western Sierras Pampeanas: Protracted Grenville-age history (1330–1030 Ma)of intra-oceanic arcs, subduction–accretion at continental-edge and AMCGintraplate magmatism
A1 Rapela, Carlos W.
A1 Pankhurst, R.J.
A1 Casquet Martín, César
A1 Baldo, Edgardo G.
A1 Galindo Francisco, María Del Carmen
A1 Fanning, C.M.
A1 Dahlquist, Juan A.
AB New U–Pb SHRIMP zircon ages combined with geochemical and isotope investigation in the Sierra deMaz and Sierra de Pie de Palo and a xenolith of the Precordillera basement (Ullún), provides insight intothe identification of major Grenville-age tectonomagmatic events and their timing in the Western SierrasPampeanas. The study reveals two contrasting scenarios that evolved separately during the 300 Ma longhistory: Sierra de Maz, which was always part of a continental crust, and the juvenile oceanic arc andback-arc sector of Sierra de Pie de Palo and Ullún. The oldest rocks are the Andino-type granitic orthogneissesof Sierra de Maz (1330–1260 Ma) and associated subalkaline basic rocks, that were part of anactive continental margin developed in a Paleoproterozoic crust. Amphibolite facies metamorphismaffected the orthogneisses at ca. 1175 Ma, while granulite facies was attained in neighbouring meta-sedimentsand basic granulites. Interruption of continental-edge magmatism and high-grade metamorphismis interpreted as related to an arc–continental collision dated by zircon overgrowths at 1170–1230 Ma.The next event consisted of massif-type anorthosites and related meta-jotunites, meta-mangerites(1092 ± 6 Ma) and meta-granites (1086 ± 10 Ma) that define an AMCG complex in Sierra de Maz. Theemplacement of these mantle-derived magmas during an extensional episode produced a widespreadthermal overprint at ca. 1095 Ma in neighbouring country rocks. In constrast, juvenile oceanic arc andback-arc complexes dominated the Sierra de Pie de Palo–Ullún sector, that was fully developed ca.1200 Ma (1196 ± 8 Ma metagabbro). A new episode of oceanic arc magmatism at 1165 Ma was roughlycoeval with the amphibolite high-grade metamorphism of Sierra de Maz, indicating that these two sectorsunderwent independent geodynamic scenarios at this age. Two more episodes of arc subduction areregistered in the Pie de Palo–Ullún sector: (i) 1110 ± 10 Ma orthogneisses and basic amphibolites withgeochemical fingerprints of emplacement in a more mature crust, and (ii) a 1027 ± 17 Ma TTG juvenilesuite, which is the youngest Grenville-age magmatic event registered in the Western Sierras Pampeanas.The geodynamic history in both study areas reveals a complex orogenic evolution, dominated by convergenttectonics and accretion of juvenile oceanic arcs to the continent.
PB Elsevier Science B.V., Amsterdam.
SN 0895-9811
YR 2010
FD 2010
LK https://hdl.handle.net/20.500.14352/41857
UL https://hdl.handle.net/20.500.14352/41857
LA eng
DS Docta Complutense
RD 7 abr 2025