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Petrogenesis of Early Paleozoic basalts and gabbros in the western Cuyania terrane: Constraints on the tectonic setting of the southwestern Gondwana margin (Sierra del Tigre, Andean Argentine Precordillera)

GONDWANA RESEARCH (2013)

期刊

GONDWANA RESEARCH

卷 24, 期 1, 页码 359-376

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ELSEVIER

DOI: 10.1016/j.gr.2012.09.011

关键词

Andean basement; Precordillera; Cuyania terrane; Gondwana margin; Basalt/gabbro; Geochemical modeling

类别

Geosciences, Multidisciplinary

资金

I + D + I Spanish Programs [CGL2006-12415-C03, CGL2009-13706-C03, CSD2006-0041]

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摘要

Early Paleozoic mafic igneous rocks from the Central Andean basement are located in N-S belts interpreted as suture zones among different terranes. In the western Cuyania terrane (Andean Argentine Precordillera), Sierra del Tigre mafic rocks are part of one of these belts and consist of clinopyroxene + plagioclase basalts and gabbros of tholeiitic-transitional geochemistry. These rocks were emplaced as volcanic-subvolcanic bodies during the Mid/Late Ordovician/Silurian. Distinctive geochemical features include moderate to slightly elevated light rare earth element (LREE) concentrations; low to moderate large ion lithophile element (LILE)/high field strength element (HFSE) ratios; absence of negative Nb-Ta anomalies; low Rb concentrations; negative anomalies of K (strong) and positive Ba anomalies. This geochemistry differs from that of normal-type mid-oceanic ridge basalt (N-MORB) or oceanic island basalt (OIB) and excludes the existence of subduction components. REE patterns and LILE/HFSE ratios are similar to those of enriched MORB (E-MORB) and some continental flood basalts. Geochemical modeling suggests that the parental magmas of these basalts and gabbros derived from mantle sources with compositions similar to that of the primordial mantle in the garnet-spinel transition zone. Further magmatic evolution consisted of olivine crystal fractionation and olivine + clinopyroxene + plagioclase equilibrium crystallization under low pressure, H2O, and oxidation conditions. Continental crust contamination may have occurred, but only in low proportions. Post-magmatic hydrothermal alteration consisted of slight to moderate metasomatism that added Ba, removed K +/- Rb, and generated the observed secondary mineral assemblage (mainly chlorite, epidote, and carbonates). The most probable tectonic setting for the generation and emplacement of this mafic suite is an evolved rifted margin (tholeiitic-transitional nature, E-MORB) within a thin continental crust that was unrelated to subduction-type margins. This model suggests that a western terrane (Chilenia) rifted partially from Cuyania during the Late Ordovician. (C) 2012 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

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Neoproterozoic and Early Paleozoic magmatism in the eastern Lhasa terrane: Implications for Andean-type orogeny along the northern margin of Rodinia and Gondwana

Yanfei Chen, Zeming Zhang, Xuanhua Chen, Richard M. M. Palin, Zuolin Tian, Zhaogang Shao, Shengkai Qin, Yuelei Yuan

Summary: The magmatic activities in the Lhasa terrane during the Precambrian and Early Paleozoic are crucial for understanding the geological history of the North and South Lhasa terranes as well as the northern margins of the Rodinia and Gondwana supercontinents. A study of the Bomi complex in the Lhasa terrane revealed Neoproterozoic and Cambrian magmatic events, with evidence of crustal melting and mantle-derived magmas. These findings suggest the presence of distinct Precambrian basements in the North and South Lhasa terranes.

PRECAMBRIAN RESEARCH (2022)