| 秘鲁南部海岸岩基带基底杂岩的锆石U-Pb年龄和Lu-Hf同位素约束 |
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| 关键词:basement complex plagioclase amphibole gneiss zircon U-Pb geochronology zircon Lu-Hf isotopes LA-ICP-MS Columbia supercontinent coastal batholith Peru |
| 基金项目:本文由国家重点研发计划项目(编号: 2021YFC2901804)和中国地质调查局地质调查项目(编号: DD20230900702; DD202309007; DD20230051)联合资助。 |
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| Zircon U-Pb Geochronology and Lu-Hf Isotope Constraints of the Basement Complex in the Coastal Batholith, Southern Peru |
| The basement complex of the coastal batholith in Arequipa Province, Peru, is a unique crustal component at the root of the Neogene orogenic belt in the South American Andes. It is a critical tectonic rock unit for understanding the early evolution of the continent. However, its rock composition, tectonic deformation, and high-precision geochronology remain unclear. This has become a significant obstacle in fully comprehending its tectonic history. Detailed geological investigations conducted in the Atico–Chala region revealed that the basement gneiss consists of supracrust and metamorphic plutons. These rocks experienced ductile shear deformation and amphibolite-to-granulite facies metamorphism. Layered plagioclase-hornblende gneisses have been identified in supracrust. Integrated petrological, geochemical, zircon U-Pb geochronological, and Lu-Hf isotopic analyses indicated that the protolith corresponded to fine-basaltic volcanic lava classified as either island arc tholeiitic or oceanic island basalt. This classification aligns with geochemical signatures indicative of subduction-related processes, specifically Nb-enriched basalts associated with oceanic plate subduction. LA-ICP-MS U-Pb zircon dating yielded a crystallization age of (1 863±8) Ma for the plagioclase amphibolite gneiss, followed by an initial metamorphic event at (1 798±58) Ma. The εHf(t) values ranged from –0.7 to 4.3, whereas the two-stage depleted mantle model ages (TDM2) varied between 2 196 and 2 467 Ma. These results suggest that the parent magma originated primarily from the partial melting of deep mantle components, with minor contributions from ancient crustal materials during magmatism. This study indicates that the basement gneiss formed during the Late Paleoproterozoic orogeny (~1.86 Ga), likely in a continental margin arc or oceanic island setting on the eastern edge of the Nena supercontinent. Subduction of the oceanic lithosphere beneath this region triggered asthenospheric upwelling, leading to mixing with the depleted mantle wedge beneath the island arc and the subsequent eruption of Nb-rich basalt. The first metamorphic transformation occurred during the Early Paleoproterozoic consolidation period (~1.79 Ga), leading to the formation of Paleoproterozoic volcanic complexes. These geological features provide critical evidence for the preservation of tectonic remnants associated with the assembly of the Columbia supercontinent. |
| LIU Jun'an,GUO Weimin,ZENG Yong,Ccallo WALTER,Soberon DANTE,Santos ALAN.2026.Zircon U-Pb Geochronology and Lu-Hf Isotope Constraints of the Basement Complex in the Coastal Batholith, Southern Peru[J].Acta Geoscientica Sinica,47(5):1117-1132. |
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