Temporalidad del magmatismo del borde paleo-Pacífico de Gondwana: geocronología U-Pb de rocas ígneas del Paleozoico tardío a Mesozoico temprano de los Andes del norte de Chile entre los 20° y 31°S.

Victor Maksaev,Colombo Tassinari,Francisco Munizaga

doi:10.5027/andgeov41n3-a01

Abstract

U-Pb zircon geochronological data provide record of about 130 Ma of igneous activity in the Andes of northern Chile, which extended episodically from the latest Early Carboniferous to Early Jurassic (328-194 Ma). The overall U-Pb data show that volcanism and plutonism were essentially synchronous and major episodes of igneous activity developed during the Late Carboniferous to Mid-Permian (310 to 260 Ma) and from Late Permian to Late Triassic (255-205 Ma), with less prominent episodes in the mid-Carboniferous (330 to 320 Ma), and Early Jurassic (200-190 Ma). Thus, from the Carboniferous to the Early Triassic dominantly silicic magmatism developed along the Chilean segment of the southwestern border of Gondwana supercontinent. Further magmatism developed during the Mid-Late Triassic (250-194 Ma) was bimodal and synchronous with rift-related, continental and/or marine sedimentary strata related to the early stages of break-up of Gondwana. Most of the silicic volcanic rocks of the Precordillera and Domeyko Cordillera of northern Chile (21°30’ to 25°30’S) are older than the silicic rocks assigned to the Choiyoi succession in Argentina, being instead equivalent in age to Carboniferous to Early Permian marine sedimentary sequences present in the eastern Argentinean foreland. On the other hand, silicic volcanic successions exposed in the easternmost part of northern Chile are equivalent in age to the Choiyoi succession of the San Rafael Block of Argentina. An eastward expansion or migration of the volcanism during the Mid-Permian to Early Triassic is inferred, interpretation that is consistent with expansion of the volcanism at that time in Argentina. The timing of the Late Paleozoic to Early Jurassic magmatism is coincident with that of the Andes of Perú and of western Argentina according to the available U-Pb data, revealing a rather consistent evolution in time of the magmatism along the southwestern, paleo-Pacific border of Gondwana.

Highlights

The Late Paleozoic-Early Mesozoic magmatism is a significant, but not completely understood geological event, which has been recognized along much of the length of western South America (e.g., Vaughan and Pankhurst, 2008)
The overall U-Pb data show that volcanism and plutonism were essentially synchronous and major episodes of igneous activity developed during the Late Carboniferous to Mid-Permian (310 to 260 Ma) and from Late Permian to Late Triassic (255-205 Ma), with less prominent episodes in the mid-Carboniferous (330 to 320 Ma), and Early Jurassic (200-190 Ma)
From the Carboniferous to the Early Triassic dominantly silicic magmatism developed along the Chilean segment of the southwestern border of Gondwana supercontinent

Summary

Introduction

The Late Paleozoic-Early Mesozoic magmatism is a significant, but not completely understood geological event, which has been recognized along much of the length of western South America (e.g., Vaughan and Pankhurst, 2008). Mesozoic igneous rocks of northern Chile (north of 31°S latitude), which we have compiled in Tables 1 and 2 (references therein), and in Argentina (i.e., Pankhurst et al, 2006; Gulbranson et al, 2010; Rocha-Campos et al, 2011) In this contribution we present 41 new SHRIMP U-Pb dates for volcanic and plutonic rocks of northern Chile, which together with the compilation of U-Pb dates from previous studies, provide a more accurate timing for the Late Paleozoic to Early Jurassic magmatism of the north-Chilean segment of the southwestern border of Gondwana. The numerical ages are assigned to the International Stratigraphic Chart of the International Commission on Stratigraphy 2013 (Cohen et al, 2013)

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Conclusion