Title
Structural characterization by anisotropy of magmatic fabrics and microstructures of the Nahuelbuta Batholith and its emplacement within the Metamorphic Complex of the Eastern Series, South-Central Chile
Date Issued
01 July 2022
Access level
metadata only access
Resource Type
journal article
Publisher(s)
Schweizerbart Science Publishers
Abstract
The Nahuelbuta Batholith (~37°–38.5° S) represents the southern end of the Chilean Coastal Batholith (~33°–38.5° S) from South-Central Chile. In the Late Carboniferous intruded in the Metamorphic Complex of the Eastern Series, a turbiditic sequence representing a fossil accretionary wedge. Typical intrusive rocks are coarse-grained diorites, tonalites to monzogranites with I-type geochemical characteristics, but showing a crustal-derived geochemical component. They were syntec-tonically emplaced in a N–S striking shear zone as a result of the Late Paleozoic subduction beneath the southwestern margin of Gondwana. These intrusive rocks were exposed before the Upper Triassic. During this time a volcano-sedimentary sequence was deposited and deformed by two folding events in the mid-and Upper Cretaceous. The intrusive rocks and their hosts were affected by subsequent brittle deformation. In this work, the structures of the batholith and the host rock are analyzed to decipher its emplacement mechanism and deformation history of the plutonic rocks. At the northern end of the Nahuelbuta Batholith the magmatic structures were overprinted by high temperature solid-state fabrics. Garnet, andalusite, staurolite and/or sillimanite appear predominantly along the western contact with the metamorphic schists and migmatites of the Eastern Series. At the northern end, the Eastern Series is represented by amphibolite to granulite facies mylonites that are moderately to high-ly dipping to the East. The down-dip stretching lineation denotes a reverse sense of shear. Microgran-ular mafic enclaves, which are abundant in a few zones in the igneous host, show a preferred shape alignment, striking ENE–WSW to NE–SW. They are considered as directions of the feeder channels, which opened in high angle to the σ1-direction. The batholith is elongated in a N-S direction, parallel to the current margin of the continental crust. Based on these directions and considering the evolution of the SW margin of South America, the emplacement mode can be derived as being almost coaxial.
Start page
39
End page
74
Volume
305
Issue
1
Language
English
OCDE Knowledge area
Ciencias del medio ambiente Ingeniería arquitectónica Geología
Scopus EID
2-s2.0-85134715301
Source
Neues Jahrbuch fur Geologie und Palaontologie - Abhandlungen
ISSN of the container
00777749
Sponsor(s)
netic laboratory in Buenos Aires. We are in debt to Scott Giorgis and his knowledge about ascent and emplacement of the magma. We thank Oscar Figueroa for his knowledge about the structures in the region and Luis Vásquez for the introduction in AutoCAD and ArcGIS. Critical remarks by Esther Izquierdo, Lucio Pinotti, Jean Louis Vigneresse, Antonio Castro, Juan Díaz Alvarado, Jeffrey Webber and Carmen Martínez Dopico are highly acknowledged. This study was supported by FONDECYT Project #1140669.
Sources of information: Directorio de Producción Científica Scopus