Pillow metabasalts in a mid-Tertiary extensional basin adjacent to the Liquiñe-Ofqui fault zone: the Isla Magdalena area, Aysén, Chile
Pillow metabasalts and interbedded slates adjacent to the Liquiñe-Ofqui fault zone (LOFZ) of the southern Chilean Andes have been studied using electron-microprobe mineral analysis, major and trace element whole-rock geochemistry and RbSr geochronology. The rocks show previously unrecognized mineralogical evidence of two metamorphic events in a low-pressure environment: an early greenschist-facies metamorphism, possibly during emplacement on the sea-floor, and a patchy amphibolite-facies overprint, which could represent either continuing sea-floor metamorphism or contact metamorphism associated with Miocene plutons. The meta-igneous rocks are considered to have formed from mid-Tertiary basaltic magmas with mixed within-plate/volcanic arc characteristics as seen in present-day volcanoes in the area, but enriched in immobile elements such as Ti, Zr, And Y. They were probably emplaced between 45 and 20 Ma, into a contemporaneous marine pull-apart or extensional basin with thin continental or oceanic floor. Many of the petrological and geochemical features of an ophiolite suite may be recognized in the immediate area.A chain of such basins developed immediately west of the LOFZ strike slip system, probably during an Eocene- Early Miocene period of oblique subduction-convergence in southern Chile, and closed when the approach angle became more orthogonal 25 Ma. Magmatic arc plutonism was resumed at about 20 Ma and continued into the latest Cenozoic.
Authors: Hervei, F., Pankhurst, R.J., Drake, R., Beck, M.E.
Privacy & Cookies Policy
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.