Some paleomagnetic constraints on the tectonic evolution of the coastal cordillera of central Chile

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Abstract
Paleomagnetic samples collected from 19 sites in radioisotopically dated Jurassic mafic dykes and plutons in the coastal cordillera of Chile between latitude 32°15′ and 33°30′ S yield Paleomagnetic poles (calculated by averaging the virtual geomagnetic poles from approximately coeval sites) at latitude 85.9°S, longitude 36.7°E (N = 8, a95 = 11.9°) for sites dated at close to 170 Ma and at latitude 80.3°S, longitude 207.8°E (N = 10, a95 = 9.5°) for sites dated at close to 145 Ma. These paleomagnetic poles from the coast of Chile coincide with poles from coeval sequences within the South American craton. Some of the igneous rocks that constitute these sampling sites crosscut a high‐grade metamorphic complex that is distinct from other segments of the coastal cordillera in age, structural style, and metamorphic grade. This complex cannot be correlated with metamorphic rocks anywhere else in central western South America and could be considered a potentially “exotic” allochthonous terrane. If this terrane has been added to the western South American margin, then accretion occurred prior to 170 Ma. Paleomagnetic results presented here indicate that no major rotation or large‐scale latitudinal translation of crustal blocks has taken place in this part of central Chile since Middle Jurassic time.