Further evidence of widespread Permian remagnetization in the North Patagonian massif, Argentina

摘要: Abstract A paleomagnetic study on accurately dated (472–476 Ma) Early Ordovician undeformed granitoids exposed in the northeastern margin of North Patagonian massif (41.5°S, 65.0°W) was carried out, with main goal comparing paleogeographic position Patagonia relative to Gondwana. About one hundred specimens were processed, from ten sites plus two quartzites and sandstones unconformably overlying Devonian Sierra Grande Formation. Seven out twelve sites, all granitoids, provided consistent directions a characteristic remanent magnetization. Structural correction data plutons could only be applied at few bedding attitudes or Tertiary sedimentary rocks. The failed recover primary remanence. Thermal demagnetization isolated reversed magnetic component high unblocking temperatures. Magnetic properties petrographic analyses suggest that remagnetization is by secondary minerals grew circulating temperature fluids inferred pervasive localized hydrothermal alteration. This led formation magnetite and/or hematite after biotite. pole (PP) computed mean site directions. this PP (011°E, 65.0°S; A95 = 12°, K = 24.5) apparent polar wander path South America suggests magnetization probably acquired during Permian. Syntectonic Permian times has been reported for lower member Formation nearby outcrops. Our affected as well. Many American poles have derived syn- postectonic magnetizations along southwestern Gondwana margin, Argentine Precordillera Sierras Australes belt related ca. 290–270 Ma San Rafael tectonic phase. Slightly younger remagnetizations found affecting rocks foreland both Argentina Uruguay, suggesting migration front towards North-Northeast. similarity our new remagnetized those units southern confirms already part Whether associated widespread well 290–280 Ma magmatism northern major can attributed processes collision Patagonia, post-collision adjustment minor plates, discussed.