PALEOMAGNETISM OF A PERMO-TRIASSIC BIMODAL DIKE SWARM OF NORTHERN PATAGONIA

MIGUEZ, M.R.; MARTÍNEZ DOPICO, C.I.; RAPALINI, A.E.; LUPPO, T.; LÓPEZ DE LUCHI, M.G.

Sao Paulo

Congreso; 4ta Reunión Bienal LATINMAG; 2015

IAG- Universidade de Sao Paulo; Asociación lationamericana de Paleomagnetismo y Geomagnetismo

Paleomagnetic data was obtained from 16 sites collected from mafic and acid dikes (< 250 Ma) of the La Esperanza Plutono-Volcanic Complex, outcropping in the northern Patagonia, Argentina. AF and thermal demagnetization procedures revealed mostly north-northwestern directions with moderate upward inclinations on specimens from 13 out of 16 analyzed sites. Site mean direction for the dikes clusters around Dm = 346°; Im = -60°, which allowed calculating a paleomagnetic pole for the La Esperanza dikes (LE pole), located at -82,5° (lat), 11,9° (long) (A95=10,9º; N=13, k=17). The magnetization is primary and mainly carried by MD magnetite and minor hematite as evidenced by textures observed by ore microscope and IRM and thermomagnetic curves. The LE pole is the first pole bracketed in age for the Permo-Triassic interval for central northern Patagonia calculated with a primary magnetization on igneous rocks. The comparison of the position of the LE pole with other poles of Patagonia and neighbouring areas of Gondwana suggests that these blocks were already juxtaposed earlier than 250 Ma, as suggested in previous geologic models.