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

MIGUEZ, M.; MARTINEZ DOPICO, C.I.; RAPALINI, A.E.; LÓPEZ, MÓNICA GRACIELA; LUPPO, T.

LatinMag Letters

Universidad Nacional Autónoma de México

Lugar: Mexico; Año: 2015 vol. 6 p. 1 - 6

2007-9656

Paleomagneticdata was obtained from 16 sites collected from mafic and acid dikes (< 250Ma) of the La Esperanza Plutono-Volcanic Complex, outcropping in the northernPatagonia, Argentina. AF and thermal demagnetization procedures revealed mostlynorth-northwestern directions with moderate upward inclinations on specimensfrom 13 out of 16 analyzed sites. Site mean direction for the dikes clustersaround Dm = 346°; Im = -60°, which allowed calculating a paleomagnetic pole forthe La Esperanza dikes (LE pole), located at -82.5° (lat), 11.9° (long) (α95=10.9º; N=13, k=17). The magnetizationis primary and mainly carried by PSD magnetite and minor hematite as evidencedby textures observed by ore microscope and IRM and thermomagnetic curves. TheLE pole is the first pole bracketed in age for the Permo-Triassic intervalforcentral northern Patagonia calculated with a primary magnetization on igneousrocks. The comparison of the position of the LE pole with other poles ofPatagonia and neighbouring areas of Gondwana suggests that these blocks werealready juxtaposed earlier than 250 Ma, as suggested in previous geologicmodels.