Estudio Geofísico del Plutón Trapecio, Tierra del Fuego. Argentina.

PERONI J. I,; TASSONE, A; LIPPAI H. F.; MENICHETTI, M.; VILAS, J. F.

Mendoza

Congreso; XXIV Reunión Científica de Geofísica y Geodesia; 2009

AAGG

The Sierra Sorondo, localized between the north margin of Beagle Channel and the middle course of the river Larsiparsahk, stretches WNW-ESE along 40 Km. Between the numerous mountains that compose it, the Monte Olivia with a maximum elevation of 1318 m. stands out. Belonging to the above-mentioned Sierra but of less altitude, is the Cerro Trapecio of 1029 m. and localized 16 Km. to the east of Ushuaia’s city. In the 5569-II aeromagnetic chart reduced to pole, this Cerro shows a 13 Km2 anomaly with a maximum value of 24 nT in the central zone and a minimum of -50 nT to the extremes. The anomaly reproduces the shape of the Cerro Trapecio, presenting magnetics minimums in the surrounding valleys of Encajonado’s river to the west and Escape’s river to the east. This anomaly would indicate the presence of a plutonic body, emplaced in the Andorra’s fault, which belong to the Beagle Channel fault system. In the area of Cerro Trapecio the outcrops are very scarce and are composed mainly of a monzodioritic rock, similar to the ones found in the Ushuaia Pluton, and a series of andesitic veins with thickness less than a meter and concordant with the stratification of the Fm. Yahgán. In base of aeromagnetic and geophysics-geologic data obtained in the field, it has been developed for the first time a 3D geophysics model of the Trapecio Pluton. Due to most of the intrusive surface is covered, the information contributed by the geophysics constitute an important tool for the study of its geometry.