3D GEOPHYSIC MODEL OF USHUAIA PLUTON, TIERRA DEL FUEGO, ARGENTINA

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

Bolletino di Geofisica Teorica ed Applicatta

OGS

Lugar: Trieste; Año: 2008 vol. 49 p. 262 - 267

0006-6729

The Ushuaia Pluton outcrops in the area of the homonym bay, to the south of the Isla grande de Tierra del Fuego. The pluton emplaced within sedimentary rocks ands black schists of the low Cretaceous Yahgán Fm, deformed by the Late Cretaceous Andean compression which affected the austral region of South America. The pluton is affected by strike-slip and normals faults, asociated to the Beagle Channel Fault System. An aeromagnetic survey in the study area indicates the presence of a positive magnetic anomaly of 70 km2. The contour lines range from 350 to -320 nT. On the basis of aeromagnetics and geophysicsgeologics data obtained in the field, a three dimensions geophysic model of Ushuaia Pluton has been developed for first time. This modelled body is composed of two dominants litologies, hornblendite and syenite, and displays a laccolithic form with a maximum thickness of 4000 m in its central area. To the borders the body thickness reduces to 500 meters. In plan view, the body displays an oval shape with a NS- trending major axis (around 12 km), a E-W-trending minor axis (10 km) and total volume of 140 km3.