The ultramafic intrusion of Estancia Túnel, and the meaning of garnet and biotita presence in the Deformado Complex of the Isla Grande, Tierra del Fuego (Argentina)

Abstract

?The ultramafic intrusion of Estancia Túnel, and the meaning of garnet and biotita presence in the Deformado Complex of the Isla Grande, Tierra del Fuego (Argentina)?. An ultramafic intrusion located in the coast of Canal Beagle, east of Ushuaia, in the Estancia Túnel area, is described pointing attention in the petrographic and chemical characteristics. Also the discovery of gamet, biotite and recristalized muscovite in the schist wall rock is considered as contact metamorphism related with intrusion.

The ultramafic rock is amphibolite-piroxenite with clinopiroxene, hornblende, magnetite, pyrite, esphene, epidote and intersticial alcali feldspars.

Veins of sodic leucosienite porphyry cuts the ultramafic body evidencing a contrasted differentiation.

The homblendite-piroxenite was intruded into the deformed complex Beagle-Moat-Fagnano in Sierra de Sorondo in the area referred in the geological literature as Yahgan Formation.

Finnaly are offered mineralogical and structural data about the schists and the later cristalization of garnet, biotite and muscovite, referring also the homologus localities mentioned by Kranck.