ASTM test and other methods carried out on dimension rocks from Tierra del Fuego

ACEVEDO, R.; GONZÁLEZ GUILLOT, M.

Santiago de Chile

Congreso; GeoSur; 2007

Dimension stones, which include monumental stones, are natural rocks quarried forblocks or slabs that meet specifications as to size and shape for residential construction,paving and memorials. This is the first laboratory assay ofthis type ofrock in Tierra delFuego. This land has a potential not evaluated until now in respect ofthe possible use ofnative dimension stones. Local hard rocks have not until now been used as dimensionstone in the Argentine side of the island. Metamorphic rocks (slates) only have beenapplied for facing, facades and flooring in buildings. In recent years only two smallquarries ofigneous rocks have been opened. One ofthem, at Cerro Jeu-Jepen, is workedfor building the wave-breakers of Río Grande harbour and the national railroad, and theother one, in the Ushuaia peninsula, was initiated to remo ve a hill to locate the airport·and has been recently worked for facings.In the present work, the chosen samples were put through standard ASTM testmethods for determining compressional strength and modulus of rupture, standardanalysis in accordance with IRAM specifications for determining apparent density,water absorption and open porosity, and Dorry hardness test for measuring theresistance to abrasion.In Isla Grande of Tierra del Fuego the main types of dimension rock are scarce andirregularly distributed granitic bodies. According to our analysis, they have relativelyhigh compressional (O"c)and tensional (O"f)resistance: the dioritic pluton of Cerro JeuJepen(O"c131 MPa and O"f26 Mpa), the recently discovered pluton of Cerro Kranck inthe Beauvoir range (O"c2l2 Mpa, the best resistance in this test) and also the Jeu-Jepenlamprophyres (O"c147 MPa and O"f23 MPa) and Beauvoir-Yahgan homfels (O"c177 MPaand O"f44MPa). Nevertheless, unexpectedly low results were given by the granodioriticerratic boulders of SinaÍ point (O"c77 MPa and O"f8MPa) due to glacial meteorization,and Estancia Túnel homblendite (O"c71 MPa) due to rock micro-fissuring (O"c85 MPaand O"f10 MPa).The extended volcanic rocks, rhyolites-rhyodacites of the Lemaire Fm.(O"c121 MPa), comparable with Pórfiro Patagónico in terms of origin, beauty andpotential, and andesite-basalts, diabases and spilites of the Alvear Cordillera(O"c112 MPa and O"f 25 MPa), show intermediate register contents.Sandstones outcrop extensibily but they are not significative as dimension rocksbecause of their low compressional strength (O"c28 MPa) and high water absorption (%9.50). Marbles and travertines are scarce or absent, but there is, in small amounts, abeautiful variety of limestones with bioclasts of Turritellas, considered to be a specialminor type.The resistance to abras ion of flagstones (Yahgan Formation slates) is 0.66 (excellentperformance for road building) but that of diabase is 2.01, because of the presence ofveins and pockets of calcite.