STRUCTURAL RELATIONS BETWEEN THE VICTORIA SERPENTINITE AND THE CARBONIFEROUS GRANJENO SCHIST IN THE BASEMENT OF THE SIERRA MADRE ORIENTAL, CIUDAD VICTORIA, TAMAULIPAS, MEXICO

The Novillo Canyon cuts the core of the Huizachal-Peregrina Anticlinorium, located W of Cd. Victoria, Tamaulipas. This major fold is an important locality of the Laramidic fold and thrust belt of the Sierra Madre Oriental (SMO), which displays a very thick Triassic to Upper Cretaceous sedimentary sequence. Its exposed core exhibits a variety of Precambrian and Paleozoic lithologies that represent the regional basement.

The Victoria Serpentinite is embedded discordantly in the western block of the Carboniferous Granjeno Schist, a heterogeneous lithodeme metamorphosed under green schist facies during the Carboniferous. Granjeno Schist represents the accretion prism of Gondwana's NW margin, which is composed mainly of metapelitic sediments and the metamorphosed ocean floor and corresponding mantle (Victoria Serpentinite). It was accreted against continental Gondwana and thrusted over the Precambrian Novillo Metamorphic Complex (Oaxaquia) and the Silurian to Permian Tamatán Sedimentary Sequence, probably during Triassic times, in the course of the Pangaea amalgamation and before the beginning of the Gulf of Mexico opening.

The serpentinitic unit is an elongated body with a preferential orientation NNW-SSE, with dimensions of 7 km in length to 0.9 km in width. The modal composition of the Victoria Serpentinite is dominated by lizardite with acicular habit and meshed texture, and chrysotile as filling veins in fibers perpendicular to them. As accessory minerals appear opaque phases, such as magnetite and chromite. Along highly deformed zones with fluid transit the presence of exotic rose-pink to purple stichtite, a Mg-Cr hydrated carbonate, is highly notorious.

The goal of this contribution is to provide structural data, like representative foliations and faults, determining the characteristics of the tectonic contacts with the other lithologies, to allow the postulation of a comprehensive geological interpretation in relationship to the Granjeno Schist. The results will provide more information in order to elucidate the geological puzzle of the Paleozoic basement of NE Mexico.