TIME ASSOCIATED MAGMATISM AND MINERALIZATION AT THE CENTRAL PART OF MEXICO

In this study, we present 14 age K-Ar determinations of rocks and ore deposits, and a geological interpretation of Landsat 5-7 images of the central part of Mexico. The goal of this study is to determine the relation of the age of the ore deposits, the weakness structures and to set them in a regional geologic framework of Central part of Mexico. The oldest rocks of the region are the upper Jurassic volcanic and volcanic-sedimentary formations, over these rocks are layering the early cretaceous limestones and finally upper cretaceous terrigenous age rocks. All the Mesozoic rocks are folded and cover by volcanics of Oligocene of rhyolitic and dacitic composition and of different facies. There are known about 20 small stocks and two big granites bodies. The majority of these are of alaskitic, monzonites, dioritic and granitic composition. A lot of dikes of several compositions, the majority are of porphiritic textures and rhyolitic to andesitic composition. It is often to see subvolcanic bodies like dikes or stocks that cut the oldest sequences. At the region are known ore deposits of skarn silver-polimetalic type, hydrothermal vein Ag-Au, and the biggest fluorite deposits of the world. It is very interesting that all the ore deposits are locate at the lower creataceous limestones and near the base of the oligocenic acid volcanic rocks. From the obtained K-Ar ages we could get several interpretations: 1.- There is a trend of decresing age from SE to NW, from several granitic stocks to sub-volcanic and volcanic rhyolite rocks. 2.- This reflects the evolution of the subducted slab or the wandering of the inclined slab from 43 Ma to 29 Ma and back to 15 Ma to the south of the area studied. The 43 Ma is the oldest age of stocks that intruded the cretaceous rocks after the Laramide Orogeny was already finished. 3.- The skarn deposits of the SE are older than the Hydrothermal fluorite deposits for more than 13 Ma. 4.- All the ore deposits follow a SE-NW trend along the zones of faults or weakness zones that have been working since the opening of the gulf of Mexico, forming several metallogenetic belts.