Geochemistry of some metamorphic and sedimentary rocks from the mineral district of Zacatecas, Zac., México.

Abstract

The area of study is caracterized by a thick succesion of mainly rhyolitic flows which cover Mesozoic and older metamorphic rocks and a large porphyritic andesite body of Early Tertiary age. Metamorphic rocks have rare earth element (REE) patterns similar to the North American Shale Composite (NASC) which posibly indicates a Post-Archean source. One mineral vein sample consisting mainly of quartz and calcite shows REE contents and pattern similar to those of chondrites. Considerable experimental errors at such low concentrations warrant further research on such samples.