Geochemical signature of hydrothermal alteration in surface rocks of Cerritos Colorados geothermal field of Mexico

Abstract

Several reliable and extensively applied traditional geochemical, mineralogical, and petrography methods exist for identifying hydrothermal alteration of rocks. However, many of these methods require tedious and laborious sample preparation and analysis procedures. Therefore, there is a need for faster methods and reliable in their application. Binary diagrams of felsic vs mafic components, Na₂O content, porosity, and permeability of the rocks are newer methods that are faster in their application and more reliable and have the potential to be considered for this purpose. These methods are successfully applied to the surface rocks of Cerritos Colorados Geothermal Field (CCGF) providing consistent results that are comparable to those obtained by extensively applied and highly reliable mineralogical and geochemical methods. Most of these altered rocks are from the formation of the Post-Tala Quaternary Lacustrine Sediments and are located near the faults and fumaroles. Evaluation of the results obtained by all applied methods confirms that the new methods are easy to measure and reliable, which can be useful as additional tools during the initial stage of geothermal exploration in identifying altered rocks and zones of hydrothermal alteration. Mass change values reveal the highest mobility for the major elements and the lowest mobility for the trace elements in the rocks of the study area.