Characterization, temporality, and distribution of veinlets in the Cu-Mo Warintza Central-East porphyry deposit, southeastern Ecuador

Abstract

The cluster called Warintza is located in the southeastern part of Ecuador, it is divided into five targets: Warintza West, Warintza Central, Warintza East, Warintza South and El Trinche, defined by Cu (>400ppm) and Mo (>30ppm) soil anomalies. This study was done in Warintza Central and Warintza East targets, both are in initial exploration stage and have inferred/indicated resource of 1,5Bt @ 0,5 % of equivalent copper (CuEq). The information about the type, temporality, and spatial distribution of the veinlets obtained in the geological drillcore mapping is ambiguous and poorly documented. For this reason, the goal of this study was to order, and compile the information about mineral paragenesis, veinlets cut relationship, macroscopic characterization of each type of veinlets, and the volumetric percent of each type and subtype of veinlets in the deposit, obtained during geological drillcore mapping; statistical analysis of the distribution of the volumetric percent of veinlets was done taking in count their measures of central tendency and dispersion; and, the definition of the threshold value for the percent of each type of veinlet, the thresholds were used for modelling them and generate a longitudinal section, which represents the spatial relationship among the threshold value of veinlets, Cu values greater than 0,3% and the geological-structural information. Ten types of veinlets were defined and they were classified according to their temporal relation in: pre-porphyry skarn veinlets, early veinlets: Eb type (early biotite), EDM (green dark micas, pyrite and chalcopyrite), Fk-Py (Kspar and pyrite) and “A” type veins composed of quartz with a few quantities of pyrite/chalcopyrite; transitional veinlets, “B” type veins of quartz with molybdenite, pyrite and chalcopyrite, “C” type veins of chalcopyrite and pyrite with green sericite halo, pyrrhotite veins; and late veins, which are “D” type veins of pyrite with white sericite halo and late D type veins composed of calcite-gypsum with kaolinite and sericite halos.