The kaolin deposit at the Adelita mine, located in the province of Rí;o Negro (Patagonia, Argentina), was studied. Petrographic studies on thin sections and chemical analyses of major, minor and trace elements on bulk samples were carried out. The kaolin content of the rock ranges from 31% to 65%. The mineralogy of the working front, which is about 45 m thick, varies from the upper zone, where the rock is strongly silicified, stained with iron oxides and carbonated, grading downwards to a kaolinized zone, with a quartz-kaolinite-dickite assemblage with relict lithic particles and a smaller amount of iron oxides, and ending in the deepest zone where dickite, alunite, diaspore, quartz and scarce associated kaolinite occur.The kaolin mineralogy was determined by SEM, XRD, DTA-TG, IR and δ¹⁸O and δD isotope analyses. The S, Ba and Sr contents are enriched during hydrothermal alteration, whereas Cr, Nb, Ti and lanthanide elements are concentrated mainly during weathering. The (Ba+Sr) concentrations in the samples studied vary between 600 and 6000 ppm and (Ce+Y+La) between 2 and 150 ppm; (Cr+Nb) remains constant for all the samples, whereas (TiO₂+Fe₂O₃) is below 0.3%. In the hypogene deposits P₂O₅ is also more abundant and increases with the degree of alteration. Chondritenormalized rare earth element diagram shows a marked enrichment in LREE relative to HREE, with negative europium anomalies and D¹⁸O values range between 3.8‰ and 7.7‰ and δD between –123‰ and –103‰, suggesting that kaolin formed from the hydrothermal alteration of rhyolitic tuffs.

The Loma Blanca mine is in one of the northwest kaolinized zones of the Los Menucos area (Patagonia, Argentina). The parent rocks are andesites and andesitic tuffs from the Vera Formation, Los Menucos Group (Lower Triassic). Hayase & Maiza (1974) proposed a concentric zonation model. From the parent rock outward, four different alteration patterns were recognized: Zone 1, with sericite, chlorite and montmorillonite; Zone 2, with kaolinite and dickite; Zone 3, with dickite, pyrophyllite and alunite; and Zone 4, with quartz, disseminated sulphides and diaspore.The relationship between the chemical composition of major, minor and trace elements and the mineralogical alteration zonation was evaluated to confirm the genesis of the deposit. Fe₂O₃, CaO, Na₂O and K₂O contents decrease from Zone 1 to Zone 3, whereas Al₂O₃ and LOI increase in the kaolinite-alunite zone. In the chemical composition of alunite, Na > K. Large Ba, Sr, V and Zr contents were observed mainly in Zones 2 and 3. Co, Ni, Cu, Zn and Rb are more common in Zone 1. LREE are more abundant than HREE in Zones 2 and 3. In kaolinites, δ¹⁸O values range from 10.8% to 13.2%, and δD from –83% to –85%.The mineral assemblage (dickite-alunite-pyrophyllite-diaspore), the alteration zonation pattern (laterally concentric), the geochemistry of trace elements, the relation between LREE and HREE and the small δ¹⁸O values suggest that the Loma Blanca deposit was formed by hydrothermal processes.

Nowadays, concrete is one of the most widely used construction materials due to its low price, appropriate mechanic characteristics and durability. Also, due to its ease to adopt diverse forms and sizes (Najimi et al., 2012). Owing to the importance in the use of concrete as a structural material and to its impact in the environment as a consumer of great quantities of natural resources and emitter of CO2 in the concrete industry, it is necessary to develop, from the science of materials, mixtures that support the growth of the construction industry and that consider the environment. Therefore, it becomes necessary to develop energetically efficient materials. A natural zeolite was studied as a material with potential pozzolanic activity and as partial replacement in different percentages of Portland cement in structural concrete. The results of the mechanic trials in concrete samples prove the feasibility of using this element as pozzolanic material.

A vitreous breccia with variable amount of mordenite was studied for its use as pozzolan. The raw material was characterized by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and the zeolite content was estimated by the methylene blue staining technique. After being ground, physical characteristics, cation exchange capacity (CEC), pozzolanicity, and the compressive strength activity index (SAI) were determined. The staining technique and the CEC measurement were used to evaluate the average content of zeolite. The vitreous breccia has pozzolanic activity after 7 days, the water demand increases slightly, and its addition stimulates the early hydration of portland cement. At later ages, the pozzolanic reaction around the grains, as revealed by SEM studies, improves the compressive strength of blended cements having a SAI > 0.85 at 28 days.