Abstract

GAYTAN-MARTINEZ, Rafael; NOYOLA-MEDRANO, Cristina  and  ROJAS-BELTRAN, Marco Antonio. SPECTRAL AND PETROGRAPHIC ANALYSIS OF THE VOLCANIC COMPLEX SIERRA DE SAN MIGUELITO, S.L.P. MEXICO. Ser. correl. geol. [online]. 2017, vol.33, n.1, pp.1-10. ISSN 1666-9479.

This paper presents the analysis of spectroradiometric and petrographic data from lithological units of the Sierra de San Miguelito Volcanic Complex (SSMVC), located in the central region of the State of San Luis Potosí, Mexico. The CVSSM consists of ten felsic volcanic units of the Oligocene with variations in the degree of alteration of silicification, argilization, and oxidation. The lithological units were grouped into fve classes: rhyolite, rhyodacita, latite, trachyte and basalt. The spectral signatures were recorded using a hyperspectral spectroradiometer Apogee model UV-NIR PS-300. The obtaining of spectral signatures was for each outcrop in the feld and on hand samples of rock in the laboratory. The protocol of the spectral sampling includes three records in each point of the feld, as well as, three records of each sample in the laboratory. The data reported is the spectral signature average (feld and laboratory) from the fresh and the altered rock. Also, for fve representative samples of each kind of lithology, a petrographic analysis was performed to establish the mineralogy and the textural relationships of the SSMVC rocks. The results show that the spectral signatures of the rhyolites, trachytes, and riodacites are very similar. The three kinds of rock have an ascending pattern until 600 nm, and a re-fectivity peak is evident at the 750 nm. In addition, in the rhyolite unit is observed a stable plateau at 900 nm. In the feld and laboratory signatures, the latite shows high values of refectivity, but at 500 nm the spectral curves of the altered and fresh rock are intercepted by changing upside down their percentages of refectivity. The basalt presents the values of refectivity lowest in the entire sequence volcanic. The records of spectral signatures of the altered rock reveal that the argilización displays values of refectivity that varies from 40 % to > 100 %. The oxidation shows two peaks of refectivity, one at 600 nm and ano-ther at 700 nm, generating a distinctive pattern between the fresh and the altered rock. The silicification is commonly associated with oxidation, for that reason, it was not possible to separate its spectral response.

Keywords : Spectral signature. Petrography. Spectroradiometer. Sierra San Miguelito..

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