Prospección magnética en el área de Marayes Viejo, Sierras Pampeanas Occidentales, San Juan, Argentina

ALVARADO, PATRICIA; MACHUCA, EDUARDO; CASTRO DE MACHUCA, BRÍGIDA; BLANCO, SILVANA

Río de Janeiro

Congreso; VI International Congress of the Geophysical Society of Brazil; 1999

Sociedad Brasilera de Geofísica (SBGf)

A geological and geophysical study was carried out in a small igneous outcrop located in the western border of the La Huerta Range, San Juan province. The geologic work consisted in a detailed petrographic and metallogenic study over the Marayes Viejo andesitic porphyry, in the eastern border of the Marayes-EI Carrizal triassic subsiding basin. The andesitic porphyry was intruded within metamorphic host rocks. Through a magnetic survey executed in the area, it was possible to delimitate shape and dimensions of the igneous body. Ten N45°W trending magnetic profiles, 400 m in length, separated 50 m, and stations each 25 m were deployed in the area of interest. The main total field magnetic anomaly could be related to the presence of the igneous body in depth. The qualitative interpretation shows a clear difference between the metamorphic host rocks (magnetic low) and the porphyry (magnetic high). The magnetic anomaly extends about 400 m along a north-south direction and approximately 100-300 m in the east-west direction. Several small anomalies within the main body were also visualized. In the southern end of the study area a structure such as a fault, which affect all the lithologies, was observed. Works are still in progress to add more magnetic profiles mainly to the south, to achieve a quantitative interpretation using specific softwares in addition to other geophysical methods. These works will intend to define more exactly the morphostructure and dimensions of the Marayes Viejo porphyry by means of a magnetic model of the subsurface.