Prospección Magnética En El Área De Marayes Viejo, Sierras Pampeanas Occidentales, San Juan, Argentina

A geological and geophysical study was carried out in a small andesitic porphyry outcrop, located in the western border of the La Huerta Range (San Juan province). The geological works consisted in a detailed petrographic and metallogenic study over the igneous outcrops of the Marayes Viejo district, in the eastern border of the Marayes-El Carrizal Triassic subsiding basin. The andesitic porphyry is intruded within metamorphic host rocks. Through a magnetic survey executed in the area, it was possible to delimitate this igneous body. Ten N45°W tend 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 obtained is related to the presence of the porphyric body. The qualitative interpretation shows a clear difference between the metamorphic host rocks (magnetic low) and the porphyry body (magnetic high). The magnetic anomaly is extending about 400 m along a north-south direction and approximately 100-300 m in the perpendicular direction; several small anomalies within the main body were visualized, too. In the southern end of the map a structure such as a fault -which affect all the lithologies- was observed. Works are still in progress to add more similar magnetic profiles mainly to the south, to achieve a quantitative interpretation using specific software and to complement with other geophysical methods. These works will intend to define the morph-structure and dimensions by means of a magnetic model of the subsurface.