Electromagnetic and magnetic surveys for delineate a skarn mineralization (Montseny Massif-NE Spain)

In the Montseny Massif (NE-Iberian Peninsula) a strata bound skarn-type deposit exists. Skarn is a term that is applied to a wide variety of calc-silicate rocks that are rich in calcium, iron and magnesium, which have formed by the replacement of carbonate-rich rocks by contact metamorphic processes or metasomatism (Einaudi et al., 1981). Often, skarns are associated with magnetite and sulphide (pyrrhotite, pyrite) mineralizations, having pronounced magnetic anomalies (Grant, 1985). Skarns of the study area were classified by Viladevall (1975) in three main types according to their mineralogical composition: andradite-garnet skarns, diopside skarns and amphibole-epidote skarns having magnetite-pyrrhotite and metal sulphides (Pb-Zn-Cu) paragenesis. Some of these ore bodies were exploited for cooper at the beginning of the 20th century until the Spanish Civil War, but subsequently were abandoned due to their scarce economic interest. The study zone has few rock-outcrops due to the development of very dense vegetation. Kurdiyeh (1986) used the magnetic prospecting technique to locate the ore deposits, but in the zones where the predominant mineral is not the magnetite, magnetic method was insensitive. With the aim to delineate the non-magnetic skarns a FDEM (Frequency Domain Electromagnetics) survey has been conducted.