Seismic Properties of Rocks from the Flin Flon Volcanogenic Massive Sulfide Camp

Abstract

Seismic properties of rocks from the Flin Flon volcanogenic massive sulfide (VMS) camp were determined to evaluate the suitability of seismic reflection imaging for mineral exploration and have subsequently aided interpretation of 2-D and 3-D seismic data acquired in the camp. Seismic impedances of Flin Flon rocks were determined from laboratory measurements of compressional and shear wave velocity (Vp, Vs) and density for 61 core samples. Complementary in situ measurements of Vp and density provided by sonic and density logs acquired in nine drill holes allow calculation of synthetic seismic responses. Sandstones of the Missi Group show low reflectivity with sparse strong internal reflections resulting from intrusions or thrust-interleaved mafic rocks. Basaltic sequences are generally moderately reflective due to variability in their composition, alteration, and the effects of foliation and shearing. The mine horizon, which hosts the known orebodies, should be reflective, based on the impedance contrast of constituent rhyolite and mafic igneous rocks and the presence of sulfide mineralization. However, reflectivity of this horizon should be variable due to the significant alteration of the footwall basalt. Ore zones (solid sulfide) should range from moderately to very highly reflective, depending on their sulfide compositions. Vertical seismic profiles demonstrate that contacts between major stratigraphic units (e.g., Missi Group contact with Hidden Formation volcanic rocks or felsic igneous rocks within the basalts) should produce significant reflections, whereas some of the internal reflectivity predicted for the basaltic sequences will not be as prevalent.