Regional target generation for porphyry Cu?Mo systems in the Erdenet area, Mongolia

Abstract

A regional structural interpretation was undertaken from an integrated study of high-resolution airborne geophysics, JERS-1/SAR and geological data around the Erdenet porphyry Cu?Mo deposit in northern Mongolia. Geophysical signatures of the Erdenet deposit have been identified and extrapolated regionally. The district-scale area was divided into five domains based on a combination of structural and geophysical character. The most prospective domain contains numerous concentric, high to low magnetically zoned bodies, that represent igneous plutons of the Selenge Complex and a series of discrete low or remanently magnetised bodies of the younger Erdenet Complex porphyries. The domains are delineated or enveloped by a series of major regional fault or shear zones, with approximate N-, W- or NW-trends. The porphyries of the Erdenet Complex appear to align along a NW-trending sub-domain boundary. Major ?late? W-trending, left-lateral transpressional structures, such as the Vitim Suture Zone, dominate the region and appear to control the distribution and orientation of the magnetic/structural domains. Application of a Riedel, simple shear ellipsoid model, suggests that NW-trending structures that appear to control the current position of the Erdenet Complex porphyries are equivalent to X or P shears. Target areas were delineated based on structural and/or litho-magnetic features. Subsequent ground verification, IP surveys and drilling have tested some of these targets and identified significant hydrothermal alteration.