Abstract

Aeromagnetic anomalies overlying the Pre-cambrian Lake Owens layered mafic complex and adjacent bodies in the Medicine Bow Mountains of southeast Wyoming help constrain their geometric and magnetic properties. Modeling of these anomalies shows that the magnetic part of the Lake Owens Complex corresponds well with its surface outcrop and is only about 1 km thick. The remanent magnetization is approximately as strong as the induced magnetization. The total magnetization of the complex is 5.8 x 10-3 emu/cc. Rocks this strongly magnetized, were they located in the deep crust, could account for long-wavelength magnetic anomalies. The anomaly also shows the presence of a small, strongly magnetic body to the northeast of the Lake Owens Complex. This is probably a small, separate mafic body or a piece of the complex broken and disrupted during tectonic activity and/or during later granite intrusion. The Mullin Creek layered mafic complex, to the west of the Lake Owens Complex, has weaker magnetization dominated by induced magnetization or a viscous remanent overprint in the direction of the present Earth's magnetic field. Its surface outcrop corresponds poorly with boundaries of magnetic units. A magnetic unit between the two mafic complexes may be a quartz diorite or a separate, shallow mafic body.

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