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Geochemical patterns from two la anomalies in the Cobar region of central New South Wales are described. The region is semi-arid, deeply weathered and some areas are covered by variable thicknesses of aeolian and alluvial transported overburden.

Lag morphology and mineralogy are related to landform. In erosional landforms the surface is covered by lag, which is composed of coarse fragments derived locally from bedrock and displays varying degrees of ferruginization. together with a range of secondary pisoids. In depositional landforms the lag is less abundant and contains more pisoids. Deflation by sheetwash may lead to lag being partially buried by alluvium. In a large proportion of pisoid lag, hematite and goethite have been converted to maghemite, allowing ready separation into magnetic and non-magnetic fractions. The non-magnetic fraction is dominated by the lithic lag whereas the magnetic fraction is dominated by pisoid lag.

The magnetic and non-magnetic components of the 2-11 mm lag fraction, milled to < 75 mu m and subjected to HF-HNO3-HClO4 attack, give rise to distinct geochemical patterns at targets related to a variant of the Cobar style of Pb-Zn mineralization with variable silicification and to Zn mineralization in a swarm of quartz and carbonate veinlets. The patterns are influenced by metal source, lag type, surface chemical conditions and landform. Differences in the correlation between metal contents in the magnetic and non-magnetic lag components, and between trace elements and Fe, indicate variable loss of Cu and Zn from the magnetic lag at some targets but retention of Pb. The presence of a readily extractable base metal component in the lag has implications for detecting anomalies in transported cover in the region.