The Putorana basalts, comprising ~90% of the Siberian Traps (ST), have had their chemistry modified from primary tholeiitic picritic magmas by ~12% crystallization of olivine. Major-trace element ratios, and Nd isotopes of these lavas are consistent with their origin from a relatively undepleted plume by 12--16% rapid decompressional melting at ~50--80 km depths within the lithosphere. ¿ 1998 American Geophysical Union