REVIEW OF DEVELOPMENTS IN TRACE-ELEMENT FINGERPRINTING OF GEODYNAMIC SETTINGS AND THEIR IMPLICATIONS FOR MINERAL EXPLORATION

Mineral deposits are not evenly distributed through Earth history and examples of individual deposit classes are restricted to narrow time i ntervals over geological time. This pattern reflects direct links betw een long-term geodynamic cycles, which control styles of heat flow and magmatism, and metallogenic processes. Significant improvements in tr ace-element analytical techniques have led to refined understanding of igneous processes and the construction of comprehensive geodynamic mo dels. These in turn permit increasingly sophisticated applications of igneous trace-element geochemistry in mineral deposit exploration. Ana lytical advances, principally ICP-MS, include lowered detection limits , increased numbers of elements analysed and greatly reduced turnaroun d times. Whereas early exploration applications of igneous trace-eleme nt analyses focused upon felsic rocks with high concentrations of elem ents such as Zr and Y, new methodologies allow routine analysis of inc ompatible elements at far lower abundances in mafic and ultramafic roc k types. Multi-element normalised diagrams are useful aids in assessme nt of modern datasets and highlight those element-element systematics which can be used to monitor the possible effects of alteration and cr ustal contamination. Once data have been screened, the distinct geoche mical signatures of individual geodynamic settings (ocean plateaus ver sus island are) and subsettings (juvenile or mature are) can be relate d to a given terrane's prospectiveness for particular deposit classes. Exploration programs cannot rely solely upon high-precision trace-ele ment analyses. However, when used to complement traditional lithogeoch emical pathfinder studies based on large numbers of low-precision anal yses, mapping and geophysical investigations, the technique promotes a ccurate and cost-efficient geological evaluations at the regional to t he local scale.