Review of developments in trace-element fingerprinting of geodynamic settings and their implications for mineral exploration
Titel:
Review of developments in trace-element fingerprinting of geodynamic settings and their implications for mineral exploration
Auteur:
Kerrich, R. Wyman, D. A.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 44 (1997) nr. 4 pagina's 465-487
Jaar:
1997-08
Inhoud:
Mineral deposits are not evenly distributed through Earth history and examples of individual deposit classes are restricted to narrow time intervals over geological time. This pattern reflects direct links between long-term geodynamic cycles, which control styles of heat flow and magmatism, and metallogenic processes. Significant improvements in trace-element analytical techniques have led to refined understanding of igneous processes and the construction of comprehensive geodynamic models. These in turn permit increasingly sophisticated applications of igneous trace-element geochemistry in mineral deposit exploration. Analytical advances, principally ICP-MS, include lowered detection limits, increased numbers of elements analysed and greatly reduced turnaround times. Whereas early exploration applications of igneous trace-element analyses focused upon felsic rocks with high concentrations of elements such as Zr and Y, new methodologies allow routine analysis of incompatible elements at far lower abundances in mafic and ultramafic rock types. Multi-element normalised diagrams are useful aids in assessment of modern datasets and highlight those element-element systematics which can be used to monitor the possible effects of alteration and crustal contamination. Once data have been screened, the distinct geochemical signatures of individual geodynamic settings (ocean plateaus versus island arc) and subsettings (juvenile or mature arc) can be related to a given terrene's prospectiveness for particular deposit classes. Exploration programs cannot rely solely upon high-precision trace-element analyses. However, when used to complement traditional lithogeochemical pathfinder studies based on large numbers of low-precision analyses, mapping and geophysical investigations, the technique promotes accurate and cost-efficient geological evaluations at the regional to the local scale.
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