Molybdenum isotopic composition of molybdenite and the fertility potential of the Ekomédion U–Mo prospect, SW Cameroon

[摘要] We present Mo isotope data for molybdenite from the Ekomédion U–Mo prospect, SW Cameroon, a Late Neoproterozoicgranite–pegmatite–quartz vein system. Disseminated and veinlet-controlled molybdenite in granite and pegmatitic podsyields a narrow range of δ98Mo values from –0.06 to +0.24 ‰, with two overlapping populations of +0.03±0.07 ‰(n=4) in granite, and slightly heavier of +0.11±0.10 ‰ (n = 5) in pegmatite. By contrast, molybdenite from a quartz–muscovite vein has an isotopically heavy δ98Mo value of +1.61 ‰. We interpret this trend from granite through pegmatiteto vein system towards isotopically heavy Mo to reflect the fractionation of an evolving magmatic–hydrothermal system.Furthermore, the LREE-enriched bulk-rock patterns with largely negative Eu anomalies and the overall enrichment ofHREE in zircon indicate plagioclase fractionation as the dominant petrogenetic process during melt evolution. Furthermore, the presence of accessory ilmenite indicates relatively reducing conditions of the melt system, unfavorable forsignificant Mo accumulation. Therefore, the Ekomédion granite system seems to have limited economic potential formolybdenum despite the advanced degree of magmatic evolution.

[学科分类] 自动化工程

[关键词] granite;pegmatite;molybdenum isotopes;geochemistry;redox-state;Cameroon