97/95Mo VARIATION IN MOLYBDENITES: A LINK WITH MINERALIZING PROCESSES?

Molybdenum (Mo) isotopic compositions are usually studied to reconstruct (paleo-) redox conditions in ocean (e.g., Siebert et al., 2003). Some studies also focus on isotopic compositions of Mo in molybdenite in order to decipher a possible genetic link between isotopic variations and mineralizing processes. This is also the aim of our work based on a wide molybdenite databank. We propose here a comparison of δ97/95Mo of 101 molybdenite samples from different localities, different types of occurrences and different ages. This databank of 101 molybdenites, presently analyzed, represents various types of mineralization as samples from 5 skarns, 7 porphyry deposits, 9 pegmatites, 5 granites, 2 greisens, 7 perigranitic veins and 9 alpine-type fissure veins have been studied. Molybdenite sample ages vary from 5Ma to 2.7Ga. The Mo isotopic composition has been determined on molybdenites using a MC-ICP-MS Neptune after aqua regia dissolution and adjustment to [Mo] = 1µg.g-1. Mass bias was corrected by using Zr as dopant and standard-sample-standard bracketing. The δ97/95Mo ratios have been normalized to NIST 3134. The external reproducibility is 0.07 ‰ (2σ). The overall range of the δ97/95Mo ratio in the 101 molybdenite samples varies from-0.58 t