Diagenetic-metallogenic ages of pyritic cherts and their implications in Mojiang nickel-gold deposit in Yunnan Province, China

Diagenetic-metallogenic ages of pyritic cherts formed by the syn-sedimentat ion of hydrothermal vent and ages of the Jinchang Rock Formation in the Moj iang large nickel-gold deposit in the Ailaoshan gold metallogenic belt have been discussed on the basis of chronology of isotopic geochemistry. Nickel -gold-bearing pyritic cherts in the mining were formed by syn-sedimentation of hydrothermal vent in the Late Devonian, i.e. age by Sm-Nd isochronal me thod (t) = (358 +/-8.6) (2 sigma) Ma and age by Rb-Sr isochronal method (t) = (354.7 +/-0.72) (2 sigma) Ma. On the other hand, deep-water cherts from the Jinchang Rock Formation of the Upper Devonian in the area were initiate d at the same time; that is, age by Sm-Nd isochronal method (t) = (359 +/- 21) (2 sigma) Ma and age by Rb-Sr isochronal method (t) = (358.02 +/-0.30) (2 sigma) Ma.