The Duocaima Pb-Zn deposit is located in the northern Sanjiang polymetallic metallogenic belt. The values of δ

34

S in main sulfides are significantly variable

mainly ranging in between-26.72 ‰ and-4.1 ‰ with a normal distribution. The maximum δ

34

S value of galena is larger than the corresponding value of pyrite

indicating that the sulfur isotopes are in disequilibrium during the process of mineralization and that sulfur is originated mainly from bacterial sulfate reduction. The

208

Pb/

204

Pb values vary from 38.985 to 39.253

and

206

Pb/

204

Pb from 18.825 to 18.918 Tectonic evolution and Δβ~Δγ genetic classification diagrams of lead isotope show that the source of lead is complex and diverse. It is not only originated from the upper crust and orogenic belts

but also from the subducted zone with crust and mantle mixed. The values of δ

13

C

V-PDB

=1.2‰~6.7‰ and δ

18

O

V-SMOW

=16.4‰~23.4‰ show that the C and O are derived from marine carbonates

accompanied by carbonate dissolution. The origin of the Duocaima PbZn deposit is complex

The hosting carbonates and the mantle may provide metals

while biomineralization may play an important role in the oreforming process.