Abstract:

The Luanchuan district in Henan Province is known as a porphyry molybdenum concentrated area in China. Recently, numerous leadzinc lodes have been found there. However, there are many divergent opinions on the genesis and controllingfactors of these leadzinc deposits. The leadzinc deposits in Luanchuan district are distributed around the Yanshannian porphyry molybdenum intrusions and hosted in a metamorphic sedimentary formation consisting of terrigenous clastic rock and carbonatite of either mesoproterozoic age (the Guandaokou group) or neoproterozoic age (the Luanchuan group), which is intruded by neoproterozoic (Jinning stage) gabbro and syenite and Yanshannian acidic porphyries. The leadzinc deposits are of vein or lenticular shape, and can be divided into three types: (1) the skarn type leadzinc deposits controlled by the contact zone between Yanshannian porphyries and proterozoic calcareous strata; (2) the veintype leadzinc deposits controlled by the WNW interlayer fault; (3) the veintype leadzinc deposits controlled by the NENNE extensional torsional fault. The sulfur isotope compositions of sulfides suggest the following points of information: (1) the δ34SVCDT of sulfides in leadzinc ores are positive values that close to 0‰, which appear obviously to have had a source of magmatic sulfur (Luotuoshan deposit=0.37‰4.20‰, Chitudian deposit=-032‰830‰, Bailugou deposit=-1.20‰10.90‰, Lengshuibeigou deposit=0.70‰12.10‰); (2) the δ34SVCDT of the sulfides of skarn leadzinc ore are very close to that of the sulfides in porphyry molybdenum ore (1.24‰3.30‰), and the δ34SVCDT of the sulfides of veintype leadzinc ore overlap mostly with that of the sulfides in porphyry molybdenum ore but influenced by the sulfur in the wallrock (δ34SVCDT=12.43‰1863‰); (3) as a whole, δ34Spyrite>δ34Ssphlaerite>δ34Sgalena, which shows the sulfur isotope fractionations of the dominating sulfides in leadzinc ore basically reach equilibria, and a pair of paragenetic sphalerite and galena from Chitudian deposit gives a high sulfur isotope equilibrium temperature of 38829 ℃. All the above suggest that the leadzinc deposits in Luanchuan district, Henan Province, are principally meso to hypothermal leadzinc deposits controlled by Yanshannian structuralmagmatic activity.

Key words: ore geology, sulfur isotope, leadzinc deposits, Chitudian, Bailugou, Lengshuibeigou, Luanchuan