Summary

Mineralogical characteristics of tin – silver ores in some polymetal deposits at Ng©n S¬n

NguyÔn V¨n Nh©n, Hoµng Minh Th¶o

There are many ore – bearing lots of tin – silver polymetal deposits at Ng©n S¬n area, such as Nµ §eng, B¶n Piªn, Niªn S¬n, Bolaimi, NËm Tèc Lu, Cèc S©u, Phóc S¬n, Ph­¬ng S¬n, Nµ DiÕu... Ore deposits are located in the Lower Devonian terrigenous - carbonate rocks of the Cèc X« Formation. Granite and leucogranite are also widespread in the area. Ore bodies consist of veins, nests, filling up the faults or distributed along tectonic crushed zones. The main minerals are sphalerite, galenite, pyrite and arsenopyrite. Minor minerals are chalcopyrite, pyrrhotine, cassiterite, stannite and tetraedrite. Rare minerals are proustite, pyrargyrite, canfieldite, stephanite, bournonite and so on. ore deposits belong to height – medium temperature hydrothermal group.

The mineralization has clear zonation around the Ng©n S¬n granite massif; from the contact of the intrusion toward the surrounding rocks it can be divided into 3 zones:

  1. Sulphide ores zone (pyrite, arsenopyrite) containing cassiterite, located in the external contact or in the surrounding sericite schist;

  2. Sphalerite – galenite zone containing stannine (cassiterite) in sericite schist and limestone;

  3. Galenite zone mainly consisting of Ag sulfosalt minerals lying in limestone.

Ngµy nhËn bµi: 15-11-2001

Ng­êi biªn tËp: D­¬ng §øc Kiªm