Geological characteristics and lead-zinc mineralization in the Cam Nhan area, Yen Bai

Abstract

Based on the combined use of mineralogy and chemical analysis methods, combined with modeling methods, some conclusions are drawn about the geological and lead-zinc mineralization points in the Cam Nhan area as follows:

The study area has a complex geological structure, with the presence of formations belonging to the Ha Giang formation; the Mia Le formation and unconsolidated sediments of the Holocene and Quaternary systems. Acidic magma formations belonging to phase 1 of the Phia Bioc complex and mafic rocks of the Mau A complex are distributed over a fairly large area in the west and less in the center of the region.

Lead-zinc ores are distributed discontinuously, forming a mineralized zone extending from the Northeast to the Southwest and sub-meridional. The lead-zinc mineralized zone contains ore bodies that meet industrial requirements and are mainly related to faults in the northeast to the southwest and sub-meridional directions. The ores are concentrated in marble and altered dolomite marble belonging to group 3 of the Ha Giang formation.

The ore bodies primarily occur as veins, lens veins, and monoclines, predominantly towards the west and northwest with slopes ranging from 20 - 70⁰; the thickness varies from 0.80 to 3.40m. The concentrations of lead (Pb) and zinc (Zn) in the ore bodies ranges from 0.048% to 16.5%, with averages of 0.124% to 3.343%, exhibiting significant and uneven variations.

The primary ore minerals include galena, sphalerite, pyrite, and lesser amounts of chalcopyrite, pyrrhotite, and magnetite; the non-ore minerals include calcite, dolomite, diopside, phlogopite, and quartz. The characteristic thermal metasomatism includes dolomitization, calcitization, quartzization, and talcization.

The ore has a low-medium temperature hydrothermal origin, with the symbiotic mineral assemblage, characterized by pyrite-sphalerite-galena during the industrial ore-forming phase