MINERALIZATION WITHIN THE DONG GOU PORPHYRY MOLYBDENUM DEPOSIT, EASTERN QINLING MOUNTAINS, HENAN, CHINA

Mesoproterozoic Xiong’er Group andesite hosts Cretaceous molybdenum ores in the Dong Gou molybdenum deposit in the eastern Qinling Mountains of Henan, China. Current mining activity is done by hand mucking and hauling high grade ores from shallow underground workings. Thin, discontinuous K-feldspar veins characterize earliest mineralization styles, which are cut by quartz-molybdenum veins associated with hydrothermal biotite alteration of andesite. Where hairline quartz-molybdenite veins cut feldspar phenocrysts in the andesite, K-feldspar overgrowths fill the vein. Quartz-molybdenite veins became thicker, more continuous, and planar as the system evolved, reflecting cooling and transition to a more brittle strain environment. Molybdenite-barren, blue apatite-K-feldspar veins crosscut early quartz-molybdenite and evolved through time from apatite-dominant to K-feldspar-dominant modes with minor molybdenum on vein margins. Thick quartz-molybdenite-pyrite veins that crosscut barren apatite-rich veins record a second stage of molybdenite mineralization. K-feldspar-chlorite-quartz-pyrite veins postdate both molybdenite stages.

Early fluorine-rich phases such as fluorite and topaz reported at Dong Gou by Wei et al. (2009) were not exposed at mine levels examined in this study, suggesting fluorine in this part of the deposit may be locked up in apatite veins.

The Dong Gou deposit represents an important variation on the extension-related, high-fluorine-type molybdenite deposits in the eastern Qinling metallogenic belt.