Hénán molybdenum project -
What is a porphyry molybdenum deposit?

Kurt Friehauf - 2008

under construction graphic(A brief description of porphyry deposits coming soon.)
We have made two presentations of our work at national Geological Society of Amercia meetings.  The abstracts of those papers is given below:

Xiao, Ping, Friehauf, Kurt, Wang, Yanbin, and Wang, Cuizhi, 2010, The implication of similarities and systematic variations among the monometallic high-fluorine porphyry deposits in the East Qinling Molybdenum Belt, China [abs]: : Geological Society of America - Denver Annual Meeting (31 October –3 November 2010), Vol. 42, No. 5, p. 580.

Storm, Lauren, Friehauf, Kurt, Yuan, Zhenlei, Xiao, Ping, and Moorehead, Anthony, 2009, Mineralization within the Dong Gou porphyry molybdenum deposit, Eastern Qinling Mountains, Henan, China [abs]: 2009 Portland GSA Annual Meeting (18-21 October 2009), Geological Society of America Abstracts with Programs, Vol. 41, No. 7, p. 84.


The implication of similarities and systematic variations among the monometallic high-fluorine porphyry deposits in the East Qinling Molybdenum Belt, China

Xiao, Ping, Friehauf, Kurt, Wang, Yanbin, and Wang, Cuizhi, 2010, The implication of similarities and systematic variations among the monometallic high-fluorine porphyry deposits in the East Qinling Molybdenum Belt, China [abs]: : Geological Society of America - Denver Annual Meeting (31 October –3 November 2010), Vol. 42, No. 5, p. 580.


Xiao Ping with Kurt Friehauf at Denver GSASituated on the southern margin of the North China Craton, mirroring the Yan-Liao molybdenum belt on the northern margin, and with more than 5million metric tons of explored Mo metal reserves, the East Qinling Molybdenum Belt (EQMB) is the largest molybdenum producing region in China. Molybdenum deposits in the EQMB include porphyry Cu-Mo, porphyry Mo, skarn Mo-W, and carbonatite deposits.

The five known major monometallic high-fluorine porphyry Mo deposits in the EQMB – Jinduicheng, Shijiawan, Leimengou, Yuchiling, and Donggou – bear a striking similarity in mineralization, hydrothermal alteration, and igneous geochemistry. Mineralization of four of the deposits is associated with a small granite porphyry stock, and the Yuchiling deposit is related to a composite granitoid batholith. Porphyries related to mineralization share broad likenesses in major elemental features (SiO2- and Al2O3-rich, MgO- and CaO-poor, TiO2 depletion, A/CNK > 1.1, (Na2O+K2O) > 7.5, (K2O/Na2O) > 1) and high LREE/HREE ratios.
The East Qinling Molybdenum Belt shows systematic variation along its axis. Published molybdenite Re-Os ages indicate mineralization progressed from west to east: Jinduicheng (138.3 ± 0.8 Ma), Shijiawan (138.0 ± 8 Ma), Leimengou (132.4 ± 1.9 Ma), Yuchiling (131.2 ± 1.4 Ma), and Donggou (116.0 ± 1.7 Ma). Re content of molybdenite and alkali-lime index decrease gradually, and Eu anomaly systematically increases eastward.

Prior researchers suggested that the five deposits formed at different times with different magmatic source regions (upper mantle, lower crust, and upper crust). Alternatively, we propose the systematic differences in geochemistry, mineralization age, REE pattern, and isotopic characteristics, may have resulted from magmas of similar primary source region that experienced progressively greater degrees of crustal interaction and fractionation during ascent, as post-orogenic extension of the Qinling Mountains progressed eastward.




Mineralization within the Dong Gou porphyry molybdenum deposit, Eastern Qinling Mountains, Henan, China 

Storm, Lauren, Friehauf, Kurt, Yuan, Zhenlei, Xiao, Ping, and Moorehead, Anthony, 2009, Mineralization within the Dong Gou porphyry molybdenum deposit, Eastern Qinling Mountains, Henan, China [abs]: 2009 Portland GSA Annual Meeting (18-21 October 2009), Geological Society of America Abstracts with Programs, Vol. 41, No. 7, p. 84.

GSA 2009 - Lauren StormMesoproterozoic 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.



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