Distribution of the main ore elements in the Tumurtijn-ovoo Fe–Mn–Zn skarn deposit, Mongolia

The submarine hydrothermal Tumurtijn-ovoo skarn deposit contains large concentrations of Zn related to sphalerite, Mn predominantly hosted in jacobsite and bustamite, and Fe mainly fixed in jacobsite, magnetite, and andradite. The quantitative distribution of these ore elements was studied with special emphasis on the Zn-bearing Mn-rich upper part of the skarnbody. Here, Zn is negatively correlated with Fe, but positively with Mn. The Mn/Fe ratio of the main skarn type reflects whether sphalerite is associated either with jacobsite or magnetite. In vertical direction, Zn shows minima–maxima distributions that imply stratiform mineralization. This genetic concept is in agreement with the sedimentary characteristics of the deposit as deduced from conformable marble–skarn alternations in the transitional zone between marble and skarn and from internal laminations within the skarn. In the Zn-rich skarn sections lateral differentiations have been recognized. Highest values of Zn content and the Mn/Fe ratio are spatially correlated and are interpreted to represent ore centres. Large ore centres show elongated contours and are suggested to be formed along synsedimentary faults. Analogically, the lateral differentiations within the Zn-free, Mn-poor, and quartz-rich lower part of the skarnbody have been studied using the Fe content and the Mn/Fe ratio. It could be ascertained that the position of the ore centres changed with time from the lower to the upper skarn.