2005 Volume 56 Issue 7-8 Pages 245-258
The granitic rocks of the Hotont area were classified into the Late Paleozoic Delgerhaan batholithic complex and Mesozoic Egiindavaa stocks, the latter of which is further divided into normal granitoids and Sn-rich granitoids. The Delgerhaan granitoids are weakly magnetic, their oxygen fugacity being at QMF buffer, while the Egiindavaa granitoids are more reduced belonging generally to ilmenite series. The Sn-rich granites are completely magnetite free and most reduced. The Delgerhaan granitoids are shoshonitic, whereas the Egiindavaa granitoids are shoshonite to high-K series. Both the granitoids are similar in most of chemical components in the Harker’s diagrams, but the Delgerhaan granitoids are richer in P2O5 and poorer in Fe2O3, TiO2 and MgO than the Egiindavaa granitoids. Both the granitoids seem to be generated within continental crust in islandarc setting and not fractionated. The Sn-rich granite may be a later intrusion and generated in anorogenic tectonic setting, and well fractionated. Weak Au-mineralizations are related to the Late Paleozoic Delgerhaan granitic complex. The Late Paleozoic granitoids are too well exposed to have primary base-metal deposits, and the Mesozoic granitoids are not oxidized enough to have base metal mineralizations. Sn and W mineralizations and some Ti-Ta-Nb occurrences are possibly associated with reduced granitoids of the Mesozoic age,particularly with the Sn-rich granites, which may have formed in anorogenic setting.
