WEI Can-kun¹, WEN Shou-qin^1*, YANG Tian-yao², YANG Hong-zhang¹, ZHANG Guang-liang¹, LI Jian-yuan³, XIE Wei¹, YAN Ying-can¹, ZHANG Shuai¹

(1. College of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China;
2. Baojin Mining Group, Eerguna 022250, China; 3. Liaoning Metallurgical Geological Exploration Research Institute Co. Ltd., Anshan 114000, China)

Abstract: The Ulgan Pb-Zn-Ag deposit in Eerguna City of Inner Mongolia is one of the representative meso-epithermal type Pb-Zn-Ag deposits in the Derbugan metallogenic belt. The mineralogical evidences obtained microscope observation and electron probe analyses, show that there are two stages of mineralization in this deposit. The early-stage metallic sulfides formed by the early volcanic hydrothermal fluid are generally transformed by stress, and are widely replaced or metasomatized by late-stage hydrothermal minerals. The typical early-stage ore mineral is chalcopyrite-free sphalerite which has high contents of Fe, Mn and low content of Cu. However, the late-stage metallic sulfides formed by the late-stage subvolcanic (cryptoexplosive breccia) hydrothermal fluid are dominant ones which partly replaced or commonly coexisted with early-stage hydrothermal minerals. The typical late-stage ore mineral is sphalerite containing chalcopyrite of solid solution. It is characterized with medium contents of Fe, Mn and high content of Cu. At the end of the late subvolcanic hydrothermal stage, a kind of pure transparent sphalerite with colors varying from brownish yellow to colorless was formed by the residual hydrothermal fluid. It is characterized with high content of Zn and low contents of Fe, Mn and Cu. Combined with the dating results of volcanic rocks and minerals and analytical data of major elements of volcanic rocks in the study area by previous researchers, it is speculated that the early-stage mineralization could be closely related to the volcanic hydrothermal fluid derived from the magma of intermediate basic volcanic rocks in the Tamulangou Formation, while the late-stage mineralization could be related to the subvolcanic hydrothermal fluid, which could be rich in Cu and other ore-forming materials, derived from the magma of (intermediate) acidic cryptoexplosive breccia in the Manketouebo Formation. Thus, the cryptoexplosive breccia is an important clue for finding other kinds of minerals besides lead and zinc in the study area.

Keywords: Inner Mongolia; the Ulgan Pb-Zn-Ag deposit; mineralogy; metallogenetic period and stage

ACTA MINERALOGICA SINICA Vol. 40, No.2, 2020, page 201-212