LA-ICP-MS cassiterite U-Pb ages and the geological significance of the Maogaitu Sn ore spot in Hexigten Banner, Inner Mongolia

Abstract

The Maogaitu Sn ore spot in Hexigten Banner, Inner Mongolia is a newly discovered ore spot in the south section of Greater Khingan Range by Beijing Institute of Geology for Mineral Resources. It is tectonically located in the polymetallic metallogenic belt in the south centralsection of Greater Khingan Range, and the mineralization is characterized by cassiterite-quartz veins. Ore minerals of the ores are dominated by cassiterite with trace amounts of sphalerite, galena, chalcopyrite and silver minerals, while gangue minerals are mainly quartz and fluorite. As discovered recently without detailed studies, the genesis and age of the Maogaitu Sn ore spot are not clearly addressed. A number of tin polymetallic deposits are documented to develop in the polymetallic metallogenic belt in the south central section of Greater Khingan Range. The ages of these tin polymetallic deposits are constrained to be mostly around the Early Cretaceous, and to be genetically related to the Early Cretaceous granite. In order to address the relationship of the Maogaitu Sn ore spot with regional metallogeny, we obtained the age of the Maogaitu Sn ore spot by using LA-ICPMS U-Pb isotopic dating of cassiterite from a quartz vein-type tin ore sample. The results show that the sample yields a 207Pb/206Pb-238U/206Pb concordant age of (130.2±3.4) Ma (MSWD=2.9), similar to the timing of the major tin mineralization event in the region. The new findings imply that the middle and south sections of Greater Khingan Range could be good targets for Sn polymetallic exploration.

Keywords

• cassiterite u-pb age
• maogaitu sn deposit
• inner mongolia
• middle-southern sections of greater khingan range