Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (5): 74-92.DOI: 10.13745/j.esf.sf.2023.5.18

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Early Miocene leucogranitic magmatism in Cuonadong, southern Tibet: Constraints from whole-rock geochemical and mineralogical characteristics

HUANG Chunmei(), LI Guangming(), FU Jiangang, LIANG Wei, ZHANG Zhi, WANG Yiyun   

  1. Chengdu Center, China Geological Survey(Geosciences Innovation Center of Southwest China), Chengdu 610218, China
  • Received:2022-12-10 Revised:2023-01-06 Online:2023-09-25 Published:2023-10-20
  • Contact: LI Guangming

Abstract:

In order to better understand the petrogensis of Himalayan leucogranites and its role in the mineralization of rare metals, we performed whole-rock major and trace element, monazite age and trace element, and main mineral composition analyses of weakly oriented two-mica granite and garnet-bearing muscovite granite in the Cuonadong Be-W-Sn polymetallic deposit in eastern Himalayas. Results show the Cuonadong two-mica and muscovite granites are formed during the same magmatic event and dated respectively to (20.1±0.3) Ma and (20.7±0.2) Ma. Whole-rock geochemical analysis shows the granites are rich in Si/Al, and monazite and the muscovite granite both exhibit REE tetrad effect. According to mineral analysis, plagioclase in the muscovite granite is more sodic, and the muscovite granite has higher FeO, MnO and F contents and higher spessartine content compared to the two-mica granite. These characteristics suggest the muscovite granite is more evolved and likely formed from highly evolved interstitial melt/fluid within the magmatic crystal mush, while the two-mica granite likely formed from the residual melt. Early (~20 Ma) differentiation of leucogranites in the Cuonadong dome promoted the initial enrichment of ore-forming elements such as Be and Sn, which is the key to late mineralization.

Key words: Cuonadong leucogranite, petrogenesis, magmatic evolution, tetrad effect, rare-metal mineralization

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