Geochemical characteristics of tourmaline in the Jinchanghe iron-copper-lead-zinc polymetallic deposit in the Baoshan block in the western Yunnan
The Jinchanghe iron-copper-lead-zinc deposit is located in the northern part of the Baoshan block in the western Yunnan.In this paper,the newly discovered tourmaline in the Jinchanghe deposit is taken as the research object.Combined with the field geological investigation and petrographic observation,the electron probe and laser ablation analytical techniques have been used to analyze compositions of tourmalines in three different occurrences(TurⅠ,TurⅡ,and TurⅢ).The TurⅠ tourmaline occurred mainly in patchy aggregates of small particles;The TurⅡ tourmaline occurred in needle-column crystals with medium sizes;The TurⅢ tourmaline occurred mainly in bundle-,fan-,and radial-shaped aggregates with relatively large sizes of euhedral crystals.Based on analytical results,tourmalines in the deposit belong to the schorl-dravite solid solution series of the alkaline tourmaline with substitution mechanisms of FeMg-1,Fe3+Al-1 and x□ Al(NaR2+)-1.Generally,tourmalines of the deposit are predominantly characterized with positive Eu anomalies and negative Ce anomalies,indicating that they were formed in a relatively high oxygen fugacity(fo2)environment.In addition,tourmalines with different occurrences have similar REE distribution patterns,indicating that they were mostly fromed in a same hydrothermal system.It is believed that the formation of tourmalines in the Jinchanghe deposit was mainly related to the interaction of fluids sourced from metasedimentary rocks and metamorphic volcanic rocks.
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