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Preliminary Study on Fluid Inclusion Planes for Dabie Mountain Granite

NI Pei, FAN Jian-guo, ZHOU Jin, DING Jun-ying, MA Dong-sheng, HUA Ren-min,, LING Hong-fei, JIANG Shao-yong   

  1. State Key Lab. For Mineral Deposits Research, Nanjing University, Nanjing 210093, China
  • Received:2003-12-20 Revised:2003-12-20 Online:2003-12-20 Published:2003-12-20

Abstract: The devolvement and migration of geo-fluids is controlled by regional stress.Fluid inclusion planes(FIP)are a bridge to link the geo-fluid and the stress.It is a useful means to investigate the migration of the geo-fluid under certain regional stress field.Fluid inclusion planes kept in the granites provide the best way for US to study the regional stress field change and the fluid evolution when the granites intrude into the country rocks and cool down at the crustal environment.This paper statistically surveys FIPs attitudes for three granitic intrusives in Dabie Mountain,Anhui province(Zhubeyuan,Tianzhushan and Sikongshan granites).Microthermometric works were also done on the fluid inclusions in FIPs.It is revealed that the characteristics of FIPs in the Zhubeyuan and Tianzhushan grantes are similar ,but obviously different from the Sikongshan granite.The FIP in Zhubeyuan and Tianzhushan granites have preferred orientations of NE and NW W .The NW W striking FIP are cross-cut by the NE striking FIP.The homogenization temperature, salinity and CO2 contents of the fluid inclusions in NW W striking FIP are higher than those of NE striking FIP, which indicate regional paleo-stress change from NWW to NE strike accompanying the intrusion and cooling of the above two granites,and fluids evolved from CO2—H2O-NaC1 type to H2O-NaCl type with declined temperatures and salinities.FIP in Sikongshan granite have preferred orientations of SN and EW .The EW striking FIP are cross-cut by the SN striking FIP.While cooling, the Sikongshan granite experienced a regional stress field changing from EW to SN and fluid types changing from CO2-CH4-H2O-NaC1 type to H2O-NaC1 type with the declined fluid temperatures and salinities.