9 Structural Geology and Tectonics (Posters)

FLUID INCLUSION MICROTHERMOMETRY OF FAULT ZONE MINERALS FROM THE HARTFORD BASIN: EVIDENCE FOR FAULT REACTIVATION AND FLUID MIGRATION

Paper number: 9-9
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

  • Earl B. Manning Presenting Author
    Central Connecticut State University, New Britain, CT
  • Mark Evans
    Central Connecticut State University, New Britain, CT
  • Ann Alampi
    Central Connecticut State University, New Britain, CT
  • Anthony Bishop
    Central Connecticut State University, New Britain, CT

Abstract

Fluid inclusion microthermometry of fault zone minerals is used to infer the syn-deformational fluid history of the Hartford Basin. The western border fault zone consists of a large displacement (100s m) normal dip-slip fault plus numerous strike- and oblique-slip faults that cut the metamorphic rocks of the footwall. The wide variety of fault orientations indicates a long and complex fault history. Quartz mineralization on the faults reveals three primary NaCl-rich fluid types that are correlative with fault orientation: NNE-SSW sinistral faults have inclusions with Th values of 172° - 311°C and with 0.0 to 12.8 wt. % NaCl equiv. salinity. These faults also contain CO2 inclusions with Th values of -5° to 26°C, and H2O-CO2 inclusions with Th values of 229° - 305°C, and <3.0% salinity. Dip-slip faults contain inclusions with Th values of 163° - 267°C and 0.0 to 5.3 wt. % NaCl equiv. salinity. NE-SW sinistral faults have NaCl-rich inclusions with Th values between 224° - 293°C and 17.0 - 17.8 wt. % NaCl equiv. salinity. All three fault sets have pseudosecondary inclusions of NaCl-CaCl2 rich fluids with Th values of 121° - 147°C and 5.5 -12.8 wt. % NaCl equiv. salinity.

NE-SW striking normal dip-slip faults that cut the central part of the Hartford Basin are commonly mineralized with dolomite, calcite, quartz, barite, sulfides and bitumen. Inclusions in early calcite contains NaCl-rich fluids with Th values of 140° - 158°C and 3.2 - 10.5 wt. % NaCl equiv. salinity. Inclusions in later quartz contains NaCl-CaCl2 fluids that fall into two groups: 1) Th values of 63° - 149°C and 0.4 - 12.8 wt. % NaCl equiv. salinity, and 2) Th values of 71° - 158°C and 16.0 - 23.7 wt. % NaCl equiv. salinity. Liquid hydrocarbon inclusions in quartz that have Th values of 30° - 192°C.

Late quartz within the eastern border fault zone contains NaCl-CaCl2 inclusions with Th values of 134° - 160°C and up to 14.0 wt. % NaCl equiv. salinity.

The distinct difference in the types of fluids in the western border faults vs. fluids within the basin faults, indicate little fluid interconnectivity early during the deformation history of the Hartford Basin. However, later inclusions in quartz along the western border faults and primary inclusions from the eastern border fault indicate reactivation of all of the fault sets, and the mobility and influx of basinal fluids into the border faults.