The Haughton impact structure is a 23 Ma old unaltered meteorite crater, located in the Paleozoic sediments of Devon Island in the Canadian Arctic Archepelago. Fluid inclusions found within shock metamorphosed sandstone fragments were microthermometrically investigated. The Onaping Formation of the 1850 Ma old Sudbury Structure is breccia zone that is of controversial origin. The fluid inclusions found within these rocks were also analyzed and compared to the Haughton study and other previous studies.
Fluid inclusions found in shocked Haughton sandstones exhibit a wide range of eutectic and homogenization temperatures. Eutectic temperatures are found to be extremely variable, suggesting the presence of complex, low- to high-salinity, aqueous solutions. CO2 was positively identified to be present in only one relict inclusion.
Fluid inclusions found within the rocks of the Onaping Formation also have variable eutectic and homogenization temperatures. Many of the inclusions from the Onaping Formation decrepitated prior to homogenization. The inclusions found within the matrix of the Onaping Formation are generally of low salinity and are found to contain some metastable ice phases. Fluid inclusions found within the xenoliths are of highly variable compositions and often contain CO2 phases and saturated salt solutions.
The presence of low salinity inclusions and metastable ice from the matrix of the Onaping Formation, is alalogous to the fluid inclusions studied in the melted rocks of the Haughton Structure. The wide range of homogenization and eutectic temperatures, recorded from inclusions in shocked xenoliths of the Sudbury Structure, is also consistent with the measurements on shocked, unmelted rocks from Haughton and other meteorite impact sites. This study supports an impact origin of the Onaping Formation rocks and thus the Sudbury Structure.