Chi replies that the question raised by Burlinson (2018) about the validity of hydrogen gas (H2) data as determined by mass spectrometry is not a new one. The same question was raised five years ago by Burlinson (2013) and was rebutted by Hofstra and Landis (2013), who defended the validity of their data and pointed out that Burlinson’s perception of the analytical procedure of mass spectrometry and preservation of H2 in fluid inclusions was incorrect. Although Burlinson (2018) recognized that the low levels of H2 in our analytical results (Rabiei et al., 2017) have no impact on our mineralization models or conclusions, he insisted that “it is highly misleading
to report such H2 analyses, as H2 is an instrumental artifact of the mass spectrometer ionizer and not a component of the fluid inclusion volatiles at all” (p. 997).
We would like to take this opportunity to further clarify Burlinson’s misperception of the issue and make two important points: (1) H2 is a common component in geologic fluids, and it is normal to detect it in fluid inclusions, and (2) the mass spectrometric analytical procedure that was used in our study (Rabiei et al., 2017) has already taken into account the background H2 that might be produced in the ionization process, and the data reported are above background and above the blanks.
H2 in geologic fluids can be produced by two major processes in geologic environments—i.e., radiolysis of water (dissociation of water molecules by ionizing radiation) and water-rock reaction (e.g., 3FeO (in silicates) + H2O = Fe3O4 (magnetite) + H2 (aq.))—and H2-rich fluids have been widely documented in hydrothermal vents and seafloor spreading centers as well as saline fracture waters in Precambrian continental crustal rocks (Sherwood Lollar et al., 2014). H2-rich fluid inclusions, as shown by Raman spectroscopic studies, have been reported for samples from uranium (Dubessy et al., 1988; Richard, 2017) and rare earth element (REE) deposits (Vasyukova et al., 2016) as well as melt inclusions (Li and Chou, 2015). Although it has been well established that H2 in fluid inclusions in quartz may be lost due to diffusion (Kats
et al., 1962; Mavrogenes and Bodnar, 1994), it is also known that the diffusion rate exponentially decreases with decreasing temperature (Kats et al., 1962; Mavrogenes and Bodnar, 1994; Li and Chou, 2015) such that H2 diffusion in quartz may be insignificant below 200° to 300°C (Morgan et al., 1992, 1993; Hall and Sterner, 1995). Therefore, preservation of H2 in fluid inclusions in quartz is not a problem in many geologic environments.
Burlinson’s criticism of our work further reflects his unfamiliarity with the analytical procedures commonly exercised in mass spectrometry, as already pointed out by Hofstra and Landis (2013).
Managed & Built by I2M Consulting, LLC | © 2010-
