ORE GENESIS CONSTRAINTS ON THE IDAHO COBALT BELT FROM FLUID INCLUSION GAS, NOBLE GAS ISOTOPE, AND ION RATIO ANALYSES--A REPLY

摘要

Sir: Burlinson (2013) questions the veracity of the H_2 concentrations reported for fluid inclusion extracts from minerals in the Idaho cobalt belt (Table 2; Landis and Hofstra, 2012) and suggests that they are an analytical artifact of electron-impact mass spectrometry. He also declares that H_2 should not be present in fluid inclusions because it is invariably lost by diffusion and is never detected in fluid inclusions by laser Raman. We welcome this opportunity to reply and maintain that the reported H_2 contents are accurate. Below we explain why Burlinson's criticisms are invalid. Burlinson (2013, p. 1211) begins by stating that "... it is highly unlikely that hydrogen is really that common in geofluids...." Although H_2 is a trace component of ordinary geochemical environments, most ore-forming environments are extraordinary. In fact, numerous studies of modern magmatic and hydrothermal systems have shown that H_2 is present in detectable amounts and that it actually participates in a variety of important redox and sulfidation reactions (Einaudi et al., 2003). Consequently, H_2 measurements are used to calculate the redox parameter R_H and the sulfidation state parameter Rs (Giggenbach, 1987) and are employed in the H_2-CH_4-CO_2-H_2S geothermometer (D'Amore and Panichi, 1980).