![]() ![]() ≤ 700 MPa) and temperatures up to 1,100☌, the most commonly used methods are based on the progressive increase of the melting temperature of halide salts (most commonly NaCl), and/or of the H 2O solubility in natural or synthetic glasses ( e.g., Bohlen 1984, Baker 2004, Moore et al. Several methods based on well-constrained natural or synthetic phase relations and/or melting reactions can be used to calibrate high-temperature piston-cylinder assemblies at medium- to high-pressure conditions ( e.g., Boettcher & Wyllie 1968, Johannes et al. Given the great interest in the development of low-pressure (200-400 MPa) petrologic process simulations, as well as mineral synthesis, we work on the calibration of the available end-loaded piston-cylinder apparatus for such conditions. (2012) designed new –” and 1” (19-25 mm) furnace assemblies using similar solid media components to expand the pressure range accessible with the non-end loaded QUICKpress (Depths of the Earth Co, USA) piston-cylinder apparatus down to 150 MPa. (2008), who replaced crushable alumina by crushable MgO and used both massive and powdered pyrex glass to carry out experiments down to 300 MPa. This assembly was later modified by Moore et al. For instance, Baker (2004) calibrated a –” (19.1 mm) crushable alumina-pyrex glass-NaCl assembly in the 400-500 MPa range. Thus, some recent efforts have been made to develop and optimize piston-cylinder furnace assemblies for low-pressure environments. ![]() Nevertheless, there are some inherent advantages in using a piston-cylinder apparatus over internally/externally heated pressure vessels, such as faster heating and cooling rates, easier maintenance and superior safety. ![]() Due to issues with internal friction and experimental assembly (solid media) reliability, however, the piston-cylinder press has rarely been used to simulate pressure conditions lower than 500 MPa, and both the internally or externally heated pressure vessels have been preferred for (see Holloway & Wood 1988, for descriptions and applicability of the available experimental devices). The apparatus has been the work-horse of experimental petrology laboratories worldwide in studies of phase equilibria, melting and crystallization ( e.g., Holloway & Wood 1988, Young 2003). Its original design allowed high-temperature experiments in the pressure range between 0.5 and 4.0 GPa (5-40 Kbar), covering lower crust down to upper mantle conditions. The piston-cylinder press is an apparatus developed by Boyd & England (1960) to simulate P-T conditions in the Earth’s interior. KEYWORDS: End-loaded piston-cylinder apparatus low-pressure calibration NaCl melting method experimental petrology and geochemistry Our results confirm the applicability of Bristol-type end-loaded piston-cylinders coupled with appropriate furnace assemblies in assessing relatively low-pressure conditions (down to ~ 200 MPa, ~ 7 km depth) found in the Earth’s upper crust, where important magmatic, hydrothermal and metamorphic processes occur. Larger offsets (to -120 MPa) were obtained under pressure conditions around and lower than 300 MPa with the 1” assembly. However, if the NaCl melting points (918-920☌) obtained by Bohlen (1984) at 500 MPa are used as reference, no pressure correction is needed. 300-400 MPa pressure ranges for the 3/4” and 1” assemblies, respectively. (1998), but offsets by ~ -55 MPa, implying the need of a constant P upward correction in the 300-600 MPa and ca. The obtained curve slope fits that given by Siewert et al. ![]() Twenty-one experiments were carried out over a range of pressures (200-600 MPa) and temperatures (870-945☌) to determine the liquidus curve of NaCl. The furnace assemblies were made up by crushable MgO, graphite heater, pyrex glass spacer, and NaCl sleeve. We present pressure calibration results for piston-cylinder –” and 1” high temperature furnace assemblies in the 200-600 MPa range aiming to expand its applicability to simulate upper crustal conditions. ![]()
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