| Abstract: | Gold is used widely for capsules in high-temperature rock-melting studies because it is generally thought to absorb negligible Fe from silicate samples. However, we observed significant losses of Fe from fluid-absent melting experiments on hornblende gabbros at 800-975 ??C and 8 kbar, using standard piston-cylinder techniques. The extent of Fe loss from the sample is dependent on the relative masses of the sample and the capsule. Low sample to capsule mass ratios (~0.04) lead to the highest Fe losses (32-49% relative). Concentrations of Fe in silicate melt and used gold capsules define an apparent equilibrium constant (K‘) that follows a linear 1n K‘ vs. 1/T relation (at an estimated log f(O)(2) of QFM-1). The apparent equilibrium constant is used to make limiting upper estimates on the amount of Fe that could be lost during rock-melting experiments for a range of f(O)(2) and sample to capsule mass ratios. At high f(O)(2) (NNO + 2), loss of Fe to gold is negligible (<2% relative) for a wide range of sample to capsule mass ratios. At an f(O)(2) of NNO, Fe loss can be kept to <10% relative by using a sample to capsule mass ratio of 0.2 or greater. At low f(O)(2) (QFM-1), presaturating the Au with Fe would be necessary to ensure that Fe losses remained <10% relative. Fe loss can compromise experimental results for small samples run at low f(O)(2) conditions, be they buffered, imposed by the pressure media, or produced by intrinsically reduced (graphitic) starting materials. |
| Genre: | Article |
| ProdID: | 70021195 |
| Citation Author: | Ratajeski, K.; Sisson, T. W. |
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| Citation End Page: | 1527 |
| Citation Issue: | 10 |
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| Citation Language: | English |
| Citation Larger Work Title: | American Mineralogist |
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| Citation Number Of Pages: | 7 |
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| Citation Search Results Text: | Loss of iron to gold capsules in rock-melting experiments; 1999; Article; Journal; American Mineralogist; Ratajeski, K.; Sisson, T. W. |
| Citation Start Page: | 1521 |
| Citation Volume: | 84 |
| Citation Year: | 1999 |
| Type: | citation/reference |
| Text: | Loss of iron to gold capsules in rock-melting experiments; 1999; Article; Journal; American Mineralogist; Ratajeski, K.; Sisson, T. W. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Fri, 1 Jan 1999 00:00 -0600 |
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