Abstract:Inclusions represent ore-forming media and might be regarded as codes containing information on mineralization. Serving as a sort of major typomorphic characteristics of minerals, they can be widely used in geologic exploration and other fields of geology, including the study of mineral deposits. They are likely to be of some help in looking into such problems as the sources, migration and accumulation of ore materials, as well as in the search for ore deposits. Unfortunately, little attention has yet been paid to anomalous gas-liquid inclusion, a type which is sure to be most useful in research into some basic theoretical problems of inclusions. A supremely beautiful miarolitic cavity of gypsum, which contains a great abundance of gigantic gypsum crystals, has recently been discovered in the oxidation zone of an antimony ore deposit in China. The crystals generally have a length of l m, but the greatest one can reach 2.4 m. They contain not merely a large number of monophase liquid inclusions but some gas-liquid inclusions as well. Some of these inclusions are strikingly enormous, the biggest of which is 40 cm long and might be considered the "king" of inclusions. Such inclusions used to be classified as normal inclusions and were measured for formation temperatures. Feeling rather doubtful about this conclusion, the author has studied almost 100 plates from 5 crystals in this gypsum cavity. The filling degrees of gas phase were determined to be 0-65%, homogenization temperatures 84-900℃, decrepitation temperatures 108-128℃ and salinity 7.5%. Gas phase of these inclusions was determined chemically to contain CO2 only (2ppm) and the temperatures of some inclusions were calculated graphically to be 500℃, 330℃, 425℃ and 430℃ respectively. From these data and the Criteria put forward by the author in 1977 for distinguishing anomalous inclusions from normal ones, some conclusions might be drawn: 1. The inclusions studied are actually typical anomalous inclusions and the temperatures obtained from them offer false information. These inclusions, therefore, cannot act as codes for illustrating ore-forming processes. 2. These gypsums, formed under ordinary temperature and pressure, are products of oxiduation zone of sulfide deposits. Numerous monophase liquid inclusions within them could be regarded as normal ones, which undoubtedly demonstrate that these gypsum crystals have crystallized from cold fluids. 3. These anomalous gas-liquid inclusions are genetically similar to those within stalactite and stalagmite. All of them have probably been produced as a result of the following reaction during the formation of the minerals: H2SO4+CaCO3+2H2O→CaS04·2H2O+H2O+CO2. 4. The results obtained from this study suggest the possible presence of some other chemical decomposition anomalous gas-liquid inclusions. They would be formed provided that H2O CO2 or other gases could be released during cryrstallization.
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何知礼.1983.我国一锑矿石膏中异常包体的发现及其成因的初步研究[J].矿床地质,2(3):88~95.1983.The discovery of anomalous gas-liquid inclusions in Gypsum from an antimony ore deposit in China and a preliminary study on their genesis[J].Mineral Deposits2(3):88~95
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