大红山古火山口的碳酸盐围岩的氧和碳同位素研究

云南大红山矿区为我国著名的同海底火山喷发有关的铁铜矿床。矿区地质、岩石学研究工作已相当详尽。据云南省地质九队等单位研究,从喷发物的产状分布特点推断为中心式喷发。由于火山喷发这种巨大热源将引起围岩的同位素交换反应而导致同位素分

A Study of Oxygen and Carbon Isotopes of Carbonate Wall Rocks of Paleovolcanic Crater in Dahongshan District

The authors have studied the oxygen and carbon ssotopic compositions ofthe carbonate wall rocks from the Dahongshan mining area, Yunnan Provinceand, combining with geological features, laid emphasis on the study of theunderlying marble which is most greatly affected by the ancient volcanic erup-tion. The analyses of 31 samples indicate that there is a distinct pattern forthe variation of oxygen and carbon isotopic compositions, which is in coinci-dence with the pattern of the central-volcanic eruption and volcanic neckemplacement inferred from geological and petrological studies. The oxygen andcarbon isotopic data also show that the carbona.tite rocks in the Dahongshanarea were most likely formed by melting of the marble. As a supplement tothe data appeared in the paper[1], the oxygen and carbon isotopic data of 13siderite samples are presented here. They may be characteristic of the moder-ately metamorphosed volcanic-sedimentary siderites.