Abstract

Tholeiitic basalts and trachytes of the bimodal association of Wangtian’e volcano are studied. It is shown that trachytes formed with the leading role of crystal fractionation of the parental tholeiitic magma. It has been identified from the melt inclusion study that hedenbergite and plagioclase phenocrysts of trachytes from Wangtian'e volcanic neck crystallized in the temperature range of 1080–1100 and 1050–1060°C, respectively. After heating experiments with melt inclusions in plagioclase of trachytes, in some cases relics of carbonates and CO₂ were observed in the inclusions. The trachyte phenocrysts host water-bearing Fe-rich globules and CO₂ inclusions with carbonate phases. The Fe-rich silicate globules are often intergrown with titanomagnetite and are covered by amorphous carbon films. A model is suggested explaining the formation of water-bearing Fe-rich globules and CO₂ inclusions with carbonate relics as a result of silicate–silicate and silicate–carbonate liquid immiscibility, that was caused by the evolution of the parental basaltic melt. Upon the trachytic melt ascending to the surface, the ferrocarbonate liquid was decomposed on magnetite, carbon, and carbon dioxide.

中文翻译：

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长白山地区望天鹅火山颈拉斑岩岩浆晶体分异作用形成粗面岩

摘要

对望天鹅火山双峰组合的拉斑玄武岩和粗面岩进行了研究。结果表明，粗面岩的形成是在母拉斑岩浆的晶体分异作用下形成的。熔体包裹体研究表明，望天鹅火山颈粗面岩中的红辉石和斜长石斑晶分别在1080～1100℃和1050～1060℃范围内结晶。对粗面岩斜长石熔融包裹体进行加热实验后，有时在包裹体中观察到碳酸盐和CO _{2残留物。}粗面岩斑晶含有含水的富铁球体和具有碳酸盐相的CO ₂包裹体。富铁硅酸盐球通常与钛磁铁矿共生，并被无定形碳膜覆盖。提出了一个模型来解释由于母体玄武岩熔体演化引起的硅酸盐-硅酸盐和硅酸盐-碳酸盐液体不混溶性，导致含水富铁球体和CO ₂包裹体与碳酸盐遗迹的形成。当粗面岩熔体上升到表面时，碳酸铁液体分解为磁铁矿、碳和二氧化碳。