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正如Rutherford和Heming(1978)所证实的,用热力学方法,对火山岩中常见的斑晶组合,可以测定H-O-S系统中喷发前岩浆挥发组份的丰度。这些方法,可应用于Tenerife(Canary岛)、Sao Miguel及Faial(Azores)的大气降落和熔结凝灰岩型的碱性浮岩堆积物。表明由含有可估量的次要元素的钛磁铁矿-钛铁矿矿物对,能获得可靠的温度及 fO_2的估算值。然而在流纹岩岩浆中所见到的 fO_2缓冲机理,在更碱性的液体中似乎不起作用。利用黑云母估算 fH_2O,得出高的 fH_2O值,表明与岩浆有关的强烈爆炸现象是符合的.由磁黄铁矿成分,可估算 fS_2。由气体平衡,可算出 fH_2、fH_2S、fSO_2、fSO_3。从硫组份的数据可很粗略地估算不含黑云母样品的水逸度。在碱性及钙碱性的硅铝质岩浆中,这些组份的丰度是类似的。重视有关爆炸性喷发过程中,挥发物的喷出在火山学上的含义。
As evidenced by Rutherford and Heming (1978), thermodynamic methods are used to determine the abundance of volatile component of magma in the H-O-S system prior to eruptions for the common porphyry assemblages in volcanic rocks. These methods are applicable to the atmospheric fall and tuffaceous alkaline buildup deposits of Tenerife (Canary Island), Sao Miguel and Faial (Azores). This shows that reliable estimates of temperature and fO 2 can be obtained from pairs of titanomagnetite-ilmenite minerals that contain appreciable secondary elements. However, the fO 2 buffering mechanism seen in rhyolite magma does not seem to work in more alkaline liquids. The use of biotite to estimate fH_2O gives a high fH_2O value, indicating that a strong explosion associated with the magma is consistent with the pyrite component fS_2. By gas balance, can be calculated fH_2, fH_2S, fSO_2, fSO_3. From the sulfur component data it is possible to estimate the waterfluid of a sample without biotite very roughly. The abundance of these components is similar in alkaline and calc-alkaline sialon magmas. Attention is paid to the volcanological implications of the discharge of volatiles during an explosive eruption.