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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The volcanic activity of Stromboli in the 1906-1998 AD period: mineralogical, geochemical and isotope data relevant to the understanding of the plumbing system
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The volcanic activity of Stromboli in the 1906-1998 AD period: mineralogical, geochemical and isotope data relevant to the understanding of the plumbing system

机译：斯特龙博利岛在1906年至1998年的火山活动：与了解管道系统有关的矿物学，地球化学和同位素数据

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Volcanic activity of Stromboli in the last 100 years was characterised by regular Strombolian eruptions with some occurrences of major explosions and paroxysms at the summit crater and lava flows down into the Sciara del Fuoco. Two types of juvenile fragments, shoshonitic to high-K basalts in composition, are peculiarly outpoured during major explosions: black scoriae, similar to those erupted by the normal Strombolian activity, representing a highly porphyritic (45-60 vol%), volatile-poor magma (HP magma) and a small volume of light pumice, representing a low-porphyritic (< 10 vol%), volatile-rich magma (LP magma). Lava flows are constituted by the HP magma. The LP magma has a less evolved composition, lower incompatible trace element contents and Sr isotope ratios (0.70610) than the HP magma. Mineral phases in equilibrium with the LP and HP magmas have distinct compositions (Fo% in olivine: 80-85 and around 70, Mg# in clinopyroxene: 0.83-0.91 and around 0.75, An% in plagioclase: 80-90 and around 65, respectively), in spite of syn-eruptive mingling, and disequilibrium processes lead to large compositional ranges in minerals of both LP and HP magmas. Olivine and clinopyroxene of pumice were equilibrated at higher temperatures (and probably higher pressures) than the same crystals of scoriae. All these data provide evidence that the two magmas are characterised by sharply distinct physico-chemical conditions. It has also been pointed out that the plumbing system is under overall steady-state conditions. The HP magma resides at shallow level and evolves in a continuously erupting, crystallising (olivine+clinopyroxene+plagioclase) and replenished reservoir, which is fed by the LP magma. The LP magma derives from a deeper reservoir in which it undergoes limited crystallisation of femic phases. Plagioclase begins to crystallise only at lower depth. Significant geochemical, mineralogical and isotope variations with time in scoriae and lavas of the 20th century are observed. The MgO, V, Ni and Cr contents of magmas slightly increase from 1906 to 1930, then decrease from 1965 towards the present. Mineral chemistry data also vary accordingly. An increase of incompatible trace element contents after 1930 and a decrease of Sr isotope ratios after 1980-85 (from 0.70626 to 0.70616) have also been pointed out. These variations are thought to be due to changes in the crystallisation/replenishment equilibrium of the magma reservoir or to compositional modifications of the feeding magma. Some correlations between the main compositional variations and the type of eruptive activity also seem to be present. The occurrence of relatively frequent paroxysms during the first part of the 20th century, associated with the observed decrease of magma evolution, seems to indicate that more energetic explosions are associated with the rise of a higher volume of refreshing magma.
机译：在过去的100年中，斯特龙博利火山活动的特征是定期的斯特龙博伦火山喷发，在山顶火山口发生了一些重大爆炸和阵发性事件，熔岩流入了Sciara del Fuoco。在重大爆炸期间，两种类型的少年碎片，组成为生钾盐至高K玄武岩，其倾倒点尤为丰富：黑鳞屑，类似于正常的Strombolian活性喷发的黑鳞屑，代表高度斑状（45-60％），挥发性差岩浆（HP岩浆）和少量轻浮石，代表低斑岩（<10 vol％），富挥发分的岩浆（LP岩浆）。熔岩流是由HP岩浆构成的。 LP岩浆的成分比HP岩浆少，演化成分少，微量元素的不相容含量和Sr同位素比（0.70610）低。与LP和HP岩浆处于平衡状态的矿物相具有不同的组成（橄榄石中的Fo％：80-85和约70，斜py石中的Mg＃：0.83-0.91和约0.75，斜长石的An％：80-90和约65，尽管存在协同增生作用，但不平衡过程导致LP和HP岩浆矿物的成分范围较大。浮石的橄榄石和clinopyroxene在比（石相同晶体更高的温度（可能更高的压力）下达到平衡。所有这些数据提供了证据，表明这两个岩浆具有明显不同的理化条件。还已经指出，管道系统处于整体稳态条件下。高压岩浆位于浅水层，并以不断喷发，结晶（橄榄石+斜向辉石+斜长石岩）和补充储层的形式演化，并由低压岩浆供入。 LP岩浆来自较深的储层，在该储层中它经历了有限的女性相结晶。斜长石酶仅在较低深度开始结晶。在20世纪的火山灰和熔岩中，观察到地球化学，矿物学和同位素随时间的显着变化。岩浆中的MgO，V，Ni和Cr含量从1906年到1930年略有增加，然后从1965年到现在下降。矿物化学数据也相应地变化。还指出了1930年后不相容微量元素含量的增加和1980-85年后Sr同位素比的降低（从0.70626降至0.70616）。这些变化被认为是由于岩浆储层的结晶/补充平衡的变化或进料岩浆的成分变化引起的。似乎也存在主要成分变化与喷发活动类型之间的一些相关性。在20世纪上半叶发生的相对频繁的阵发性事件，与观察到的岩浆演化减少有关，似乎表明更多的高能爆炸与更大数量的刷新岩浆相关。

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