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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Comagmatic granophyre and dacite from Karymsky volcanic center, Kamchatka: experimental constraints for magma storage conditions
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Comagmatic granophyre and dacite from Karymsky volcanic center, Kamchatka: experimental constraints for magma storage conditions

机译：来自堪察加半岛卡里姆斯基火山中心的岩浆花岗岩和陶粒：岩浆储存条件的实验约束

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Despite a ～ 30 000 years difference in age, two caldera-forming eruptions at Karymsky volcanic center, Kamchatka - Karymsky (7900 yr BP) and Academy Nauk (ca. 40 000 yr BP) - produced two-pyroxene dacites with the same composition and mineralogy. Granophyric xenoliths of the identical whole-rock chemistry were found in basalts erupted within Academy Nauk caldera in 1996. Unlike the dacites, however, the granophyres are holo-crystalline and contain biotite and amphibole. Large amphibole phenocrysts contain rare inclusions of clinopyroxenes, which compositionally overlap with clinopyroxenes in the dacites. The Al content of the amphibole suggests it grew at a pressure of about 100 MPa. Results of hydrothermal experiments and petrologic observations indicate that Academy Nauk and Karymsky dacites were last equilibrated at 883+-19℃, 100+-15 MPa and 871+-19℃, 85+-18 MPa, respectively, both at water-saturated conditions. The mineral assemblage of granophyre is reproduced by isobaric crystallization of the dacite at 100 MPa, implying that the granophyres were sampled from the crystallized silicic reservoir that produced the caldera-forming eruption of Academy Nauk. Similar chemical compositions of Karymsky and Academy Nauk dacites indicate that both were derived from the same crustal-level source. The eruptive history of the calderas can best be explained by two 10-12-km~3 dacitic batches that detached from a parental body situated in the lower crust, then ascended to 3-4 km depth, re-equilibrated, and erupted.
机译：尽管年龄相差约30,000年，但在Karymsky火山中心，堪察加半岛的Karymsky（7900年BP）和Academy Nauk（约40000 BP）的两次火山口形成喷发产生了具有相同成分的二py矿物学。在1996年的Nauk火山口火山喷发的玄武岩中发现了具有相同全岩石化学性质的粒状异岩。但是，与dacites不同，粒状异物是全结晶的，含有黑云母和闪石。大型角闪石隐晶含有稀有的斜辉石夹杂物，在分子组成上与斜辉石在成分上重叠。闪石的铝含量表明它在约100 MPa的压力下生长。水热实验结果和岩石学观察结果表明，Naus Academy Nauk和Karymsky dacites在水饱和条件下最后分别在883 + -19℃，100 + -15 MPa和871 + -19℃，85 + -18 MPa达到平衡。 。通过在100 MPa下对辉绿岩进行等压结晶，可以再现出花岗石的矿物组合，这意味着这些花岗石是从结晶的硅质储层中取样的，而该硅质储层中产生了Academy Nauk的破火山口喷发。 Karymsky和Academy Nauk数据的相似化学成分表明，两者均来自相同的地壳水准。破火山口的爆发历史可以用两个10-12 km〜3的菊苣批次来解释，这些批次从位于下地壳的母体中分离出来，然后上升到3-4 km的深度，重新平衡并爆发。

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