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Petrological and geochemical modeling of magmas erupted at Vulcano Island in the period 54–8 ka: Quantitative constraints on the sub-volcanic architecture of the plumbing system
Lithos ( IF 2.9 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.lithos.2020.105715
Flavia Palummo , Silvio Mollo , Gianfilippo De Astis , Flavio Di Stefano , Manuela Nazzari , Piergiorgio Scarlato

Abstract In this study, we present new mineralogical and petrological data from fifteen eruptive products erupted at Vulcano Island (Aeolian Arc, Italy) over a period of time from 54 to 8 ka and representative of the Eruptive Epochs from 5 to 8 of this volcanic system. These rocks show shoshonitic (SHO) to high-K calc-alkaline (HKCA) affinity, with compositions changing from primitive basalts-shoshonites (Mg#35–60) to intermediate latites (Mg#32–54) to evolved trachytes-rhyolites (Mg#23–40). The intensive variables driving the crystallization path of magmas were reconstructed through mineral-melt equilibrium and thermodynamic models, as well as barometers, thermometers, hygrometers and oxygen barometers. The stability of olivine (Fo59–91), as first phase on the liquidus, is more favored at low-P (100–300 MPa) and high-H2O (4 wt%) contents dissolved in the melt. Afterwards, the melt is co-saturated with clinopyroxene (Mg#92, diopside), whose composition progressively evolves (Mg#71, augite) as the temperature decreases to 1100 °C. The crystallization pressure recorded by clinopyroxene decreases from basalts (550–750 MPa) to shoshonites-latites-trachytes (100–450 MPa) to rhyolites (~50 MPa). The melt-H2O content (0.5–4.2 wt%) is sensitive to either pressure or melt composition, thereby controlling the plagioclase stability and chemistry (An13–77) within a thermal path of ~860–1100 °C. Titanomagnetite (Usp11–39) equilibrates with progressively more oxidized melts as the magma composition changes from basalt (ΔQFM+1.5) to rhyolite (ΔQFM+3). Mass balance calculations and trace element modeling indicate that basaltic to trachytic magmas are prevalently controlled by fractional crystallization processes, in concert with variable degrees of assimilation of crustal rocks. Conversely, rhyolitic and highly differentiated trachytic magmas are generated by extraction of interstitial melts from shallow mush zones dominated by feldspar and titanomagnetite saturation. We conclude that the architecture of the plumbing system at Vulcano Island is characterized by multiple reservoirs in which compositionally distinct magmas pond and undergo polybaric-polythermal differentiation, before erupting to the surface.

中文翻译:

54-8 ka 期间 Vulcano 岛喷发的岩浆的岩石学和地球化学模拟:管道系统亚火山结构的数量限制

摘要 在这项研究中,我们展示了在 54 至 8 ka 期间在 Vulcano 岛(意大利伊奥利亚弧)喷发的 15 种喷发产物的新矿物学和岩石学数据,这些产物代表了该火山系统 5 至 8 年的喷发期。 . 这些岩石显示出钾长石 (SHO) 对高钾钙碱性 (HKCA) 的亲和力,其成分从原始玄武岩-钾长石 (Mg#35-60) 到中级拉长岩 (Mg#32-54) 再到演化的粗面-流纹岩 ( Mg#23-40)。通过矿物熔体平衡和热力学模型,以及气压计、温度计、湿度计和氧气气压计,重建了驱动岩浆结晶路径的密集变量。橄榄石(Fo59-91)的稳定性,作为液相线上的第一相,溶解在熔体中的低 P (100-300 MPa) 和高 H2O (4 wt%) 含量更受青睐。之后,熔体与单斜辉石(Mg#92,透辉石)共饱和,随着温度降低到 1100°C,其成分逐渐演变(Mg#71,辉石)。单斜辉石记录的结晶压力从玄武岩 (550–750 MPa) 到钠长石-红云石-粗面岩 (100–450 MPa) 再到流纹岩 (~50 MPa)。熔体-H2O 含量(0.5-4.2 wt%)对压力或熔体成分敏感,从而在~860-1100 °C 的热路径内控制斜长石稳定性和化学性质(An13-77)。随着岩浆成分从玄武岩 (ΔQFM+1.5) 变为流纹岩 (ΔQFM+3),钛磁铁矿 (Usp11-39) 与逐渐氧化的熔体平衡。质量平衡计算和微量元素建模表明,玄武质到粗质岩浆普遍受分步结晶过程控制,与地壳岩石的同化程度不同。相反,流纹质和高度分化的粗面岩浆是通过从以长石和钛磁铁矿饱和为主的浅层泥状带中提取间隙熔体而产生的。我们得出结论,Vulcano 岛管道系统的结构以多个水库为特征,其中在喷发到地表之前,岩浆池的成分不同,并经历多元多热分异。流纹质和高度分化的粗面岩浆是通过从以长石和钛磁铁矿饱和为主的浅层泥状带中提取间隙熔体而产生的。我们得出结论,Vulcano 岛管道系统的结构以多个水库为特征,其中在喷发到地表之前,岩浆池的成分不同,并经历多元多热分异。流纹质和高度分化的粗面岩浆是通过从以长石和钛磁铁矿饱和为主的浅层泥状带中提取间隙熔体而产生的。我们得出结论,Vulcano 岛管道系统的结构以多个水库为特征,其中在喷发到地表之前,岩浆池的成分不同,并经历多元多热分异。
更新日期:2020-11-01
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