Glass inclusions and melt volatile contents at Parícutin Volcano, Mexico
Glass inclusions and melt volatile contents at Parícutin Volcano, Mexico
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墨西哥帕里库廷火山的玻璃夹杂物和熔体挥发物含量
DOI：
10.1007/s004100100293
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发表时间：
2001
影响因子：
3.5
通讯作者：
J. Luhr
中科院分区：
文献类型：
--
作者：
J. Luhr
摘要。对Parícutin火山在1943年5月26日和8月1日四个不同日期喷发的火山样品进行了橄榄石玻璃包裹体的研究；1945年1月23日；1948年3月31日。这些日期跨越了9年喷发的前三分之二，在此期间火山/熔岩的大规模喷发率急剧下降。它们也跨越了1947年整个岩石组成的强烈转变，这归因于地壳污染的重要性增加。在分析的26个玻璃包裹体中，有9个的SiO2含量低于之前分析的Parícutin熔岩样品，其含量低于53%。这些不含硅的玻璃是在1943年和1945年喷发的橄榄石中发现的，并为主要Parícutin熔岩套件的母代熔体提供了证据。傅里叶变换红外（FTIR）光谱测量的玻璃夹杂物中总含水量在所有样品中变化很大，总范围为1.8-4.0 wt%。总含水量与玻璃的SiO2、邻近橄榄石的mg#或喷发日期无关。只有两个玻璃夹杂物的碳酸盐含量（248和296 ppm CO2）高于FTIR检测限~50 ppm CO2；重要的是，这些包裹体也具有最高的总含水量和最高的SO3t值。这两个包裹体被困在火山下方9.0-9.6公里的最小深度。因此，早期脱气过程很可能从Parícutin中地壳水平的熔体中剥离了大部分碳。其他玻璃内含物根据水溶性极限产生的最小包裹深度为1.3-5.1 km。随着SiO2含量从52.7%增加到60.5 wt%，总硫含量（SO3为0.30 ~ 0.01 wt%）下降。这一趋势和玻璃包裹体总含水量的大范围变化被解释为反映了在地壳上层伴随分馏结晶和同化的脱气过程。
Abstract. Olivine-hosted glass inclusions were investigated from tephra samples erupted at Parícutin volcano on four different dates: May 26 and August 1, 1943; January 23, 1945; and March 31, 1948. These dates span the first two thirds of the 9 year eruption, during which time the tephra/lava mass-eruption rate fell dramatically. They also span the strong whole-rock compositional shift of 1947, attributed to the increased importance of crustal contamination. Nine of the 26 analyzed glass inclusions have lower SiO2 contents than any previously analyzed Parícutin lava sample, ranging to below 53 wt%. These silica-poor glasses are found in olivines erupted in 1943 and 1945, and provide evidence for melts that are parental to the main Parícutin lava suite. Total water contents in the glass inclusions measured by Fourier transform infrared (FTIR) spectroscopy vary considerably in all individual samples, with a total range of 1.8–4.0 wt%. Total water contents are not correlated with SiO2 of the glass, Mg# of the adjacent host olivine, or eruption date. Only two glass inclusions have carbonate contents (248 and 296 ppm CO2) above the FTIR detection limit of ~50 ppm CO2; importantly, these inclusions also have the highest total water contents and among the highest SO3t values. These two inclusions were trapped at minimum depths of 9.0–9.6 km beneath the volcano. Thus, early degassing likely stripped most carbon from Parícutin melts at mid-crustal levels. Other glass inclusions yield minimum entrapment depths of 1.3–5.1 km based on water solubility limits. Total sulfur (0.30 to 0.01 wt% SO3) declines as SiO2 contents increase from 52.7 to 60.5 wt%. This trend and the wide range of glass inclusion total water contents are interpreted to reflect degassing accompanied by fractional crystallization and assimilation at upper crustal levels.