40Ar/39Ar and paleomagnetic constraints on the evolution of Volcán de Santa María, Guatemala
40Ar/39Ar and paleomagnetic constraints on the evolution of Volcán de Santa María, Guatemala
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40Ar/39Ar 和古地磁对危地马拉圣玛丽亚火山演化的限制
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
W. Rose
中科院分区：
文献类型：
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作者：
R. Escobar;J. Diehl;B. Singer;W. Rose
对15个熔岩流的40 Ar/ 39 Ar测年表明，圣玛利亚火山在103 ~ 35 ka之间以0.12km3/ka的平均速率间歇性地增长到8 km 3。复合锥的生长分为四个阶段，包括两个时期的强烈活动，在约。72卡和CA。35 ka，分别有1.5km3和3 km 3的玄武质-安山质岩浆喷发。没有证据表明公元后还有进一步的火山活动。距今35 ka，直到1902年英安质火山大爆发。如果把1902年火山喷发和随后的火山穹丘产物计算在内，平均喷发速率为0.16km3/ka。而莫诺湖游览没有清楚地记录在火山德圣玛利亚，从早期的研究中推断，虚拟地磁极（VGPs）的35万年锥形形成熔岩表现出高振幅的paleosecular变化，可能对应的时间莫诺湖游览。两个老包的熔岩流都与一个独特的集群VGP，这支持40 Ar/ 39 Ar年龄模型和锥建设的结论是情节。在最后60%的锥增长，熔岩演化从玄武岩安山质（51%-57%SiO2）随着时间的推移，但与回归到轻微的进化组合物在最后的锥建设阶段的开始。尽管圣玛利亚的体积相对较小，但锥形生长过程和地球化学演变反映了对沿着中美洲火山弧的其他目前活跃的火山的观测，并可能证明在评估其他主要是玄武岩-安山质复合火山所造成的长期危害时作为类比是有用的。
40 Ar/ 39 Ar dating of 15 lava flows indicates that Volcan de Santa Maria grew episodically to 8 km 3 in size at an average rate of 0.12 km 3 /ka between 103 and 35 ka. The composite cone grew in four phases, including two periods of intense activity at ca. 72 ka and ca. 35 ka, during which 1.5 km 3 and 3 km 3 of basaltic to andesitic magmas were erupted. There is no evidence of further volcanism after ca. 35 ka until the great dacitic eruption in 1902. The average eruptive rate is 0.16 km 3 /ka, if products of the 1902 eruption and subsequent Santiaguito dome are included. Whereas the Mono Lake excursion is not clearly recorded at Volcan de Santa Maria, as had been inferred from earlier studies, virtual geomagnetic poles (VGPs) of the 35 ka cone-forming lavas exhibit high-amplitude paleosecular variation that may correspond in time to the Mono Lake excursion. Two older packages of lava flows are each associated with a distinctive cluster of VGPs, which supports the 40 Ar/ 39 Ar age model and the conclusion that cone building was episodic. During the final 60% of cone growth, lavas evolved from basaltic to andesitic (51%–57% SiO 2 ) with time, but with a regression to slightly less evolved compositions during the onset of the final cone-building phase. Despite the relatively small volume of Santa Maria, cone-growth processes and geochemical evolution through time mirror observations at other currently active volcanoes along the Central American volcanic arc, and may prove useful as an analogy in assessing long-term hazards posed by other predominantly basaltic-andesitic composite volcanoes.