Crustal migration of CO2-rich magmatic fluids recorded by tree-ring radiocarbon and seismicity at Mammoth Mountain, CA, USA
Crustal migration of CO2-rich magmatic fluids recorded by tree-ring radiocarbon and seismicity at Mammoth Mountain, CA, USA
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DOI：
10.1016/j.epsl.2013.12.035
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发表时间：
2014-03
影响因子：
5.3
通讯作者：
J. Lewicki;G. Hilley;D. Shelly;J. King;J. McGeehin;M. Mangan;W. Evans
中科院分区：
文献类型：
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作者：
J. Lewicki;G. Hilley;D. Shelly;J. King;J. McGeehin;M. Mangan;W. Evans
猛犸山的地震活动、地表变形、CO2的扩散和火山气体中He 3/He 4比值的升高，是由中下地壳玄武岩侵入体释放的富CO2流体所驱动的。最近的动荡包括2006年、2008年和2009年在猛犸山下发生了三次下地壳（32-19公里深）地震群，随后一直是浅层（10公里深）地震发生率的高峰。我们测量了生长在猛犸山（马蹄湖树杀死; HLTK）上最大（约0.3平方公里）弥散性CO2排放区的树木的年轮（1998-2012年）中的C14，并应用大气CO2浓度源区建模来确认该树木是该地区大部分岩浆CO2排放的可靠集成商。树木年轮C14记录表明，HLTK的岩浆CO2排放量在1998年至2009年期间相对稳定，从2009年至2011年几乎翻了一番，然后在2012年生长季节下降。在生长季节期间检测到二氧化碳排放量的最初增加，紧接着浅层地震发生率的最大峰值（2010年2月）。富CO2岩浆流体的迁移可能驱动了观测到的升高的深，然后浅地震活动的模式，而浅（地壳上3公里）流体储层和储层盖层的渗透率结构的孔隙流体压力之间的关系可能控制了地表CO2排放的时间模式。
Abstract Unrest at Mammoth Mountain over the past several decades, manifest by seismicity, ground deformation, diffuse CO 2 emissions, and elevated He 3/He 4 ratios in fumarolic gases has been driven by the release of CO 2-rich fluids from basaltic intrusions in the middle to lower crust. Recent unrest included the occurrence of three lower-crustal (32–19 km depth) seismic swarms beneath Mammoth Mountain in 2006, 2008 and 2009 that were consistently followed by peaks in the occurrence rate of shallow (⩽ 10 km depth) earthquakes. We measured C 14 in the growth rings (1998–2012) of a tree growing in the largest (∼ 0.3 km 2) area of diffuse CO 2 emissions on Mammoth Mountain (the Horseshoe Lake tree kill; HLTK) and applied atmospheric CO 2 concentration source area modeling to confirm that the tree was a reliable integrator of magmatic CO 2 emissions over most of this area. The tree-ring C 14 record implied that magmatic CO 2 emissions from the HLTK were relatively stable from 1998 to 2009, nearly doubled from 2009 to 2011, and then declined by the 2012 growing season. The initial increase in CO 2 emissions was detected during the growing season that immediately followed the largest (February 2010) peak in the occurrence rate of shallow earthquakes. Migration of CO 2-rich magmatic fluids may have driven observed patterns of elevated deep, then shallow seismicity, while the relationship between pore fluid pressures within a shallow (upper 3 km of crust) fluid reservoir and permeability structure of the reservoir cap rock may have controlled the temporal pattern of surface CO 2 emissions.