Timescales of Magma Reservoir Processes Beneath Hawaii

夏威夷下方岩浆库过程的时间尺度

• 批准号: 9980646
• 负责人: Mary Reid
• 金额: $ 13.15万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-08-01 至 2004-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9980646&HistoricalAwards=false
• 关键词: Timescales; Magma; Reservoir; Processes; Beneath

ReidEAR-9980646Time scales of magma residence and differentiation are difficult to quantify bur are important in understanding the evolution and dynamics of the magmatic reservoir system. No quantitative estimates for magma residence in Mauna Loa Volcano in Hawaii are currently available, and estimates for Kilauea Volcano range from tens to thousands of years. Most of these estimates represent average residence times, and are subject to assumptions about the size of the reservoir and the magma supply rate. We propose a different approach to determining timescales of magmatic processes by using Ra-Th disequilibria to measure the time since crystal growth rates, which is a minimum residence time. Such analysis will yield cooling rates, and combined with crystal size data, will yield crystal growth rates, both of which have not been measured directly for sub-surface reservoirs in basaltic volcanoes. Preliminary data from the 1955 east rift eruption of Kilauea suggest that residence is longer (and therefore that cooling and crystallization rates are lower) than most previous estimates. Our data also suggest that Ra and Ba are differentially fractionated during crystal growth, requiring fractionation correction when using Ba as a chemical analog for Ra. We propose to analyze additional samples to test the generality of these results and to determine whether the predicted Ra/Ba fractionations are consistent with data for young lavas. These results will have important implications not only for studies of magma reservoir processes in Hawaiian volcanoes, but also more generally to timescales of basaltic differentiation.

Reidear-9980646Timer的岩浆居住尺度和分化很难量化，对于理解岩浆储层系统的演变和动态非常重要。目前尚无对夏威夷Mauna Loa火山岩浆居住地的定量估计，估计基拉韦阿火山范围从数十到数千年。 这些估计中的大多数代表平均停留时间，并受到有关储层大小和岩浆供应率的假设。 我们提出了一种不同的方法来确定岩浆过程的时间尺度，通过使用RA-The-the平衡来测量自晶体生长速率以来的时间，这是最小的停留时间。这种分析将产生冷却速率，并结合晶体尺寸数据，将产生晶体生长速率，两者均未直接测量玄武岩火山中的地下储层。 1955年东裂口爆发的初步数据表明，居住时间更长（因此，冷却和结晶速率低于大多数先前的估计。 我们的数据还表明，在晶体生长过程中，RA和BA在晶体生长过程中被差异分离，在使用BA作为RA的化学类似物时，需要分馏校正。 我们建议分析其他样本以测试这些结果的普遍性，并确定预测的RA/BA分馏是否与幼年熔岩的数据一致。 这些结果不仅对夏威夷火山中岩浆储层过程的研究具有重要意义，而且更普遍地对玄武岩分化的时间标准。