DEGASSING HISTORY OF WATER, SULFUR, AND CARBON IN SUBMARINE LAVAS FROM KILAUEA VOLCANO, HAWAII
DEGASSING HISTORY OF WATER, SULFUR, AND CARBON IN SUBMARINE LAVAS FROM KILAUEA VOLCANO, HAWAII
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DOI：
10.1086/629501
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发表时间：
1991-05-01
影响因子：
1.8
通讯作者：
STOLPER, EM
中科院分区：
文献类型：
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作者：
DIXON, JE;CLAGUE, DA;STOLPER, EM
在夏威夷基拉韦厄火山东部裂谷带海底部分（普纳海岭）的拉斑斑斑玄武岩玻璃中测量了主要、次要和溶解的挥发性元素浓度。 相对于所有深度的非挥发性不相容元素，溶解的 H2O 和 S 浓度显示出较宽的范围。 这个范围不能轻易地用分步结晶、海底喷发过程中水和硫的脱气或源区异质性来解释。 相反，溶解的二氧化碳浓度与喷发深度呈正相关，并且通常与该深度的溶解度在误差范围内一致。 我们认为，沿普纳海脊的大多数岩浆是由于（1）相对富含挥发物、未脱气的成分与经历低压（可能是地面）脱气的岩浆混合而成，在此期间大量的H2O、S和CO2损失，随后（2）橄榄石、单斜辉石和斜长石从该混合物中分步结晶，产生残留液体； (3) 在海底喷发过程中，对喷发深度超过 1000 米的样品进行进一步脱气，主要是脱除 CO2。 脱气的端部成员可能在地壳浅层停留期间或持续的山顶喷发期间在山顶岩浆室的上层形成（假设小于岩石静压力梯度）。 海底喷发期间脱气的最后阶段发生得足够慢，以在典型富含二氧化碳的蒸气相的溶出过程中实现熔体/蒸气平衡。 我们预测平均含 16% MgO 的基拉韦斯原生岩浆含有约 0.47 wt% H2O、约 900 ppm S，并且 delta-D 值约为 -30 至 -40%。 我们的模型预测，来自完全海底火山（即洛伊希）的海底熔岩，由于没有机会通过低压脱气产生脱气的端部成员，因此相对于那些山顶已经突破海面的火山（即基拉韦厄火山和莫纳罗亚火山）的火山岩浆，其挥发物含量会更高。
Major, minor, and dissolved volatile element concentrations were measured in tholeiitic glasses from the submarine portion (Puna Ridge) of the east rift zone of Kilauea Volcano, Hawaii. Dissolved H2O and S concentrations display a wide range relative to nonvolatile incompatible elements at all depths. This range cannot be readily explained by fractional crystallization, degassing of H2O and S during eruption on the seafloor, or source region heterogeneities. Dissolved CO2 concentrations, in contrast, show a positive correlation with eruption depth and typically agree within error with the solubility at that depth. We propose that most magmas along the Puna Ridge result from (1) mixing of a relatively volatile-rich, undegassed component with magmas that experienced low pressure (perhaps subaerial) degassing during which substantial H2O, S, and CO2 were lost, followed by (2) fractional crystallization of olivine, clinopyroxene, and plagioclase from this mixture to generate a residual liquid; and (3) further degassing, principally of CO2 for samples erupted deeper than 1000 m, during eruption on the seafloor. The degassed end member may form at upper levels of the summit magma chamber (assuming less than lithostatic pressure gradients), during residence at shallow levels in the crust, or during sustained summit eruptions. The final phase of degassing during eruption on the seafloor occurs slowly enough to achieve melt/vapor equilibrium during exsolution of the typically CO2-rich vapor phase. We predict that average Kilauean primary magmas with 16% MgO contain approximately 0.47 wt % H2O, approximately 900 ppm S, and have delta-D values of approximately -30 to -40%. Our model predicts that submarine lavas from wholly submarine volcanoes (i.e., Loihi), for which there is no opportunity to generate the degassed end member by low pressure degassing, will be enriched in volatiles relative to those from volcanoes whose summits have breached the sea surface (i.e., Kilauea and Mauna Loa).