Subduction cycling of volatiles and trace elements through the Central American volcanic arc: evidence from melt inclusions
Subduction cycling of volatiles and trace elements through the Central American volcanic arc: evidence from melt inclusions
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DOI：
10.1007/s00410-007-0251-3
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发表时间：
2008-04
影响因子：
3.5
通讯作者：
S. Sadofsky;M. Portnyagin;K. Hoernle;P. Bogaard
中科院分区：
文献类型：
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作者：
S. Sadofsky;M. Portnyagin;K. Hoernle;P. Bogaard
利用危地马拉、尼加拉瓜和中美洲火山弧沿线11个地点的橄榄石(FO90-)熔体包裹体成分，对母质熔体中主量元素、微量元素和挥发性成分(H2O、S、Cl、F)的组合系统进行了约束，并估算了挥发性元素的火山通量。熔融包裹体覆盖了中美洲报道的整个岩石的全部成分。它们指出，岩浆来源在地方和区域尺度上具有很大的不均一性，这与参与岩浆成因的不同地壳(来自俯冲和俯冲板块)和地幔(来自楔形和来袭板块)成分的不同贡献有关。母质熔体中的水与Ti、Y、Na呈负相关，与BA/La和B/La呈正相关(伊拉苏火山除外)，这表明弧下大部分地区的地幔熔融是由富BA、B和H2O的蛇纹岩流体提供的。具有类熔体特征的不同组分(高LREE、La/Nb，可能还有Cl、S、F和低BA/La)控制着危地马拉和哥斯达黎加岩浆的地球化学性质。利用母岩浆的组成以及已公布的火山体积和卫星测量的二氧化硫总通量数据来限制挥发性组分的通量，并估计中美洲的总岩浆通量。我们发现，火山通量只占总岩浆通量和挥发通量的13%。其余87%的岩浆留在岩石圈形成堆积体(∼39%)和侵入岩(∼48%)。与哥斯达黎加相比，尼加拉瓜地下岩浆流量的侵入比例可能要大得多。有趣的是，中美洲岩浆和挥发分的总通量与全球平均估计值非常相似。
Compositions of melt inclusions in olivine (Fo90-64) from 11 localities in Guatemala, Nicaragua and Cost Rica along the Central American Volcanic Arc are used to constrain combined systematics of major and trace elements and volatile components (H2O, S, Cl, F) in parental melts and to estimate volcanic fluxes of volatile elements. The melt inclusions cover the entire range of compositions reported for whole rocks from Central America. They point to large heterogeneity of magma sources on local and regional scales, related to variable contributions of diverse crustal (from the subducting and overriding plates) and mantle (from the wedge and incoming plate) components involved in magma genesis. Water in parental melts correlates inversely with Ti, Y and Na and positively with Ba/La and B/La (with the exception of Irazú Volcano), which indicates mantle melting fluxed by Ba-, B- and H2O-rich, possibly, serpentinite-derived fluid beneath most parts of the arc. Different components with melt-like characteristics (high LREE, La/Nb and probably also Cl, S and F and low Ba/La) control the geochemical peculiarities of Guatemalan and Costa Rican magmas. The composition of parental magmas together with published data on volcanic volumes and total SO2flux from satellite measurements are used to constrain fluxes of volatile components and to estimate total magmatic flux in Central America. We found that volcanic flux accounts for only 13% of total magmatic and volatile fluxes. The remaining 87% of magmas remained in the lithosphere to form cumulates (∼39%) and intrusives (∼48%). The intrusive fraction of magmatic flux may be significantly larger beneath Nicaragua compared to Costa Rica. Interestingly, total fluxes of magmas and volatiles in Central America are quite similar to the global average estimates.