Geochemical variation along and across the Central American Miocene paleoarc in Honduras and Nicaragua
Geochemical variation along and across the Central American Miocene paleoarc in Honduras and Nicaragua
复制标题
洪都拉斯和尼加拉瓜沿中美洲中新世古弧的地球化学变化
DOI：
10.1016/j.gca.2007.05.013
复制
发表时间：
2007
影响因子：
5
通讯作者：
Jan Ehrenborg
中科院分区：
文献类型：
--
作者：
B. R. Jordan;H. Sigurdsson;S. Carey;R. Rogers;Jan Ehrenborg
70个样品，收集在68个地点在尼加拉瓜和洪都拉斯的中新世时代熔结凝灰岩的分析表明，地球化学过程和俯冲带的几何形状类似于现代弧也存在于古弧。样品沿沿着两条平行和垂直于推断的古弧的横断面绘制。大多数氧化物图显示出平坦的轮廓沿着弧从西北到东南，除了二氧化硅，它减少。FeO、CaO、TiO 2和MgO含量从NW向SE逐渐增加。除K_2O外，氧化物从SW到NE没有明显的变化趋势。K2 O增加SW。大多数微量元素表现出很小的变化沿着全省从西北到东南，与La，Ce，Rb，Ba，Th，Nb，Ta，Pb和Sr，这一切都出现在丰富的减少从西北到东南。虽然Ba增加到西南部，向古海沟，它也显示出显着的变化平行于弧，高在尼加拉瓜，并减少浓度的西北和东南。这一趋势在Ba/La特别明显，西北部的低点接近1，尼加拉瓜的高点接近80。这一趋势与现代弧相似，这表明中新世弧的几何形状与现代弧非常相似。此外，随着基底边界的跨越（由重力异常绘图确定），数据也变得更加分散到东南部，这可能是由于大陆地壳的污染程度较高。
An analysis of 70 samples, collected from Miocene-age ignimbrites in 68 locations in Nicaragua and Honduras, indicates that geochemical processes and a subduction zone geometry similar to those in the modern arc were also present in the paleoarc. Samples were plotted along two transects, parallel and perpendicular to the inferred paleoarc. Most of the oxide plots exhibit flat profiles along the arc from NW to SE, except for SiO2, which decreases. FeO, CaO, TiO2, and MgO increase from NW to SE. There are no clear trends in the oxides from SW to NE, except K2O. K2O increases to the SW. Most trace elements show little to no variation along the province from NW to SE, with the exception of La, Ce, Rb, Ba, Th, Nb, Ta, Pb, and Sr, which all appear to decrease in abundance from NW to SE. While Ba increases to the SW, toward the paleotrench, it also shows remarkable variation parallel to the arc, with highs in Nicaragua, and decreasing concentrations to the NW and SE. This trend is especially apparent in Ba/La with lows near 1 in the NW and highs approaching 80 in Nicaragua. This trend is similar to that of the modern arc, which suggests that the geometry of the arc in the Miocene was very similar to that of the modern arc. In addition, the data also becomes more scattered to the southeast as a basement boundary is crossed (determined by gravity-anomaly mapping), probably due to a higher degree of contamination by continental crust.