A comparison of volcanic edifices at the Reykjanes Ridge and the Mid‐Atlantic Ridge at 24°–30°N
A comparison of volcanic edifices at the Reykjanes Ridge and the Mid‐Atlantic Ridge at 24°–30°N
复制标题
北纬 24°–30° 雷克雅内斯海脊和大西洋中脊火山建筑物的比较
DOI：
--
复制
发表时间：
1995
期刊：
影响因子：
--
通讯作者：
W. Bryan
中科院分区：
文献类型：
--
作者：
Deborah K. Smith;S. Humphris;W. Bryan
对高分辨率侧扫声纳资料的详细分析表明，建在缓慢扩张(20 mm/年)的雷克雅尼斯海脊和缓慢扩张(25毫米/年)中大西洋海脊轴带内的火山建筑物非常相似。事实上，雷克扬斯山脊的个别海山、山丘(圆形丘陵)和山丘山脊在中大西洋山脊(MAR)的形态上几乎相同，认为两个山脊的喷发条件通常是相似的。这些火山建筑物是典型的缓慢扩张的山脊，尽管雷克雅内斯山脊靠近冰岛热点，而且该热点对山脊轴的其他特征有影响，如其整体形状(轴向高度约在59°N以北)、轴向深度较浅以及地壳剖面较厚，但这些火山建筑物的建造发生在雷克扬斯山脊。使用多波束测深数据计算了在MAR的12个部分和雷克雅内斯山脊的4个区域的每一个区域建造火山建筑物所需的岩浆体积。我们的结果表明，单位海底面积上的建筑物体积，相当于感兴趣区域上的均匀厚度，平均而言，在MAR比在雷克扬斯海脊更大。考虑到扩散速率，我们然后估计B，即沿轴线单位长度的平均建筑速率，它在MAR处也较大。我们得出的结论是，在雷克雅内斯海脊和3月，同样的火山建筑物建造了地壳，但它们在3月更频繁地侵位。为了解释我们的结果，并将其与Magde和Smith(1995)的结果相一致，他们记录了雷克雅尼海脊的海山比Mar海山更高、更丰富，我们考虑了两个海脊轴线区域内的海堤和喷发的控制。我们认为，较慢的扩散速度和雷克扬斯山脊倾斜的扩散几何结构相结合，导致了较少的喷发，这些喷发在轴带上的分布比在MAR更广泛。如果这一假设是正确的，那么被随后的喷发改变的海山比例将会更小。这也可能解释了如果建筑物之间的重叠和填充较少，海山的高度会更高。
A detailed analysis of high-resolution side-scan sonar data shows that the volcanic edifices built within the axial zones of the slow spreading (20 mm/yr) Reykjanes Ridge and the slow spreading (25 mm/yr) Mid-Atlantic Ridge are remarkably similar. In fact, individual seamounts, hummocks (rounded mounds), and hummocky ridges at the Reykjanes Ridge have nearly identical morphological counterparts at the Mid-Atlantic Ridge (MAR), arguing that commonly eruptive conditions are similar at the two ridges. The construction of these volcanic edifices, typical of slow spreading ridges, occurs at the Reykjanes Ridge despite its proximity to the Iceland hot spot and the influence of the hot spot on other characteristics of the ridge axis, such as its overall shape (an axial high north of about 59°N), its shallow axial depths, and its thicker crustal section. The volume of magma that goes into constructing volcanic edifices at each of 12 segments of the MAR and four regions of the Reykjanes Ridge is calculated using multibeam bathymetry data. Our results indicate that edifice volume per unit seafloor area, equivalent to a uniform thickness over the area of interest, is larger at the MAR than at the Reykjanes Ridge, on average. Taking into account spreading rate, we then estimate B, the average building rate per unit length along the axis, which is also larger at the MAR. We conclude that the same volcanic edifices build the crust at the Reykjanes Ridge and MAR, but that their emplacement is more frequent at the MAR. To explain our results and reconcile them with those of Magde and Smith (1995) who documented that seamounts are taller and more abundant at the Reykjanes Ridge than at the MAR, we consider the controls on diking and eruption within the axial zones of the two ridges. We suggest that the combination of slower spreading rate and the oblique geometry of spreading at the Reykjanes Ridge leads to fewer eruptions which are more widely dispersed across the axial zone than at the MAR. If this hypothesis is correct, the proportion of seamounts modified by subsequent eruptions will be less. This might also explain the taller heights of the seamounts if there is less overlap and infilling between edifices.