Emplacement mechanism of off-axis large submarine lava field from the Oman Ophiolite
Emplacement mechanism of off-axis large submarine lava field from the Oman Ophiolite
复制标题
阿曼蛇绿岩离轴大型海底熔岩场的侵位机制
DOI：
10.1029/2012jb009198
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S.
中科院分区：
文献类型：
--
作者：
Umino;S.
厚达100米、体积超过几公里的大型海底熔岩流并不是罕见的大洋中脊和夏威夷群岛周围的火山构造，但人们对这些大型熔岩流喷发的物理过程的细节知之甚少。阿曼蛇绿岩的V3单元随着厚厚的熔岩流动，挤压到远离古扩张轴线的远洋沉积物上，面积为11×1.5公里，最大厚度为270×270米，估计体积为1.2×10公里。V3流场的补给层厚度异常，厚度高达60米，与古扩散轴成大角度撞击。厚度的倾斜变化表明，在离轴地壳中中性浮力的表观水平上有侵入。厚片状流由块状核和柱状节理地壳组成。细粒、细节理的岩层和镶嵌在粗粒、粗略节理熔岩中的透镜显示了熔岩地壳复杂的冷却和生长历史。在流场的外围，席状流缺乏发育的岩心结构，横向上转变为枕状和水下泡状叶的复合流，偶尔与远洋页岩混合。另一方面，岩心缺乏细小的柱状节理，呈典型的辉绿岩结构。我们的结论是，V3流是由熔岩以中低速挤出到覆盖着厚厚的远洋沉积物的亚水平海底，掩埋了100米的深海丘陵和断陷形成的。
Large submarine lava flows with thicknesses >100 m and volumes exceeding a few km3are not uncommon volcanic constructs of mid‐ocean ridges and around Hawaii Islands, yet details of the physical processes of eruption of these large lava flows are poorly understood. The V3 unit of the Oman Ophiolite extruded onto pelagic sediment far off the paleospreading axis as thick lava flows with an areal extent of >11 km by 1.5 km and the maximum thickness >270 m, yielding an estimated volume >1.2 km3. The feeder dike for the V3 flow field has an unusual thickness up to 60 m, striking at a high angle to the paleospreading axis. The skewed variation in thickness suggests an intrusion at the apparent level of neutral buoyancy in off‐axis crust. The thick sheet flows consist of massive core and columnar jointed crust. Finer‐grained, finely jointed layers and lenses embedded in coarser‐grained, roughly jointed lava show a complex cooling and growth history of the lava crust. In the periphery of the flow field, sheet flows lack developed core textures and change laterally into compound flows of pillow and subaqueous pahoehoe lobes, which are occasionally intermingled with pelagic shale. On the other hand, core lacks fine columnar joints and shows a typical doleritic texture. We conclude that the V3 flow field formed by extrusion of lava at low to moderate rates onto a subhorizontal seafloor covered with thick pelagic sediment, burying topographic relief >100 m of abyssal hills and fault grabens.