Continental magmatism, volatile recycling, and a heterogeneous mantle caused by lithospheric gravitational instabilities
Continental magmatism, volatile recycling, and a heterogeneous mantle caused by lithospheric gravitational instabilities
复制标题
DOI：
10.1029/2005jb004072
复制
发表时间：
2007-03-20
影响因子：
3.9
通讯作者：
Elkins-Tanton, Linda T.
中科院分区：
文献类型：
--
作者：
Elkins-Tanton, Linda T.
[1] 通过延性重力不稳定性去除下层岩石圈（带有或不带有部分地壳的地幔岩石圈）可以在大陆下产生岩浆。通过近似大陆地壳和岩石圈以及底层软流圈流变学的数值实验，并使用文献中的相平衡，我研究了岩石圈重力不稳定的地形和岩浆结果，以及下沉物质的命运。无论机制如何，岩石圈去除通常称为分层，可能会导致软流圈材料上升并绝热融化，并且该软流圈可以传导加热先前处于较低温度的岩石圈部分。下沉材料的尺寸和流变性极大地影响最终的表面形貌以及是否发生熔化。下沉的物质在达到更高的温度和压力时可能会挥发，就像俯冲板片一样，引发进一步的熔化。重力不稳定性可能是造成非岩浆盆地、在没有俯冲作用的情况下体积和成分不同的大陆岩浆作用、高热流和隆起区域以及上地幔主量和微量元素及挥发物异质性的形成的原因。岩浆作用可能与地形沉降同时发生，也可能与随后的隆起同时发生。在产生岩浆的情况下，熔化可能发生在大约 30 至 200 公里的深度范围内，尽管需要异常炎热的地幔才能达到溢流玄武岩的体积。
[1] Removal of the lower lithosphere ( mantle lithosphere with or without portions of the crust) through ductile gravitational instabilities can produce magma under continents. Using numerical experiments approximating the rheology of continental crust and lithosphere and underlying asthenosphere and using phase equilibria from the literature, I investigate the topographic and magmatic results of lithospheric gravitational instabilities, along with the fate of the sinking material. Lithospheric removal, commonly referred to as delamination regardless of the mechanism, may allow asthenospheric material to rise and to melt adiabatically, and this asthenosphere can conductively heat portions of the lithosphere previously at lower temperatures. The size and rheology of the sinking material greatly influence the resulting surface topography as well as whether or not melting occurs. The sinking material may devolatilize as it reaches higher temperatures and pressures, just as a subducting slab does, triggering further melting. Gravitational instabilities are possible causes of nonmagmatic basins, continental magmatism of varying volume and composition in the absence of subduction, areas of high heat flow and uplift, and creation of an upper mantle heterogeneous in major and trace elements and volatiles. Magmatism can be simultaneous with topographic subsidence and possibly with subsequent uplift. In those cases that produce magma, melting can occur over a depth range from similar to 30 to 200 km, though anomalously hot mantle is required to reach the volume of flood basalts.