Mantle flow at oceanic spreading centers: Models derived from ophiolites
Mantle flow at oceanic spreading centers: Models derived from ophiolites
复制标题
海洋扩张中心的地幔流：来自蛇绿岩的模型
DOI：
10.1016/0040-1951(82)90136-6
复制
发表时间：
1982
期刊：
影响因子：
2.9
通讯作者：
J. Violette
中科院分区：
文献类型：
--
作者：
A. Nicolas;J. Violette
The internal structures of eleven ophiolite complexes have been structurally investigated. The attitude of the foliation and the lineation in the peridotites is related to asthenospheric flow in the uppermost mantle at an oceanic spreading center. From the orientation of these structures with respect to the paleohorizontal plane, two oceanic situations are distinguished.The horizontally spreading asthenosphere illustrated by the Table Mountain massif (Newfoundland) is characterized by:1.(a) homogeneous, regular and sub-horizontal plastic flow pattern: over large distances;2.(b) flat paleo Mono and absence of large scale folding;3.(c) rare economical chromite deposits and depleted mantle.The diapirically spreading asthenosphere illustrated by the Acoje type (Philippines) displays:1.(a) inhomogeneous and sub-vertical plastic flow pattern;2.b) deformed paleo Moho and large scale folds;3.(c)important economical chromite deposits and less depleted mantle, presumably due to secondary magmatic impregnation.This leads to Vogt's model of asthenospheric flow beneath an oceanic ridge (the direction of which being equated with the dike swarm). In this model the horizontally spreading asthenosphere is derived from the diapirically spreading one in the following way. The vertical mantle flow at the diapir center diverges horizontally, in every direction including that parallel to the ridge. At about 50 km from the diapir center the mantle flow becomes progressively perpendicular to the ridge due to the damming effect of transform faults.An important economical consequence of this model is that large chromite deposits are expected preferentially in the diapiric type of ophiolite because chromite is preferentially precipitated at the diapir center from pristine magma.
