Preface — Some words on the post-collisional magmatism
Preface — Some words on the post-collisional magmatism
复制标题
DOI：
--
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
中科院分区：
文献类型：
--
作者：
碰撞后的地球动力学背景没有完全纳入板块构造模型，该模型以主要板块边缘、大洋中脊、活动边缘和壮观的洲际碰撞中发生的地质过程为基础。板内研究，特别是板内非造山岩浆作用的研究，对板块构造的关注较少。流行的地幔热柱假说只与板块运动有微弱的联系。在这个框架中，碰撞后的环境只有很小的考虑因素，通常被简单地描述为碰撞后的“松弛阶段”。这导致了对后碰撞的一个模糊的定义。然而，巨大的岩浆作用似乎是在碰撞后时期产生的。The CollŽ。Lision S.S.最大聚集期不利于岩浆上升；板内期以广泛但往往稀疏的岩浆活动为特征。来自板块边缘活动俯冲的岩浆作用将在随后不可避免的碰撞中变质。因此，许多岩浆体肯定与一个独特的后碰撞时期有关。然而，我们如何理解这种岩浆作用，取决于对碰撞后这一表述的理解。前缀‘POST’表示该周期比碰撞更年轻，但也表示它仍然与碰撞有关。在这本书中，大多数作者认为这次碰撞是两个或更多大陆板块最初的重大碰撞，以主要冲断和高压变质为特征。这将碰撞事件本身与大洋闭合后更长的板块会聚周期区分开来。从这个意义上说，碰撞后时期通常开始于陆内环境--主要海洋是封闭的--但仍有沿大剪切带的大型水平地体运动，排除了它与板块内环境的同化。西藏和东南亚是当今后碰撞背景的例子：它们受到巨大的水平运动的影响，碰撞本身代表着最古老的主要冲断。随着这些运动的结束，板内设置将在该区域开始，因为整个区域获得了一个独特的旋转极，并构成了一个单一的板块。因此，从碰撞后时期到板内时期的这种转变也标志着造山期的结束。板块内期的开始可以被认为是后造山作用，其定义与碰撞后类似。例如，这将是在SaŽ3.hara 900万公里的Tassilis寒武纪-奥陶纪砂岩沉积的情况，该沉积发生在泛非Ž之后。碰撞后岩浆作用580-525 Ma，包括晚期碱性岩浆作用，以及沿剪切带的大型水平运动。然而，其巨大的体积覆盖了从毛里塔尼亚到阿拉伯的新形成的非洲板块的主要部分，这是泛非造山作用的结果。在这个时期，如果有岩浆的话，也很少有岩浆形成。一些地质学家认为，碰撞后板块会聚的整个阶段是一个单一的碰撞环境，上述碰撞后阶段称为晚碰撞阶段，碰撞后阶段代表着这一阶段的结束。虽然我以前持这种观点，但我现在认为这个定义是模糊的，前缀“迟到”比“帖子”更模糊。从碰撞后期到碰撞后的过渡也不清楚。事实上，前缀“Late”可以去掉而不会丢失
The post-collisional geodynamic setting has not been fully integrated in the model of plate tectonics, which is based on geological processes occurring at major plate edges, mid-ocean ridges, active margins and in spectacular intercontinental collisions. Studies on intraplate, in particular those devoted to intraplate anorogenic magmatism, have paid little attention to plate tectonics. The popular mantle plume hypothesis has only weak links with plate movements. In that framework, the post-collisional setting has had only minor consideration, often being described simply as a ‘relaxation phase’ following collision. This has resulted in a poor definition for the post collisional. It appears however that voluminous magmatism is produced during the post-collisional period. The colŽ . lision s.s. period of maximum convergence is not favourable for the ascent of magmas; and the intraplate period is characterized by widespread but often sparse magmatism. Magmatism from active subduction at a plate margin is to be metamorphosed during the collisions that inevitably follow. Many magmatic bodies must therefore be related to a distinctive post-collisional period. How we understand this magmatism depends however on the sense given to the expression postcollision. The prefix ‘post’ indicates that the period is younger than the collision, but also that it is still related to it. Most authors in this volume consider the collision as the initial major impact of two or more ‘continental’ plates, characterized by major thrusts and high-pressure metamorphism. This differentiates the collision event itself from the much longer period of plate convergence that follows ocean closure. In that sense, the post-collisional period begins generally in an intracontinental environment —the major ocean is closed—but still with large horizontal terrane movements along mega-shear zones, precluding its assimilation to an intraplate setting. Tibet and south-eastern Asia are present-day example of post-collisional setting: they are affected by large horizontal movements, the collision itself with India being represented by the oldest main thrusts. The intraplate setting will begin in this region with the end of these movements, as the entire area acquires a unique pole of rotation and constitutes a single plate. This transition from post-collisional to intraplate period thus marks also the end of the orogenic period. The beginning of the intraplate period can be considered as post-orogenic in the sense defined similarly as for post-collisional. This would be the case, for instance, of the Tassilis Cambrian–Ordovician sand sedimentation in the SaŽ 3. hara 9 millions km which post-dates Pan-African Ž . post-collisional magmatism 580–525 Ma , including late alkaline magmatism, as well as large horizontal movements along shear zones. However, its enormous volume, covering a major part of the newly formed African plate from Mauritania to Arabia, is a consequence of the Pan-African orogeny. Few magma emplace in this period, if any. Some geologists consider the whole period of plate convergence following impact as being a single collisional setting, the post-collisional period described above being called late-collisional, and the post-collision representing the end of this period. Although I had previously held this view, I now believe that this definition is blurring, the prefix ‘late’ being more vague than ‘post’. The transition from lateto post-collisional also is not clear. In fact, the prefix ‘late’ could be dropped without loss of