Crust-Mantle Interaction in Continental Collision Zones

主要研究结果如下：1）苏鲁超高压带北方具有等温减压的特征。此外，P-T路径已被严格限制，并显示出非常低的热梯度。减压路径和压缩路径都可以与定量热模拟结合使用，以测试构造模型。2）超高压变质岩的研究已经确定了Sr等多种元素的载体矿物，这对认识会聚板块边缘陆壳的再循环具有重要意义。这些矿物的稳定性将控制碰撞带中元素可能释放的区域。3）在日本西南部新发现的高压榴辉岩体具有特别重要的意义，因为它可能具有与西部其他类似岩石不同的P-T路径。这种差异有助于制约该地区沿着向的三维热历史。4）关于造山作用的年龄和速率的研究还有待发表。然而，初步结果给出了变形的年龄c。230 Ma与变质作用同期。因此，这些构造可以用来约束与变质作用和碰撞作用有关的构造模型。此外，对苏禄海区域酸性片麻岩中夹带的岩块的大小和密度的研究表明，折返速率为每年厘米。这反过来又限制了下地壳的可能粘度--这是任何碰撞定量模型中最不明确的参数之一。

The main results of our work can be summarized as follows.1) The northern part of the Sulu UHP terrane is characterized by isothermal decompression. In addition the prograde P-T path has been closely constrained and shows a very low thermal gradient. Both the prograde and decompression paths can be used in conjunction with quantitative thermal modelling to test tectonic models. Qualitatively both P-T paths suggest rapid burial and exhumation of the whole UHP Sulu terrane.2) Studies of UHP metamorphic rocks have identified the carrier minerals for a variety of elements such as Sr important in understanding the recycling of continental crust in convergent plate margins. The stability of these minerals will control the regions in collision zones where the elements may be released.3) A new discovery of a body of high-pressure eclogitic rocks in southwest Japan is particularly significant because it probably has a distinct P-T path from other similar rocks to the west. This difference can help constrain the along strike 3-d thermal history of the region.4) Research on the age and rates of orogenesis has still to be published. However, preliminary results give an age of deformation of c. 230 Ma contemporaneous with metamorphism. The structures can, therefore, be used to constrain tectonic models related to metamorphism and collision. In addition, a study of the size and density of blocks entrained in the regional acidic gneisses of the Sulu terrane suggests that the exhumation rate was of the order of cm per year. This in turn places constraints on the possible viscosities of the lower crust - one of the least clear parameters in any quantitative model of collision.