Crust-Mantle Interaction in Continental Collision Zones

主要工作成果如下：1)苏鲁超高压地体北部具有等温减压的特征。此外，前进的P-T路径受到了严格的限制，并显示出非常低的温度梯度。前进式和减压式路径都可以与定量热模拟结合使用，以检验构造模型。定性上，这两条P-T轨迹都表明整个超高压苏鲁地体的快速埋藏和折返。2)对超高压变质岩的研究已经确定了各种元素的载体矿物，如锶，这对理解会聚板块边缘大陆地壳的再循环很重要。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，因为它可能与西侧其他类似岩石具有明显的P-T路径。这种差异有助于限制该地区沿走向的三维热历史。4)造山作用的年龄和速率的研究仍有待发表。然而，初步结果给出了与变质作用同期的230 Ma左右的变形年龄。因此，这些构造可以用来约束与变质和碰撞有关的构造模式。此外，对苏鲁地体区域性酸性片麻岩中块体的大小和密度的研究表明，折返速度约为每年厘米。这反过来又限制了下地壳可能的粘性--这是任何碰撞定量模型中最不清晰的参数之一。

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.