Convective coupling between lower crust and upper mantle

下地壳与上地幔之间的对流耦合

• 批准号: 05640469
• 负责人: NAKADA Masao
• 金额: $ 1.22万
• 依托单位: KYUSHU UNIVERSITY (1994)Kumamoto University (1993)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05640469/
• 关键词: RHEOLOGY; CONVECTION; LOWER CRUSTAL EROSION; MANTLE DIAPIR; 下部地殻侵食; トモグラフィー; カップリング

In order to examine the relationship between surface geological phenomena in island-arcs and lower crustal and upper mantle dynamics, crustal and upper mantle responses induced by the upper mantle density heterogeneities with the magnitude expected from the seismic tomography beneath northeastern Japan arc have been evaluated. For the rheological model with a low-viscosity lower crust and low-viscosity uppermost mantle, low-density lower crustal material above mantle diapiric upwelling is mechanically dragged along by the asthenospheric shear stresses, and then lower crustal material flows from the back-arc corner to fore-arc corner. The surface subsidence for this process is about 300m on the geological time scale of 5-50 Ma, and formation of sedimentary basin with about the same lateral scale as mantle diapir can be expected in the area above the mantle diapir (stage "S"). The subducted slab in island-arc will operate as a barrier to the lateral movement of lower crustal material. Th … More en accumulation of low-density lower crustal material may occur at the edge of the overriding plate as the progress of this process. At a critical stage of the pressure in the mantle wedge of fore-arc region, high temperature lower crustal material may be therefore exposed along the tectonic line (stage "E"). As the result of discharging lower crustal material along the tectonic line, the pressure in the lower crust will be decreased and the accelerated subsidence accompanied by volcanism is expected in the sedimentary basin. The Cretaceous geological phenomena in Southwest Japan may be explained by this physical mechanism and its linked surface crustal movement and the flow of lower crustal material. A relatively slow deposition in the period of about 140-120 Ma observed in the Kanmon sedimentary basin may be interpreted as the geological event of stage "S". From about 110Ma, the Kanmon sedimentary basin was supplied with a large quantity of volcanic sediments, and simultaneously expanded and suddenly subsided. At about the same time, low pressure-high temperature metamorphism and granitic activity (Ryoke Belt) occurred along the areas to the south of the Kanmon Group. It may be possible to interpret these geological phenomena along the Median Tectonic Line (MTL) as the surface geological events corresponding to stage "E". It is, however, stressed that the time and spatial scale for this coupling is determined by the rheological structure of the lower crust and upper mantle and by the scale of mantle diapir. Less

为了研究岛弧表面地质现象与下地壳上地幔动力学之间的关系，对日本东北弧下地震层析成像所预测的上地幔密度不均匀引起的地壳和上地幔响应进行了评价。对于低粘度下地壳、低粘度上地幔的流变学模型，地幔底辟上涌以上的低密度下地壳物质在软流圈剪应力的作用下被机械地拖着前进，下地壳物质从弧后角流向弧前角。这一过程的地表沉降量在5-50 Ma的地质时间尺度上约为300m，在地幔底辟以上地区(S期)有望形成与地幔底辟具有大致相同横向规模的沉积盆地。岛弧俯冲板块将起到阻挡下地壳物质横向运动的作用。TH…随着这一过程的进行，在覆盖板块边缘可能会出现更多低密度下地壳物质的聚集。在弧前区地幔楔体压力的临界阶段，高温下地壳物质可能沿构造线暴露(阶段“E”)。由于下地壳物质沿构造线排出，下地壳压力降低，沉积盆地有望发生伴随火山作用的加速下沉。日本西南部白垩纪的地质现象可以用这种物理机制及其关联的地表地壳运动和下地壳物质的流动来解释。坎门沉积盆地在14 0~12 0 Ma期间的沉积相对较慢，可解释为“S”期的地质事件。距今约110 Ma，坎门沉积盆地获得大量火山沉积，并同时膨胀和突然下沉。大约在同一时间，坎门群以南地区发生了低压-高温变质作用和花岗岩活动(Ryoke带)。可以将中值构造线(MTL)上的这些地质现象解释为与“E”期相对应的地表地质事件。但强调指出，这种耦合的时间和空间尺度取决于下地壳和上地幔的流变结构和地幔底辟的规模。较少

项目成果

Masao NAKADA: "Roles of mantle diapir and ductile lower crust on island-arc tectonics" Tectonophysics. (印刷中). (1995)

Masao NAKADA：“地幔底辟和延性下地壳在岛弧构造中的作用”，构造物理学（1995 年）。

中田正夫: "ハイドロアイソスタシ-と西九州の水中遺跡" 第四紀研究.33. 361-368 (1994)

Masao Nakata：“Hydroisostasi 和九州西部的水下遗址”第四纪研究.361-368 (1994)。

Nakada, M.and Takeda, Y.: "Roles of mantle diapir and ductile lower crust on island-arc tectonics" Tectonophysics. (in press). (1995)

Nakada, M. 和 Takeda, Y.：“地幔底辟和延性下地壳在岛弧构造中的作用”构造物理学。

Masao NAKADA: "Convective coupling between ductile lower crast and upper mantle and its tectonic implications" Geophysical Journal International. (印刷中).

Masao NAKADA：“韧性下地壳和上地幔之间的对流耦合及其构造意义”《国际地球物理杂志》（正在出版）。

中田正夫: "ハイドロアイソスタシ-と西九州の水中遺跡" 第四紀研究. 33. 361-368 (1994)

Masao Nakata：“Hydroisostasi 和九州西部的水下遗址”第四纪研究 33. 361-368 (1994)。