| 苏鲁—大别超高压变质带地壳速度结构及其俯冲、折返机制 |
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| 引用本文： | 徐纪人,赵志新.苏鲁—大别超高压变质带地壳速度结构及其俯冲、折返机制[J].中国地质,2005,32(2):310-319. |
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| 作者姓名： | 徐纪人 赵志新 |
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| 作者单位： | 中国地质科学院地质研究所,北京,100037 |
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| 基金项目： | 国家重点基础研究发展(973)项目(2003CB716505)和国家自然科学基金项目(40399141)资助. |
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| 摘 要： | 三维P波速度解析研究结果表明，苏鲁-大别超高压变质带岩石圈地壳速度结构均具有上地壳明显高速且上凸、中地壳增厚、下地壳埋藏较深且莫霍面下凹等基本特征。与大别地区相比较，苏鲁超高压变质带存在着上地壳波速更高，且地表高速区面积与上地壳高速体体积大于大别；而莫霍面下凹程度不如大别地区，地壳山根已逐步趋向消失等独特的区域特征。显示了苏鲁地区曾发生过更激烈的俯冲与折返构造运动，与大别地区相比，有更多高速、高密度的超高压变质岩折返到上地壳与地表；然而在造山运动过程中比大别更早进入了造山运动后期等特征。对比研究结果表明，苏鲁-大别地段的造山、演化过程中，在构造运动基本相似的背景下，存在着区域性特征。苏鲁地区的造山运动以及超高压变质作用，有起始略晚、发生时期较短但相对激烈、结束早、比大别更早进入了造山运动的后期等特征。笔者分析了苏鲁区域性特征形成的主要构造原因是，郯庐断裂带的大规模左旋走滑运动以及通过中国华北区域的大范围NXV—SE向扩张应力场的影响。其中，中生代以来大华北地区的大区域扩张应力场的影响可能是该区俯冲到地幔内的超高压变质岩能够大量折返回地表或上地壳的重要构造原因。
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| 关 键 词： | 苏鲁-大别超高压变质带 地壳结构 P波速度高速异常 郯庐断裂 扩张应力场 |
| 文章编号： | 1000-3657(2005)02-0310-10 |
Crustal P-wave velocity structure of the Dabie-Sulu ultrahigh-pressure metamorphic belt and mechanisms of its subduction and exhumation |
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| XU Ji-ren,ZHAO Zhi-xin.Crustal P-wave velocity structure of the Dabie-Sulu ultrahigh-pressure metamorphic belt and mechanisms of its subduction and exhumation[J].Chinese Geology,2005,32(2):310-319. |
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| Authors: | XU Ji-ren ZHAO Zhi-xin |
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| Abstract: | Analysis of 3-D P-wave velocity structure shows that the crustal velocity structure below the Sulu-Dabie ultrahigh-pressure metamorphic belt has the following basic features: the upper crust has a markedly high velocity and is upwarped, the middle crust thickens, the lower crust is deeply buried and the Moho is downwarped. Compared with the Dabie area, the upper crust below the Sulu-Dabie ultrahigh-pressure metamorphic belt has a high P-wave velocity,and the area of the high-velocity region at the surface and volume of the high-velocity body of the upper crust are large. However, the Moho beneath the Dabie orogen is more deeply downwarped than that beneath the Sulu UHPM terrain, and the mountain root of the crust beneath the Sulu region gradually wore away. All these indicate that more intense subduction and exhumation took place in the Sulu terrain, and more UHP metamorphic rocks with higher velocity and density were exhumed to the crust and surface in the Sulu orogen than in the Dabie region. However, in Sulu, orogeny and UHP metamorphism started later but ended earlier. The orogeny in Sulu probably underwent a relatively short but intense evolution process. The formation and evolution of the orogeny and UHP metamorphic belt in Sulu may probably be related to the large-scale sinistral strike-slip motion of the Tanlu fault belt and the effects of the NW-SE extensional stress field in North China. Especially, the effects of the regional-scale extensional stress field in the North China region since the Mesozoic is probably an important tectonic cause for the exhumation of voluminous UHP metamorphic rocks subducted into the mantle to the upper crust or the surface. |
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| Keywords: | Sulu-Dabie ultrahigh pressure (UHP) metamorphic belt crustal structure high P-wave velocity anomaly Tanlu Fault extensional stress field |
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