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| 大洋岩石圈拆沉与大陆下地壳拆沉：不同的机制及意义——兼评“下地壳＋岩石圈地幔拆沉模式” | |
| 引用本文： | 张旗,金惟俊,王元龙,李承东,王焰,贾秀勤.大洋岩石圈拆沉与大陆下地壳拆沉：不同的机制及意义——兼评“下地壳＋岩石圈地幔拆沉模式”[J].岩石学报,2006,22(11):2631-2638. |
| 作者姓名： | 张旗 金惟俊 王元龙 李承东 王焰 贾秀勤 |
| 作者单位： | 1. 中国科学院地质与地球物理研究所,北京,100029 2. 中国地质调查局天津地质矿产研究所,天津,300170 3. 香港大学地球科学系,中国香港 4. 中国科学院高能物理研究所,北京,100039 |
| 基金项目： | 中国科学院知识创新工程项目 |
| 摘 要： | 拆沉作用(delamination)是地球科学中一个重要的科学问题。本文认为,大洋岩石圈拆沉和大陆下地壳拆沉是不一样的:(1)拆沉的物质不同。大洋岩石圈拆沉的物质包括大洋地壳、岩石圈地幔甚至一部分软流圈地幔,它们共同进入地幔深部;而大陆下地壳拆沉仅仅限制在下地壳,不包括岩石圈地幔。(2)拆沉的动力不同。大洋岩石圈拆沉是由板块俯冲引起的,是地幔对流的产物,因此是一种快速的主动的拆沉;而下地壳拆沉是由于下地壳加厚使下地壳密度增加引起的,还要求其下刚性的岩石圈地幔转变成塑性的软流圈地幔才有可能发生。因此下地壳拆沉要克服许多阻力才能实现,使拆沉成为一个漫长的过程,是慢速的和被动的拆沉。(3)拆沉的过程不同。大洋岩石圈拆沉是由板块俯冲触发的,俯冲导致碰撞,大洋岩石圈从根部断裂,拆沉进入地幔。大陆下地壳拆沉由地壳加厚开始,使下地壳转变为榴辉岩相;随后,岩石圈地幔减薄,直至全部转化为软流圈地幔;下地壳发生部分熔融,形成大规模的(埃达克质)岩浆,使下地壳榴辉岩的密度大于下伏的地幔,从而引发拆沉。大陆下地壳拆沉不大可能是整体进行的,可能是一块一块地被蚕食、被拆沉的。(4)拆沉后的效应不同。大洋岩石圈地幔拆沉,使热的软流圈地幔上涌,从而引发了一系列地质效应:如岩浆活动、地壳抬升、构造松弛以及随后的造山带垮塌等。而下地壳拆沉只引起地壳减薄,高原和山脉垮塌,并不伴有大规模的岩浆活动和地壳抬升等过程。(5)拆沉与岩浆活动的关系不同。主动拆沉导致大规模岩浆活动,而被动拆沉是在大规模岩浆活动的基础上开始的。此外,文中还对"下地壳 岩石圈地幔拆沉"模式提出了质疑,认为该模式有许多难以理解的问题和太多推测的成分,而且与现在保存的地质事实不符。 |
| 关 键 词： | 大洋岩石圈 大陆下地壳 拆沉作用 机制 岩浆活动 |
| 文章编号： | 1000-0569/2006/022(11)-2631-38 |
| 收稿时间： | 08 17 2006 12:00AM |
| 修稿时间： | 11 14 2006 12:00AM |
Ocean lithosphere delamination and the lower crust delamination: the different mechanism and geological implication: Comment on the delamination model of lower crust and lithosphere mantle |
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| ZHANQ Qi,JIN WeiJun,WANG YuanLong,LI ChengDong,WANG Yan,JIA XiuQin.Ocean lithosphere delamination and the lower crust delamination: the different mechanism and geological implication: Comment on the delamination model of lower crust and lithosphere mantle[J].Acta Petrologica Sinica,2006,22(11):2631-2638. | |
| Authors: | ZHANQ Qi JIN WeiJun WANG YuanLong LI ChengDong WANG Yan JIA XiuQin |
| Abstract: | Delamination is an important scientific problem in earth science.The author thinks that the ocean lithosphere delamination(OLD) is different from the continental lower crustal delamination(CLCD) in the paper:(1) The different delamination material.The material from OLD includes the ocean crust,the lithosphere mantle even a part of ashenosphere mantle,which sink into the deep mantle together,while CLCD is occurred on the crustal bottom,does not include the lithosphere mantle. (2) The different delamination mechanism.The OLD is caused by plate subduction resulted from the mantle convection,and is an active fast delanfination.And CLCD is caused by the crust thickening to increase the crust's density,and require the underlying lithosphere mantle to change from rigidity into plasticity.CLCD may happen by overcoming a lot of obstruction,and is a slow passive processing. (3)The different delamination processing.OLD is trigged by plate subduction which results in collision.The ocean lithosphere is break from the root,and sinks into the mantle.But CLCD is initiated by the crust thickening to change lower crust into the eclogite, and makes the lithosphere mantle thin until it is changed into the ashenosphere totally.The partial melt has taken place in the lower crust to form the extensive (adakite) magma.The delamination is occurred because the eclogite's density in the lower crust is greater than that of the underlying mantle.CLCD is unlikely carried on a whole,may eroded to delaminate piece by piece.(4)The different consequence.OLD caused the hot ashenosphere upwelling,thus result in a series of geological consequence:such as magma activity, the crust uplift,tectonics relaxation and orogenic collapse etc..While CLCD only causes the lower crust thinning and collapse of plateau and/or mountains,does not occur the extensive magma activity and the crust uplift etc..(5)The different relation between the magma activity and delamination.The active delamination causes the extensive magma activity,and passive delamination is based on the extensive magma activity.Besides we are also discuss on"lower crust lithosphere mantle delamination" model in the article, and point out that the model is difficult to understand and much infers,and does not fit to geological data now. |
| Keywords: | Ocean lithosphere Continental lower crust Delamination Mechanism Magmatism |
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