Orogenic plateau magmatism

造山高原岩浆作用

• 批准号: NE/H021620/1
• 负责人: Mark Allen
• 金额: $ 49.87万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH021620%2F1
• 关键词: Orogenic; plateau; magmatism

This study will show why some of the highest regions on Earth contain young and active volcanoes. Our particular study area is the high plateau of Iran, which has a unique combination of young volcanic rocks, known tectonic plate thickness and variation in plate thickness, in a region where the plates are actively colliding. Combined with background information on the rock types and thicknesses of the tectonic plates in this region, it will tell us which part of the deep Earth generates the magma, why it is melting, and what controls the ascent to the surface. Volcanoes and mountain ranges show how Earth is active: forces and processes arising from deep within the planet shape the landscapes on which we live. Risks from eruptions, earthquakes and landslides threaten millions of people, but at the same time control the distribution of land, nutrients and water on which we all depend. There are many ways to generate volcanoes and chains of mountains, some of which are entirely separate. But there are certain tectonic settings where they come together, where the moving plates collide continents to create vast regions of deformation known as collision zones. Many of these have occurred through geological time and are now inactive. The mountains of Scotland are the eroded roots of such chains, and the volcanoes once within their midst. But in SW Asia the processes continue at the present day, as the Arabian plate moves northward, pushing in to Eurasia. The rate of motion is roughly 20 mm/yr, but over geological timescales this translates to a considerable amount of deformation: ~700 km of convergence has occurred since initial plate collision ~35 million years ago. Volcanism was common before the collision, in a setting similar to the modern Andes. It reduced in intensity after the initial collision, because one of the main triggers for magmatism ended at this time - downgoing of oceanic plate beneath the Eurasian continent. Later, sporadic magmatism probably represented the tail-off from this process. But in the last few million years there has been an upsurge of volcanic activity across the collision zone, for reasons not entirely understood, but possibly related to a general re-organization of deformation of the Eurasian plate. The volcanic centres are not randomly distributed. We can determine patterns in their locations that give us clues about why the deep Earth is melting. First, they are concentrated in a region within the collision zone that is no longer shortening, known as the Turkish-Iranian plateau. As its name implies, this is a vast, high area with subdued relief, that no longer undergoes the kind of mountain building that once deformed the Earth in this area. That mountain building carries on at the margins of the broad zone that is the site of collision between the Arabian and Eurasian plates. Second, the volcanoes are almost always in the original Eurasian plate, which once lay above a slab of an oceanic plate that has now passed underneath it ('subducted' in the jargon). This slab is a source of water and other volatile compounds that could have been responsible for melting the deep Earth and causing the volcanoes. But it is unclear why water would be present tens of millions of years after the ocean plate stopped moving under Eurasia. Third, many of the volcanoes are located in regions which are still faulting, even if the mountains are not building up. This suggests a link between the faulting and either the generation of the magmatism, or at least its ascent to the surface. Again, the details are not understood and form part of this study. Whereas we generally understand the generation of volcanoes in settings like the Andes, Hawaii and Iceland, the high plateaux of the Earth like Iran and Tibet represent a frontier for science, and an opportunity to comprehend how the end result of plate tectonics can be volcanoes within the highest places on Earth.

这项研究将表明为什么地球上一些最高的地区含有年轻和活跃的火山。我们的特定研究区域是伊朗高原，在板块积极碰撞的区域中，伊朗的高原，已知的火山岩，已知的构造板厚度和板厚度变化的独特组合。结合有关该区域构造板的岩石类型和厚度的背景信息，它将告诉我们深地球的哪一部分产生岩浆，为什么熔化以及是什么控制表面上升的原因。火山和山脉范围显示了地球的活跃方式：地球内深处产生的力和过程形成了我们所居住的景观。爆发，地震和滑坡的风险威胁着数百万人，但同时控制着我们所有人所依赖的土地，养分和水的分布。有很多方法可以生成山脉的火山和链，其中一些是完全分开的。但是在某些构造环境中，它们聚集在一起，移动板碰撞的大洲碰撞了巨大的变形区域，称为碰撞区域。其中许多是通过地质时代发生的，现在是不活跃的。苏格兰的山脉是这种链条的侵蚀根，火山曾经在其中间。但是在西南亚亚洲，这一过程仍在今天继续，随着阿拉伯板块向北移动，推向欧亚大陆。运动速度约为20毫米/年，但是在地质时间尺度上，这转化为相当多的变形：自初始板碰撞〜3500万年前以来，发生了〜700 km的收敛性。在碰撞之前，火山主义在类似于现代安第斯山脉的环境中很普遍。最初碰撞后的强度降低了，因为岩浆作用的主要触发因素在这个时候结束 - 欧亚大陆下方的海洋板块下降。后来，零星的岩浆作用可能代表了这一过程的尾声。但是在过去的几百万年中，由于尚未完全理解的原因，整个碰撞地区的火山活动都激增，但可能与欧亚板块变形的一般重组有关。火山中心不是随机分布的。我们可以在他们的位置确定模式，这为我们提供了有关为什么深层融化的线索。首先，它们集中在不再缩短的碰撞区域内的地区，称为土耳其 - 伊朗高原。顾名思义，这是一个宽敞的宽松区域，不再经历那种曾经在该地区变形地球的山地建筑。那座山区建筑在宽阔区域的边缘，这是阿拉伯人和欧亚盘子之间碰撞所在地。其次，火山几乎总是在原始的欧亚盘子中，欧亚板块曾经躺在一个海洋板的平板上方，该板已经通过了它的下方（术语中的“俯冲”）。该平板是水和其他挥发性化合物的来源，可能导致融化深地球并造成火山。但是目前尚不清楚为什么在欧亚大陆以下海板停止移动后，水会出现数千万年。第三，许多火山都位于仍然有缺点的地区，即使山区没有建成。这表明断层和岩浆的产生或至少在表面上的上升之间有联系。同样，细节不了解并构成了本研究的一部分。尽管我们通常了解安第斯山脉，夏威夷和冰岛等环境中的火山产生，而像伊朗和西藏这样的地球高原代表了科学的边界，并且有机会理解板块构造的最终结果如何成为地球上最高位置的火山。

项目成果

Distinct sources for high-K and adakitic magmatism in SE Iran

• DOI: 10.1016/j.jseaes.2020.104355
• 发表时间: 2020-07
• 期刊: Journal of Asian Earth Sciences
• 影响因子: 3
• 作者: M. Kheirkhah;I. Neill;M. Allen;M. Emami;Ali Shahraki Ghadimi

Generation of Arc and Within-plate Chemical Signatures in Collision Zone Magmatism: Quaternary Lavas from Kurdistan Province, Iran

碰撞区岩浆作用中电弧和板内化学特征的生成：伊朗库尔德斯坦省第四纪熔岩

• DOI: 10.1093/petrology/egs090
• 发表时间: 2013
• 期刊: Journal of Petrology
• 影响因子: 3.9
• 作者: Allen M

Orogenic plateau growth: Expansion of the Turkish-Iranian Plateau across the Zagros fold-and-thrust belt

• DOI: 10.1002/tect.20025
• 发表时间: 2013-03-01
• 期刊: TECTONICS
• 影响因子: 4.2
• 作者: Allen, M. B.;Saville, C.;Nissen, E.
• 通讯作者: Nissen, E.

Insight into collision zone dynamics from topography: numerical modelling results and observations

• DOI: 10.5194/se-3-387-2012
• 发表时间: 2012-11
• 期刊: Solid Earth
• 影响因子: 3.4
• 作者: A. Bottrill;J. Hunen;M. Allen

Small-volume melts of lithospheric mantle during continental collision: Late Cenozoic lavas of Mahabad, NW Iran

大陆碰撞期间岩石圈地幔的小体积熔化：伊朗西北部马哈巴德的晚新生代熔岩

• DOI: 10.1016/j.jseaes.2013.06.002
• 发表时间: 2013
• 期刊: Journal of Asian Earth Sciences
• 影响因子: 3
• 作者: Kheirkhah M