Absolute Motion of Plumes and Plates

羽流和板块的绝对运动

基本信息

批准号：
1953499
负责人：
Garrett Apuzen-Ito
金额：
$ 27.7万
依托单位：
University of Hawaii
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1953499&HistoricalAwards=false
关键词：
Absolute Motion Plumes Plates

项目摘要

The jostling of Earth’s tectonic plates at plate boundaries give rise to natural hazards such as earthquakes and volcanism as observed along the Pacific “Ring of Fire”. This motion represents the surface expression of the Earth’s heat loss by convection currents in the mantle. Thus, the history of plate motions provides fundamental insight into the internal operations of the planet. As a consequence of the changing polarity of the Earth’s magnetic field, magnetic isochrons on either side of spreading ridges can be identified and used to infer relative motions between two or more plates. Armed with a database of magnetic picks and additional constraints on convergence at subduction zones, scientists have produced reconstructions of global plate motions extending back over 200 million years. Yet, observations of ridge spreading and subduction convergence only constrain relative plate motions (RPM) not linked to the deep mantle. In fact, deep mantle forces that propel tectonic plates and the sub-lithospheric deformation that slows them are best understood within the context of absolute plate motions (APM). Most methods for determining APM use observed age progressions along linear island and seamount chains produced by a deep-seated mantle plume bringing hot materials to the surface. If these plumes remain fixed in the mantle then it is possible to directly solve for the APM. However, evidence is mounting that the plumes themselves are also moving and thus do not represent the desired fixed reference frame. A new method has been discovered that may solve for both absolute plate and plume motions simultaneously, and this project will develop this new method and calibrate it with the most comprehensive datasets on seamount chain geometry, age, paleomagnetic latitude, and more. An improved understanding of APMs has broad benefits for other studies of the Earth. It determines a framework for relating the surface to the mantle, which allows other geoscience data, such as geochemistry and seismology, to be linked. The project will train a student in plate kinematics and data analysis. Besides data and software products, the collaborating institutions will offer a joint plate tectonic seminar using remote guest speakers, with recordings made available as video podcasts on YouTube.Observed paleomagnetic anomalies interpreted as plume drift make modeling of APM challenging as direct observations of plume drift are lacking. Using plume drift predictions from mantle circulation models that broadly satisfy observed paleolatitudes has so far been the best approach for deriving APM over moving hotspots. Yet, uncertainties in mantle rheology, temperature, and initial conditions make such models nonunique. A new approach (plume-spotting) has been discovered to address this unresolved problem. It is demonstrated that age progressions along Pacific hotspot trails provide strong constraints on allowable plume motions, making it possible to derive models for relative plume drift from these data alone. Relative plume drifts are estimated from inter-hotspot distances derived from age progressions, but these lack a fixed reference point and azimuthal orientation. Interpolated paleolatitude histories for Hawaii and Louisville add further constraints on plume motion, yet one parameter remains unresolved: a longitude history shared by all plumes beneath the Pacific plate. Thus, it is possible to only resolve the motion of hotspots relative to an unknown longitudinal shift. Consequently, and per Euler’s theorem, resolved APM rotations are therefore corrupted by a corresponding rotation about the north pole. Yet, such APM models still satisfy the data, forcing the use of methods involving RPM as new constraints. One such method is ridge-spotting, a technique that uses RPM models to examine the viability of APM models. Ridge-spotting has reconstructed the Pacific-Farallon ridge since 80 Ma and implies northward migration and monotonic clockwise rotation of the ridge. Some APM models imply large rotations of the ridge system and exhibit intermittent erratic behaviors. These properties suggest ridge- and plume-spotting combined may yield an optimal data-driven APM. The new plume- and ridge-spotting methods will be developed to handle the inconsistencies and uncertainties of plate kinematic data and used to derive data-driven models of plume and plate motions. Hotspot trail age-progressions will be developed and inter-hotspot age-distance curves with confidence limits will be published; these data and paleolatitudes will be used in the plume-spotting inversion. Paleolatitudes uncertainties, true polar wander, and alternative paleomagnetic interpretations will be considered in a Bayesian inversion framework. APM models will be tested for compatibility with RPM models via the ridge-spotting method. Additional considerations, such as geodynamic limits on both plate and plume speeds, net lithospheric rotation, the proximity of plumes to LLSVP edges and plate boundaries, and overall model smoothness will add further constraints to produce a unique model of Pacific absolute plate and plume motions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

板块边界处地球构造板的争吵会引起天然危害，例如地震和火山，如太平洋“火环”所观察到的。这种运动代表了地幔中的会议电流的地球热损失的表面表达。这是板块运动的历史提供了对地球内部操作的基本见解。由于地球磁场的极性不断变化，因此可以识别出扩散脊的两侧的磁等质素，并用于推断两个或多个板之间的相对运动。科学家们凭借磁取片的数据库和俯冲区收敛的其他限制，对全球板块运动的重建产生了超过2亿年的重建。然而，对脊扩散和俯冲收敛的观察仅限于与深地幔相关的相对板运动（RPM）。实际上，在绝对板运动（APM）的背景下，最好理解推动构造板的深幔力和放慢它们的亚地层变形的力。确定APM使用的大多数方法在线性岛上观察到的年龄进度以及由深层地幔羽流产生的海底链，将热材料带到表面。如果这些李子保留在地幔中，则可以直接求解APM。但是，有证据表明，羽毛本身也在移动，这就是为什么我确定将表面与地幔联系起来的框架，这允许这种新方法并用隔山链几何，年龄，古磁纬度等上最全面的数据集进行校准。对APM的改进的了解对地球的其他研究具有广泛的好处。它决定了将表面与地幔联系起来的框架，该框架允许将其他地球科学数据（例如地球化学和地震学）联系起来。该项目将培训学生进行板运动学和数据分析。除了数据和软件产品外，合作机构还将使用远程访客扬声器提供联合板构造的半手，并在YouTube上作为视频播客提供了录音。观察的古磁异常被解释为羽流漂移使APM挑战的建模，因为缺乏直接观察羽流漂移的挑战。迄今为止，使用从地幔圆模型中进行羽流预测，这些预测是在移动热点上推导APM的最佳方法。然而，地幔风湿病，温度和初始条件的不确定性使得这种模型不合时宜。已经发现了一种新方法（羽流）来解决这个尚未解决的问题。已经证明，沿Pacific Hotspot Trails的年龄进度在允许的羽流运动上提供了强大的限制，从而使仅这些数据从这些数据中得出相对羽流的模型成为可能。相对羽流饮料是根据来自年龄进度的热点间距离估计的，但是这些饮料缺乏固定的参考点和方位角取向。夏威夷和路易斯维尔的插值古老历史增加了对羽流运动的进一步限制，但一个参数仍未解决：太平洋板下面的所有羽毛共享的经度历史。这是可以仅解析热点相对于未知纵向移动的运动。因此，根据Euler的定理，解决的APM旋转被相应的北极旋转所破坏。但是，此类APM模型仍然满足数据，迫使使用涉及RPM作为新约束的方法。一种这样的方法是脊斑，这是一种使用RPM模型来检查APM模型的可行性的技术。自80 mA以来，山脊斑点已重建了太平洋 - 法拉隆山脊，这意味着山脊的北向迁移和单调的顺时针旋转。一些APM模型意味着山脊系统的旋转幅度很大，并且裸露的间歇性不稳定行为。这些特性表明脊和李子斑点合并可能会产生最佳数据驱动的APM。将开发新的李子和山脊斑点方法来处理板运动学数据的不一致和不确定性，并用于得出羽流和板运动的数据驱动模型。将开发Hotspot Trail Trail年龄创作，并将发布具有信心限制的速度相互距离曲线；这些数据和古介质将用于羽流反转。贝叶斯反演框架将考虑古呈现的不确定性，真正的极地徘徊和替代的古磁解释。 APM模型将通过脊斑点方法测试与RPM模型的兼容性。其他考虑因素，例如在板和羽流方面的地球动力限制，岩石圈旋转净旋转，羽毛与LLSVP边缘和板界的接近性和板界的近端，以及整体模型的平滑度将增加进一步的限制，以产生太平洋绝对板和羽流的独特模型，以反映NSF的范围范围的范围。影响审查标准。