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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.

地球构造板块在板块边界的推挤引起了自然灾害，如地震和火山活动，正如沿着太平洋“火环”所观察到的那样。这种运动代表了地幔对流引起的地球热损失的表面表现。因此，板块运动的历史提供了对地球内部运行的基本见解。由于地球磁场极性的变化，扩张脊两侧的磁等时线可以被识别出来，并用来推断两个或多个板块之间的相对运动。有了一个磁拾取数据库和对俯冲带会聚的额外限制，科学家们已经重建了2亿多年前的全球板块运动。然而，海岭扩张和俯冲会聚的观测结果只限制了与深部地幔无关的相对板块运动（RPM）。事实上，在绝对板块运动（APM）的背景下，最好理解推动构造板块的深地幔力和减缓它们的岩石圈下变形。大多数确定APM的方法都利用观测到的沿沿着线性岛屿和海山链的年龄进展，这些岛屿和海山链是由深部地幔柱将热物质带到地表而产生的。如果这些地幔柱仍然固定在地幔中，那么就有可能直接求解APM。然而，越来越多的证据表明，羽流本身也在移动，因此并不代表理想的固定参考系。已经发现了一种新方法，可以同时解决绝对板块和羽流运动，该项目将开发这种新方法，并使用海山链几何形状，年龄，古地磁纬度等最全面的数据集进行校准。提高对杀伤人员地雷的认识对地球的其他研究有着广泛的好处。它确定了一个将地表与地幔联系起来的框架，这使得其他地球科学数据，如地球化学和地震学，能够联系起来。该项目将训练学生板块运动学和数据分析。除了数据和软件产品，合作机构还将提供一个联合板块构造研讨会，邀请远程客座演讲者，并将录音作为视频播客在YouTube上提供。由于缺乏对羽流漂移的直接观测，观测到的被解释为羽流漂移的古地磁异常使APM建模具有挑战性。使用地幔环流模型的羽流漂移预测，广泛地满足观测到的古纬度，迄今为止是最好的方法来获得移动热点的APM。然而，地幔流变学，温度和初始条件的不确定性使得这种模型不唯一。一种新的方法（羽流探测）已经被发现来解决这个悬而未决的问题。它表明，年龄的进展沿着太平洋热点的痕迹提供了强有力的限制，允许羽流运动，使之有可能从这些数据单独推导出相对羽流漂移模型。相对烟羽漂移估计从热点之间的距离来自年龄的进展，但这些缺乏一个固定的参考点和方位角方向。内插的古纬度历史夏威夷和路易斯维尔增加进一步的限制羽运动，但一个参数仍然没有得到解决：一个经度的历史共享的所有羽下太平洋板块。因此，可以仅解析热点相对于未知纵向移位的运动。因此，根据欧拉定理，解析的APM旋转因此被绕北极的相应旋转破坏。然而，这样的APM模型仍然满足数据，迫使使用的方法涉及RPM作为新的约束。一种这样的方法是脊定位，一种使用RPM模型来检查APM模型的可行性的技术。80 Ma以来，洋脊定位重建了太平洋-法拉隆洋脊，并意味着洋脊向北迁移和单调的顺时针旋转。一些APM模式意味着脊系统的大旋转，并表现出间歇性的不稳定行为。这些特性表明，脊和羽流定位相结合，可能会产生一个最佳的数据驱动的APM。将开发新的羽流和洋脊定位方法，以处理板块运动学数据的不一致性和不确定性，并用于推导羽流和板块运动的数据驱动模型。将开发热点轨迹年龄进展，并将公布热点间年龄距离曲线和置信限;这些数据和古纬度将用于羽流定位反演。古纬度的不确定性，真正的极地漂移，和替代古地磁解释将被认为是在贝叶斯反演框架。APM模型将通过脊点法测试与RPM模型的兼容性。其他考虑因素，如板块和地幔柱速度的地球动力学限制，净岩石圈旋转，地幔柱与LLSVP边缘和板块边界的接近程度，该奖项反映了美国国家科学基金会的法定使命，并通过利用基金会的知识价值和更广泛的知识价值进行评估，被认为值得支持。影响审查标准。