Accomplishment Based Renewal: Evolution of the Lau Basin-A Reappraisal

摘要-0727138知识价值。这一基于成果的更新将利用重力数据、磁力数据和测深数据，为西太平洋的西劳扩散中心建立洋壳厚度变化模型。该项目还将努力查明海底磁化的线理，并利用这些线理以及重力和磁力模型研究Lau盆地的早期演变。西劳扩张中心比中劳扩张中心和东劳扩张中心更古老，现有的模型表明，它是在活跃的海底扩张开始之前通过构造裂谷形成的。该项目的中心重点是质疑WLSC的起源，指出测深数据表明西部盆地形态与活跃的中部和东部Lau扩展中心相似。在这些较新的中心，目前的理解表明，水深和岩石化学是由接近弧后强烈决定。CLSC离弧后最远，最像洋中脊，而ELSC离弧最近，岩石类型有梯度，从离弧后最远的点向北的玄武岩到最靠近弧的点向南的安山岩。海底测深也沿沿着这一断面从较深的中洋脊状（3 000米）过渡到较浅的（~ 1 600米）。当靠近弧和地壳厚度增加时，地震岩浆透镜反射体也占优势，而在北部则基本上不存在。在这种背景下，问题出现了：西刘盆地的形态出现的盆地形成的岩浆生产力的变化，因为他们迁移到一个地幔楔的可变组成的扩展中心？这与西刘盆地形成的纯粹构造裂谷模型的现有观点形成对比。这个问题也可以反过来来解决地壳成分和其他特征的变化如何提供关于地幔楔成分变化的空间模式和性质的信息。例如，挥发物和水通过与俯冲有关的运输释放到地幔中，降低了地幔固相线温度，并应导致产生比脱水地幔预期更大量的熔体。更广泛的影响。更广泛的影响，包括研究和培训经验的研究生，以及更广泛的利益都脊2000和边缘社区的地壳形成过程的基本见解。

ABSTRACTOCE-0727138Intellectual Merit. This Accomplishment Based Renewal of the investigator's ongoing studies of Lau Basin will make use of gravity data, magnetic data and bathymetry to model the variations in thickness of the ocean crust for the Western Lau Spreading Center in the western Pacific. The project will also include efforts to identify lineations in seafloor magnetization, and to use these as well as the gravity and magnetics models to study the early evolution of Lau Basin. The Western Lau Spreading Center is older than Central and Eastern Lau Spreading Centers, and existing models suggest that it formed through tectonic rifting prior to the inception of active seafloor spreading. The central emphasis of this project is to question this origin for WLSC, pointing out that bathymetric data indicates that western basin morphologies are similar to those of the active Central and Eastern Lau Spreading Centers. At these newer centers, current understanding suggests that bathymetry and rock chemistry is determined strongly by proximity to the back-arc. CLSC is furthest from the back-arc, and is most mid-ocean ridge-like, whereas ELSC is nearest the arc and shows a gradient in rock types, ranging from basaltic to the north at points furthest from the back-arc, to andesitic to the south at points closest to the arc. Seafloor bathymetry also transitions along this transect, from deeper Mid Ocean Ridge-like (3000 m) to shallower (~1600m). There is also a preponderance of seismic magma lens reflectors as one moves closer to the arc and crustal thicknesses increase, whereas these are largely absent to the north. Given this backdrop, the question arises: Did the Western Lau basin morphology arise as the basin formed by changes in magmatic productivity of spreading centers as they migrated over a mantle wedge of variable composition? This is in contrast to the existing view of a purely tectonic rifting model for the formation of the Western Lau basin. The question may also be inverted to address the issue of how changes in crustal composition and other characteristics might provide information on the spatial patterns and the nature of the compositional variations in the mantle wedge. For instance, the release of volatiles and water into the mantle through subduction-related transport lowers mantle solidus temperatures, and should lead to production of a greater quantity of melt than expected for a dehydrated mantle. Broader impacts. Broader Impacts include research and training experiences for a graduate student, and fundamental insights into crustal formation processes of wider interest both to Ridge 2000 and Margins communities.