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

0727138智力功绩。本次成果更新了调查员正在进行的刘盆地研究，将利用重力数据、磁数据和水深测量来模拟西太平洋西刘扩张中心的洋壳厚度变化。该项目还将努力识别海底磁化作用中的线条，并利用这些线条以及重力和磁学模型来研究刘盆地的早期演化。西部刘氏扩张中心比中部和东部刘氏扩张中心更古老，现有的模型认为它是在海底活动扩张开始之前通过构造裂谷作用形成的。这个项目的中心重点是质疑WLSC的起源，指出水深数据表明西部盆地的地貌与活跃的中部和东部刘氏扩张中心的地貌相似。在这些较新的中心，目前的理解表明，水深和岩石化学在很大程度上取决于弧后的接近程度。CLSC距离弧后最远，最像大洋中脊，而ELSC最接近弧形，岩石类型呈梯度，从最远离弧后的玄武岩向北，到最接近弧后的安山岩向南。海底水深测量也沿该断面过渡，从较深的中脊状(3000米)过渡到较浅的(约1600米)。地震岩浆透镜反射体也占优势，随着一个人向弧线靠近，地壳厚度增加，而在北部基本上没有这些反射体。在这样的背景下，问题出现了：西刘盆地的形态是由于扩张中心在不同成分的地幔楔形上迁移时岩浆生产力的变化而形成的吗？这与现有的关于西部刘盆地形成的纯粹构造裂谷模式的观点形成了鲜明对比。这一问题也可反过来处理地壳成分和其他特征的变化如何提供有关地幔楔体成分变化的空间模式和性质的信息的问题。例如，通过俯冲相关的运输将挥发物和水释放到地幔中，降低了地幔固相线的温度，应该会导致产生比脱水地幔预期更多的熔融量。更广泛的影响。更广泛的影响包括研究生的研究和培训经验，以及对地壳形成过程的基本见解，这对Ridge 2000和边缘社区都有更广泛的兴趣。

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.