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

abstractoce - 0727138知识价值。这项基于成就的更新研究人员正在进行的劳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劳扩张中心的海洋地壳厚度变化。该项目还将努力确定海底磁化的线状，并利用这些线状以及重力和磁学模型研究劳盆地的早期演化。西劳扩张中心比中劳扩张中心和东劳扩张中心更古老，现有的模式表明它是在海底活动扩张开始之前通过构造裂谷形成的。本项目的中心重点是质疑西陆盆地的这一成因，指出水深资料表明西部盆地的形态与活跃的中、东陆扩张中心相似。在这些较新的中心，目前的理解表明，测深和岩石化学在很大程度上取决于是否接近弧后。CLSC离弧后最远，最像洋中脊，而ELSC离弧后最近，岩石类型呈梯度，从离弧后最远的玄武岩向北，到最靠近弧的安山岩向南。海底测深也沿着这条样带过渡，从较深的洋中脊状（3000米）到较浅的（~1600米）。地震岩浆透镜反射体在离弧越近和地壳厚度越厚的地方也占优势，而在北部则基本没有。在这样的背景下，问题就出现了：西劳盆地的形态是由扩张中心在不同成分的地幔楔上迁移时岩浆生产力的变化而形成的吗？这与现有的西律盆地形成的纯构造裂谷模式相反。这个问题也可以反过来，以解决地壳组成和其他特征的变化如何可能提供关于地幔楔体组成变化的空间格局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，降低了地幔固体温度，并应导致产生比脱水地幔更多的熔融物。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Ridge 2000和margin社区更感兴趣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.