Site survey data evaluation IODP Proposal 633

IODP钻探计划（哥斯达黎加泥丘）旨在提高对哥斯达黎加和尼加拉瓜外侵蚀俯冲系统复杂的弧前脱水过程的一般认识。最近的科学评估结果表明，该钻井方案的排名很高。计划钻探的主要脱水地点是与泥底辟/火山作用和自生碳酸盐降水有关的土丘，以及与海山俯冲有关的大规模滑坡。2008年，Marcus Langseth号勘测船在丘库莱布拉和丘11和丘12的拟议地点进行巡航时，收集了新的现场前勘测地震数据。这些新数据连同重新处理的现有地球物理数据一起提交给IODP安全小组，以进行R/V Joides Resolution leg的最终决策和调度。新的数据质量非常高，可以对控制哥斯达黎加边缘流体运移的过程进行详细分析。因此，我们建议：(1)研究声波基底对流体上升的作用；(2)了解泥火山作用对天然气水合物体系的影响以及天然气水合物形成和分离与深部流体上升的相互作用；(3)反演天然气和天然气水合物浓度的地震数据。该项目的延长将提供丰富的地质信息，并进一步推动钻井建议。

IODP drilling proposal (Costa Rica Mud Mounds) aims to enhance the general understanding of complex forearc dewatering processes of the erosive subduction system off Costa Rica and Nicaragua. Scientific evaluation recently resulted in a high ranking of the drilling proposal. Major sites of dewatering planned for drilling are mounds, related to mud diapirism/volcanism and precipitation of authigenic carbonates, and large-scale slides related to the subduction of seamounts. New pre-site survey seismic data was collected during a cruise of R/V Marcus Langseth in 2008 at the proposed sites of Mound Culebra and Mounds 11&12. These new data – together with the reprocessed pre-existing geophysical data – were submitted to the IODP safety panel for a final decision and scheduling of the R/V Joides Resolution leg. The new data are of exceptionally high quality and allow a detailed analysis of the processes that control fluid migration in the Costa Rican margin. Therefore we propose to (1) investigate the role of the acoustic basement for the fluid ascent, (2) understand the effect of mud volcanism on the gas hydrate system and the interactions between gas hydrate formation and dissociation with the fluid ascent from the deep sources, and (3) to invert the seismic data for gas and gas hydrate concentrations. The extension of the project will provide a wealth of geological information and further promote the drilling proposal.