RAPID proposal: Site characterization cruise to document the active and extensive subsurface biosphere in the Guaymas Basin

位于加利福尼亚湾中部的瓜伊马斯盆地是一个活跃的构造扩张中心，其上覆盖着厚而富有机质的沉积物。与典型的深水、洋中脊扩张中心的岩浆活动非常集中，很少或没有沉积相比，瓜伊马斯基的岩浆活动分布更为广泛。这种广泛分布的岩浆活动极大地扩大了富有机质沉积物中可能受到岩浆热蚀变的部分，从而极大地扩大了沉积物中支持生烃和微生物种群的环境范围。认识到岩浆活动并不局限于扩张轴，而是分布在整个瓜伊马斯盆地，这表明应该重新考虑碳的自然封存、海洋地壳的形成以及边缘裂谷盆地地下生命的模式，因为这对大气中二氧化碳的长期清除（从而潜在的气候影响）有影响。这项RAPID提案的首席研究员是国际海洋发现计划（IODP）提案的主要支持者，该提案通过科学的海洋钻探深入研究该系统。为了正确规划这次昂贵的IODP考察，需要从沉积物采样和地震数据中获得额外的现场特征。本提案要求为首席研究员参加墨西哥研究船“美洲豹”号（RV）上已经计划好的现场调查巡航提供资金。此次巡航的结果将以极低的投资提供有价值的数据，以指导Guaymas盆地未来潜在的科学钻探决策。2014年10月，首席研究员将乘坐“美洲豹号”（RV El Puma）参加墨西哥现场调查，收集横跨瓜伊马斯盆地的广泛沉积物样带的5米重力岩心，并将基于测序的地下细菌和古细菌微生物群落分析与这些地下沉积物的生物化学特征相结合。重力取心和微生物群落分析将针对寒冷的非热液沉积物以及离轴热液影响的沉积物。重力取心活动和地球化学/微生物学研究与热流测量、广泛的二维地震分析和高分辨率三维地震测绘相协调，由其他计划中的墨西哥和德国巡航进行。这种多管齐下的策略将提供额外的数据，并完成JOIDES Resolution所需的现场特征，以正确规划潜在的IODP钻井考察。

The Guaymas Basin in the central Gulf of California is an active tectonic spreading center overlain with thick, organic-rich sediments. In contrast to typical deep-water, mid-ocean ridge spreading centers that have very focused magmatism and little or no sediment, magmatism in the Guaymas Basis is more broadly distributed. This broadly-distributed magmatism significantly expands the fraction of organic-rich sediments that may be subject to alteration by the magmatic heat and thus it greatly expands the range of environments that support hydrocarbon generation and microbial populations in the sediments. Recognition that magmatism is not confined to the spreading axis, but instead is distributed throughout Guaymas Basin, suggests that models for the natural sequestration of carbon, the formation of oceanic crust, and life in the subsurface in marginal rift basins should be reconsidered as this has implications for the long-term removal of atmospheric carbon dioxide (and hence potential climatic implications). The Principal Investigator of this RAPID proposal is a lead proponent on an International Ocean Discovery Program (IODP) proposal to study this system in depth through scientific ocean drilling. To properly plan this expensive IODP expedition, additional site characterization gained from sediment sampling and seismic data is required. This proposal requests funds for the Principal Investigator to participate on an already planned site survey cruise aboard the Mexican Research Vessel (RV) El Puma. The results from this cruise will provide valuable data, at an exceptionally low investment, to guide decisions about potential future scientific drilling in the Guaymas Basin.This RAPID proposal requests funds for the Principal Investigator to participate on a Mexican site survey cruise in October 2014 on RV El Puma to collect five-meter gravity cores of an extensive sediment transect across the Guaymas Basin and to integrate sequencing-based microbial community analyses of subsurface bacteria and archaea with biogechemical characterizations of these subsurface sediments. Gravity coring and microbial community analysis will target cold non-hydrothermal sediments as well as off-axis hydrothermally-influenced sediments. The gravity coring campaign and the geochemistry/microbiology studies are coordinated with heatflow measurements and extensive 2D seismic analysis and high-resolution 3D seismic mapping by other planned Mexican and German cruises. This multi-pronged strategy will deliver the additional data and complete the site characterizations that are required to properly plan a potential IODP drilling expedition by the JOIDES Resolution.