Lucky Strike records of hydrothermal outflow temperatures

We deployed autonomous temperature sensors at black smoker chimneys, cracks, and diffuse flow areas at the Lucky Strike hydrothermal field (Mid-Atlantic Ridge, ~37°17'N) between summer 2009 and summer 2012 and contemporaneously measured tidal pressures and currents as part of the long-term MoMAR experiment to monitor hydrothermal activity. We classify the temperature data according to the hydrogeologic setting of the measurement sites: a high-temperature regime (>190°C) representing discharge of essentially unmixed, primary hydrothermal fluids through chimneys, an intermediate-temperature regime (10-100°C) associated with mixing of primary fluids with cold pore fluids discharging through cracks, and a low-temperature regime (<10°C) associated with a thermal boundary layer forming over bacterial mats associated with diffuse outflow of warm fluids. Temperature records from all the regimes exhibit variations at semi-diurnal tidal periods, and cross-spectral analyses reveal that high-temperature discharge correlates to tidal pressure while low-temperature discharge correlates to tidal currents. Intermediate-temperature discharge exhibits a transitional behavior correlating to both tidal pressure and currents. Episodic perturbations, with transient temperature drops of up to ~150°C, which occur in the high-temperature and intermediate-temperature records, are not observed on multiple probes (including nearby probes at the same site), and they are not correlated with microearthquake activity, indicating that the perturbation mechanism is highly localized at the measurement sites within the hydrothermal structures. The average temperature at a given site may increase or decrease at annual time scales, but the average temperature of the hydrothermal field, as a whole, appears to be stable over our 3 year observation period.2009年夏季至2012年夏季期间，我们在大西洋中脊约37°17′N处的幸运斯特赖克（Lucky Strike）热液场的黑烟囱、裂隙及弥散流区域部署了自主式温度传感器，并作为长期MoMAR热液活动监测实验的组成部分，同步测量了潮汐压力与海流数据。我们根据测量测点的水文地质背景对温度数据进行分类：高温温区（>190℃）对应未混合的原生热液流体通过黑烟囱喷溢的过程；中温温区（10~100℃）与原生流体经裂隙渗出的冷孔隙流体混合的过程相关；低温温区（<10℃）则与弥散流暖流体渗出所关联的细菌垫表面形成的热边界层有关。所有温区的温度记录均呈现出半日潮汐周期的变化特征，交叉谱分析结果显示，高温喷溢活动与潮汐压力呈显著相关，而低温喷溢活动则与潮汐海流相关；中温喷溢活动则表现出过渡性特征，同时与潮汐压力和海流均存在关联。在高温与中温温区的温度记录中曾出现瞬时降温幅度最高可达约150℃的间歇性扰动，但此类扰动未在多个探测设备（包括同一测点附近的探测设备）中被观测到，且与微地震活动无相关性，表明该扰动机制高度局限于热液构造内部的测量测点范围内。单个测点的平均温度会在年际尺度上出现升高或降低的变化，但整个热液场的平均温度在我们为期3年的观测周期内整体保持稳定。