Fluid chemistry in the Solitaire and Dodo hydrothermal fields of the Central Indian Ridge

Fluid chemistry and microbial community patterns in chimney habitats were investigated in two hydrothermal fields located at the Central Indian Ridge. Endmember hydrothermal fluid of the Solitaire field, located ~3 km away from the spreading center, was characterized by moderately high temperature (307°C), Cl depletion (489 mm ), mildly acidic pH (≥4.40), and low metal concentrations (Fe ≤ 105 μm and Mn = 78 μm ). Chloride depletion indicates that the subseafloor source fluid had undergone phase separation at temperatures higher than ~390°C while the metal depletion was likely attributable to fluid alteration occurring at a venting temperature of around 307°C. These different temperature conditions suggested from fluid chemistry might be associated with an off‐spreading center location of the field that allows subseafloor fluid cooling prior to seafloor discharge. The microbial community in the chimney habitat seemed comparable to previously known patterns in typical basalt‐hosted hydrothermal systems. Endmember hydrothermal fluid of the Dodo field, standing on center of the spreading axis, was characterized by high H₂ concentration of 2.7 mm . The H₂ enrichment was likely attributable to fresh basalt–fluid interaction, as suggested by the nondeformed sheet lava flow expansion around the vents. Thermodynamic calculation of the reducing pyrite–pyrrhotite–magnetite (PPM) redox buffer indeed reproduced the H₂ enrichment. The quantitative cultivation test revealed that the microbial community associated with the hydrothermal fluid hosted abundant populations of (hyper)thermophilic hydrogenotrophic chemolithoautotrophs such as methanogens. The function of subseafloor hydrogenotrophic methanogenic populations dwelling around the H₂‐enriched hydrothermal fluid flows was also inferred from the ¹³C‐ and D‐depleted signature of CH₄ in the collected fluids. It was observed that the hydrothermal activity of the Dodo field had ceased until 2013.     

辽朝科举与辟召

辽朝前半期官员入仕的主要途径有恩荫、流外和辟召,尤其藩镇辟召、奏荐州县官幕职官广泛流行,估计有许多汉人由此途径担任地方官,从而确保了各级机构所需要的官僚数。因此,可知辽朝的藩镇应具有与唐朝后半期和五代时期藩镇相同的人事权,即这一时期朝廷的人事权受到一定的限制。辽朝后半期确立科举制度之后,朝廷通过任命新取进士为地方官,逐渐将藩镇的用人权收归中央。因此,辟召任官的现象明显减少。可以说辽朝通过采用科举制度实现对汉地的深入统治。