Microbial sulfate reduction plays an important role at the initial stage of subseafloor sulfide mineralization
Microbial sulfate reduction plays an important role at the initial stage of subseafloor sulfide mineralization
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DOI：
10.1130/g47943.1
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发表时间：
2021-02-01
期刊：
影响因子：
5.8
通讯作者：
Ishibashi, Jun-ichiro
中科院分区：
文献类型：
--
作者：
Nozaki, Tatsuo;Nagase, Toshiro;Ishibashi, Jun-ichiro
海底热液矿床是在热液流体与环境海水混合时形成的，组成硫化物矿物通常被解释为非生物沉淀。最近在冲绳海槽（东海）中部Izena Hole和Iheya North Knoll进行的研究钻探，结合二次离子质谱法测定黄铁矿颗粒中的S-34，提供了令人信服的证据，表明海底硫化物矿化的初始阶段与微生物硫酸盐还原密切相关。在硫化物的成熟过程中，黄铁矿结构经历了从草莓状到胶体状再到自形的演变过程。黄铁矿三角洲S-34在草莓状黄铁矿中具有高度负值（低至-38.9 ‰），在胶状和自形黄铁矿中系统地向正值增加。海水硫酸盐（+21.2ppm）和草莓状黄铁矿（-38.9ppm）之间的硫同位素分馏高达-60ppm，只有在开放体系中通过微生物硫酸盐还原才能实现。由于草莓状黄铁矿通常被黄铜矿、方铅矿和闪锌矿取代，草莓状黄铁矿似乎是其他硫化物矿物的起始材料（核）。我们的结论是，草莓状黄铁矿，含有微生物还原硫，在海底硫化物成矿的初始阶段起着重要的作用。
Seafloor hydrothermal deposits form when hydrothermal fluid mixes with ambient sea-water, and constituent sulfide minerals are usually interpreted to precipitate abiogenically. Recent research drilling at Izena Hole and Iheya North Knoll in the middle Okinawa Trough (East China Sea), combined with secondary ion mass spectrometry determinations of delta S-34 in pyrite grains, provides compelling evidence that the initial stage of subseafloor sulfide mineralization is closely associated with microbial sulfate reduction. During the sulfide maturation process, pyrite textures progress from framboidal to colloform to euhedral. Pyrite delta S-34 has highly negative values (as low as -38.9 parts per thousand) in framboidal pyrite, which systematically increase toward positive values in colloform and euhedral pyrite. Sulfur isotope fractionation between seawater sulfate (+21.2 parts per thousand) and framboidal pyrite (-38.9 parts per thousand) is as great as -60 parts per thousand, which can be attained only by microbial sulfate reduction in an open system. Because framboidal pyrite is commonly replaced by chalcopyrite, galena, and sphalerite, framboidal pyrite appears to function as the starting material (nucleus) of other sulfide minerals. We conclude that framboidal pyrite, containing microbially reduced sulfur, plays an important role at the initial stage of subseafloor sulfide mineralization.