Seafloor hydrothermal deposits form when hydrothermal fluid mixes with ambient seawater, 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 δ³⁴S 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 δ³⁴S has highly negative values (as low as –38.9‰) in framboidal pyrite, which systematically increase toward positive values in colloform and euhedral pyrite. Sulfur isotope fractionation between seawater sulfate (+21.2‰) and framboidal pyrite (–38.9‰) is as great as –60‰, 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.

中文翻译：

---

在海底硫化物矿化的初始阶段，微生物硫酸盐还原起着重要作用。

当热液与周围的海水混合时，就会形成海底热液沉积物，通常将硫化物矿物成分解释为非生物沉淀。最近的研究钻探伊是名洞和伊平屋村北诺尔在冲绳海槽中段（东中国海），有δ的二次离子质谱法测定结合³⁴在黄铁矿颗粒S，提供了令人信服的证据表明，海床下硫化物矿化的初始阶段密切相关与硫酸盐还原。在硫化物的成熟过程中，黄铁矿的质地从软糖状发展到共晶状，再到软化。黄铁矿δ ³⁴S在黄铁矿黄铁矿中具有很高的负值（低至–38.9‰），在胶体状和半面状黄铁矿中，系统地向正值增加。海水硫酸盐（+ 21.2‰）和黄菊黄铁矿（–38.9‰）之间的硫同位素分馏高达–60‰，这只能通过在开放系统中还原微生物硫酸盐来实现。因为黄铁矿黄铁矿通常被黄铜矿，方铅矿和闪锌矿代替，所以黄铁矿黄铁矿似乎是其他硫化物矿物的起始材料（核）。我们得出的结论是，含有微生物还原硫的黄铁矿黄铁矿在海底硫化物矿化的初始阶段起着重要作用。