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东海冲绳海槽中部79站位A孔发育强烈的甲烷厌氧氧化作用,表层沉积物中发育大量自生黄铁矿沉积.本文开展了该站位自生黄铁矿形貌特征及其硫同位素特征研究,研究发现自生黄铁矿主要以条状、管状以及有孔虫壳体填充状产出.通过铬还原法(CRS)实验提取黄铁矿并测试其硫同位素?34S在?41.20‰~8.92‰V-CDT之间,随着深度增加,黄铁矿硫同位素呈现34S逐渐富集的特征,278 cmbsf(17.18 ka)之上黄铁矿?34S均为负值且稳定在?32.73‰~?41.20‰,278 cmbsf之下?34S出现急剧增大并正偏的特征(?21.49‰~8.92‰V-CDT),对应的黄铁矿含量也出现突增,沉积物总硫含量(TS)则在100 cmbsf突增且在之下地层中相对稳定维持在1.04%~0.55%.278 cmbsf之上,稳定且负偏的黄铁矿硫同位素特征以及降低的TS特征指示了17.18~5.3 ka甲烷厌氧氧化活动的减弱;而之下逐渐增加的?34S特征和黄铁矿含量的增加则表明18.86~17.18 ka期间曾发育强烈的甲烷厌氧氧化活动和甲烷渗漏,18.78 ka时黄铁矿?34S最为正偏,指示了AOM活动此时达到最强烈,SMI的发育层位可能极浅,下覆地层较高的甲烷通量支撑了这一强烈的AOM活动.
Hole A 79 in the middle of the Okinawa Trough in the East China Sea developed a strong methane anaerobic oxidation and a large amount of authigenic pyrite deposits were formed in the surface sediments.This paper carried out the study on the morphological characteristics of authigenic pyrite and the characteristics of sulfur isotopes , The results show that the authigenic pyrite is mainly produced in the form of packing in the form of strip, tube and foraminifera. The pyrite was extracted by chromium reduction (CRS) and the sulfur isotopes of 34S were measured at 41.20 ‰ ~ 8.92 ‰ With the increase of depth, the sulfur isotopes of pyrite show the characteristics of 34S enrichment. The pyrite 34S over 278 cmbsf (17.18 ka) is negative and stable at 32.73 ‰ ~ 41.20 ‰ 278 cmbsf at 34S showed a sharp increase and is positive (21.49 ‰ ~ 8.92 ‰ V-CDT), the corresponding pyrite content also showed a sudden increase in sediment total sulfur content (TS) in the The 100 cmbsf abrupts and remains relatively stable below 1.04% -0.55% below 278 cmbsf. Stable and negatively biased pyrite sulfur isotopes and reduced TS characteristics indicate 17.18-5.3 ka methane anaerobic The decrease of oxidation activity, while the increasing of 34S characteristic and pyrite content increase 18.86-17.18 ka During 18.78 ka pyrite 34S was the most positive, indicating that the AOM activity reached the strongest at this time, and the SMI developmental horizon may be extremely shallow. The overlying strata High methane flux supports this intense AOM activity.