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对ODP(大洋钻探Ocean Drilling Program)204航次在水合物海岭南峰钻取的1245B、1249C、1251B和1252A孔岩心进行磁学分析,结合自生黄铁矿集合体结果探讨沉积物中的铁硫化物的磁学特征及其与甲烷渗漏、水合物赋存的关系。结果表明:4个钻孔岩心中磁性矿物含量总体不高,主要为中、低矫顽力的软磁性矿物,载磁矿物为亚铁磁性的磁铁矿、胶黄铁矿和磁黄铁矿。沉积物中自生黄铁矿是甲烷厌氧氧化(AOM)作用下硫酸盐还原的主要产物,减缓了磁性矿物含量、颗粒大小差异对χARM、HIRM和SIRM/χ的影响,加大了χ/χARM、ARM/SIRM对磁性矿物含量的敏感度。自生黄铁矿集合体含量随深度的变化可能反映古代AOM活动。在甲烷渗漏、水合物赋存背景下,胶黄铁矿和磁黄铁矿的赋存可能是局部与水合物相关的氧化还原作用产物,也可能是早更新世末、中更新世以来某一时期硫酸盐-甲烷转换带(SMTZ)快速上移的产物。早更新世沉积层内连续的胶黄铁矿沉积反映了孔隙水中HS-不足的还原成岩环境,与甲烷渗漏、水合物的赋存无关。
Magnetic properties of cores 1245B, 1249C, 1251B and 1252A drilled at the ODP (Ocean Drilling Program) 204 voyage at the southern peak of the hydrate Ridge are analyzed magnetically in association with the results of spontaneous pyrite assemblages to investigate the effects of iron sulphides Magnetic characteristics and their relationship with methane seepage and hydrate occurrence. The results show that the contents of magnetic minerals in the four boreholes are generally not high, mainly composed of soft magnetic minerals with moderate and low coercivity, magnetic minerals carrying ferrimagnetism magnetite, pyroxene and pyrrhotite . The authigenic pyrite in sediments is the main product of sulfate reduction under the action of methane anaerobic oxidation (AOM), and the effects of magnetic mineral content, particle size difference on χARM, HIRM and SIRM / χ are slowed down and χ / χARM , ARM / SIRM sensitivity to magnetic mineral content. The variation of authigenic pyrite assemblages with depth may reflect ancient AOM activities. In the background of methane seepage and hydrate occurrence, the occurrence of pyrite and pyrrhotite may be the product of redox reaction locally associated with hydrate, and may also be the result of the late Pleistocene and Middle Pleistocene A period of sulfate - methane conversion zone (SMTZ) quickly up the product. The continuous deposition of pyroxene in the Early Pleistocene sediments reflects the HS-deficient reductive diagenetic environment in pore water, which is not related to methane leakage or hydrate occurrence.