东帝汶海MD98-2172岩芯磁记录与还原成岩作用过程

MINERAL MAGNETIC INVESTIGATION OF CORE MD98-2172 IN EASTERN TIMOR SEA AND REDUCTIVE DIAGENESIS PROCESS

MD98—2172岩芯位于印度尼西亚穿越流的帝汶通道上。多参数的岩石磁学测量结果表明，该岩芯的磁性矿物组合很好地记录了海洋沉积物中的还原成岩作用过程：0～3．85m段岩芯以亚铁磁性准单畴（PSD）磁铁矿为主，其含量和粒度基本不随深度而变，受还原成岩作用的影响不明显；3．85～5．35m段岩芯也以PSD磁铁矿为主，但其含量随深度的增加而快速减少，粒度随深度的增加而变粗，或粗粒磁铁矿的相对含量随深度的增加而增多，处于铁氧化物还原阶段；5．35～15．00m层段以顺磁性颗粒为主，并出现黄铁矿，处于硫酸盐还原阶段。

Detailed mineral magnetic measurements coupled with bulk grain size and X-ray diffraction （ XRD ） analyses were made on the marine sediments of Core MD98-2172, collected from the Timor Passage of Indonesia Throughflow. Values of magnetic susceptibility of this core drop sharply downcore at ca. 5.35m. But both results of XRD and grain size show no sudden change of detrital origin for the whole upper 15m of the core. Mineral magnetic results, including χ, χARM, SIRM, HIRM,S300, SIRM/χ, IRM%, κ/T curves, χARM/χ, ARM/SIRM, and magnetic hysteresis parameters, etc., show that this core has recorded the process of reductive diagenesis in marine sediments：（1 ）The upper 3.85m sediments were little affected by reductive diagenesis. The magnetic mineral assemblage of this section is dominated by pseudo-single domain magnetite, with little variations of its content and grain size. （2）Sediments of the 3.85 -5.35m interval are within the stage of iron oxide reduction. Pseudo-single domain magnetite also dominates the magnetic properties of the sediments, with less abundant and coarser grains downcore. （3）The 5.35- 15.00m sediments are within the stage of sulphate reduction. Paramagnetic minerals contribute to sediments of this section, including pyrites as evidenced by high-temperature magnetic susceptibility measurements.