A profile of multiple sulfur, oxygen, strontium isotopes and related chalcophile elements through lower slow-spreading crust (IODP Expedition 360, Atlantis Bank, Southwest Indian Ridge)

位于西南印度洋海脊(SWIR)的IODP第360次远征前往亚特兰蒂斯浅滩，于2016年1月30日结束，是SloMo项目的第一阶段，该项目是一个多阶段钻探计划，旨在在缓慢扩张的大洋脊钻探地壳/地幔边界。斯洛莫项目的主要目标是检验关于缓慢扩张的大洋岩石圈中莫霍面性质的相互竞争的假说。探险360井U1473A钻穿块状橄榄辉长岩、辉长岩、富铁钛氧化物辉长岩、辉长岩，被大量长英脉切割，钻进深度达789.7米。许多斑岩碎屑到超糜棱岩的辉长岩，代表着600米厚的剪切带，表明这是在一个动态的环境中发生的，开始于辉长岩部分熔融，随着它们冷却而继续，并以底辟和构造向上侵位到裂谷底部之下的岩脉地带。借助360探险期间钻探的U1473U孔，我们的目标是量化典型缓慢扩张洋壳中硫和相关亲硫元素的循环。分析方法将包括测量多种硫同位素和微量元素，主要是在钻探的岩芯中的辉长岩和长英质岩石中，由来自该地区的挤出地壳和地幔岩石的少数样品支持，这些样品通常是通过其他轮船回收的。井下硫和亲硫元素的浓度分布将使我们能够确定它们的富集和枯竭的主要趋势。多种硫同位素与硅酸盐氧同位素和块状岩石锶同位素相结合，将有助于确定在各种共生矿物组合中观察到的硫化物是由原始岩浆作用形成的，还是由次生作用形成的，即由导致水-岩相互作用的海水流体形成的。光学显微镜和反射光学显微镜以及电子探针(EMPA)的原位分析和激光烧蚀电感耦合等离子体质谱(LA ICPMS)将揭示深海缓慢扩张的洋壳中与硫成矿有关的相关过程的特征。

IODP Expedition 360 to Atlantis Bank, at Southwest Indian Ridge (SWIR), ended at 30.01.2016, and is Leg 1 of the SloMo Project, a Multi Phase Drilling Program to drill through the crust/mantle boundary at a slow spreading ocean ridge. The primary objective of the SloMo Project is to test competing hypotheses on the nature of the Moho at the slow spreading oceanic lithosphere. Expedition 360 Hole U1473A was drilled 789.7 m through massive olivine gabbro, gabbro, Fe Ti rich oxide gabbro, gabbronorite, cut by numerous felsic veins. Numerous long intervals of porphyroclastic to ultramylonitic, gabbro, representing a 600 meter thick shear zone, demonstrate that this occurred in a dynamic environment, beginning while the gabbros were partially molten, and continuing as they cooled and were emplaced diapirically and tectonically upward into the zone of diking beneath the rift valley floor. With the help of the Hole U1473U core drilled during Expedition 360, we aim at quantifying the cycling of sulfur and related chalcophile elements in typical slow spreading oceanic crust. The analytical approach will include measuring of multiple sulfur isotopes and trace elements mostly in gabbros and felsic rocks from the drilled core, supported by a few samples from the extrusive crust and from mantle rocks from that area, recovered conventionally by other ship cruises. Downhole concentration profiles of sulfur and chalcophile elements will enable us to identify the main trends of their enrichment and depletion. Multiple sulfur isotopes, in combination with silicate oxygen isotopes and bulk rock Sr isotopes will help to identify whether sulfides observed in various paragenetic mineral assemblages have been formed by primary magmatic or secondary processes, i.e. by seawater derived fluids resulting in water rock interaction. Optical and reflected light microscopy as well as in situ analysis with electron microprobe (EMPA), and laser ablation inductively coupled plasma mass spectrometry (LA ICPMS) will reveal fundamental understanding of the characteristics of related processes involving sulfur mineral formation in the deep slow spreading oceanic crust.