Description: One kinds of glycolipid (SBI) have been isolated from the marine brown alga Sargassum hemiphyllum (Turn.) Ag. The structures of SBI have been determined as the sodium salt of 1-0-acyl-3-0-(6′-sulfo-α-D-quinovopyrannosyl) glycerol (acyl: tetradecanoyl, pentadecanoyl, 11-hexadecenoyl, hexadecanoyl, 10,13-octadecadienoyl, 9-octade cenoyl, 15-metylheptadecanoyl and 11-eicosenoyl 17:1.5:19:153:1:19:1:2) on the basis of chemical and spectral evidence and GC-MS analysis, respectively. Four constituents of the SBI were new compounds [the sodium salt of 1-0-(11″-hexadecenoyl)-3-0-(6′-sulfo-α-D-quinovopyrannosyl) glycerol, the sodium salt of 1-0-(10″,13″-octadecadienoyl)-3-0-(6′-sulfo-α-D-quinovopyrannosyl) glycerol, and the sodium salt of 1-0-(15″-metylhexadecenoyl)-3-0-(6′-sulfo-α-D-quinovopyrannosyl) glycerol, and the sodium salt of 1-0-(11″-eicosenoyl)-3-0-(6′-sulfo-α-D-quinovopyrannosyl) glycerol]. All compounds were isolated from marine brown alga for the first time.

Description: The ocean floor is leaky because it has numerous faults, cracks and joints upon formation and during the process of seafloor spreading. In time, these fractures are often closed after ocean floor cooling, hydrothermal circulation, and vein filling. The crack-seal mechanism of fractures of the oceanic crust is thus important for understanding its kinematics, kinetics and evolution. Coring and log data from IODP Expedition 324 reveal that the Shatsky Rise, an oceanic plateau in the NW Pacific Ocean, developed abundant joints and veins, and some veins formed along previous joints. We use log data from the Formation Micro-scanner Scanner (FMS) to reconstruct the original dip and dip direction of these structural elements. Using FMS microstructural analyses, the dip directions of joints and arrangement of solid inclusions in fibrous veins were examined for Holes U1347A, U1348A and U1349A. We found two types of veins, non-fibrous and fibrous, based on their physical appearance and mineralogical composition. Common to all samples is a straight fibrous inclusion fabric, associated with bands oriented parallel to the vein wall and trails typically at high angles to the vein wall. Cross-cutting relationships between the bands and the straight fibrous inclusions imply that inclusion bands reflect simple crack-seal increments. In the veins, inclusion bands are a sufficient criterion to infer the crack-seal mechanism. Further evidence for solid inclusions formed by the classic crack-seal mechanism is given by inclusion bands in carbon crystals grown in basalts. During incorporation, solid inclusions can remain undeformed, depending on their orientation with respect to the opening and spreading direction of mid-oceanic ridges. Simple displacement fields within the veins are recorded by straight crystal fibres, which track the opening direction. Based on the arrangement of solid inclusions within the veins, we suggest that the veins grew continuously during post-tectonic vein formation. Solid inclusions formed by steady adhesion at the vein wall interface during crack sealing and growth of a few veins were driven by the force of crystallization and extension of mid-oceanic ridges. Based on these two lines of evidence, we conclude that the formation of the Tamu Massif is consistent with the seafloor spreading history revealed by magnetic lineations, possibly accompanied with an interaction to the mantle plume head. In contrast, the formation of the Ori Massif, off the mid-ocean ridge, has no obvious preferred stress field, deduced to be related to a mantle plume tail with interaction to the mid-oceanic ridge.

Description: Numerous calcium carbonate veins were recovered from the igneous basement of the Early Cretaceous Shatsky Rise during Integrated Ocean Drilling Program (IODP) Expedition 324. The chemical (Sr/Ca, Mg/Ca) and isotopic (87Sr/86Sr, 143Nd/144Nd, !18O, !13C) compositions of these veins were determined to constrain the timing of vein formation. A dominant control by seawater chemistry on calcite composition is evident for most vein samples with variable contributions fromthe basaltic basement. Slightly elevated precipitation temperatures (as inferred from oxygen isotope ratios), indicative of hydrothermal vein formation, are only observed at Site U1350 in the central part of Shatsky Rise. The highest 87Sr/86Sr ratios (least basement influence) of vein samples at each drill site range from 0.70726 to 0.70755 and are believed to reflect the contemporaneous seawater composition during the time of calcite precipitation. In principle, age information can be deduced by correlating these ratios with the global seawater Sr isotope evolution. Since the Sr isotopic composition of seawater has fluctuated three times between the early and mid Cretaceous, no unambiguous precipitation ages can be constrained by this method and vein precipitation could have occurred at any time between ~80 and 140 Ma. However, based on combined chemical and isotopic data and correlations of vein compositionwith formation depth and inferred temperature, we argue for a rather early precipitation of the veins shortly after basement formation at each respective drill site.