This study reports the occurrence of anhydrite in hydrothermally altered pillow basalt （12°50.55＇N, 103°57.62＇W, water depth 2 480 m）, which may have been produced in the basalt during seawater-basalt in...This study reports the occurrence of anhydrite in hydrothermally altered pillow basalt （12°50.55＇N, 103°57.62＇W, water depth 2 480 m）, which may have been produced in the basalt during seawater-basalt interaction in the laboratory. The existence of anhydrite in the altered basalt indicates extensive high- temperature hydrothermal alteration at the surface of seafloor pillow basalt. Microprobe analysis shows significant chemical zoning in the hydrothermally altered pillow basalt, in which Ca, Si and A1 contents de- crease and P, Fe, Mn, Cr and S contents increase from fresh basalt to altered basalt. The negative correlation between Rb-Sr and Li-Sr, and negative correlation between Li-Ca and Rb-Ca in the high-temperature vent fuids show that these fluids underwent anhydrite precipitation before fluid jetting due to mixing with sea- water in the sub-seafloor. Based on these observations, we show that not all Ca in the anhydrite comes from basalt in the reaction zone, and that the basalts on the seafloor or in the upflow zone may also provide Ca for anhydrite.展开更多
基金The National Key Basic Research Program of China under contract No. 2013CB429700the National Special Fund for the 12th Five Year Plan of COMRA under contract Nos DY125-12-R-02, DY125-11-R-05+1 种基金the National Natural Science Foundation of China under contract Nos 40830849, 40976027 and 40906029Shandong Province Natural Science Foundation of China for Distinguished Young Scholars under contract No. JQ200913
文摘This study reports the occurrence of anhydrite in hydrothermally altered pillow basalt （12°50.55＇N, 103°57.62＇W, water depth 2 480 m）, which may have been produced in the basalt during seawater-basalt interaction in the laboratory. The existence of anhydrite in the altered basalt indicates extensive high- temperature hydrothermal alteration at the surface of seafloor pillow basalt. Microprobe analysis shows significant chemical zoning in the hydrothermally altered pillow basalt, in which Ca, Si and A1 contents de- crease and P, Fe, Mn, Cr and S contents increase from fresh basalt to altered basalt. The negative correlation between Rb-Sr and Li-Sr, and negative correlation between Li-Ca and Rb-Ca in the high-temperature vent fuids show that these fluids underwent anhydrite precipitation before fluid jetting due to mixing with sea- water in the sub-seafloor. Based on these observations, we show that not all Ca in the anhydrite comes from basalt in the reaction zone, and that the basalts on the seafloor or in the upflow zone may also provide Ca for anhydrite.
