Hydrothermal alteration processes at midocean ridges: Experimental and theoretical constraints from Ca and Sr exchange reactions and Sr isotopic ratios

摘要: Diabase and basalt were reacted with Na-Ca-K-Cl fluids of seawater chlorinity at 375–425°C, 375–400 bars, fluid/rock mass ratios 0.5–1.0 to assess the role chemistry texture on Sr Ca mobility during high-temperature hydrothermal alteration. An additional experiment, utilizing an 84Sr spiked fluid, was performed help quantify reaction rates processes affecting mobility. The experimental results constrain responsible for hot spring midocean ridges. Alteration diabase is characterized by formation tremolite-actinolite-smectite-chlorite clinozoisitic epidote-smectite-chlorite, respectively. alteration produced dissolved Sr/Ca similar those observed ridge crest fluids, whereas a mostly crystalline significantly lower ratios. This observation supports premise that in vent may be deep-seated dikes and/or gabbro relatively low suggests primary igneous minerals high temperatures (400°C) leads mineral DSr/Ca, Possibly plagioclase. Results experiment indicated only 4% mobilized after 800 hours despite fact B Li nearly quantitatively leached. It thus suggested are good indicators amount fresh rock encountered while concentration isotopic data can used estimate degree Sr-bearing have undergone. subsurface reservoirs estimated dividing ratio obtained highly mobile elements from path-integrated isotope data. Based this method, example, it 5% EPR 21°N actually converted secondary phases.