Chloride depletions and enrichments in seafloor hydrothermal fluids: Constraints from experimental basalt alteration studies
Chloride depletions and enrichments in seafloor hydrothermal fluids: Constraints from experimental basalt alteration studies
复制标题
海底热液中氯化物的消耗和富集：实验玄武岩蚀变研究的限制
DOI：
10.1016/0016-7037(86)90200-0
复制
发表时间：
1986
影响因子：
5
通讯作者：
D. Janecky
中科院分区：
文献类型：
--
作者：
W. Seyfried;M. Berndt;D. Janecky
在400°和425° C、400巴、流体岩质比为0.5的条件下，用Na-K-Ca-Cl流体与Dibromide反应，测定溶解Cl的相对迁移率。从本实验的流体揭示了相对较大的时间和温度依赖性降低氯;温度升高提高氯的去除，而反应进程具有相反的效果。这些变化不是由于沸腾和/或相分离引起的。在400° C和425° C，400巴下，溶液中Cl的去除分别伴随着Ca和Na的固定。两个实验都产生了混合层蒙脱石/蒙皂石、斜生石和钠长石。橄榄石没有检测到X-射线衍射或岩相分析的运行产品从两个实验，但是，我们建议溶解氯的时间依赖性变化的结果从橄榄石替换由Fe-羟基氯化物相，然后由水合作用。淬火和洗涤蚀变产物，但是，没有发现异常氯，这表明含氯相的特点是逆行溶解度。这是一致的相对幅度的Cl固定实验中观察到的温度和等压冷却实验的结果。实验结果为玄武岩热液蚀变过程中Cl的非保守行为提供了证据。鉴于某些脊顶温泉流体的贫Cl性质，这些数据特别重要，并表明这些流体的形成温度约为410° C，假设海底压力为400 bar。此外，在高温玄武岩蚀变过程中负责Cl固定的含Cl相的逆溶解度可能有助于解释传导冷却至350° C以下的温泉流体中Cl的富集
Abstract Na-K-Ca-Cl fluid was reacted with diabase at 400° and 425° C, 400 bars and fluid rock mass ratio of 0.5 to assess the relative mobility of dissolved Cl. Fluids from the present experiments reveal relatively large time and temperature dependent decreases in Cl; temperature increase enhances Cl removal, whereas reaction progress has the opposite effect. These changes are not due to boiling and/or phase separation. At 400° and 425° C, 400 bars, Cl removal from solution is accompanied by Ca and Na fixation, respectively. Both experiments produced mixed-layer chlorite/smectite, clinozoisite and albite (?). Olivine was not detected by X-ray diffraction or petrographic analysis of run products from either experiment, however, we propose that the time dependent changes in dissolved Cl result from olivine replacement by an Fe-hydroxy chloride phase followed by hydration effects. Quenched and washed alteration products, however, did not reveal anomalous Cl, which suggests that the Cl-bearing phase is characterized by retrograde solubility. This is consistent with the relative magnitude of Cl fixation observed for experiments at both temperatures and from results of an isobaric cooling experiment. The experiments provide evidence for the non-conservative behavior of Cl during hydrothermal alteration of basalt. The data are particularly important in light of the Cl-depleted nature of some ridge crest hot spring fluids, and suggest temperatures of formation for these fluids of approximately 410° C, assuming sub-seafloor pressure of 400 bars. In addition, the retrograde solubility of the Cl-bearing phase responsible for Cl fixation during high temperature basalt alteration, may help to explain Cl enrichment in hot spring fluids which have conductively cooled below 350° C