Abstract

The paper presents results of experimental studies of the behavior of volatile components (Cl, F, CO₂, and H₂O) in fluid–magmatic systems. The maximum Cl content in magmatic melts depends mainly on the composition of the melt and less on pressure (10–300 MPa) and temperature (800–1000°C). The Cl content in the melt increases from 0.2–0.3 to 3–5 wt % with increasing Ca content during the transition from polymerized granitoid to depolymerized basaltic melts. The pressure dependence of the solubility has a maximum at a pressure of about 100–200 MPa. The Cl and F contents in the melt tend to increase and decrease, respectively, at the transition from acid and alkaline to basalt melts. The maximum Cl content in the melt significantly increases from rhyolite (no more than 0.25 wt %) to phonolite (no more than 0.85 wt %), and dacite (no more than 1.2 wt %) melts at temperatures of 1000–1200°C and a pressure of 200 MPa. The addition of CO₂ to the system leads to an increase in the Cl content in the melt by 20–25 relative %, which is likely explained by an increase in Cl activity in the fluid. Thereby the H₂O content in the melt decreases by ~0.5–1.0 wt %. Hydrolysis is demonstrated to strongly affect interaction between alumina-rich granitic melt and ~0.5–1 N chloride fluid. This effect shows that the fluid is acidic (pH after the experiment is ~1–1.5) at hypabyssal magmatic conditions (P = 100 MPa, T = 750°C) and is characterized by a high dissolving power. The experiments show that interaction between aqueous Na–K–Ca–chloride fluid of variable composition and granodioritic and granitic melts in the pressure range of ~100–200 MPa, temperatures of 820–1000°C, and an increasing total salt content leads to that Na and K substitute Ca in the silicate melt, with Ca simultaneously passing into the fluid. The latter is enriched in CaCl₂ and is depleted in NaCl. Experimental results on the coupled Cl and F partitioning provide a quantitative basis for understanding degassing processes in the course of the evolution of alkaline and basaltic magmas. They are important for assessing the extent of Cl and F removal into the Earth’s atmosphere during volcanic activity and the effects of this removal on climate changes.

中文翻译：

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不同组成的水饱和流体-岩浆系统中挥发性成分（Cl，F和CO 2）的分配

摘要

本文介绍了挥发性成分（Cl，F，CO ₂和H _2）行为的实验研究结果。O）在流体-岩浆系统中。岩浆熔体中的最大Cl含量主要取决于熔体的成分，而对压力（10–300 MPa）和温度（800–1000°C）的影响较小。在从聚合的类花岗岩转变为解聚的玄武质熔体的过程中，随着Ca含量的增加，熔体中的Cl含量从0.2–0.3 wt％增加到3-5 wt％。在约100-200 MPa的压力下，溶解度的压力依赖性最大。从酸性和碱性熔体到玄武岩熔体的转变，熔体中的Cl和F含量分别趋于增加和降低。熔体中的最大Cl含量从流纹岩（不超过0.25 wt％）到方沸石（不超过0.85 wt％）显着增加，而方晶石（不超过1.2 wt％）在1000-1200°C和压力为200 MPa。一氧化碳的添加系统的图₂导致熔体中Cl含量增加了20-25相对％，这很可能是由于流体中Cl活性的增加所致。因此，熔体中的H ₂ O含量降低了〜0.5–1.0 wt％。已证明水解会严重影响富含氧化铝的花岗岩熔体和〜0.5-1 N氯化物流体之间的相互作用。这种效果表明，在震颤下岩浆条件下（P = 100 MPa，T，该流体呈酸性（实验后的pH约为1–1.5）= 750°C），并且具有较高的溶解力。实验表明，在压力范围为〜100-200 MPa，温度为820-1000°C且总盐含量增加的情况下，可变组成的Na-K-Ca-氯化物水溶液与花岗闪长岩和花岗石熔体之间的相互作用Na和K替代硅酸盐熔体中的Ca，同时Ca进入流体。后者富含CaCl ₂，而不含NaCl。Cl和F分区耦合的实验结果为理解碱性和玄武岩浆演化过程中的脱气过程提供了定量基础。它们对于评估火山活动期间向大气中清除Cl和F的程度以及清除对气候变化的影响非常重要。