Chol‐qeshlaghi altered area lies in the northwestern part of the post‐collisional Urumieh‐Dokhtar magmatic arc, NW Iran. Pervasive silicic, argillic, phyllic and propylitic altered zones appears to be intimately affiliated to the fluids derivative of upper Oligocene Khankandi granodiorite. This paper is dedicated to the identification of geochemical characteristics of hydrothermal alterations, focusing on the determination of the mass gains and losses of REEs, to gain significant insights regarding the chemical exchanges prevailed between the host rocks and hydrothermal fluids. The low pH and high activity of SO₄^‐2 ligands in silicic alteration fluids, resulting in depletion of entire REEs. Decreasing of LREEs appeared in argillic zone may attributed to reduce in adsorption ability of clay minerals in low pH; whereas HREEs enrichment in phyllic zone was inclined to put it down to the abundance of sericite (± Fe oxides). A significant reduction of Eu/Eu* ratio in silicic zone can be attributed to negligible sulfides and clay minerals as some effective agents in adsorption of released Eu⁺². Factors such as changes in pH, the abundance of absorptive neomorph mineral phases, activity of ligands play an important role in controlling the distribution and concentration of REEs in Chol‐qeshlaghi alteration system.

中文翻译：

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伊朗西北部乔尔－克什拉格希地区次生质热液蚀变带的地球化学特征：对稀土元素的约束

Chol-qeshlaghi蚀变区位于伊朗西北部碰撞后的Urumieh-Dokhtar岩浆弧的西北部。普遍的硅质，泥质，叶状和丙炔化蚀变带似乎与上渐新世汉康迪花岗闪长岩的流体衍生物密切相关。本文致力于确定热液蚀变的地球化学特征，着重于确定稀土元素的质量得失，以获取有关基质岩和热液之间普遍存在的化学交换的重要见解。SO ₄ ^‐2的pH低且活性高硅蚀变流体中的配体，导致整个稀土元素的消耗。泥质带中LREEs的减少可能是由于低pH条件下粘土矿物的吸附能力降低所致。而在叶状区的HREEs富集倾向于将其归因于绢云母（±Fe氧化物）的丰度。硅质区中Eu / Eu *比的显着降低可归因于硫化物和黏土矿物可忽略不计，因为硫化物和粘土矿物是一些有效的吸附释放的Eu ^+2的试剂。pH的变化，吸收性新形态矿物相的丰度，配体的活性等因素在控制Chol-qeshlaghi蚀变系统中REE的分布和浓度方面起着重要作用。