鄂东南丰山矿田铜金矿床方解石的稀土元素地球化学特征

REE geochemistry of calcites from copper-gold deposits in Fengshan ore field,southeastern Hubei

中文关键词:成矿流体  稀土元素  C-O同位素  丰山矿田  鄂东南矿集区

keywords:ore-forming fluid  REE geochemistry  C-O isotope  Fengshan ore field  southeastern Hubei ore concentration area

中文摘要:矽卡岩铜金矿与外围的低温金矿的成因联系存在争议，方解石是这2类矿床普遍发育的热液蚀变矿物，其地球化学特征可用于示踪成矿过程。文章以鄂东南丰山矿田鸡笼山矽卡岩型铜金矿床、曹家山和竹林塘远端低温热液金矿床为对象，开展热液方解石的稀土元素（REE）研究，探讨不同类型矿床的成因联系。结果表明，2类矿床的方解石均呈现轻稀土元素（LREE）富集（La_N/Yb_N范围2.21～20.28）的配分模式，主要受控于流体中REE络合物稳定性及矿物结晶分异；方解石REE配分模式指示成矿流体主要来源于燕山期岩浆热液。Eu异常特征（δEu）有效记录了成矿环境的氧化还原状态与温度，鸡笼山矽卡岩型铜金矿床方解石的正Eu异常（δEu=0.92～1.45）指示高温还原性条件；曹家山金矿床成矿期和成矿后方解石在稀土元素总量与Eu异常方面均表现不同，竹林塘金矿床成矿期方解石多具负Eu异常（δEu可低至0.56）和较低的ΣREE，反映低温氧化条件。曹家山金矿床由于锰离子的影响造成稀土元素总量和Eu异常值成矿后比成矿期高的现象。结合区域地质证据，文章提出远端低温金矿床与矽卡岩型铜金矿床同属一个岩浆热液成矿系统。

Abstract:The genetic connection between skarn Cu-Au deposits and peripheral distal low-temperature Au deposits remains controversial. Calcite, a ubiquitous alteration mineral in both deposit types, provides a valuable geochemical tracer for mineralization processes. This study investigates the hydrothermal rare earth element（REE） geochemistry of calcites from the Jilongshan skarn Cu-Au deposit, and the Caojiashan and Zhulintang distal lowtemperature Au deposits within the Fengshan orefield, southeastern Hubei, to elucidate genetic links between these contrasting deposit styles. Results show that calcites from both deposit types exhibit light REE（LREE）-enriched patterns（La_N/Yb_N=2.21～20.28）, primarily controlled by REE complex stability in the fluid and mineral crystallization differentiation. REE patterns indicate a dominant magmatic-hydrothermal fluid source associated with Yanshanian magmatism. Europium anomalies（δEu） effectively record redox conditions and temperature:calcites from the Jilongshan Cu-Au deposit display positive δEu anomalies（0.92～1.45）, indicating a high-temperature reducing environment; ore-stage calcites from Zhulintang typically show negative δEu anomalies（as low as 0.56） and lower ΣREE, reflecting a low-temperature oxidizing environment; ore-stage and post-ore calcites from Caojiashan differ significantly in both ΣREE and δEu, with the latter's elevated values attributed to Mn²⁺ influence.Integrating these findings with regional geological evidences, we propose that the distal low-temperature Au deposits and the skarn Cu-Au deposit constitute a unified magmatic-hydrothermal mineralization system.