阿尔金卡尔恰尔超大型萤石矿床成矿流体特征及形成机制探讨

新近发现的卡尔恰尔超大型热液脉状萤石矿床位于阿尔金造山带中部，矿体主要沿中奥陶世二长花岗岩及变质杂岩的接触带产出，并受韧性剪切断裂及裂隙构造控制。矿石主要类型为萤石方解石脉型，矿物组成以萤石和方解石为主，含少量石英和钾长石。矿石呈粗晶粒状和伟晶状结构，条带状、团块状和角砾状构造。包裹体研究表明，萤石和方解石中包裹体具有近似特征，均发育CO₂包裹体、含CO₂三相包裹体、气液两相包裹体和含子矿物多相包裹体等4种类型的原生包裹体，各类包裹体均一温度为135℃~359℃，盐度为2.07%~7.59%，反映成矿流体为中-中低温、低盐度不混溶NaCl-H₂O-CO₂热液体系类型。萤石和方解石流体包裹体氢氧同位素测试，反映该成矿流体来源于岩浆水与大气降水的混合热液。推测岩浆期后初步形成富CO₂、富F热液，在上升过程中淋滤萃取变质杂岩中的Ca质形成成矿流体，后因大气降水加入发生降温、降压与流体沸腾作用，在断裂-裂隙构造的有利部位充填-交代形成萤石方解石矿脉。

Study on fluid characteristics and metallogenic mechanism of the super-large Kalqiar fluorite deposit in Altyn Tagh area

The Kalqiar super-large fluorite deposit discovered recently was located at the middle Altyn Tagh Orogen. The ore bodies were distributed in the contact zone of Middle Ordovician monzogranite and metamorphic rock, and controlled by ductile shear zone and fracture structure. The main ore type is fluorite-calcite veins. The mineral composition of ore vein is mainly calcite and fluorite with a small amount of quartz and K-feldspar. The ore show coarse grain texture, block, breccia and banded structure. The inclusion study shows that fluorite and calcite develop CO2 inclusions, CO2-bearing three-phase inclusion and gas-liquid two-phase inclusion and multiphase inclusions containing daughter minerals; the homogenization temperature is 135℃~359℃ and the salinity is 2.07%~7.59%(NaCl)eq. It shows that the ore-forming fluids is an immiscible H2O-NaCl-CO2 hydrothermal system with medium to medium-low temperature and low salinity. Determination of hydrogen and oxygen isotopes of fluorite and calcite mineral inclusions show that the ore-forming fluids comes from the mixed hydrothermal solution of magmatic water and atmospheric water. It is speculated that the hydrothermal solution CO2 and F-rich was initially formed after the magmatic stage, with the addition of atmospheric precipitation, Ca in the metamorphic complex is leached and extracted to form ore-bearing hydrothermal solution. It is suggested that the fluorite calcite vein is formed by filling and metasomatism in the favorable part of fault and fracture structure.