滇东南都龙锡锌多金属矿床中符山石的发现与地质意义

Discovery of Vesuvianit in Dulong Sn-Zn Polymetallic Ore Deposit, Southeastern Yunnan Province, China and its Geological Significance

云南省马关县都龙超大型锡锌多金属矿床是我国重要锡锌资源基地之一,夕卡岩化是矿床中最主要近矿围岩蚀变,近年的地质勘探与找矿过程中,发现了前人所忽视的符山石,该类夕卡岩矿物主要分布于无水夕卡岩与含水夕卡岩过渡部位,属于含水夕卡岩阶段的产物,并与Zn-Cu矿化关系密切,可以作为相关矿化找矿标志。本文通过LA-ICP-MS对该类矿物进行了原位主、微量及稀土元素分析,结果表明,符山石中富集Zn、Sn、W和Bi等成矿元素,这些成矿元素以类质同象形式置换了符山石的晶格中的Mg2＋和Fe2＋,暗示在湿夕卡岩阶段成矿流体中已经大量富集了这类成矿元素,有利于后期相关矿化的形成。此外,该类矿物稀土配分模式为中等向右倾斜曲线,Y/Ho比值在22.3～34.4之间,与矿区深部燕山期隐伏花岗岩较为相似,表明其形成与该岩体关系密切。

Dulong Sn-Zn polymetallic ore deposit, Maguan area, Yunnan Province, China is one of most important producing areas of Sn and Zn resource in China, and its wall rock alteration is dominated by skarn. Vesuvianit, being ignored by researchers, has been discovered during recent geological exploring. The mineral occurs in the transition part between anhydrous skarn and hydrous skarn, belonging to the product in hydrous skarn stage, and is relate closely to Zn-Cu mineralization. It is suggested that vesuvianit is a prospecting indicator for Zn-Cu. Researched by LA-ICP-MS, it shows that vesuvianit is rich in Zn, Sn, W and Bi; those ore-forming elements replace Mg2＋ and Fe2＋ in the crystal lattice of vesuvianit, and present as isomorphism, implying that the ore-forming fluid is rich in metallogenic elements during hydrous skarn stage, which is beneficial to the mineralization. Furthermore, the chondrite-normalized REE patterns of vesuvianit belong to the LREE-rich type, and Y/Ho ratio value is between 22.3 and 34.4, corresponding to that of Later Yanshanian concealed granite, and suggesting that the formation of vesuvianit is related closely to the rock mass.