豫西银家沟硫铁多金属矿床元素地球化学特征研究

Study on element geochemical characteristics of the Yinjiagou pyritepolymetallic deposit,western Henan Province

银家沟硫铁多金属矿床位于华北克拉通南缘,受地层、构造控矿作用强烈。本文对银家沟硫铁多金属矿床的成矿地质背景、岩(矿)石主量、微量、稀土元素地球化学特征进行了系统研究。主量元素特征为矿石中SiO2含量普遍很低,矿石和蚀变岩亏损TiO_(2)、Al_(2)O_(3)、Na_(2)O、K_(2)O,强烈富集Fe_(2)O_(3)和FeO;矿石、蚀变岩微量元素富集和亏损基本一致,与银家沟岩体相比,Th、Nb、Ta、Zr、Hf、Rb、Ba、Sr元素显著亏损,Pb、Zn、Mo、Au成矿元素显著富集。稀土元素配分曲线可分为3类:①稀土配分曲线平坦,重稀土略高于轻稀土,Eu元素无明显异常;②轻重稀土分馏程度低,稀土配分曲线斜率小;③轻重稀土分馏程度差异较大,轻稀土分异强度较大,Eu多为弱负异常,少数为无异常。矿石Eu强负异常,可能是矿石中含有菱铁矿和(铁)白云石或重晶石所致。综合以往同位素年代学、成矿流体和成矿物质来源等研究资料,认为银家沟硫铁多金属矿床成矿与区内发育的燕山期碱长花岗斑岩关系密切。

The Yinjiagou pyrite-polymetallic deposit,located in the southern margin of North China Craton,is mainly controlled by the strata,structures and magmatic rocks.In this paper,metallogenic geological background and deposit geology of the deposit are studied.A systematic research is carried out on rock(ore)geochemical characteristics of the major,trace and rare earth elements.Characteristics of the major elements show that content of SiO_(2) is generally low in pyrite-polymetallic ores,and the ores and altered rock are deficientin TiO_(2),Al_(2)O_(3),Na_(2)O,K_(2)O,and great enrichment of Fe_(2)O_(3) and FeO in the ores and altered rocks.Enrichment and deficiency of the trace elements in the ores and altered rocks are basically consistent.Compared with the Yinjiagou magmatic rocks,there exist obvious deficiency of Th,Nb,Ta,Zr,Hf,Rb,Ba,Sr,and enrichment of metallogenic elements Pb,Zn,Mo and Au.The REE distribution patterns can be divided into three types:①The REE distribution curves show flat pattern,with HREE slightly higher than LREE,and no remarkable Eu anomaly;②LREE and HREE exhibit low fractionation,with small distribution curve slope.③LREE and HREE show significant fractionation differ⁃ence,with great differentiation of LREE,and mostly slightly negative Eu anomalies or no anomalies.The pyritepolymetallic ores exhibit strongly negative Eu anomalies,which may be caused by the presence of siderite,(iron)dolomite or barite.Based on previous research data on isotopic geochronologies,metallogenic fluids and metal⁃logenic material sources,it is recognized that the Yinjiagou pyrite-polymetallic deposit is closely related to the widely distributed K-feldspar granite porphyries of Yanshanian.