青海野马泉矽卡岩铁锌多金属矿区侵入岩、交代岩及矿化蚀变特征

Characteristics of intrusive rock,metasomatites,mineralization and atteration in Yemaquan skarn Fe-Zn polymetallic deposit,Qinghai Province

野马泉铁锌多金属矿床位于柴达木盆地西南缘和青海祁漫塔格山之间的盆山结合部位。矿区出露有印支期及海西期侵入岩。矿区内矽卡岩呈层状、似层状产于上石炭统四角羊沟组中,矽卡岩矿物主要是石榴子石、单斜辉石、角闪石、绿帘石、符山石等;金属矿物主要有磁铁矿、黄铜矿、黄铁矿、闪锌矿等。文章基于详细野外地质调查、剖面和钻孔岩芯观察结果,开展了侵入岩和交代岩的岩石地球化学及矽卡岩矿物学的系统研究。结果表明,野马泉矿区闪长岩具有低w（SiO2）（51·90%-59·03%）、高w（MgO）（2·04%-3·44%）、w（TFeO）（5·33%-11·67%）,高REE〔（318·57×10-6-327·67×10-6）〕,低LREE/HREE比值（7·36-7·48）的特点;二长花岗岩具有高w（SiO2）（77·36%-77·41%）、低w（MgO）（0·04%-0·10%）、w（TFeO）（0·76%-1·08%）的特点,LREE/HREE比值较高（9·14-9·37）。透辉石-钾长石交代岩比原岩低w（MgO）（1·17%-2·86%）、低w（TFeO）（3·89%-7·76%）,且具有更强的Eu负异常（δEu=0·07-0·52）,LREE/HREE比值更低（3·19-7·87）。透辉石-钠长石交代岩相对原岩具有低w（MgO）（0·36%-0·92%）、高w（TFeO）（3·05%-8·13%）的特点。野马泉矿区的矽卡岩包括钙矽卡岩和锰质矽卡岩,钙矽卡岩主要产于接触带附近,组成矿物主要为单斜辉石和石榴子石,接近岩体的单斜辉石中透辉石端员组分较高,石榴石主要分布在接触带附近,内环带钙铁榴石组分高于外环带。综合矿物学、岩石地球化学结果,推断野马泉矿区闪长岩具有较大成矿潜力,野马泉矿区钙矽卡岩主要形成于氧化条件,锰质矽卡岩形成于还原条件。

The Yemaquan Fe-Zn polymetallic deposit is located at the junction belt between Chaidamu basin and Qimantag area,Qinghai.There are some Hercynian and Indosinian intrusive rocks exposed in the ore district.The strata in the ore district are mainly Sijiaoyanggou Group.The skarn mainly occurs within the carbonate rocks and igneous conversion boundaries.The skarn minerals are mainly garnet,clinopyroxene,vesuvianite and epidote.Metallic minerals mainly include magnetite,chalcopyrite,galena,sphalerite and pyrrhotite.Based on the detailed field geological investigation and the observation of geological sections and drill cores,the authors studied the petrogeochemical characteristics and mineralization of this deposit.The petrochemistry of diorite is characterized by low SiO2（51.90%~59.03%）,high MgO（2.04%~3.44%） and TFeO（11.39%~11.67%）,rich REE（318.57×10-6~327.76×10-6）,and low LREE/HREE ratios（7.36~7.48）.The monzonitic granite is characterized by high SiO2（77.36%~77.41%）,low MgO（0.04%~0.10%）,low TFeO（0.76%~1.08%）,and high LREE/HREE ratios（9.14~9.37）.The diopside-alkali metasomatites show stronger δEu negative anomaly（δEu=0.07~0.52） and lower LREE/HREE ratios（3.19~7.87）than its original rock.The diopside-sodic metasomatites have low MgO（0.36%~0.92%）,high TFeO（3.05%~8.13%） than its original rock.The skarn from Yemaquan deposit can be further divided into two types：calcic skarn and magnesian skarn.The calcic skarn is mainly distributed in the contact zone and consists of garnet and clinopyroxene.The clinopyroxenes distributed near the intrusion have high content of diposide end-member,and the garnet has more andradite end-members at the edge.According to the mineral composition and mineral intergrowth association,the authors have inferred that the diorite possesses remarkable mineralization potentiality,and calcic skarn was formed at an oxidation stage,whereas the magnesian skarn was formed in a reduction state.