滇中楚雄盆地老街子铅-银矿床镜铁矿特征及地质意义  

Signature and geological significance of the specularite from the Laojiezi Pb-Ag deposit in the Chuxiong basin,central Yunnan,SW China

作　　者：吴鹏[1] 杨航 韩润生[1] 姜龙燕 江小均[1] 王蝶[1] 管申进 WU Peng;YANG Hang;HAN RunSheng;JIANG LongYan;JIANG Xiaojun;WANG Die;GUAN Shenjin(Faculty of Land Resource Engineering,Kunming University of Science and Technology,Kunming,650093,China)

机构地区：[1]昆明理工大学国土资源工程学院,昆明650093

出　　处：《岩石学报》2019年第5期1489-1502,共14页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2015CB452600);国家自然科学基金项目(41102049);国家重点研发计划项目(SQ2018YFC06017102);云南省矿产资源预测评价工程实验室(2010);云南省地质过程与矿产资源创新团队(2012)联合资助

摘　　要：滇中老街子铅-银矿床位于楚雄盆地中部,金沙江-哀牢山富碱侵入岩带南段,是与富碱火山-岩浆热液密切相关的典型矿床。近年来,矿床深部(2073m中段)新揭露出铁氧化物,显微镜下呈亮白色、蓝灰色,针状、放射状、板状构造。通过X射线微区衍射及电子探针分析,确认其为镜铁矿,产出方式有两种:①呈密集星点状,平行岩脉具定向排列,充填于灰紫色黑云母正长斑岩脉长石溶蚀孔洞中;②呈斑点状,分布于岩脉东侧肉红色正长斑岩中,沿岩石裂隙矿化增强。岩脉两侧金属矿物组合差异(方铅矿+黄铁矿+铜氧化物→黄铁矿+铜氧化物+镜铁矿)及正长斑岩颜色差异(灰白→肉红色),与岩脉的侵位密切相关,是构造-岩浆(流体)-蚀变耦合作用的结果。与白马苴金(铜)矿床中镜铁矿对比研究,认为老街子矿床深部镜铁矿对金矿化具有找矿指示意义。相对于星点状、斑点状镜铁矿,呈脉状、网脉状及岩脉内镜铁矿的V2O5、Ti O2含量更高,指示老街子矿床2073m以深可能存在更具规模的脉状镜铁矿。镜铁矿出露位置Cu含量显著增高,局部超过工业品位,达2. 05%,并出现Mo异常(最高含量达0. 11%)、Au异常(最高含量达0. 585g/t),呈现出浅部Pb-Ag矿化和深部Cu-Mo-Au矿化的结构特征,指示深部有斑岩型铜、钼、金的找矿潜力。The Laojiezi Pb-Ag deposit,located in the Chuxiong basin,southern section of the Jinshajiang-Ailaoshan alkali-rich intrusive belt of central Yunnan Province,is a typical alkali-rich volcanic-magmatic hydrothermal deposit.In recent years,iron oxide was found at greater depths of the deposit(2073 m level).Under the microscope,iron oxide is bright white or gray-blue in color,and acicular,radial and tabular in shape.It was identified as specularite by the X-ray diffraction analysis and electron microprobe analysis.Two types of specularite have been recognized according to their occurrences:(i) One type occurs as densely star-shaped filling in the corrosion holes of the feldspar in the gray purple biotite syenite porphyry dike,and they are characterized by directional arrangement and parallel with the dike;(ii) Another type occurs as speckled in the flesh red syenite porphyry with highly mineralization along fractures.The difference in metallic mineral assemblages at the two sides of the biotite syenite porphyry dike(galena + pyrite + copper oxide→pyrite + copper oxide + specularite),and the color difference(gray→fleshy red) in the syenite porphyry are closely related to the dike intrusion,and were probably resulted from tectono-magmatic(fluid)-alteration coupling.Based on the comparative study of Baimaju Au(Cu) deposit with specularite,we suggested that the specularite in the deeper part of the Laojiezi deposit has important implications on Au exploration.Compared to the disseminated specularite,the specularite in veins/stockworks/dike contain higher V2 O5 and Ti O2 contents,suggesting that larger specularite ores may exist at > 2073 m depth.Where the specularite occurs,Cu contents increase significantly(locally over the industrial grade and up to 2.05%),Mo(up to 0.11%) and Au anomalies(up to 0.585 g/t)also are present.Metal zonation from Pb-Ag to Cu-Mo-Au at depth is also found,which indicates exploration potential for porphyry-type Cu-Mo-Au deposits.

关 键 词：镜铁矿 找矿指示意义 富碱斑岩 老街子铅-银矿床 楚雄盆地 

分 类 号：P578.497[天文地球—矿物学]