新疆阿尔泰凯勒克赛依铁矿地质特征、锆石LA-MC-ICP-MS U-Pb年龄及其意义

摘要

凯勒克赛依铁矿床是新疆阿尔泰唯一的小型镜铁矿床,赋存于一套变质火山-沉积岩系中,近矿围岩为白云母石英片岩,矿体呈层状,与地层产状一致,矿石具有块状、条带状、条纹状构造,矿石中金属矿物主要为镜铁矿(TFeO=87.349％ ～88.988％,TiO2=0 ～1.042％,Al2O3 =0.036％ ～0.256％),矿化具有沉积特征.近矿围岩镜铁矿白云母石英片岩锆石LA-MC-ICP-MS U-Pb谐和年龄为(375.6±0.6)Ma,限定成矿时代在376 Ma左右,即中泥盆世成矿,是阿尔泰为数不多的中泥盆世成矿作用的产物.同时也厘定含矿的变质火山-沉积岩系属中—晚泥盆世阿勒泰镇组,不是前人认为的早泥盆世康布铁堡组.%Kailekesaiyi iron deposit,the unique small specularite deposit in Alaay,Xinjiang,occurs in a sequence of metamorphic volcanic-sedimentary rocks.The wall-rock is muscovite quartz schist,and the orebodies are stratiform and in accordance with the stratigraphic occurrence.The ores occur as massive,banded,and striped structures.Ore minerals are dominated by specularite (TFeO =87.349％-88.988％,TiO2 =0-1.042％,Al2O3 =0.036％-0.256％) with sedimentary characteristics.Zircons from the specularite muscovite-quartz schist yield a LA-MC-ICP-MS U-Pb concordant age of (375.6 ⑾ 0.6) Ma,and constrained the ore forming age to the Middle Devonian (ca.376 Ma),suggesting that this deposit is one product of the few Middle Devonian mineralization in Altay.Meanwhile,the ore-bearing metamorphic volcanic-sedimentary rocks are dated to the Middle-Late Devonian Altay Formation,rather than the Early Devonian Kangbutiebao Formation which is considered by the previous scholars.