内蒙古北山地区小狐狸山钼矿辉钼矿Re-Os年龄和LA-ICP-MS锆石U-Pb年龄
Rock-forming and ore-forming ages of the Xiaohulishan molybdenum deposit in Beishan area, Inner Mongolia
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摘要: 小狐狸山钼矿是内蒙古北山地区近年来新发现的一个中型规模的斑岩型矿床。通过对成矿斑岩锆石和成矿晚阶段石英脉型钼矿的同位素研究，获得小狐狸山含矿花岗岩锆石LA-ICP-MS U-Pb年龄216.9Ma±0.5Ma（MSWD=0.41），与斑岩型钼矿化的时间220Ma±2.2Ma在误差范围内基本一致，为该矿床主要为一个斑岩型钼矿床提供了同位素年代学的佐证；晚成矿阶段辉钼矿单矿物Re-Os模式年龄加权平均值为213.2Ma±4.6Ma(MSWD=1.3)。小狐狸山钼矿床成矿岩体的展布受控于沿黑河展布的北东东向构造，该组构造切割了早期形成的北西向区域构造，暗示216~220Ma为北山地区由后碰撞进入板内伸展环境提供了初步的年龄约束，北山地区印支期的成矿作用值得重视。Abstract: The Xiaohulishan molybdenum deposit is a medium-size concealed porphyry molybdenum deposit recently discovered in Beishan area, Inner Mongolia. The authors studied isotopes of the ore-bearing porphyries and the quartz vein type molybdenum deposit in late mineralization stage, and obtained the zircon LA-ICP-MS U-Pb age of 216.9Ma±0.5Ma（MSWD=0.41）for Xiaohulishan porphyry granite, which is close to the Re-Os model age of 213.2Ma±4.6Ma (MSWD=1.3) for molybdenite, thus providing isotope age evidence for porphyry genesis of the Xiaohulishan molybdenum deposit. The molybdenite Re-Os isotope age in late metallogenic stage is 213.2Ma±4.6Ma(MSWD=1.3). The ore-forming porphyry of the Xiaohulishan Mo deposit was distributed along the Heihe River which was controlled by NEE-trending faults that cut the early NW-trending regional structure, implying that 216-220Ma was the age restriction for the evolution of the post-collision stage to the intraplate extension stage in Beishan area. Importance should be attached to mineralization in Indosinian period in Beishan area.
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