The ore-bearing pluton in the Suonaga Pb-Zn-Ag deposit is composed of medium-coarse-grained granite,fine-grained biotite granite and pseudoporphyritic K-feldspar granite.The zircon U-Pb dating results show that the medium-coarse-grained granite was formed at 319.6±4.1 Ma,the fine-grained biotite granite was formed at 172.5 ±1.4 Ma,and the pseudoporphyritic K-feldspar granite was formed at 165.5 ±1.8 Ma.The petrogeochemistry of the three rock bodies is characterized by high K,rich alkali and poor magnesium,so they all belong to calcium-basic,quasi-aluminous to weakly peraluminous and highly-differentiated rocks.All of the granites have high REE and negative Eu anomalies,exhibiting relative enrichment of LREE.These rock bodies belong to S-type granites,because they are enriched in U and Th and their Rb/Sr ratios are higher than those of the crustal source.Regional geology and granite geochemistry indicate that the medium-coarse-gained granite was formed in a post-collisional extensional environment in Late Carboniferous； the Middle Jurassic fine-grained biotite granite and pseudoporphyritic K-feldspar granite were formed in an intraplate extensional environment,and they were products of different evolutionary stages of a comagmatic region.The pseudoporphyritic Kfeldspar granite was probably the ore-forming parent rock,because its diagenetic age is consistent with the molybdenite Re-Os ages (163.4±2.4Ma to 166.6±2.4Ma) and the rocks are enriched in metallogenic elements Pb and Zn.%内蒙古东乌旗索纳嘎铅锌银矿区赋矿侵入岩为一由中粗粒花岗岩、细粒黑云母花岗岩和似斑状钾长花岗岩组成的杂岩体.三种岩石的锆石U-Pb同位素年龄依次为(319.6±4.1)Ma、(172.5±1.4)Ma和(165.5±1.8)Ma.三者均以高钾、富碱、贫镁为特征,均属钙碱性、准铝质-弱过铝质岩石,分异程度较高.岩石稀土总量较高,轻稀土相对富集,均具负铕异常；均富集U、Th,Rb/Sr值大于壳源Rb/Sr值,应属S型花岗岩.根据花岗岩地球化学和区域地质特征分析认为,中粗粒花岗岩形成于晚石炭世后碰撞伸展构造环境；中侏罗世细粒黑云母花岗岩和似斑状钾长花岗岩产于板内伸展构造环境,为同源岩浆演化不同阶段的产物.似斑状钾长花岗岩富含成矿元素Pb和Zn,而且其成岩年龄与辉钼矿(163.4±2.4) Ma～(166.6±2.4) Ma的Re-Os同位素年龄基本一致,可能为成矿母岩.
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