小兴安岭北麓高松山金矿床赋矿围岩锆石U-Pb年代学、地球化学、岩石成因及其地质意义

在矿床地质特征研究的基础上,对高松山金矿床赋矿围岩中代表性的粗安岩进行了锆石U-Pb同位素年龄测定和元素地球化学成分分析;实验结果揭示:(1)获得6组单颗粒锆石年龄,第一组为2 422~2 683 Ma,为残留锆石年龄;第二、三、四和五组分别为606~943 Ma、428~437 Ma、281~303 Ma和169~221 Ma,为捕获锆石年龄;第六组为121~129 Ma,代表火山作用过程形成的锆石年龄;(2)主量元素地球化学特征揭示该套火山岩为高钾钙碱性-钾玄岩系列岩石;(3)微量元素和REE指示岩石明显富集Rb、Ba、K等大离子亲石元素(LILE)和轻稀土元素(LREE),亏损Nb、Ta和Ti等高场强元素(HFSE)和重稀土元素(HREE)。结合相关成果,初步厘定该区可能存在古元古代—新太古代结晶基底或碎屑物,该期火山作用在古太平洋板块俯冲引发的岩石圈伸展和减薄环境下富集地幔部分熔融、岩浆上侵、喷发作用形成,岩浆在上升演化过程中受到早侏罗世中酸性侵入岩的混染,该次岩浆活动与东北地区早白垩世早期大规模火山喷发岩浆事件相吻合。

Zircon U-Pb geochronology,geochemistry,petrogenesis and geological implications of host rocks of Gaosongshan gold deposit in northern Lesser Xing'an Range

Based on the study of geological characteristics of the deposit,the authors undertook zircon U-Pb dating and geochemical analysis of the representative trachyandesites in the host rock of the deposit,the results reveal:(1) six groups of single grained zircon U-Pb ages were obtained,of which ① is 2 422~2 683 Ma, for residual zircon ages, whereas ② to ⑤ are 606~943 Ma, 428~437 Ma, 281~303 Ma and 169~221 Ma, respectively, for captured zircon ages. The zircon age of ⑥ is 121~129 Ma, representing the formation of zircon in the processes of volcanism;(2) geochemical characteristics of major elements reveal that these volcanic rocks belong to high-potassium calc-alkaline series to shoshonite series;(3) trace elements and REE indicate that the rocks are characterized by enrichment of large ion-lithophile elements (LILE)(Rb,Ba,K, etc.) and light rare earth elements (LREE), but depletion of the HFSE elements (Nb,Ta,Ti, etc.) and heavy rare earth elements (HREE). Integrating all the relevant results,it is preliminary believed that there may exist a Paleoproterozoic-Neoarchaean basement or debris in the study area. The volcanism of this period was related to the partial melting of enriched mantle,magma intrusion and eruption in the tectonic background of lithospheric extension and thinning due to the subduction of the paleo Pacific Plate. The magma was contaminated by Early Jurassic intermediate-acidic intrusive rocks during the evolution process of rising. This magmatic activity is coincided with Early Cretaceous large-scale volcanic and magmatic events of Northeast China.