黑龙江三道湾子金矿区龙江组安山岩的年代学与地球化学

发布时间：2018-03-07 10:15

本文选题：安山岩　切入点：U-Pb年代学　出处：《岩石学报》2017年08期 　论文类型：期刊论文

【摘要】：三道湾子金矿是我国东北地区重要的浅成低温热液金矿之一,金矿赋存在龙江组安山岩和安山质火山角砾岩中。本文对三道湾子金矿赋矿围岩进行了锆石U-Pb年代学和Hf同位素、岩石元素和Sr-Nd同位素地球化学研究。LA-ICP-MS锆石U-Pb测年获得龙江组安山岩加权平均年龄为121.4±1.8Ma,表明其喷出时代为早白垩世。在地球化学组成上,龙江组火山岩具有明显的轻重稀土分馏和弱Eu负异常,微量元素富集Rb、Ba、Th、U等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE),岩石与岛弧安山岩地球化学特征相似。龙江组安山岩具有低的Sr初始比值[(87Sr/86Sr)i=0.704798~0.704919]和正的εNd(t)(0.7~1.8),说明岩浆源区具有弱亏损地幔的特征。三道湾子金矿区的龙江组安山岩可能形成于早白垩世岩石圈大规模伸展减薄的动力学背景下,由于伊泽奈崎板块运动方向的改变致使整个东北地区处于伸展构造背景中,软流圈上涌的同时下地壳与岩石圈地幔发生部分熔融,导致整个东北地区广泛发育晚中生代岩浆作用,构成了三道湾子金矿的赋矿围岩。
[Abstract]:Sandaowanzi gold deposit is one of the most important epithermal gold deposits in northeast China. The gold deposit occurs in the andesite of Longjiang formation and the Anshanian volcanic breccia. The zircon U-Pb geochronology and HF isotope of the surrounding rock of Sandaowanzi gold deposit are studied in this paper. LA-ICP-MS zircon U-Pb dating obtained a weighted mean age of 121.4 卤1.8 Ma for the Longjiang formation andesite, indicating that its ejection age was early Cretaceous. The volcanic rocks of Longjiang formation have obvious fractionation of light and light rare earth elements and negative anomalies of weak EU. The trace elements are rich in large ion lithophile elements, such as RbBX, Baer, Th, U and so on, and depleted in high field strength elements such as NbLi Tahti. The geochemical characteristics of the rocks are similar to those of the island-arc andesite. The low initial Sr ratio of the andesite in the Longjiang formation [Li 87Sr86 / S] 0.704798 0.704919 and the positive 蔚 ND ~ (2 +) T _ (0. 7) ~ 1. 8 ~ (-1) indicate that the magmatic source area is characterized by a magmatic source region with a low Sr initial ratio of 0.704798 0.704919. The andesite of Longjiang formation in Sandaowanzi gold mining area may have been formed under the dynamic background of large-scale extension and thinning of early Cretaceous lithosphere. As a result of the change in the direction of the Isenazaki plate movement, the whole northeast area is in the extensional tectonic setting, and the lower crust and lithospheric mantle are partially melted along with the upwelling of the asthenosphere. The late Mesozoic magmatism formed the host rock of Sandaowanzi gold deposit.
【作者单位】：地质过程与矿产资源国家重点实验室中国地质大学地球科学与资源学院;黑龙江省地质调查研究总院齐齐哈尔分院;
【基金】：中国地质调查局项目(12120114028101、12120114051201) 国家国际科技合作专项(2011DFA22460)联合资助
【分类号】：P588.144;P618.51

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