延边官地铁矿构造背景与和龙地块太古宙地壳增生:来自岩石地球化学、锆石U-Pb年代学及Hf同位素证据

发布时间：2018-06-18 04:03

本文选题：Hf同位素 + 锆石U-Pb定年　；参考：《地球科学》2017年12期

【摘要】：延边地区官地铁矿床地处华北克拉通北缘与兴蒙造山带东段接合带附近的和龙地块北部,是东北地区发现和开发较早的典型BIF型铁矿床之一.该矿床的主矿体呈层状、似层状、透镜状赋存于鞍山群甲山组上段.为确定该矿床的形成与变质时代以及构造背景,重点对含矿岩系中的斜长片麻岩、角闪斜长片麻岩和斜长角闪岩进行岩石地球化学、锆石U-Pb年代学以及Hf同位素研究.原岩恢复表明,斜长片麻岩的原岩为流纹英安质-英安质火山碎屑岩,角闪斜长片麻岩的原岩为安山岩,斜长角闪岩的原岩为玄武岩.LA-ICP-MS锆石U-Pb年代学研究发现,官地地区在新太古代末-古元古代初期发生了岩浆作用(2 508~2 483Ma)和变质事件(2 472~2 459Ma),且该期岩浆-变质事件与铁矿的形成有着密切的联系.斜长角闪岩的原岩-玄武岩形成于弧后盆地环境,反映了官地铁矿形成时的构造环境;角闪斜长片麻岩中锆石的εHf(t)值介于-5.0~+4.2,二阶段Hf模式年龄(tDM2)为3 182~2 889Ma,表明岩浆源区以中太古代古老地壳物质的熔融为主.通过与国内外典型BIF型铁矿床的对比研究认为,官地铁矿属Algoma型BIF,与新太古代晚期华北克拉通大规模BIF成矿事件密切相关;官地地区在新太古代初期(2.8~2.7Ga)可能存在地壳增生事件;和龙地块亲华北克拉通的构造属性,为索伦-西拉木伦-长春缝合带的东延问题研究提供了新的证据.
[Abstract]:The Guansubway deposit in Yanbian area is located near the northern margin of the North China Craton and the northern junction belt of the Xingmeng orogenic belt. It is one of the typical BIF iron deposits discovered and developed earlier in Northeast China. The main orebody of the deposit is stratiform, laminar and lenticular in the upper segment of Jiashan formation of Anshan Group. In order to determine the formation, metamorphism and tectonic setting of the deposit, the geochemistry, zircon U-Pb dating and HF isotopic studies of the plagioclase gneiss, hornblende gneiss and amphibolite in the ore-bearing series are emphasized. The original rocks of the plagioclase gneiss are fluid-amphibole pyroclastic rock, the hornblende gneiss is andesite, and the amphibolite is basalt. LA-ICP-MS zircon U-Pb chronological study shows that the protolith of the plagioclase gneiss is composed of amphibolite and amphibolite. Magmatism occurred in Guandi area during the late NeoArchaean and early Paleoproterozoic periods, and the magmatic and metamorphic events were closely related to the formation of iron ore. The proto-basalt of amphibolite was formed in the back-arc basin environment, which reflects the tectonic environment of Guandi iron deposit. The 蔚 Hft) values of zircon in hornblende gneiss ranged from -5.0 to 4.2, and the two-stage HF model age was 3 182U 2889 Ma, indicating that the magmatic source region was dominated by the melting of the Middle Archean ancient crustal material. By comparing with the typical BIF iron deposit at home and abroad, it is concluded that Guandi iron ore belongs to Algoma type, which is closely related to the large-scale BIF mineralization event in the late NeoArchean North China Craton, and that there may be crustal accretion in Guandi area in the early NeoArchean period (2.82.7Ga). The tectonic properties of the Hulong block, which is pro-North China craton, provide new evidence for the study of the eastward extension of the Suoren-Silamulan-Changchun suture zone.
【作者单位】：吉林大学地球科学学院;中国地质调查局沈阳地质调查中心;武警黄金部队第三支队;吉林省有色金属地质勘查局603队;
【基金】：国家重点基础研究发展计划973课题(No.2013CB429802) 吉黑东部地区资源远景调查评价(No.12120113098300)
【分类号】：P59;P618.31

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