發(fā)布時(shí)間：2018-06-18 04:03

  本文選題：Hf同位素 + 鋯石U-Pb定年�。� 參考：《地球科學(xué)》2017年12期

【摘要】：延邊地區(qū)官地鐵礦床地處華北克拉通北緣與興蒙造山帶東段接合帶附近的和龍地塊北部,是東北地區(qū)發(fā)現(xiàn)和開發(fā)較早的典型BIF型鐵礦床之一.該礦床的主礦體呈層狀、似層狀、透鏡狀賦存于鞍山群甲山組上段.為確定該礦床的形成與變質(zhì)時(shí)代以及構(gòu)造背景,重點(diǎn)對含礦巖系中的斜長片麻巖、角閃斜長片麻巖和斜長角閃巖進(jìn)行巖石地球化學(xué)、鋯石U-Pb年代學(xué)以及Hf同位素研究.原巖恢復(fù)表明,斜長片麻巖的原巖為流紋英安質(zhì)-英安質(zhì)火山碎屑巖,角閃斜長片麻巖的原巖為安山巖,斜長角閃巖的原巖為玄武巖.LA-ICP-MS鋯石U-Pb年代學(xué)研究發(fā)現(xiàn),官地地區(qū)在新太古代末-古元古代初期發(fā)生了巖漿作用(2 508~2 483Ma)和變質(zhì)事件(2 472~2 459Ma),且該期巖漿-變質(zhì)事件與鐵礦的形成有著密切的聯(lián)系.斜長角閃巖的原巖-玄武巖形成于弧后盆地環(huán)境,反映了官地鐵礦形成時(shí)的構(gòu)造環(huán)境;角閃斜長片麻巖中鋯石的εHf(t)值介于-5.0~+4.2,二階段Hf模式年齡(tDM2)為3 182~2 889Ma,表明巖漿源區(qū)以中太古代古老地殼物質(zhì)的熔融為主.通過與國內(nèi)外典型BIF型鐵礦床的對比研究認(rèn)為,官地鐵礦屬Algoma型BIF,與新太古代晚期華北克拉通大規(guī)模BIF成礦事件密切相關(guān);官地地區(qū)在新太古代初期(2.8~2.7Ga)可能存在地殼增生事件;和龍地塊親華北克拉通的構(gòu)造屬性,為索倫-西拉木倫-長春縫合帶的東延問題研究提供了新的證據(jù).
[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.
【作者單位】： 吉林大學(xué)地球科學(xué)學(xué)院;中國地質(zhì)調(diào)查局沈陽地質(zhì)調(diào)查中心;武警黃金部隊(duì)第三支隊(duì);吉林省有色金屬地質(zhì)勘查局603隊(duì);
【基金】：國家重點(diǎn)基礎(chǔ)研究發(fā)展計(jì)劃973課題(No.2013CB429802) 吉黑東部地區(qū)資源遠(yuǎn)景調(diào)查評價(jià)(No.12120113098300)
【分類號】：P59;P618.31

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