鲁西韩旺BIF铁矿的形成时代——锆石SHRIMPU-Pb定年证据  

Formation Age of the Hanwang BIF Deposit in Western Shandong:Evidence from Zircon SHRIMP U-Pb Dating

作　　者：王宇晴 单吉成 董春艳[2] 王世进[4] 董津蒙 颉颃强[2] 万渝生[2] WANG Yuqing;SHAN Jicheng;DONG Chunyan;WANG Shijin;DONG Jinmeng;XIE Hangqiang;WAN Yusheng(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083;Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037;Natural Resources Bureau of Yiyuan County,Zibo,Shandong 256100;Shandong Institute of Geological Survey,Jinan,Shandong 250013;5514 Brigade of North China Geological Exploration Bureau,Chengde,Hebei 067040)

机构地区：[1]中国地质大学(北京),地球科学与资源学院,北京100083 [2]中国地质科学院地质研究所,北京离子探针中心,北京100037 [3]山东省沂源县自然资源局,山东淄博256100 [4]山东省地质调查院,山东济南250013 [5]华北地质勘查局五一四地质大队,河北承德067040

出　　处：《地球学报》2024年第6期903-912,共10页Acta Geoscientica Sinica

基　　金：国家自然科学联合基金项目(编号:U2344210);国家自然科学重点基金项目(编号:42130311);国家自然科学基金项目(编号:41872200);中国地质调查局地质调查项目(编号:DD20221645)。

摘　　要：鲁西地区太古宙表壳岩包括新太古代早期和晚期两期表壳岩,早期表壳岩主要由变质玄武岩-科马提岩组成,晚期表壳岩主要由变质火山岩-碎屑沉积岩和BIF(Banded Iron Formations)组成。韩旺铁矿位于鲁西的西北部,铁矿区内存在大量变质玄武岩-科马提岩,早期认为该BIF形成于新太古代早期,而新的研究认为鲁西地区BIF都形成于新太古代晚期。本文对韩旺铁矿区内与BIF互层的黑云变粒岩和侵入其中的片麻状花岗闪长岩开展锆石SHRIMP U-Pb定年,获得年龄分别为(2529±7)Ma和(2534±11)Ma。黑云变粒岩和片麻状花岗闪长岩的TREE、(La/Yb)N、Eu/Eu*分别为76×10^(–6)、19.8、0.84和82.7×10^(–6)、17.3、1.14,它们的岩浆锆石的εHf值、单阶段Hf同位素模式年龄分别为5.5~9.46、2.5~2.6 Ga和6.3~9.4、2.48~2.60 Ga。研究支持了鲁西地区BIF形成于新太古代晚期的认识。表壳岩形成、变质变形和花岗闪长岩侵入发生在一个很短的时间范围内。研究还表明,黑云变粒岩的原岩为英安质火山岩,很可能形成于新生玄武质岩浆的强烈结晶分异作用,花岗闪长岩形成于新生玄武质岩石部分熔融,形成过程中有陆壳物质的加入。Archean supracrustal rocks in western Shandong include two stages of supracrustal rocks during the Early Neoarchean and the Late Neoarchean.Early supracrustal rocks are mainly composed of metamorphic basalt-Komatiite,whereas late supracrustal rocks are mainly composed of metamorphic volcanic rocks-clastic sedimentary rocks and BIF(Banded Iron Formations).The Hanwang iron deposit is located in the northwest of western Shandong.There are a large quantities of meta-basalt-Komatiite in the iron ore area.It is believed that the BIF was formed during the Early Neoarchean,but a recent study suggests that the BIF in western Shandong area was formed during the Late Neoarchean.In this study,the zircon SHRIMP U-Pb dating of the biotite granulite interbedded with BIF and the gneissic granodiorite intruded in the Hanwang iron ore area was carried out,and the ages were(2529±7)Ma and(2534±11)Ma,respectively.The TREE,(La/Yb)N,and Eu/Eu*of biotite granulite and gneissic granodiorite are 76×10^(–6),19.8,and 0.84 and 82.7×10^(–6),17.3,and 1.14,respectively.TheεHf values and single-stage Hf isotopic model ages of their magmatic zircons are 5.5–9.46 Ga and 2.5–2.6 Ga,and 6.3–9.4 Ga and 2.48–2.60 Ga,respectively.This study supports the recognition that BIF in western Shandong was formed during the Late Neoarchean.The formation of supracrustal rocks,metamorphic deformation,and granodiorite intrusion occurred in a very short-time range.The study also shows that the protolith of the biotite granulite is dacitic volcanic rock,which was likely to be formed by the strong crystallization differentiation of the newborn basaltic magma.The granodiorite was formed by the partial melting of the newborn basaltic rock,and the continental crust material was added during the formation process.

关 键 词：BIF 韩旺铁矿 鲁西 太古宙 锆石SHRIMP U-Pb定年 

分 类 号：P618.31[天文地球—矿床学] P597.3[天文地球—地质学]