地球学报
地毬學報
지구학보
Acta Geoscientia Sinica
2015年
5期
599-612
,共14页
杜利林%杨崇辉%路增龙%赵磊%耿元生%曹光跃%第五春荣%郭春丽%侯可军
杜利林%楊崇輝%路增龍%趙磊%耿元生%曹光躍%第五春榮%郭春麗%侯可軍
두리림%양숭휘%로증룡%조뢰%경원생%조광약%제오춘영%곽춘려%후가군
五台山%蒋村%滹沱群%石英斑岩%锆石U-Pb年龄
五檯山%蔣村%滹沱群%石英斑巖%鋯石U-Pb年齡
오태산%장촌%호타군%석영반암%고석U-Pb년령
Wutai Mountain%Jiangcun%Hutuo Group%quartz porphyry%zircon U-Pb ages
滹沱群是华北最典型的古元古界地层之一,限定其时代对建立早期地层年代格架和探讨华北早前寒武纪地质演化过程意义重大。本文对五台山地区蒋村镇附近的滹沱群地层进行了详细研究,从与蒋村砾岩中石英斑岩砾石相同的基岩中选取了2件石英斑岩样品,并获得其锆石 U-Pb 年龄结果分别为(2166±17) Ma和(2138±17) Ma。据此,限定蒋村地区碎屑沉积岩时代应小于2138 Ma。结合四集庄组底部发育厚层的砾岩和区域内2.2~2.1 Ga岩浆事件,我们进一步认为滹沱群底界年龄为~2.2 Ga。由于滹沱群豆村亚群和东冶亚群经历了同期褶皱变形作用,而侵入于蒋村四集庄组未变形正长花岗岩脉的锆石 U-Pb 年龄结果为(1816±18) Ma。因此,本文限定豆村亚群、东冶亚群的时代为2.2~1.82 Ga。石英斑岩中锆石Lu-Hf同位素分析结果为176Lu/177Hf 为0.000717~0.002239,176Hf/177Hf 为0.281399~0.281563,其176Hf/177Hfi为0.281315~0.281496和εHf(t)为–3.37~4.11,变化范围较大,初步认为其源自于新太古代早期上地壳的部分熔融并有地幔物质添加。
滹沱群是華北最典型的古元古界地層之一,限定其時代對建立早期地層年代格架和探討華北早前寒武紀地質縯化過程意義重大。本文對五檯山地區蔣村鎮附近的滹沱群地層進行瞭詳細研究,從與蔣村礫巖中石英斑巖礫石相同的基巖中選取瞭2件石英斑巖樣品,併穫得其鋯石 U-Pb 年齡結果分彆為(2166±17) Ma和(2138±17) Ma。據此,限定蔣村地區碎屑沉積巖時代應小于2138 Ma。結閤四集莊組底部髮育厚層的礫巖和區域內2.2~2.1 Ga巖漿事件,我們進一步認為滹沱群底界年齡為~2.2 Ga。由于滹沱群豆村亞群和東冶亞群經歷瞭同期褶皺變形作用,而侵入于蔣村四集莊組未變形正長花崗巖脈的鋯石 U-Pb 年齡結果為(1816±18) Ma。因此,本文限定豆村亞群、東冶亞群的時代為2.2~1.82 Ga。石英斑巖中鋯石Lu-Hf同位素分析結果為176Lu/177Hf 為0.000717~0.002239,176Hf/177Hf 為0.281399~0.281563,其176Hf/177Hfi為0.281315~0.281496和εHf(t)為–3.37~4.11,變化範圍較大,初步認為其源自于新太古代早期上地殼的部分鎔融併有地幔物質添加。
호타군시화북최전형적고원고계지층지일,한정기시대대건립조기지층년대격가화탐토화북조전한무기지질연화과정의의중대。본문대오태산지구장촌진부근적호타군지층진행료상세연구,종여장촌력암중석영반암력석상동적기암중선취료2건석영반암양품,병획득기고석 U-Pb 년령결과분별위(2166±17) Ma화(2138±17) Ma。거차,한정장촌지구쇄설침적암시대응소우2138 Ma。결합사집장조저부발육후층적력암화구역내2.2~2.1 Ga암장사건,아문진일보인위호타군저계년령위~2.2 Ga。유우호타군두촌아군화동야아군경력료동기습추변형작용,이침입우장촌사집장조미변형정장화강암맥적고석 U-Pb 년령결과위(1816±18) Ma。인차,본문한정두촌아군、동야아군적시대위2.2~1.82 Ga。석영반암중고석Lu-Hf동위소분석결과위176Lu/177Hf 위0.000717~0.002239,176Hf/177Hf 위0.281399~0.281563,기176Hf/177Hfi위0.281315~0.281496화εHf(t)위–3.37~4.11,변화범위교대,초보인위기원자우신태고대조기상지각적부분용융병유지만물질첨가。
The Hutuo Group is one of the classic Paleoproterozoic strata in North China, and its age is important for building the stratigraphy framework and investigating the early Precambrian evolution process in the North China Craton. In this paper, we probed into the stratigraphy of Hutuo Group at Jiangcun, Wutai Mountains area, and obtained the zircon U-Pb ages of (2166±17) Ma and (2138±17) Ma from two quartz porphyries, which are identical with the ages of quartz porphyry pebbles in conglomerates of the Hutuo Group. Therefore, we infer that the clastic rocks in Jiangcun were deposited after 2138 Ma. Considering the distribution of a large amount of conglomerates at the base of Sijizhuang Formation and the existence of 2.2~2.1 Ga magmatism in Wutai Mountains area, we further deduce that the initial deposition of Hutuo Group took place at ca. 2.2 Ga. In combination with the fact that Doucun and Dongye Subgroups underwent the similar deformation, and undeformed syenogranite vein of 1816±18Ma intruded into the Sijizhuang Formation, we hold that the deposition age of Doucun and Dongye Subgroup should be 2.2~1.82 Ga. A sample of quartz porphyry yielded the zircon 176Lu/177Hf of 0.000717~0.002239 and176Hf/177Hf of 0.281399~0.281563. Based on the large variation of 176Hf/177Hfi andεHf(t) in zircons, we propose that the quartz porphyry mainly originated from the upper crust with the addition of the depleted mantle.