大南澳片岩鋯石的鈾鉛定年研究

U-Pb Dating of Detrital Zircons From The Tananao Metamorphic Complex

鄧嘉翔(Deng,Shawn)

指導教授 ： 李元希

國立中正大學/理學院/地球與環境科學系地震研究所/碩士(2013年)

摘要

本研究區域主要為台灣大南澳片岩，大南澳片岩由西部太魯閣帶及東部玉里帶組成，歷經中生代變質作用與蓬萊造山運動，由於變質程度高且化石難以保存，因此對其沉積年代難以決定，此外對玉里帶與太魯閣帶沉積物來源亦多有爭議，本研究分析太魯閣帶與玉里帶的碎屑鋯石的U-Pb定年，探討兩變質帶在鈾鉛定年上的對比，可能沉積年代與變質年代。鋯石鈾鉛定年結果顯示太魯閣帶可年輕至65Ma，以碎屑鋯石鈾鉛定年的年代分布來看，太魯閣帶鋯石鈾鉛年齡集中於中生代以100-250Ma為主，而玉里帶中除中生代100-250Ma亦包含古元古代1600-2500Ma年代。此外在玉里帶中數個樣本中皆包含少數新生代鋯石，顯示玉里帶其沉積年代應為新生代，玉里帶的年代分布譜與中新世地層近似，顯示玉里帶年代可能為中新世地層。此外上覆的崙山層最年輕年代為10Ma，顯示崙山層沉積年代需年輕於10Ma。由鋯石年代譜與華南地區構造事件相對比與岩層鋯石U-Pb年代對比，太魯閣帶與玉里帶的沉積物來源應皆來自華南地區。

關鍵字

大南澳 ； 鋯石 ； 定年

並列摘要

This study area is the Tananao metamorphic complex of Taiwan, the Tananao metamorphic complex is consists of the western Tailuko belt and the eastern Yuli belt. Cause Fossils are extremely rare, making it difficult to firmly establish the architecture and geologic history of this metamorphic complex, this study analyses U-Pb dating of detrital zircons from the Tailuko belt and the Yuli belt,to test the correlation of two belt ,probably sediment time and metamorphic time.Results of the this study show that the Tailuko belt probably younger than 65 Ma, Tailuko belt contain mainly 100Ma-250Ma Mesozoic detrital zircons, Yuli belt not only contain Mesozoic detrital zircons,but also 1600Ma-2500Ma Paleoproterozoic detrital zircons. The spotlight of this study is that some sample in Yuli belt contain Cenozoic detrital zircon,showing that the formation age of Yuli belt may be younger than(or close to) Cenozoic, Detrital zircon age distribution patterns of Yuli belt is similar to Miocene Formation,showing that Yuli belt may be Miocene Formation. furthermore the 10Ma zircon in Lunshan Formation,showing that the Lunshan Formation have to younger than 10 Ma. Using comparison of Detrital zircon age distribution patterns and Cathaysian Block movement event , Tailuko belt and Yuli belt terrigenous sediments were mainly sourced from western Cathaysia.

並列關鍵字

zircon ； Tananao ； U-Pb Dating

參考文獻

李瑞清(2011)福建西南地區古生代至中生代地層的碎屑鋯石鈾鉛年代。國立台

Chen,C.H.（1979）Geology of the east-west corss-island highway in central Taiwan：Mem.Geol.Soc.China,3,219-236.

蔡宛玲(2012)台灣新生代鋯石鈾鉛年齡及其地層時代的意義。國立中正大學應用

Anderson,T.(2002).Correction of common lead in U-Pb analyses that do not Report 204Pb.Chem.Geology,192,59-79.

Hsü,K.J., Chen,H., Wang.Q.Sun,S. and Sengor,A.M.C.（1990）Tectonics of South China：Key to understanding West Pacific geology：Tectonophysics,183,9-39.