|Table of Contents|

Zircon U-Pb Dating and Hf Isotopic Composition of the Diabase Dike Swarm from Sanchazi Area, Mianlue Suture——Chronology Evidence for the Paleo-Tethys Oceanic Crust Subduction(PDF)

《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]

Issue:
2010年第01期
Page:
27-33
Research Field:
基础地质与矿产地质
Publishing date:

Info

Title:
Zircon U-Pb Dating and Hf Isotopic Composition of the Diabase Dike Swarm from Sanchazi Area, Mianlue Suture——Chronology Evidence for the Paleo-Tethys Oceanic Crust Subduction
Author(s):
LAI Shao-cong1; 2;  QIN Jiang-feng1; 2
(1.State Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, Shaanxi, China; 2.Department of Geology, Northwest University, Xi'an 710069, Shaanxi, China)
Keywords:
Zircon;  U-Pb dating;  Hf isotopic;  Mianlue ancient ocean basin;  island-arc;  Sanchazi
PACS:
P588.1
DOI:
-
Abstract:
In order to make it clear that the formation age and source region of Sanchazi island arc volcanic rocks from the Mianlue suture, Ziron U-Pb dating, Hf isotopic composition and trace element concentration on the Diabase dike swarm collected from island-arc ophiolitic mélange in Mianlue suture, south Qinling are studied. The result indicates two time periods of the zircon U-Pb ages. There are eight zirons recording the Paleozoic U-Pb ages, six of them are typical crust originated magmatic, n(206Pb)/n(238U)=264～487 Ma, w(Th)/w(U)=0.4～0.8, N(176Hf)/N(177Hf)=0.281 934～0.282 292, ε<sub>Hf(t)=-9.4～-16.4, the other two Zirons in two test points(BQG-014, BQG-021)are typical mantle originated magmatic, N(176Hf)/N(177Hf)=0.282 722～0.282 798, ε<sub>Hf(t)=4.5～6.3. There are fifteen zirons recording the Proterozoic-Archean U-Pb ages, Zircon shows distinct geochemical characteristics of mantle magmatic origination, N(207Pb)/N(206Pb)=1 713～2 559 Ma, N(176Hf)/N(177Hf)=0.281 288～0.282 263, ε<sub>Hf(t)=-1.3～8.7, and most exhibit ε<sub>Hf(t)>2. According to the zircon Hf isotopic composition, Ziron in two test points(BQG-014, BQG-021)is typical mantle originated magmatic; therefore, their forming age(264～295 Ma)indicates an important active continental margin magmatism during the Mianlue ancient ocean crust subduction process.

References:

[1] 张国伟,张本仁,袁学诚,等.秦岭造山带与大陆动力学[M].北京:科学出版社,2001.
[2] 赖绍聪,张国伟,杨永成,等.南秦岭勉县—略阳结合带蛇绿岩与岛弧火山岩地球化学及其大地构造意义[J].地球化学,1998,27(3):283-293.
[3] 赖绍聪,张国伟,杨永成,等.南秦岭勉县—略阳结合带变质火山岩岩石地球化学特征[J].岩石学报,1997,13(4):563-573.
[4] Lai S C,Zhang G W,Yang R Y.Identification of the Island-arc Magmatic Zone in the Lianghe-Raofeng-Wuliba Area,South Qinling and Its Tectonic Significance[J].Science in China D:Earth Sciences,2000,43(Supp1):69-81.
[5] Lai S C,Li S Z.Geochemistry of Volcanic Rocks from Wuliba in the Mianlue Suture Zone,Southern Qinling[J].Scientia Geologica Sinica,1999,10(3):169-179.
[6] 许继锋,于学元,李献华,等.高度亏损的N-MORB型火山岩的发现:勉略古洋盆存在的新证据[J].科学通报,1997,42(22):2414-2418.
[7] 李曙光,孙卫东,张国伟,等.南秦岭勉略构造带黑沟峡变质火山岩的年代学和地球化学——古生代洋盆及其闭合时代的证据[J].中国科学(D辑),1996,26(3):223-230.
[8] 冯庆来,杜远生,殷鸿福,等.南秦岭勉略蛇绿混杂岩带中放射虫的发现及其意义[J].中国科学(D辑),1996,26(增刊):78-82.
[9] 殷鸿福,杜远生,许继锋,等.南秦岭勉略古缝合带中放射虫动物群的发现及其古海洋意义[J].地球科学——中国地质大学学报,1996,21(2):184.
[10] Sun W D,Li S G,Chen Y D,et al.Timing of Synorogenic Granitoids in the South Qinling,Central China:Constraints on the Evolution of the Qinling-Dabie Orogenic Belt[J].The Journal of Geology,2002,110(4):457-468.
[11] Blichert-Toft J,Albarede F.The Lu-Hf Isotope Geochemistry of Chondrites and the Evolution of the Mantle-crust System[J].Earth and Planetary Science Letters,1997,148(1/2):243-258.
[12] Chu N C,Taylor R N,Chavagnac V,et al.Hf Isotope Ratio Analysis Using Multi-collector Inductively Coupled Plasma Mass Spectrometry:an Evaluation of Isobaric Interference Corrections[J]. Journal of Analytical Atomic Spectrometry,2002,17(12):1567-1574.
[13] Vervoort J D,Blichert-Toft J.Evolution of the Depleted Mantle:Hf Isotope Evidence from Juvenile Rocks Through Time-implications for Magma Origins and Crust-mantle Evolution[J].Geochimica et Cosmochimica Acta,1999,63(3):533-556.
[14] Wiedenbeck M,Alle P,Cokfu F,et al.Three Natural Zircon Standards for U-Th-Pb, Lu-Hf, Trace Element and REE Analyses[J].Geostandards and Geoanalytical Research,1995,19(1):1-23.
[15] Wu F Y,Yang Y H,Xie L W,et al.Hf Isotopic Compositions of the Standard Zircons and Baddeleyites Used in U-Pb Geochronology[J].Chemical Geology,2006,234(1/2):105-126.
[16] 王宗起,陈海泓,李继亮,等.南秦岭西乡群放射虫化石的发现及其地质意义[J].中国科学(D辑),1999,29(1):38-44.
[17] 杨志华,李 勇,邓亚婷.秦岭造山带结构与演化若干问题的再认识[J].高校地质学报,1999,5(2):121-136.
[18] 张宗清,张国伟,付国民,等.秦岭变质地层年龄及其构造意义[J].中国科学(D辑),1996,26(3):216-222.

Memo

Memo:
-
Last Update: 2010-03-20