东准噶尔乌尊塔格辉长岩LA-ICP-MS锆石U-Pb年龄、地质地球化学特征及构造意义
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摘要
乌尊塔格辉长岩位于东准噶尔地区卡拉麦里造山带东段,卡拉麦里蛇绿混杂岩带北侧。岩性为辉长岩、石英闪长岩。岩石化学成分显示,辉长岩具高Al_2O_3(18.87%～14.11%)、CaO(8.64%～12.35%),低碱K_2O(0.34%～0.86%)、Na_2O(1.68%～3.08%)、P_2O_5(0.06%～0.20%)和TiO_2(0.96%～1.76%)特征。岩石具弱富集大离子亲石元素Rb,K,Sr,Ba,显著亏损Nb,Ta,反映源区为受俯冲流体交代改造的岩石圈地幔。锆石LA-ICP-MS测年结果表明,辉长岩形成年龄为(337±17)Ma(MSWD=2.3,n=6)。结合地质背景认为,乌尊塔格辉长岩形成于俯冲结束之后挤压环境向拉张环境过渡的构造环境。
Wuzuntage gabbro rock body lies in the eastern Kalamaili Mountains,East Junggar as well as north of Kalamaili ophiolite belt.The lithology is gabbro and quartz diorite.The gabbro consists mainly gabbro is characterized by its high content of Al_2O_3(18.87% ～14.11%) and CaO(8.64% ～12.35%),low content of alkali(K_2O=0.34% ～0.86%,Na_2O=1.68%～3.08%),P_2O_5(0.06%～ 0.20%) and TiO_2(0.96%～1.76%).Rock are enriched in LILE(Rb,K,Sr,Ba) and remarkably depleted in Nb,Ta,.The characteristics of petrography and petrochemistry indicate that the source of magma may be modified by subduction metasomatic fluids.LA-ICP-MS U-Pb dating of zircons from the gabbro yielded ages of(337±17)Ma( MSWD=2.3,n=6).All of these facts suggested that the Wuzuntage gabbro were probably formed in a tectonic setting of transition from compression to extension.
Wuzuntage gabbro rock body lies in the eastern Kalamaili Mountains,East Junggar as well as north of Kalamaili ophiolite belt.The lithology is gabbro and quartz diorite.The gabbro consists mainly gabbro is characterized by its high content of Al_2O_3(18.87% ～14.11%) and CaO(8.64% ～12.35%),low content of alkali(K_2O=0.34% ～0.86%,Na_2O=1.68%～3.08%),P_2O_5(0.06%～ 0.20%) and TiO_2(0.96%～1.76%).Rock are enriched in LILE(Rb,K,Sr,Ba) and remarkably depleted in Nb,Ta,.The characteristics of petrography and petrochemistry indicate that the source of magma may be modified by subduction metasomatic fluids.LA-ICP-MS U-Pb dating of zircons from the gabbro yielded ages of(337±17)Ma( MSWD=2.3,n=6).All of these facts suggested that the Wuzuntage gabbro were probably formed in a tectonic setting of transition from compression to extension.
引文
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[25]Pearce J A,Norry M J.Petrogenetic Implications of Ti,Zr,Y and Nb Variations in Volcanic Rocks[J].Contributions to Mineralogy Petrology,1979,69(1):33-47.
[2]苏玉平,唐红峰,刘丛强等.新疆东准噶尔苏吉泉铝质A型花岗岩的确立及其初步研究.岩石矿物学杂志,2006,25(3):175-184.
[3]苏玉平,唐红峰,丛峰.新疆东准噶尔黄羊山碱性花岗岩体的锆石U-Pb年龄和岩石成因.矿物学报,2008,28(2):117-126.
[4]闫存兴,杨高学,李永军等.东准库布苏南岩体岩石化学特征及其地质意义.新疆地质,2008,26(3):220-224.
[5]杨高学,李永军,吴宏恩等.东准噶尔卡拉麦里地区黄羊山花岗岩和包体LA-ICP-MS锆石U-Pb测年及地质意义.岩石学报,2009,25(12):3197-3207.
[6]李永军,杨高学,吴宏恩等.东准噶尔贝勒库都克铝质A型花岗岩的厘定及意义.岩石矿物学杂志,2009,28(1):17-25.
[7]李锦轶.新疆东准噶尔蛇绿岩的基本特征和侵位历史[J].岩石学报,1995,(1):73-84.
[8]何国琦,李茂松,贾进斗,等.论新疆东准噶尔蛇绿岩的时代及其意义[J].北京大学学报(自然科学版),2001,37(6):852-858.
[9]唐红峰,苏玉平,刘丛强等.新疆北部卡拉麦里斜长花岗岩的锆石U-Pb年龄及其构造意义[J].大地构造与成矿学,2007,31(1):110-117.
[10]汪帮耀,姜常义,李永军,等.新疆东准噶尔卡拉麦里蛇绿岩的地球化学特征及大地构造意义[J].矿物岩石,2009,29(3):74-82.
[11]赵恒乐,许凡,张冀,等.东准噶尔卡拉麦里蛇绿岩形成时代、地质特征及构造意义[J].新疆地质,2012,30(2):161-164.
[12]黄岗,牛广智,王新录,等.新疆东准噶尔卡拉麦里蛇绿岩的形成时代和侵位时限-来自辉绿岩和凝灰岩LA-ICP-MS锆石U-Pb年龄的证据[J].地质通报,2012,31(8):1267-1278.
[13]Liu YongShen,Hu Zhaochu,Gao Shan,et al.In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MSwithout applying an internal standard[J].Chemical Geology,2008,257(1-2):34-43.
[14]Ludwing K R.User’s Manual for Isoplot 3.00:A geochronological toolkit for Microsoft Excel.[J].Berkeley,2003,Berkeley Geochronology Center Special Publication.
[15]Hoskin P W O,Black L P.Metamorphic zircon formation by solidstate recrystallization of protolith igneous zircon[J].Journal of Metamorphic Geology,2000,18(4):423-439.
[16]Middlemost E A K.Naming materials in the magma/igneous rock system[J].Earth Science Rev.,1994,37:215-224.
[17]Miller C,Schuster R,Kl tzli U,er al.Post-collisional potassic and ultra-potassic magmatism in SW Tibet:Geochemical and Sr-Nd-PbO isotopic constraints for mantle sourcecharacteristics and petrogenesis[J].Journal of Petrology,1999,40:1399-1424.
[18]Boynton W V.Geochemistry of the rare earth elements:meteorite studies.Henderson P[J].Rare Earth Element Geochemistry,1984,Elsevier,63-114.
[19]Sun S S and McDonoungh W F.Chemical and isotopic systematicsof oceanic basalt:implication for mantle composition and processes[C].In:Saunders A D,Norry M J.Magmatism in the Ocean Basins.Geol.Soc.London Spec.Pub,1989,42:313-345.
[20]Rudnick R L and Gao S.Composition of the continental crust[J].Treatise on Geochemistry,2003,1-64.
[21]Woodhead J D,Hergt J M,Davidson J P et al.Hafnium isotope evidence for“conservative”element moblility during subduction zone processes[J].Earth and Planetary Science Letters,2001,192:331-346.
[22]Fitton J G,James D,Kempton P D,et al.The role of lithosphere mantle in the generation of late Cenozoic basic magmas in the western United States[J].Journal Petrology,1998,331-349.
[23]Leat P T,Thompson R N,Morrison MA,et al.Compositionally-diverse Miocene-Recent rift-related magmatism in northwest Colorado:partial melting and mixing of mafic mafmas from 3 different asthenospheric and lithospheric mantle sources[J].Journal of Petrology,1988,351-377.
[24]Meschede,M.A Method of Discirminating between Different Types of Mid-Ocean Ridge Basalts and Continental Tholeiites With the Nb-Zr-Y Diagram[J].Chemical Geology,1986,56(3-4),207-208.
[25]Pearce J A,Norry M J.Petrogenetic Implications of Ti,Zr,Y and Nb Variations in Volcanic Rocks[J].Contributions to Mineralogy Petrology,1979,69(1):33-47.