滇西云县地区团梁子岩组变质岩锆石U-Pb年龄及其构造意义
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摘要
滇西云县—景洪一带广泛出露的中元古界团梁子岩组是一套与扬子基底岩系密切相关的中低变质沉积岩夹火山岩系,其形成时代、沉积充填序列及大地构造属性一直存在争议。出露于云县漫湾地区的团梁子岩组发育厚数米的绿片岩(原岩玄武岩)及绢云石英千枚岩(原岩流纹岩)。采集绢云石英千枚岩样品进行LA-ICP-MS锆石U-Pb定年,分别获得1497±14Ma的岩浆结晶年龄和893±17.3Ma、425±15.7Ma、321±27Ma的变质年龄。认为团梁子岩组中以绿片岩、绢云石英千枚岩为主体的原始沉积岩系形成于中元古代中期,在新元古代全球性的格林威尔造山过程中被青白口纪花岗岩侵入并发生变质作用;在古特提斯洋俯冲过程中,经历古生代造弧作用;同时还获单颗粒2310±15Ma的碎屑锆石,推测滇西云县地区应存在古元古代的结晶基底,由此可知,团梁子岩组应是扬子陆块褶皱基底岩系的组成部分。
The Middle Proterozoic Tuanliangzi Formation, widely exposed in the Yunxian-Jinghong area of western Yunnan, consists of a set of low and medium metamorphic sedimentary rocks intercalated with the Yangtze basement rock series. Its formation age, sedimentary filling sequence and tectonic attributes have been controversial. The Tuanliangzi Formation exposed in Manwan area of Yunxian County contains basalt and sericite quartz phyllite, several meters in thickness. In this study, the LA-ICP-MS zircon U-Pb dating of sericite quartz phyllite(D1016)was carried out, and the magmatic crystallization age of 1497±14 Ma and the metamorphic age of 893±17.3 Ma, 425±15.7 Ma and 321±27 Ma were obtained respectively. It is considered that the original sedimentary rock series in the Tuanliangzi Formation, mainly composed of greenschist and sericite quartz phyllite, were formed in the middle of the Mesoproterozoic period,and were intruded and metamorphosed by the Qingbaikou granite during the Neoproterozoic global Greenwell orogenic process. During the Paleo-Tethys Ocean subduction, the Paleozoic arc metamorphism was experienced, and a single grain of 2310±15 Ma detrital zircon was obtained. It is inferred that there should be an ancient crystalline basement of Guyuan in Yunxian area, western Yunnan. It can be concluded that Tuanliangzi Formation is an integral part of the folded basement rock series of Yangzi continental block.
The Middle Proterozoic Tuanliangzi Formation, widely exposed in the Yunxian-Jinghong area of western Yunnan, consists of a set of low and medium metamorphic sedimentary rocks intercalated with the Yangtze basement rock series. Its formation age, sedimentary filling sequence and tectonic attributes have been controversial. The Tuanliangzi Formation exposed in Manwan area of Yunxian County contains basalt and sericite quartz phyllite, several meters in thickness. In this study, the LA-ICP-MS zircon U-Pb dating of sericite quartz phyllite(D1016)was carried out, and the magmatic crystallization age of 1497±14 Ma and the metamorphic age of 893±17.3 Ma, 425±15.7 Ma and 321±27 Ma were obtained respectively. It is considered that the original sedimentary rock series in the Tuanliangzi Formation, mainly composed of greenschist and sericite quartz phyllite, were formed in the middle of the Mesoproterozoic period,and were intruded and metamorphosed by the Qingbaikou granite during the Neoproterozoic global Greenwell orogenic process. During the Paleo-Tethys Ocean subduction, the Paleozoic arc metamorphism was experienced, and a single grain of 2310±15 Ma detrital zircon was obtained. It is inferred that there should be an ancient crystalline basement of Guyuan in Yunxian area, western Yunnan. It can be concluded that Tuanliangzi Formation is an integral part of the folded basement rock series of Yangzi continental block.
引文
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[24]王海然,赵红格,乔建新,等.锆石U-Pb同位素测年原理及应用[J].地质与资源,2013,22(3):229-242.
(1)云南省地质调查院.云南省1:50000(那许、弯手寨、黄竹林和黄草坝幅)区域地质调查报告.2000.
(2)云南省地质矿产局.1:20万思茅幅区域地质图.1983.
(3)云南省地质调查院.云南省1:50000(亚练、曼来、大南坝和勐賴坝幅)区域地质调查报告.2007.
[2]赵靖,钟大赉,王毅.滇西澜沧变质带变形系列与变形作用初步研究[J].地质科学,1994,29(4):366-369.
[3]赵靖,钟大赉,王毅.滇西澜沧变质带变质作用和变形作用的关系[J].岩石学报,1994,10(1):27-29.
[4]李元庆.云南澜沧江地区团梁子-大新山变质岩带变质变形特征[D].中国地质大学(北京)硕士学位论文,2009.
[5]梁晓,王根厚,杨广全.滇西景谷地区澜沧江沿岸早古生代构造片岩中石英脉的成因与变形[J].地质通报,2009,28(9):1342-1349.
[6]孙载波,曾文涛,黄亮,等.滇西南团梁子岩组绿片岩、基性脉岩及构造分异石英脉岩锆石U-Pb年龄及其地质意义[J].矿物学报,2015,35(2):245-254.
[7]Ludwig K R.Isoplot 3.00:A Geochronological toolkit for Microsoft excel[M].Berkeley Geoc-hronology Center Special Publicantion,2003.
[8]Hoskin P W O,Schaltegger U.The composition of zircon and igneous and metamorphic petrogenesis[J].Reviews in Mineralogy and Geochemistry,2003,53:27-62.
[9]李再会,林仕良,丛峰,等.滇西高黎贡山群变质岩的锆石年龄及其构造意义[J].岩石学报,2012,8(5):1529-1541.
[10]王舫,刘福来,冀磊,等.澜沧江杂岩带澜沧群浅变质岩系碎屑锆石LA-ICP-MS U-Pb年代学及其构造意义[J].岩石学报,2017,33(9):2975-2985.
[11]王冬兵,唐渊,廖世勇,等.滇西哀牢山变质岩系锆石U-Pb定年及其地质意义[J].岩石学报,2013,29(4):1261-1278.
[12]王冬兵,尹福光,罗亮,等.昌宁-孟连构造带牛井山地区大勐龙岩群碎屑锆石U-Pb定年及其地质意义[J].矿物岩石,2015,35(3):72-80.
[13]唐渊,王冬兵,廖世勇,等.滇西三江地区西盟群的再认识--来自构造变形特征及锆石U-Pb年代学的证据[J].岩石学报,2017,33(9):2054-2072.
[14]刘军平,田素梅,丛峰,等.滇西澜沧江南段沙乐花岗岩的锆石U-Pb年龄、地球化学特征及其地质意义[J].沉积与特提斯地质,2017,37(4):59-70.
[15]刘军平,李静,孙柏东,等.滇中易门地区发现化石新物种[J].沉积与特提斯地质,2018,38(1):37-40.
[16]吴元保,郑永飞.锆石成因矿物学研究及其对U-Pb年龄解释的制约[J].科学通报,2004,49(16):1589-1604.
[17]翟明国,从柏林,乔广生,等.中国滇西南造山带变质岩的SmNd和Rb-Sr同位素年代学[J].岩石学报,1990,4:1-11.
[18]Hu Z C,Gao S,Liu Y S,et al.Signal enhancement in laser ablation ICP-MS by additon of nitrogen in the central channel gas[J].Journal of Analytical Atomic Spectrometry,2008,23(8):1093-1101.
[19]Liu Y S,Gao S,Hu Z C,et al.Continental and oceaniccrust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb dating,Hf isotopes and trace elements in zircons of mantle xenoliths[J].Journal of Petrology,2010,51(1/2):537-571.
[20]Liu Y S,Hu Z C,Gao S,et al.In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internalstandard[J].Chemical Geology,2008,257(1/2):34-43.
[21]Liu Y S,Hu Z C,Zong K Q,et al.Reapprai sement and refinement of zircon U-Pb isotope and trace element analyses by LA-ICP-MS[J].Chinese Science Bulletin,2010,55(15):1535-1545.
[22]Widenbeck M,Alle P,Corfu 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.
[23]Hu Z C,Liu Y S,Gao S,et al.A“wire”signal smoothing device for laser ablation inductively coupled plasma mass spectrometry analysis[J].Spectrochimica Acta Part B:Atomic Spec troscopy,2012,78(78):50-57.
[24]王海然,赵红格,乔建新,等.锆石U-Pb同位素测年原理及应用[J].地质与资源,2013,22(3):229-242.
(1)云南省地质调查院.云南省1:50000(那许、弯手寨、黄竹林和黄草坝幅)区域地质调查报告.2000.
(2)云南省地质矿产局.1:20万思茅幅区域地质图.1983.
(3)云南省地质调查院.云南省1:50000(亚练、曼来、大南坝和勐賴坝幅)区域地质调查报告.2007.