西藏班公湖怒江结合带中段恐弄拉地区卡来花岗闪长斑岩岩石地球化学特征、锆石U-Pb年代学及其构造背景
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摘要
卡来花岗闪长斑岩是班怒带演化的重要岩浆活动记录,通过采用LA-MC-ICP-MS技术对其进行锆石U-Pb同位素年龄测定,年龄为175.0±2.7Ma(n=15,MSWD=3.4)。微量元素原始地幔标准化数据显示岩石具富集K、Rb、Th大离子亲石元素,亏损Nb、Ta、Zr、Hf、P高场强元素的特征。ΣREE平均203.67×10-6,LREE平均149.12×10-6,HREE平均21.53×10-6,LREE/HREE平均为6.93,属典型轻稀土富集型,稀土元素球粒陨石标准化显示轻稀土高分馏而重稀土微弱分馏—无分馏。通过各类适用于中酸性岩石的地球化学图解判定,认为该岩体是班公湖—怒江洋盆萎缩过程中于中侏罗世早期(阿林期)向南侧冈底斯地块俯冲环境下的岛弧岩浆产物,物质来源主要为地壳熔融产物,并混入了靠近俯冲带的深海沉积物。
The Kalai granodiorite porphyry is an important magmatic activity record of the evolution of the Bangong Lake-Nujiang Belt. The zircon U-Pb isotopic age of granodiorite porphyry was determined by LA technique at 175. 0 ± 2. 7 Ma. Trace Elemental mantle normalization data show that the rocks are enriched with large ion lithophile elements including K and Rb and Th,loss high field strength elements including Nb and Ta and Zr and Hf and P. The mean values of ΣREE,LREE,HREE and LREE/HREE of the rocks are 203. 67×10-6,149. 12×10-6,21. 53×10-6 and 6. 93 respectively,the rocks are light rare earth type. Standardization of rare earth element chondrites shows that rocks have a rare fraction of light rare earth and a heavy fraction of heavy rare earth fractions. According to geochemical illustrations,the author thinks that the granodiorite porphyry is an island arc magmatic product in the subduction of the Bangong Lake-Nujiang ocean basin during the early Jurassic(Aalenian),and The main source of matter is the crustal melting product and the deep sea sediments of the subduction zone.
The Kalai granodiorite porphyry is an important magmatic activity record of the evolution of the Bangong Lake-Nujiang Belt. The zircon U-Pb isotopic age of granodiorite porphyry was determined by LA technique at 175. 0 ± 2. 7 Ma. Trace Elemental mantle normalization data show that the rocks are enriched with large ion lithophile elements including K and Rb and Th,loss high field strength elements including Nb and Ta and Zr and Hf and P. The mean values of ΣREE,LREE,HREE and LREE/HREE of the rocks are 203. 67×10-6,149. 12×10-6,21. 53×10-6 and 6. 93 respectively,the rocks are light rare earth type. Standardization of rare earth element chondrites shows that rocks have a rare fraction of light rare earth and a heavy fraction of heavy rare earth fractions. According to geochemical illustrations,the author thinks that the granodiorite porphyry is an island arc magmatic product in the subduction of the Bangong Lake-Nujiang ocean basin during the early Jurassic(Aalenian),and The main source of matter is the crustal melting product and the deep sea sediments of the subduction zone.
引文
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潘桂棠,王立全,等编著.青藏高原及邻区地质图及说明书(1∶1500000)[M].北京:地质出版社,2013.
邱瑞照,周肃,等.西藏班公湖-怒江西段舍马拉沟蛇绿岩中辉长岩年龄测定---兼论班公湖-怒江蛇绿岩带形成时代[J].中国地质,2004,31(3):262-268.
曲晓明,王瑞江,等.西藏西部与班公湖特提斯洋盆俯冲相关的火成岩年代学和地球化学[J].地球化学,2009,38(6):523-535.
曲晓明,辛洪波,等.西藏班公湖-怒江缝合带中段碰撞后A型花岗岩的时代及其对洋盆闭合时间的约束[J].地球化学,2012,41(1):1-14.
芮宗瑶,李光明,王龙生.青藏高原的金属矿产资源[J].地质通报,2004,23(1):20-23.
宋扬,唐菊兴,等.西藏班公湖-怒江成矿带研究进展及一些新认识[J].地球科学进展,2014,29(7):795-809.
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周红英,李惠民,等.U-Pb同位素定年技术及其地质应用潜力[J].地质调查与研究,2011,34(1):63-70.
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Ding L,Kapp P,Yin A,Deng WM and Zhong DL.2003.Early Tertiary volcanism in the Qiangtang terrane of central Tibet:Evidence for a transition from oceanic to continental subduction.Journal of Petrology,44:1833-1865.
Hsu KJ,Pan GT and Sengor AMC.1995.Tectonic evolution of the Tibetan Plateau:A working hypothesis based on the archipelago model of orogenesis.International Geology Review,37:473-508.
Kapp P,Murphy MA,Yin A et al.2003.Mesozoic and Cenozoic tectonic evolution of the Shiquanhe area of western Tibet.Tectonics,22(4):1029.
Murphy MA,Harrison TM,Durr SB,Chen Z,Ryerson FJ,Kidd WSF,Wang X and Zhou X.1997.Significant crustal shortening in southcentral Tibet prior to the Indo-Asian collision.Geology,25:719-722.
Pearce J A,Deng Wanming.The ophiolites of the Tibet Geotraverses,Lhasa to Golmud(1985)and Lhasa to Kathmandu(1986)[J].Phil Trans Roy Soc Lond Math Phys Sci,1988,327(1594):215-238.
Zhang KJ,Xia BD,Wang GM,Li YT and Ye HF.2004.Early Cretaceous stratigraphy,depositional environments,sandstone provenance,and tectonic setting of central Tibet,western China,GSABulletin,116(9-10):1202-1222.
曹圣华,邓世权,等.班公湖-怒江结合带西段中特提斯多岛弧构造演化[J].沉积与特提斯地质,2006,26(4):25-32.
陈玉禄,江元生,等.西藏班戈-切里错地区-早白垩世火山岩的时代确定及意义[J].地质力学学报,2002,8(1):43-49.
杜德道,曲晓明,王根厚,等.西藏班公湖-怒江缝合带西段中特提斯洋盆的双向俯冲:来自岛弧型花岗岩锆石U-Pb年龄和元素地球化学的证据[J].岩石学报,2011,27(7):1993-2002.
范建军,李才,等.青藏高原羌塘南部冈玛错地区展金组的沉积环境分析及碎屑锆石U-Pb定年[J].地质学报,2014,88(10):1820-1831.
郭铁鹰,梁定益,聂泽同,等.青藏高原南部地壳演化的特点[J].地球科学,1981,14(1):75-83.
侯可军,李延河,等.LA-MC-ICP-MS锆石微区原位U-Pb定年技术[J].矿床地质,2009,28(4):481-492.
胡隽,万永文,等.班公湖-怒江缝合带西段特提斯洋盆南向俯冲的地球化学和年代学证据[J].成都理工大学学报(自然科学版),2014,41(4):505-515.
康志强,许继峰,王保弟,等.拉萨地块北部去申拉组火山岩:班公湖-怒江特提斯洋南向俯冲的产物[J].岩石学报,2010,26(10):3106-3116.
李光明,李金祥,秦克章,等.西藏班公湖带多不杂超大型富金斑岩铜矿的高温高盐高氧化成矿流体:流体包裹体证据[J].岩石学报.2007,23(5):935-952.
李金祥,李光明,等.班公湖带多不杂富金斑岩铜矿床斑岩-火山岩的地球化学特征与时代:对成矿构造背景的制约[J].岩石学报,2008,24(3):531-543.
廖六根,曹圣华,等.班公湖-怒江结合带北侧陆缘火山-岩浆弧带的厘定及其意义[J].沉积与特提斯地质,2005,25(1-2):163-170.
莫宣学,董国臣,等.西藏冈底斯带花岗岩的时空分布特征及地壳生长演化信息[J].高校地质学报,2005,11(3):281-290.
潘桂棠,莫宣学,侯增谦,等.冈底斯造山带的时空结构及演化[J].岩石学报,2006,22(3):521-533.
潘桂棠,王立全,等编著.青藏高原及邻区地质图及说明书(1∶1500000)[M].北京:地质出版社,2013.
邱瑞照,周肃,等.西藏班公湖-怒江西段舍马拉沟蛇绿岩中辉长岩年龄测定---兼论班公湖-怒江蛇绿岩带形成时代[J].中国地质,2004,31(3):262-268.
曲晓明,王瑞江,等.西藏西部与班公湖特提斯洋盆俯冲相关的火成岩年代学和地球化学[J].地球化学,2009,38(6):523-535.
曲晓明,辛洪波,等.西藏班公湖-怒江缝合带中段碰撞后A型花岗岩的时代及其对洋盆闭合时间的约束[J].地球化学,2012,41(1):1-14.
芮宗瑶,李光明,王龙生.青藏高原的金属矿产资源[J].地质通报,2004,23(1):20-23.
宋扬,唐菊兴,等.西藏班公湖-怒江成矿带研究进展及一些新认识[J].地球科学进展,2014,29(7):795-809.
许荣科,郑有业,等.西藏东巧北尕苍见岛弧的厘定及地质意义[J].中国地质,2007,34(5):768-777.
朱弟成,潘桂棠,莫宣学,等.冈底斯中北部晚侏罗世一早白垩世地球动力学环境火山岩约束[J].岩石学报,2006,22(3):534-546.
周红英,李惠民,等.U-Pb同位素定年技术及其地质应用潜力[J].地质调查与研究,2011,34(1):63-70.
曾禹人,黄建国,等.木嘎岗日岩群时代上限的新证据---来自西藏恐弄拉地区早白垩世早期孢粉化石的报道[J].地质通报,2016,35(12):2027-2032.
Ding L,Kapp P,Yin A,Deng WM and Zhong DL.2003.Early Tertiary volcanism in the Qiangtang terrane of central Tibet:Evidence for a transition from oceanic to continental subduction.Journal of Petrology,44:1833-1865.
Hsu KJ,Pan GT and Sengor AMC.1995.Tectonic evolution of the Tibetan Plateau:A working hypothesis based on the archipelago model of orogenesis.International Geology Review,37:473-508.
Kapp P,Murphy MA,Yin A et al.2003.Mesozoic and Cenozoic tectonic evolution of the Shiquanhe area of western Tibet.Tectonics,22(4):1029.
Murphy MA,Harrison TM,Durr SB,Chen Z,Ryerson FJ,Kidd WSF,Wang X and Zhou X.1997.Significant crustal shortening in southcentral Tibet prior to the Indo-Asian collision.Geology,25:719-722.
Pearce J A,Deng Wanming.The ophiolites of the Tibet Geotraverses,Lhasa to Golmud(1985)and Lhasa to Kathmandu(1986)[J].Phil Trans Roy Soc Lond Math Phys Sci,1988,327(1594):215-238.
Zhang KJ,Xia BD,Wang GM,Li YT and Ye HF.2004.Early Cretaceous stratigraphy,depositional environments,sandstone provenance,and tectonic setting of central Tibet,western China,GSABulletin,116(9-10):1202-1222.