滇西丽江小桥头岩体时代与成因:锆石U-Pb定年与微量元素证据
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摘要
为探讨滇西丽江地区新生代岩浆侵位时代、起源及构造环境,对丽江地区小桥头岩体开展了岩相学、LA-ICP-MS锆石年代学及锆石微量元素分析。结果表明,小桥头岩体由石英二长斑岩和二长花岗斑岩组成,其中锆石U-Pb的年龄分别为35.47±0.48 Ma(MSWD=0.49,n=11)和34.70±0.54 Ma(MSWD=0.1,n=10),形成于始新世晚期;两者岩浆锆石具有一致的稀土微量元素特征, HREE强烈富集(Ce_N/Yb_N=0.00～0.55),强Ce正异常(δCe=1.2～179.4)和较弱Eu负异常(δEu=0.38～0.88),高Nb(1.26～51.07)×10~(-6)、 Ta(0.19～1.52)×10~(-6)、 Hf(0.98%～1.39%)含量,是演化程度高的岩浆产物。根据锆石Ti温度计,得出岩浆锆石结晶温度小于800℃。结合前人研究成果,认为小桥头岩体的形成除了下地壳岩石的部分熔融外,还有幔源物质的混入,是印度-亚洲大陆晚碰撞阶段的岩浆事件记录。
In order to investigate the geochronology, magma generation and structural setting of the Cenozoic igneous in Lijiang, western Yunnan, we have concentrated on the petrography, LA-ICP-MS U-Pb dating and trace element analysis of zircon of the Xiaoqiaotou porphyry. The results show that the Xiaoqiaotou porphyry consisted of masanophyre and monzonitic granite porphyry, their respective ages are 35.47 Ma±0.48 Ma and 34.70 Ma±0.54 Ma, in agreement with that of Cenozoic alkali-rich porphyry in western Yunnan. Their magmatic zircons had consistent REE and trace element characteristics, with enriched HREE(Ce_N/Yb_N=0.00-0.55), slight or none Eu negative(δEu=0.38-0.88) and Ce positive anomaly(δCe=1.2-179.4), high Nb(1.26-51.07)×10~(-6), Ta(0.19-1.52)×10~(-6), Hf(0.98%-1.39%), and they might be the products of highly evolved magma. All the zircons yield different Ti-in zircon temperatures, but all below 800 ℃. Combined with previous studies, it's strongly shown that in addition to partial melting of the thickened lower crust base, the magma of the Xiaoqiaotou porphyry located in underplating of mantle-derived magmas. It was formed from the structure transition phase of late-collisional between Indian and Asian continents,the magmatic event response to syn-collisional processes in the structural transform zone.
In order to investigate the geochronology, magma generation and structural setting of the Cenozoic igneous in Lijiang, western Yunnan, we have concentrated on the petrography, LA-ICP-MS U-Pb dating and trace element analysis of zircon of the Xiaoqiaotou porphyry. The results show that the Xiaoqiaotou porphyry consisted of masanophyre and monzonitic granite porphyry, their respective ages are 35.47 Ma±0.48 Ma and 34.70 Ma±0.54 Ma, in agreement with that of Cenozoic alkali-rich porphyry in western Yunnan. Their magmatic zircons had consistent REE and trace element characteristics, with enriched HREE(Ce_N/Yb_N=0.00-0.55), slight or none Eu negative(δEu=0.38-0.88) and Ce positive anomaly(δCe=1.2-179.4), high Nb(1.26-51.07)×10~(-6), Ta(0.19-1.52)×10~(-6), Hf(0.98%-1.39%), and they might be the products of highly evolved magma. All the zircons yield different Ti-in zircon temperatures, but all below 800 ℃. Combined with previous studies, it's strongly shown that in addition to partial melting of the thickened lower crust base, the magma of the Xiaoqiaotou porphyry located in underplating of mantle-derived magmas. It was formed from the structure transition phase of late-collisional between Indian and Asian continents,the magmatic event response to syn-collisional processes in the structural transform zone.
引文
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[12]Yuan H L,Gao S,Liu X M,et al.Accurate U-Pb age and trace element determinations of ziron by laser ablation-inductively coupled plasma-mass spectrometry[J].Geostandards and Geoanalytical Research,2004,28(3):353-370.
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[18]张玉泉,谢应雯.哀牢山-金沙江富碱侵入岩年代学和Nd,Sr同位素特征[J].中国科学(D辑),1997,27(4):289-293.
[19]洪涛,游军,吴楚,等.滇西桃花花岗斑岩中新太古代-古元古代锆石年龄信息:对扬子板块西缘基底时代的约束[J].岩石学报,2015,31 (9):2583-2596.
[20]万哨凯,夏斌,张玉泉.老君山正长岩锆石SHRIMP定年[J].大地构造与成矿学,2005,29(4):522-526.
[21]毛晓长,尹福光,廖世勇.金沙江-哀牢山构造带中段桃花村岩体的LA-ICP-MS锆石U-Pb定年及地质意义[J].矿物岩石,2012,32(3):70-76.
[22]Liang H Y,Campbell I H,Allen C A,et al.The age of the potassic alkaline igneous rocks along the Ailao Shan-Red River shear zone:implications for the onset age of left-lateral shearing:a reply[J].The Journal of Geology,2007,115(2):231-242.
[23]雷玮琰,施光海,刘迎新.不同成因锆石的微量元素特征研究进展[J].地学前缘,2013,20(4):273-284.
[24]Ferry J M,Watson E B.New thermodynamic models and revised calibrations for the Ti-in-zircon and Zr-in-rutile thermometers[J].Contributions to Mineralogy and Petrology,2007,154:429-437.
[25]Liu H Q,Xu Y G,He B.Implications from zircon-saturation temperatures and lithological assemblages for Early Permian thermal anomaly in northwest China[J].Lithos,2013,182-183:125-133.
[26]周敖日格勒,戴紧根,李亚林,等.东昆仑山脉晚志留世-早侏罗世花岗类岩石中锆石微量元素地球化学特征及地质意义[J].岩石学报,2017,33(1):173-190.
[27]Hoskin P W O.Trace-element composition of hydrothermal zircon and the alteration of Hadean zircon from the Jack Hills,Australia[J].Geochimica et Cosmochimica Acta,2005,69(3):637-648.
[28]Li N,Chen Y J,Pirajno F,et al.LA-ICP-MS zircon U-Pb dating,trace element and Hf isotope geochemistry of the Heyu granite batholiths,eastern Qinling,central China:implications for Mesozoic tectono-magmatic evolution[J].Lithos,2012,142-143:34-47.
[29]Trail D,Watson E B,Tailby N D.Ce and Eu anomalies in zircon as proxies for the oxidation state of magmas[J].Geochimica et Cosmochimica Acta,2012,97:70-87.
[30]Wang Q,Zhu D C,Zhao Z D,et al.Magmatic zircons from I-,S- and A-type granitoids in Tibet:trace element characteristics and their application to detrital zircon provenance study[J].Journal of Asian Earth Sciences,2012,53:59-66.
[31]Grimes C B,John B E,Kelemen P B,et al.Trace element chemistry of zircons from oceanic crust:a method for distinguishing detrital zircon provenance[J].Geology,2007,35(7):643-646.
[32]Hou Z Q,Ma H W,Zaw K.The Himalayan Yulong porphyry copper belt:product of large-scale strike-slip faulting in eastern Tibet[J].Economic Geology,2003,98:125-145.
[2]王登红,应汉龙,梁华英,等.西南三江地区新生代大陆动力学过程与大规模成矿[M].北京:地质出版社,2006.
[3]Huang X L,Niu Y L,Xu Y G,et al.Mineralogical and geochemical constraints on the petrogenesis of post-collisional potassic and ultrapotassic rocks from western Yunnan,SW China[J].Journal of Petrology,2010,51(8):1617-1654.
[4]郭晓冬,侯增谦,陈祥,等.云南马厂箐富碱斑岩埃达克岩性质的厘定及其成矿意义[J].岩石矿物学杂志,2009,28(4):375-386.
[5]刀艳.云南祥云宝兴厂Cu、Mo矿区喜马拉雅期岩浆演化及成因[D].昆明:昆明理工大学,2016.
[6]黄永高,罗改,张彤,等.滇西丽江地区新生代富碱斑岩年代学、地球化学特征及其地质意义[J].现代地质,2018,32(1):28-44.
[7]毕献武,胡瑞忠,叶造军,等.A型花岗岩类与铜成矿关系研究——以马厂箐铜矿为例[J].中国科学(D辑),1999,29(6):489-495.
[8]胥磊落,毕献武,苏文超,等.云南金平铜厂斑岩Cu(Mo-Au)矿床含矿石英正长斑岩地球化学特征及成因机制探讨[J].岩石学报,2011,27(10):3109-3122.
[9]张玉泉,谢应雯,李献华,等.青藏高原东部钾玄岩系岩浆岩同位素特征:岩石成因及其构造意义[J].中国科学(D辑),2000,30(5):493-498.
[10]Hou Z Q,Zhong D L,Deng W M,et al.A tectonic model for porphyry copper-molybdenum-gold deposits in the eastern Indo-Asian collision zone[C]//Porter T M.Super porphyry copper and gold deposits:a global perspective.Adelaide:PGC Publishing,2005:423-440.
[11]肖晓牛,喻学惠,莫宣学,等.滇西洱海北部北衙地区富碱斑岩的地球化学、锆石SHRIMP U-Pb定年及成因[J].地质通报,2009,28(12):1786-1803.
[12]Yuan H L,Gao S,Liu X M,et al.Accurate U-Pb age and trace element determinations of ziron by laser ablation-inductively coupled plasma-mass spectrometry[J].Geostandards and Geoanalytical Research,2004,28(3):353-370.
[13]McDonough W F,Sun S -s.The composition of the Earth[J].Chemical Geology,1995,120:223-253.
[14]Hoskin P W O,Schaltegger U.The composition of zircon and igneous and metamorphic petrogenesis[J].Reviews in Mineralogy and Geochemistry,2003,53(1):27-62.
[15]Hoskin P W O,Ireland T R.Rare earth element chemistry of zircon and its use as a provenance indicator[J].Geology,2000,28(7):627-630.
[16]Belousova E A,Griffin W L,O'Reilly S Y,et al.Igneous zircon:trace element composition as an indicator of source rock type[J].Contributions to Mineralogy and Petrology,2002,143:602-622.
[17]El-Bialy M Z,Ali K A.Zircon trace element geochemical constraints on the evolution of the Ediacaran (600-614 Ma) post-collisional Dokhan Volcanics and Younger Granites of SE Sinai,NE Arabian-Nubian Shield[J].Chemical Geology,2013,360-361:54-73.
[18]张玉泉,谢应雯.哀牢山-金沙江富碱侵入岩年代学和Nd,Sr同位素特征[J].中国科学(D辑),1997,27(4):289-293.
[19]洪涛,游军,吴楚,等.滇西桃花花岗斑岩中新太古代-古元古代锆石年龄信息:对扬子板块西缘基底时代的约束[J].岩石学报,2015,31 (9):2583-2596.
[20]万哨凯,夏斌,张玉泉.老君山正长岩锆石SHRIMP定年[J].大地构造与成矿学,2005,29(4):522-526.
[21]毛晓长,尹福光,廖世勇.金沙江-哀牢山构造带中段桃花村岩体的LA-ICP-MS锆石U-Pb定年及地质意义[J].矿物岩石,2012,32(3):70-76.
[22]Liang H Y,Campbell I H,Allen C A,et al.The age of the potassic alkaline igneous rocks along the Ailao Shan-Red River shear zone:implications for the onset age of left-lateral shearing:a reply[J].The Journal of Geology,2007,115(2):231-242.
[23]雷玮琰,施光海,刘迎新.不同成因锆石的微量元素特征研究进展[J].地学前缘,2013,20(4):273-284.
[24]Ferry J M,Watson E B.New thermodynamic models and revised calibrations for the Ti-in-zircon and Zr-in-rutile thermometers[J].Contributions to Mineralogy and Petrology,2007,154:429-437.
[25]Liu H Q,Xu Y G,He B.Implications from zircon-saturation temperatures and lithological assemblages for Early Permian thermal anomaly in northwest China[J].Lithos,2013,182-183:125-133.
[26]周敖日格勒,戴紧根,李亚林,等.东昆仑山脉晚志留世-早侏罗世花岗类岩石中锆石微量元素地球化学特征及地质意义[J].岩石学报,2017,33(1):173-190.
[27]Hoskin P W O.Trace-element composition of hydrothermal zircon and the alteration of Hadean zircon from the Jack Hills,Australia[J].Geochimica et Cosmochimica Acta,2005,69(3):637-648.
[28]Li N,Chen Y J,Pirajno F,et al.LA-ICP-MS zircon U-Pb dating,trace element and Hf isotope geochemistry of the Heyu granite batholiths,eastern Qinling,central China:implications for Mesozoic tectono-magmatic evolution[J].Lithos,2012,142-143:34-47.
[29]Trail D,Watson E B,Tailby N D.Ce and Eu anomalies in zircon as proxies for the oxidation state of magmas[J].Geochimica et Cosmochimica Acta,2012,97:70-87.
[30]Wang Q,Zhu D C,Zhao Z D,et al.Magmatic zircons from I-,S- and A-type granitoids in Tibet:trace element characteristics and their application to detrital zircon provenance study[J].Journal of Asian Earth Sciences,2012,53:59-66.
[31]Grimes C B,John B E,Kelemen P B,et al.Trace element chemistry of zircons from oceanic crust:a method for distinguishing detrital zircon provenance[J].Geology,2007,35(7):643-646.
[32]Hou Z Q,Ma H W,Zaw K.The Himalayan Yulong porphyry copper belt:product of large-scale strike-slip faulting in eastern Tibet[J].Economic Geology,2003,98:125-145.