甘肃龙首山岩带西井镁铁质岩体成因及其构造意义

doi:10.13278/j.cnki.jjuese.201503115

摘要/Abstract

摘要：

西井岩体位于北祁连造山带以北,阿拉善地块西南缘的龙首山隆起带。以往的研究多以沿龙首山断裂分布的镁铁-超镁铁质岩带作为和金川岩体相关的岩浆事件进行,而本次选择西井镁铁质岩体进行了精确的地质年代学和地球化学研究,确定了西井岩体岩性主要为橄榄辉石岩和辉长岩,成岩时代为 (421.0±9.0) Ma,可以和北祁连高压变质带榴辉岩年龄相对应;ε_Nd(t)为4.06~5.52,(⁸⁷Sr/⁸⁶Sr)_i为0.704 548~0.707 575,具有地幔岩石圈特征;微量元素及其同位素计算表明西井岩体经历了约10%的下地壳物质混染。据此得出西井岩体及其龙首山岩带早志留世镁铁质侵入岩体成因模式为:祁连洋壳连续俯冲过程中洋壳与陆壳分离,热的软流圈物质持续冲击地幔岩石圈的底部;由于热传导效应,大地热流沿着地幔岩石圈上升,使得80 km深度的湿的橄榄岩层发生熔融,产生玄武质岩浆作用,玄武质岩浆上升过程中与下地壳物质发生约10%混染,形成西井岩体及其龙首山镁铁超镁铁质岩带。

关键词: SHRIMP测年, 地球化学, 西井镁铁质岩体, 龙首山镁铁-超镁铁质岩带, 北祁连造山带

Abstract:

The Xijing mafic intrusion is located in Longshoushan terrane in the west of Alxa block and the north of Qilian orogenic belt. Previous interpretation for mafic-ultramafic intrusions along Longshoushan rift suggested that the genesis of these intrusions were related to the magmatism of Jinchuan intrusion. The major petrographic components of Xijing intrusion are olivine websterite and gabbro, and Xijing intrusion was formed in (421.0±9.0) Ma, which is consistent with the age of eclogites from North Qilian orogenic belt. The values of ε_Nd(t) and (⁸⁷Sr/⁸⁶Sr)_i are 4.06-5.52 and 0.704 548-0.707 575 respectively, which lie in the field of lithospheric mantle. The calculation of isotope and trace elements indicates that Xijing intrusion was contaminated by the lower crustal materials in about 10%. At last, we interpret the evolution of Xijing intrusion and Longshoushan intrusion belt as follows: during Qilian continental subduction, the ocean lithosphere detached from the continental lithosphere, the hot asthenosphere impinged the base of the overriding mantle lithosphere near the breakoff point. Because of the conduction, the heat flow went up and caused the melting of lithosphere at solidus of a hydrated peridotite at a depth of 80 km, which produced basalt magmatism. During the ascent of magma through the mantle into the crust, the magma was contaminated with lower crust and formed the Xijing intrusion and Longshoushan mafic-ultramafic intrusion belt.

Key words: SHRIMP dating, geochemistry, Xijing mafic intrusion, Longshoushan mafic-ultramafic intrusion belt, north of Qilian qrogenic belt

中图分类号:

P588.1

段俊, 钱壮志, 焦建刚, 鲁浩, 冯延清. 甘肃龙首山岩带西井镁铁质岩体成因及其构造意义[J]. 吉林大学学报(地球科学版), 2015, 45(3): 832-846.

Duan Jun, Qian Zhuangzhi, Jiao Jiangang, Lu Hao, Feng Yanqing. Genesis of Xijing Intrusion from Longshoushan Terrane and the Tectonic Significance[J]. Journal of Jilin University(Earth Science Edition), 2015, 45(3): 832-846.

参考文献

[1] 夏林圻, 夏祖春, 徐学义. 北祁连山海相火山岩岩石成因[M]. 北京: 地质出版社, 1996: 1-149. Xia Linqi, Xia Zuchun, Xu Xueyi. Petrogenesis of Marine Volcanic Rocks in the North Qilian Mountains[M]. Beijing: Geological Publishing House, 1996: 1-149.

[2] Xia L Q, Xia Z C, Xu X Y. Magmageneisis in the Ordovician in Back Basins of the Northern Qilian Mountains, China[J]. Geological Society of America Bulletin, 2003, 115: 1510-1522.

[3] 吴才来, 徐学义, 高前明, 等. 北祁连早古生代花岗质岩浆作用及其构造演化[J]. 岩石学报, 2010, 26(4): 1027-1044. Wu Cailai, Xu Xueyi, Gao Qianming, et al. Early Palaezoic Granitoid Magmatism and Tectonic Evolution in North Qilian, NW China[J]. Acta Petrologica Sinica, 2010, 26(4): 1027-1044.

[4] Song S, Zhang L, Niu Y. Ultra-Deep Origin of Garnet Peridotite from the North Qaidam Ultrahigh-Pressure Belt, Northern Tibetan Plateau, NW China[J]. American Mineralogist, 2004, 89: 1330-1336.

[5] 宋述光, 张立飞,Niu Y L, 等. 北祁连山榴辉岩锆石SHRIMP定年及其构造意义[J]. 科学通报, 2004, 49: 848-852. Song Shuguang, Zhang Lifei, Niu Y L, et al. Zircon U-Pb SHRIMP Ages of Eclogites from the North Qilian Mountains, NW China and Their Tectonic Implication[J]. Chinese Science Bulletin, 2004, 49: 848-852.

[6] Song S G, Zhang L E, Niu Y L, et al. Geochronology of Diamond-Bearing Zircons from Garnet-Peridotite in the North Qaidam UHPM Belt, North Tibetan Plateau: A Record of Complex Histories Associated with Continental Collision[J]. Earth and Planetary Science Letters, 2005, 234: 99-118.

[7] Song S G, Zhang L F, Niu Y L, et al. Evolution from Oceanic Subduction to Continental Collision: A Case Study of the Northern Tibetan Plateau Inferred from Geochemical and Geochronological Data[J]. Journal of Petrology, 2006, 47: 435-455.

[8] Song S G, Zhang L F, Niu Y L, et al. Eclogite and Carpholite-Bearing Meta-Pelite in the North Qilian Suture Zone, NW China: Implications for Paleozoic Cold Oceanic Subduction and Water Transport into Mantle[J]. Journal of Metamorphic Geology, 2007, 25: 547-563.

[9] Song S G, Niu Y L, Zhang L, et al. Tectonic Evolution of Early Paleozoic HP Tamorphic Rocks in the North Qilian Mountains, NW China: New Perspectives[J]. Journal of Asian Earth Sciences, 2009, 35: 334-353.

[10] 焦建刚, 闫海卿, 钱壮志, 等. 龙首山岩带典型镁铁超镁铁质岩体岩石地球化学特征[J]. 矿物岩石, 2006, 26(1): 49-56. Jiao Jiangang, Yan Haiqing, Qian Zhuangzhi, et al. Geochemical Characteristics of Typical Mafic-Ultramafic Rocks in Longshou Mountains[J]. Journal of Mineralogical and Petrological Sciences, 2006, 26(1): 49-56.

[11] 焦建刚, 闫海卿, 刘瑞平. 龙首山几个镁铁-超镁铁质岩体比较[J]. 地质与勘探, 2006, 42(5): 60-65. Jiao Jiangang, Yan Haiqing, Liu Ruiping. Comparison of Several Mafic-Ultramafic Intrusions in the Longshoushan Mountain[J]. Geology and Prospectin, 2006, 42(5): 60-65.

[12] 闫海卿, 汤中立, 焦建刚, 等. 内蒙古野芨里镁铁质-超镁铁质岩体的岩石地球化学特征[J]. 现代地质, 2005, 19(4): 515-521. Yan Haiqing, Tang Zhongli, Jiao Jiangang, et al. Petrological and Geochemical Characteristics of Yejili Mafic-Ultramafic Intrusion, Inner Mongolia[J]. Geoscience, 2005, 19(4): 515-521.

[13] 李文渊, 汤中立, 郭周平, 等. 阿拉善地块南缘镁铁超镁铁岩形成时代及地球化学特征[J]. 岩石矿物学杂志, 2004, 24(2): 117-126. Li Wenyuan, Tang Zhongli, Guo Zhouping, et al. Petrogenetic Epoch and Geochemical Characteristics of Mafic-Ultramafic Rocks on the Southern Margin of Alxa Massif in Northern China[J]. Acta Petrological Et Mineralogical, 2004, 24(2): 117-126.

[14] Song S G, Niu Y L, Su L, et al. Tectonics of the North Qilian Orogen, NW China[J]. Gondwana Research, 2013, 23: 1378-1401.

[15] 赵国春. 华北克拉通基底主要构造单元变质作用演化及其若干问题讨论[J]. 岩石学报, 2009, 25: 1772-1792. Zhao Guochun. Metamorphic Evolution of Major Tectonic Units in the Basement of the North China Craton: Key Issues and Discussion[J]. Acta Petrologica Sinica, 2009, 25: 1772-1792.

[16] Wang C Y, Zhang Q, Qian Q, et al. Geochemistry of the Early Paleozoic Baiyin Volcanic Rocks (NW China): Implications for the Tectonic Evolution of the North Qilian Orogenic Belt[J]. Journal of Geology, 2005, 113: 83-94.

[17] Liou J G, Wang X, Coleman R G. Blueschists in Major Suture Zones of China[J]. Tectonics, 1989, 8: 609-619.

[18] Liu Y J, Neubauer F, Genser J, et al.⁴⁰Ar/³⁹Ar Ages of Blueschist Facies Pelitic Schists from Qingshuigou in the Northern Qilian Mountains, Western China[J]. Island Arc, 2006, 15: 187-198.

[19] 何学贤, 唐索寒, 朱祥坤, 等. 多接收器等离子体质谱(MC-ICPMS)高精度测定Nd同位素方法[J]. 地球学报, 2007, 28(4): 405-410. He Xuexian, Tang Suohan, Zhu Xiangkun, et al. Precise Measurement of Nd Isotopic Ratios by Means of Multi-Collector Magnetic Sector Inductively Coupled Plasma Mass Spectrometry[J]. Acta Geoscience Sinica, 2007, 28(4):405-410.

[20] Compston W, Williams I S, Kirschvink J L, et al. Zircon U-Pb Ages for the Early Cambrian Time-Scale[J]. Journal of the Geological Society, 1992, 149: 171-184.

[21] Williams I S, Claesson S. Isotope Evidence for the Precambrian Province and Caledonian Metamorphism of High Grade Paragneiss from the Seve Nappes, Scandinavian Caledonides, Ⅱ Ion Microprobe Zircon U-Th-Pb[J]. Contributions to Mineralogy and Petrology, 1987, 97: 205-217.

[22] Williams I S. U-Th-Pb Geochromology by Ion Microprobe, Applications of Microanalytical Techniques to Understanding Mineralizing Processes[J]. Reviews in Economic Geology, 1998, 7: 1-35.

[23] 杨言辰, 孙德有, 马志红, 等. 红旗岭镁铁超镁铁岩侵入体及铜镍硫化物矿床的成岩成矿机制[J]. 吉林大学学报: 地球科学版, 2005, 35(5): 594-600. Yang Yanchen, Sun Deyou, Ma Zhihong, et al. The Forming Mechanisms of Hongqiling Mafic and Ultramafic Intrusive Bodies and Cu-Ni Sulfide Deposits[J]. Journal of Jilin University: Earth Science Edition 2005, 35(5): 594-600.

[24] 郝立波, 吴超, 孙立吉, 等. 吉林红旗岭铜镍硫化物矿床Re-Os同位素特征及其意义[J]. 吉林大学学报: 地球科学版, 2014, 44(2): 507-517. Hao Libo, Wu Chao, Sun Liji, et al. Re-Os Isotope Characteristics of Hongqiling Cu-Ni Sulfide Deposit in Jilin Provinece and Its Sibnificance[J]. Journal of Jilin University: Earth Science Edition, 2014, 44(2): 507-517.

[25] Sun S S, McDonough W F. Chemical and Isotopic Systematics of Oceanic Basalts: Implications for Mantle Composition and Processes[J]. Geological Society London, Speciety Publication, 1989, 42: 313-345.

[26] Lassiter J C, Depaolo D J. Plume/Lithosphere Interaction in the Generation of Continental and Oceanic Flood Basalts: Chemical and Isotope Constraints. Mahoney J Large Igneous Provinces: Continental, Oceanic, and Planetary Flood Volcanism[J].Geophy-sical Monography, American Geophysical Union, 1997: 335-355.

[27] 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): 1589-1640. Wu Yuanbao,Zheng Yongfei.The Genetic Mineralogy of Zircon and the Constraint to the Interpretation of U-Pb Age[J]. Chinese Science Bulletin,2004,49(16):1589-1640.

[28] Zhang M, Kamo S L, Li C. Precise U-Pb Zircon-Baddeleyite Age of the Jinchuan Sulfide Ore-Bearing Ultramafic Intrusion, Western China[J]. Mineral Deposit, 2010, 45: 3-9.

[29] 李献华, 苏犁, 宋彪, 等. 金川超镁铁侵入岩SHRIMP锆石U-Pb年龄及地质意义[J]. 科学通报, 2004, 49: 420-422. Li Xianhua, Su Li, Song Biao, et al. SHRIMP U-Pb Zircon Age of the Jinchuan Ultramafic Intrusion and Its Geological Significance[J]. Chinese Science Bulletin, 2004, 49: 420-422.

[30] Li X H, Su L, Chung S L, et al. Formation of the Jinchuan Ultramafic Intrusion and the World's Third Largest Ni-Cu Sulfide Deposit: Associated with the Similar to 825 Ma South China Mantle Plume?[J]. Geochemistry, Geophysics, Geosystems, 2005,doi: 10.1029/2005GC001006.

[31] Zhang J X, Meng F C, Wan Y S. A Cold Early Palaeozoic Subduction Zone in the North Qilian Mountains, NW China: Petrological and U-Pb Geochronological Constraints[J]. Journal of Metamorphic Geology, 2007, 25: 285-304.

[32] Zindler A, Hart S. Chemical Geodynamics[J]. Annual Review of Earth Planetary Sciences, 1986, 14: 493-571.

[33] Rudnick R L, Gao S. Composition of the Continental Crust[C]//Rudnick RL. Treatise on Geochemistry. Amsterdam: Elsvier, 2003: 1-64.

[34] Wilson M. Igneous Petrogenesis: A Global Tectonic Approach[M]. London: Unwin Hyman, 1989: 1-466.

[35] Kagami H, Ulmer P, Hansmann W, et al. Nd-Sr Isotopic and Geochemical Characteristics of the Southern Adamello (Northern Italy) Intrusives: Implications for Crustal Versus Mantle Origin[J]. Journal of Geophysical Research: Solid Earth, 1991, 96: 14331-14346.

[36] von Blanckenburg F, Friih-Green G, Diethelm K, et al. Nd-, Sr-and O-Isotopic and Chemical Evidence for a Two-Stage Contamination History of Mantle Magma in the Central Alpine Bergell Intrusion[J]. Contributions to Mineralogy and Petrollogy, 1992, 110: 33-45.

[37] Becker H. Garnet Peridotite and Eclogite Sm-Nd Mineral Ages from the Lepontine Dome (Swiss Alps): New Evidence for Eocene High-Pressure Metamorphism in the Central Alps[J]. Geology, 1993, 21: 599-602.

[38] Christensen J N, Selverstone J, Rosenfeld J L, et al. Correlation by Rb-Sr Geochronology of Garnet Growth Histories from Different Structural Levels Within the Tauern Window, Eastern Alps[J]. Contributions to Mineralogy and Petrollogy, 1994, 118: 1-12.

[39] Tilton G R, Schreyer W, Schertl H-P. Pb-Sr-Nd Isotopic Behavior of Deeply Subducted Crustal Rocks from the Dora Maira Massif, Western Alps, Italy-II: What Is the Age of the Ultra-High-Pressure Metamorphism?[J]. Contributions to Mineralogy and Petrollogy, 1991, 108: 22-33.

[40] Davies J H, von Blanckenburg F. Slab breakoff: A Model of Lithosphere Detachment and Its Test in the Magmatism and Deformation of Collisional Orogens[J]. Earth and Planetary Science Letters, 1995, 129: 85-102.

[41] 宋述光. 北祁连山古大洋俯冲带高压变质岩研究评述[J]. 地质通报, 2009, 28(12): 1769-1778. Song Shuguang. High-Pressure Metamorphic Rocks in the North Qilian Ocean Subduction Zone, China: A Review[J]. Geological Bulletin of China, 2009, 28(12): 1769-1778.

[42] McKenzie D, Bickle M J. The Volume and Composition of Melt Generated by Extension of the Lithosphere[J]. Journal of Petrology, 1988, 29: 625-679.

[43] Mengel K, Green D H. Stability of Amphibole and Phlogopite in Metasomatized Peridotite Under Water-Saturated and Water-Undersaturated Conditions[C]//Fourth International Kimberlite Conference. Kimberlites and Related Rocks-Their Occurrence, Origin and Emplacement. Sydney: Geological Society of Australia, Special Publication, 1989: 571-581.

[44] Kusznir N J, Park R G. The Extensional Strength of the Continental Lithosphere: Its Dependence on Geothermal Gradient, and Crustal Composition and Thickness[C]//Coward M P, Dewey J F, Hancock P L. Continental Extensional Tectonics. London: Geological Society London, Special Publication, 1987: 35-52.

[45] McKenzie D P. Some Remarks on the Movement of Small Melt Fractions in the Mantle[J]. Earth and Planetary Science Letters, 1989, 95: 53-72.

[46] Platt J P. The Uplift of High-Pressure-Low-Tempe-rature Metamorphic Rocks[J]. Philosophical Tran-sactions of the Royal Society of London, 1987, 321: 87-102.

[47] Wheeler J. Structural Evolution of a Subducted Continental Sliver: The Northern Dora Maira Massif, Italian Alps[J]. Journal of the Geological Society, 1991, 148: 1101-1113.

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