Tectonic attribute of the Shiquanhe-Namco ophiolitic belt: Constraint from geochemistry of the island-arc basalts in the Asa mélange zone, central Tibet
-
摘要:
明确狮泉河-纳木错蛇绿岩带的构造属性是重建西藏中部中特提斯演化的关键之一。报道了西藏中部阿索地区蛇绿混杂岩带中岛弧玄武岩的岩石学、地球化学特征，并讨论了该岩石的构造意义。野外和镜下观察结果显示，该样品具有枕状构造并具有细碧岩的岩石特征，表示其形成于海底喷发环境。全岩地球化学分析结果显示，该样品属于亚碱性系列中的钙碱性玄武岩。该岩石富集轻稀土元素，具有平坦的重稀土元素分布特征，轻、重稀土元素分异较强。岩石富集Ba、Th、Pb等大离子亲石元素，亏损Nb、Ta等高场强元素。地球化学分析结果显示，岩石起源于被俯冲沉积物熔体交代的亏损地幔的部分熔融，形成于洋内岛弧环境之下。结合前人研究，发现狮泉河-纳木错蛇绿岩带并非仅存在洋壳成因的蛇绿岩，还保存了一些岛弧成因的岩浆岩。这些岛弧成因岩浆岩的存在表明，狮泉河-纳木错蛇绿岩带中的岩浆岩并非单一构造背景下形成的蛇绿岩，而是包含了多种构造背景之下的岩浆产物。研究表明，狮泉河-纳木错蛇绿岩带并非仅保留了弧后盆地的遗迹，其包含了洋内俯冲环境中多种成因的岩浆作用产物。
-
关键词:
- 青藏高原 /
- 狮泉河-纳木错蛇绿岩带 /
- 岛弧玄武岩 /
- 地球化学 /
- 中特提斯洋
Abstract:The tectonic setting of the Shiquanhe-Namco ophiolitic belt in central Tibet is a key to understanding the Mesozoic tectonic evolution of the Meso-Tethys Ocean.Based on the analysis of major and trace element compositions of island arc basalts in the Asa mélange zone, central Tibet, its tectonic significance was discussed.Field observation and microscopic study indicate that they were formed in submarine eruption environment.Whole-rock geochemical analyses suggest that these rocks belong to calc-alkaline rocks, rich in light rare earth and Ba, Th, Pb large-ion lithophile elements, and depleted in Nb and Ta, with clear differentiation of light and heavy rare earth elements and flat distribution of heavy rare earth elements.Geochemical analysis shows that the rocks were originated from partial melting of depleted mantle metasomatized by melt of subducting sediments and formed under the oceanic island arc environment.Combined with previous work, it is suggested that there are some island arc basalts widely preserved in the Shiquanhe-Namco ophiolitic belt.The existence of the island-arc magmatic rocks within the Shiquanhe-Namco ophiolitic belt reveals that the Shiquanhe-Namco ophiolitic belt cannot be interpreted as an ophiolite in a single back-arc setting but contains magmatic products under various tectonic settings.The results show that the Shiquanhe-Namco ophiolite belt does not only retain the remains of backarc basin, but also contains the magmatic products of various genesis in the subduction environment.
-
Key words:
- Tibet Plateau /
- Shiquanhe-Namco ophiolite belt /
- island arc basalt /
- geochemistry /
- Meso-Tethys Ocean
-
-
图 4 阿索岛弧玄武岩球粒陨石标准化稀土元素配分模式图(a)及N-MORB标准化微量元素蛛网图(b) (原始地幔和N-MORB, E-MORB, OIB的标准值据参考文献[27])
Figure 4.
表 1 阿索岛弧玄武岩主量、微量和稀土元素测试结果
Table 1. Whole-rock major, trace elements and REE data of the Asa island arc basalt
样品号 NT38H1 NT38H2 NT38H3 NT38H4 NT38H5 样品号 NT38H1 NT38H2 NT38H3 NT38H4 NT38H5 SiO2 54.18 52.37 49.95 54.29 54.85 Nb 3.81 4.30 5.98 3.89 4.02 TiO2 0.92 1.00 0.96 0.92 0.97 Ta 0.24 0.27 0.32 0.23 0.23 Al2O3 16.35 17.41 14.76 17.27 16.67 La 12.02 12.89 30.33 13.02 13.69 TFe2O3 6.99 7.36 6.98 6.68 6.79 Ce 22.66 25.29 54.94 24.59 24.95 MnO 0.12 0.13 0.13 0.13 0.13 Pb 5.74 4.22 5.67 6.20 3.58 MgO 5.85 5.15 5.50 4.92 5.14 Pr 2.72 3.04 6.10 2.92 3.03 CaO 5.69 7.02 12.19 5.45 5.66 Sr 257.2 438.2 455.7 447.2 339.4 Na2O 6.73 6.25 4.77 6.84 7.12 Nd 10.35 11.33 20.35 10.98 11.33 K2O 0.08 0.07 0.44 0.07 0.07 Zr 88.72 98.57 84.86 92.34 93.33 P2O5 0.13 0.14 0.21 0.13 0.14 Hf 2.22 2.46 1.98 2.26 2.25 烧失量 2.68 2.95 4.09 3.02 2.16 Sm 2.51 2.82 3.77 2.67 2.76 总计 99.71 99.84 99.98 99.72 99.69 Eu 0.78 0.92 1.06 0.85 0.82 Mg# 66.11 61.98 64.75 63.18 63.86 Gd 2.71 3.06 3.47 2.88 2.95 Sc 29.24 31.54 32.87 29.32 30.40 Tb 0.48 0.52 0.53 0.49 0.50 V 211.0 225.4 244.67 209.8 220.2 Dy 3.24 3.50 3.39 3.25 3.32 Cr 90.66 74.12 229.59 73.40 92.70 Y 21.58 23.04 22.90 22.08 23.54 Co 26.58 27.56 28.65 27.28 25.64 Ho 0.69 0.74 0.71 0.69 0.71 Ni 50.22 48.12 81.40 53.16 49.96 Er 2.03 2.12 2.04 2.00 2.07 Mn 880.6 1027.4 1004.6 968.4 990.8 Tm 0.29 0.31 0.29 0.28 0.29 Cu 53.36 50.58 34.46 54.98 64.64 Yb 1.82 1.94 1.84 1.83 1.87 Zn 59.60 67.24 68.32 68.68 66.68 Lu 0.28 0.29 0.27 0.27 0.28 Ga 19.87 22.04 18.35 19.13 16.31 ∑REE 62.59 68.76 129.09 66.72 68.57 Cs 1.77 1.39 0.77 2.47 0.79 Eu/Eu* 0.91 0.96 0.90 0.94 0.88 Rb 2.37 2.26 10.18 1.99 2.27 (La/Yb)N 4.73 4.77 11.85 5.10 5.25 Ba 63.62 82.44 178.41 80.64 63.92 (La/Sm)N 3.09 2.96 5.19 3.15 3.20 Th 4.83 5.24 6.97 4.72 4.73 (Dy/Yb)N 1.19 1.21 1.24 1.19 1.19 U 0.74 0.68 1.18 0.65 0.76 注：主量元素含量单位为%，微量和稀土元素含量单位为10-6 
下载: 导出CSV
-
[1] Metcalfe I. Gondwana dispersion and Asian accretion: Tectonic and Palaeogeographic evolution of eastern Tethys[J]. Journal of Asian Earth Sciences, 2013, 66: 1-33. doi: 10.1016/j.jseaes.2012.12.020
[2] Pan G, Wang L, Li R, et al. Tectonic evolution of the Qinghai-Tibet Plateau[J]. Journal of Asian Earth Sciences, 2012, 53: 3-14. doi: 10.1016/j.jseaes.2011.12.018
[3] 刘一鸣, 李三忠, 于胜尧, 等. 青藏高原班公湖-怒江缝合带及周缘燕山期微地块聚合与增生造山过程[J]. 大地构造与成矿学, 2019, 43(4): 824-838. https://www.cnki.com.cn/Article/CJFDTOTAL-DGYK201904014.htm
[4] 徐梦婧. 青藏高原狮泉河-永珠-嘉黎蛇绿混杂岩带的构造演化[D]. 吉林大学博士学位论文, 2014.
[5] 王保弟, 刘函, 王立全, 等. 青藏高原狮泉河-拉果错-永珠-嘉黎蛇绿混杂岩带时空结构与构造演化[J]. 地球科学. 2020, 45(8): 2764-2784. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX202008002.htm
[6] 唐峰林, 黄建村, 罗小川, 等. 藏北阿索构造混杂岩的发现及其地质意义[J]. 东华理工学院学报, 2004, (3): 245-250. doi: 10.3969/j.issn.1674-3504.2004.03.009
[7] 尹滔, 尹显科, 秦宇龙, 等. 西藏隆巴俄桑地区玄武岩与安山玢岩的地球化学: 对班公湖-怒江洋构造演化的启示[J]. 地球科学. 2020, 45(7): 2345-2359. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX202007011.htm
[8] Schneider W, Mattern F, Wang P J, et al. Tectonic and sedimentary basin evolution of the eastern Bangong-Nujiang zone(Tibet): a Reading cycle[J]. International Journal of Earth Sciences, 2003, 92(2): 228-254. doi: 10.1007/s00531-003-0311-5
[9] Kapp P, Murphy M A, Yin A, et al. Mesozoic and Cenozoic tectonic evolution of the Shiquanhe area of western Tibet[J]. Tectonics, 2003, 22: 1029.
[10] Allegre C J, Courtillot V, Tapponnier P, et al. Structure and evolution of the Himalaya-Tibet orogenic belt[J]. Nature, 1984, 307(5946): 17-22. doi: 10.1038/307017a0
[11] Liu W L, Huang Q T, Gu M, et al. Origin and tectonic implications of the Shiquanhe high-Mg andesite, western Bangong suture, Tibet[J]. Gondwana Research, 2018, 60: 1-14. doi: 10.1016/j.gr.2018.03.017
[12] Li H, Wang M, Zeng X W, et al. Generation of Jurassic high-mg diorite and plagiogranite intrusions of the asa area, tibet: Products of intra-oceanic subduction of the Meso-Tethys ocean[J]. Lithos, 2020, 362/363: 105481. doi: 10.1016/j.lithos.2020.105481
[13] 吴珍汉, 叶培盛, 杨艳. 西藏阿里推覆构造与蛇绿岩构造侵位[J]. 中国地质, 2013, 40(1): 182-190. doi: 10.3969/j.issn.1000-3657.2013.01.013
[14] Wu Z, Barosh P J, Ye P, et al. Late Cretaceous tectonic framework of the Tibetan Plateau[J]. Journal of Asian Earth Sciences, 2015, 114: 693-703. doi: 10.1016/j.jseaes.2014.11.021
[15] Zeng Y C, Xu J F, Chen J L, et al. Geochronological and geochemical constraints on the origin of the Yunzhug ophiolite in the Shiquanhe-Yunzhug-Namu Tso ophiolite belt, Lhasa Terrane, Tibetan Plateau[J]. Lithos, 2018, 300/301: 250-260. doi: 10.1016/j.lithos.2017.11.025
[16] Tang Y, Zhai Q G, Chung S L, et al. First mid-ocean ridge-type ophiolite from the Meso-Tethys suture zone in the North-Central Tibetan Plateau[J]. Geological Society of America Bulletin, 2020, 132(9/10): 2202-2220.
[17] 曾孝文, 王明, 范建军, 等. 青藏高原中部阿索蛇绿岩岩石学与同位素年龄[J]. 地质通报, 2018, 37(8): 1492-1502. http://dzhtb.cgs.cn/gbc/ch/reader/view_abstract.aspx?file_no=20180813&flag=1
[18] Zhu D C, Zhao Z-D, Niu Y, et al. The origin and Pre-Cenozoic evolution of the Tibetan Plateau[J]. Gondwana Research, 2013, 23(4): 1429-1454. doi: 10.1016/j.gr.2012.02.002
[19] Zeng X W, Wang M, Fan J J, et al. Geochemistry and geochronology of gabbros from the asa ophiolite, Tibet: Implications for the Early Cretaceous evolution of the Meso-Tethys ocean[J]. Lithos, 2018, 320/321: (192-206. doi: 10.1016/j.lithos.2018.09.013
[20] Liu Y, Wang M, Li C, et al. Late Cretaceous tectono-magmatic activity in the Nize region, central Tibet: Evidence for lithospheric delamination beneath the Qiangtang-Lhasa collision zone[J]. International Geology Review, 2018, 61(5): 562-583.
[21] Wang M, Zeng X W, Xie C M, et al. Dating of detrital zircon grains and fossils from Late Palaeozoic sediments of the Baruo area, Tibet: Constraints on the Late Palaeozoic evolution of the Lhasa Terrane[J]. International Geology Review, 2020, 62(4): 465-478. doi: 10.1080/00206814.2019.1619199
[22] 唐峰林, 黄建村, 罗小川, 等. 藏北阿索构造混杂岩的发现及其地质意义[J]. 东华理工学院学报, 2004, (3): 245-250. doi: 10.3969/j.issn.1674-3504.2004.03.009
[23] Li H, Wang M, Zeng X W, et al. Slab break-off origin of 105 Ma a-type porphyritic granites in the Asa area of Tibet[J]. Geological Magazine, 2020, 157(8): 1281-1298. doi: 10.1017/S0016756819001559
[24] 于红. 陕西商南松树沟橄榄岩矿物地球化学特征及成因机理示踪[D]. 中国地质大学(北京) 硕士学位论文, 2011.
[25] Winchester J A, Floyd P A. Geochemical discrimination of different magma series and their differentiation products using immobile elements[J]. Chemical Geology, 1977, 20: 325-343. doi: 10.1016/0009-2541(77)90057-2
[26] Ross P S, Polat A, Bédard J H. Magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace-element discriminant diagrams[J]. Canadian Journal of Earth Sciences, 2009, 46(11): 823-839. doi: 10.1139/E09-054
[27] Sun S S, Mcdonough W F. Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes[J]. Geological Society London Special Publications, 1989, 42(1): 313-345. doi: 10.1144/GSL.SP.1989.042.01.19
[28] Pearce J A, Peate D W. Tectonic implications of the composition of volcanic arc magmas[J]. Annual Review of Earth & Planetary Sciences, 1995, 23(1): 251-285.
[29] Pearce J A. Geochemical fingerprinting of oceanic basalts with applications to ophiolite classification and the search for Archean oceanic crust[J]. Lithos, 2008, 100(1/4): 14-48. http://www.sciencedirect.com/science/article/pii/S0024493707001375
[30] Zhao J H, Asimow P D. Formation and evolution of a magmatic system in a rifting continental margin: Neoproterozoic arc-and MORB-like dike swarms in South China[J]. Journal of Petrology, 2018, 59(9): 1811-1844. doi: 10.1093/petrology/egy080
[31] Ma X H, Cao R, Zhou Z H, et al. Early Cretaceous high-Mg diorites in the Yanji area, northeastern China: petrogenesis and tectonic implications[J]. Journal of Asian Earth Sciences, 2015, 97: 393-405. doi: 10.1016/j.jseaes.2014.07.010
[32] Fitton J G, Saunders A D, Norry M J, et al. Thermal and chemical structure of the Iceland plume[J]. Earth & Planetary Science Letters, 1997, 153(3/4): 197-208. http://www.sciencedirect.com/science/article/pii/S0012821X97001702
[33] Pearce J A, Stern R J, Bloomer S H, et al. Geochemical Mapping of the mariana arc-basin system: Implications for the nature and distribution of subduction components[J]. Geochemistry, Geophysics, Geosystems, 2005, 6(7): Q07006. http://onlinelibrary.wiley.com/doi/10.1029/2004GC000895
[34] Dilek Y, Furnes H, Shallo M. Geochemistry of the Jurassic Mirdita ophiolite(albania) and the MORB to SSZ evolution of a marginal basin oceanic crust[J]. Lithos, 2008, 100: 174-209. doi: 10.1016/j.lithos.2007.06.026
[35] Woodhead J D, Hergt J M, Davidson J P, et al. Hafnium isotope evidence for 'conservative' element mobility during subduction zone processes[J]. Earth & Planetary Science Letters, 2001, 192(3): 331-346. http://www.sciencedirect.com/science/article/pii/S0012821X01004538
[36] Hart S R, Staudigel H. The control of alkalies and uranium in seawater by ocean crust alteration[J]. Earth and Planetary Science Letters, 1982, 58(2): 202-212. doi: 10.1016/0012-821X(82)90194-7
[37] Wood D A. The application of a Th-Hf-Ta diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary Volcanic Province[J]. Earth and Planetary Science Letters, 1980, 50: 11-30. doi: 10.1016/0012-821X(80)90116-8
[38] Cabanis B, Lecolle M. The La/10-Y/15-Nb/8 diagram: a tool for discrimination volcanic series and evidencing continental crust magmatic mixtures and/or contamination(en)[J]. Physics. Chemistry. Space sciences. Earth sciences, 1989, 309: 2023-2029. http://www.researchgate.net/publication/279899839_The_La10-Y15-Nb8_diagram_a_tool_for_discriminating_volcanic_series_and_evidencing_continental_crust_magmatic_mixtures_andor_contaminationLa_diagramme_La10-Y15-Nb8_un_outil_pour_la_discrimination_des_s
[39] Reagan M K, Pearce J A, Petronotis K, et al. Subduction initiation and ophiolite crust: New insights from iodp drilling[J]. International Geology Review, 2017, 59(11): 1439-1450. doi: 10.1080/00206814.2016.1276482
[40] Ishizuka O, Taylor RN, Yuasa M, et al. Making and breaking an island arc: A new perspective from the oligocene Kyushu-Palau arc, Philippine sea[J]. Geochemistry, Geophysics, Geosystems, 2011, 12(5): Q05005, DOI:10.1029/2010GC003440.
[41] Hawkesworth C J, Gallagher K, Hergt J M, et al. Mantle and slab contributions in arc magmas[J]. Annual Review of Earth and Planetary Sciences, 1993, 21(1): 175-204. doi: 10.1146/annurev.ea.21.050193.001135
[42] Matte P, Tapponnier P, Amaud N, et al. Tectonics of western Tibet, between the Tarim and the Indus[J]. Earth and Planetary Science Letters, 1996, 142: 311-330. doi: 10.1016/0012-821X(96)00086-6
[43] Yuan Y, Yin Z, Liu W, et al. Tectonic evolution of the Meso-Tethys in the western segment of Bangonghu-Nujiang suture zone: Insights from geochemistry and geochronology of the Lagkor Tso ophiolite[J]. Acta Geoblgica Sinica(English edition), 2015, 89: 369-388. http://www.ixueshu.com/document/e27ba01d21ad780f10e9a14f063b149f318947a18e7f9386.html
[44] Peng Y B, Yu S Y, Li S Z, et al. The odyssey of Tibetan Plateau accretion prior to Cenozoic India-Asia collision: Probing the Mesozoic tectonic evolution of the Bangong-Nujiang Suture[J]. Earth-Science Reviews, 2020, 211: 103376. doi: 10.1016/j.earscirev.2020.103376
[45] Wang B D, Wang L Q, Chung S L, et al. Evolution of the Bangong-Nujiang Tethyan ocean: insights from the geochronology and geochemistry of mafic rocks within ophiolites[J]. Lithos, 2016, 245: 18-33. doi: 10.1016/j.lithos.2015.07.016
[46] Yang P, Huang Q, Zhou R, et al. Geochemistry and geochronology of ophiolitic rocks from the Dongco and Lanong areas, Tibet: Insights into the evolution history of the Bangong-Nujiang Tethys ocean[J]. Minerals, 2019, 9(8): 466. doi: 10.3390/min9080466
[47] Zhu D C, Zhao Z D, Niu Y, et al. The lhasa terrane: Record of a microcontinent and its histories of drift and growth[J]. Earth and Planetary Science Letters, 2011, 301(1/2): 241-255. http://www.sciencedirect.com/science/article/pii/S0012821X10007004
[48] 胡承祖. 狮泉河-古昌-永珠蛇绿岩带特征及其地质意义[J]. 成都地质学院学报, 1990, (1): 23-30. https://www.cnki.com.cn/Article/CJFDTOTAL-CDLG199001005.htm
-
图(6)
表(1)
计量
- 文章访问数: 3548
- PDF下载数: 12
- 施引文献: 0