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摘要: 峨眉大火成岩省是全球最大的钒钛磁铁矿床聚集区，攀枝花岩体是其中的典型代表。根据岩性特点，攀枝花岩体主体可划分为上、中、下三个岩相带，其中中部岩相带和下部岩相带岩性旋回非常发育，每个旋回从下向上铁钛氧化物和暗色硅酸盐矿物逐渐减少，块状铁钛氧化物矿石或磁铁矿辉长岩都出现在每个旋回的底部和下部。然而，尽管钛铁矿固相线以下固溶体出溶远弱于磁铁矿，从而能更好地保留成因信息，但其成分变化的成因意义没有受到足够重视。本次研究发现作为主要金属氧化物之一的钛铁矿的成分不仅在不同岩性中有明显差异，同时，中、下部岩相带的各岩性旋回中钛铁矿成分也具有周期性变化。例如，块状矿石中钛铁矿具有最高的MgO和TiO2及最低的FeO、Fe2O3和MnO，而辉长岩中钛铁矿则具有相反的成分特征。同时，钛铁矿的MgO含量与磁铁矿的MgO含量及橄榄石的Fo牌号具有显著的正相关关系。这种规律性变化说明每个旋回可以代表一次比较明显的岩浆补充，每次新岩浆补充后，钛铁矿和磁铁矿及橄榄石都是结晶较早的矿物。与Skaergaard岩体相比，攀枝花岩体钛铁矿的MgO含量较高，表明攀枝花岩体分离结晶过程中铁钛氧化物结晶较早；与挪威Tellnes斜长岩套铁钛矿床中的钛铁矿相比，攀枝花岩体的钛铁矿不仅具有较高的MgO和FeO，还具有极高的TiO2和MnO，但Fe2O3却很低，说明地幔柱背景下形成的钛铁矿与斜长岩套中钛铁矿的成分有显著的区别。Abstract: The Panzhihua intrusion is the layered intrusion hosting Fe-Ti oxide deposit mined earliest in the Emeishan large igneous province, which is the largest ore-concentrated area of V-Ti magnetite deposits over the world. Therefore, the petrogenesis of the Panzhihua intrusion is significant for understanding of the formation of the other ore-bearing intrusions in the area. The Panzhihua intrusion can be divided into Upper, Middle and Lower zones. The lithologic cycles, shown by periodically decreases of the Fe-Ti oxides and dark silicate minerals from the bottom upwards, are well developed in the Middle and Lower zones, in which massive Fe-Ti oxide ore and magnetite gabbro occur in the bottom and lower part of each cyclic unit. However, although ilmenite can remain its original compositional feature due to weak sub-solidus exsolution relative to magnetite, the significances of the compositional variation of the ilmenite have not been well addressed yet. We find that the ilmenite compositions are distinguishable in different types of rocks, and periodically variable in each cyclic unit of the Middle and Lower zones. For example, the ilmenite of the massive ores is the highest in MgO and TiO2 and the lowest in FeO, Fe2O3 and MnO, whereas the ilmenite of the gabbro has opposite compositional characteristics. MgO content of the ilmenite and magnetite has a significant positive correlation with forsterite content (Fo) of olivine. Such regular variations in each cyclic unit represent obvious magma replenishment and the ilmenite and magnetite as well as olivine is the minerals crystallized early in each pulse of magma. This study also reveals that, MgO contents in the Panzhihua ilmenite are higher than those of the Skaergaard intrusion, indicating that the Fe-Ti oxides in the Panzhihua intrusion crystallize earlier during magma evolution. Compared with ilmenite of the Tellnes Fe-Ti oxide deposit in Norway, the ilmenite in the Panzhihua intrusion is high in MgO and FeO, very high in TiO2 and MnO, but very low in Fe2O3, suggesting that the ilmenite formed in mantle plume environment is significantly different from that in the anorthosite massif.
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Key words:
- Ilmenite /
- Electron microprobe /
- Fractional crystallization /
- Panzhihua intrusion
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[1] Cawthorn RG and Ashwal LD. 2009. Origin of anorthosite and magnetitite layers in the Bushveld Complex, constrained by major element compositions of plagioclase. Journal of Petrology, 50(9): 1607-1637
[2] Charlier B, Duchesne JC and Vander Auwera J. 2006. Magma chamber processes in the Tellnes ilmenite deposit (Rogaland Anorthosite Province, SW Norway) and the formation of Fe-Ti ores in massif-type anorthosites. Chemical Geology, 234(3-4): 264-290
[3] Charlier B, Skår Ø, Korneliussen A, Duchesne JC and Auwera JV. 2007. Ilmenite composition in the Tellnes Fe-Ti deposit, SW Norway: Fractional crystallization, postcumulus evolution and ilmenite-zircon relation. Contribution to Mineralogy and Petrology, 154(2): 119-134
[4] Chung SL and Jahn BM. 1995. Plume-lithosphere interaction in generation of the Emeishan flood basalts at the Permian-Triassic boundary. Geology, 23(10): 889-892
[5] Fan WM, Wang YJ, Peng TP, Miao LC and Guo F. 2004. Ar-Ar and U-Pb geochronology of Late Paleozoie basahs in western Guangxi and its constraints on the eruption age of Emeishan basalt magmatism. Chinese Science Bulletin, 49(18): 1892-1900 (in Chinese)
[6] Hanski E, Walker RJ, Huhma H, Polyakov GV, Balykin PV, Ngo TT and Phuong NT. 2004. Origin of the Permian-Triassic komatiites, northwestern Vietnam. Contribution to Mineralogy and Petrology, 147(4): 453-469
[7] Hao YL, Zhang ZC, Wang FS and Mahoney JJ. 2004. Petrogenesis of high-Ti and low-Ti basalts from the Emeishan Large Igneous Province. Geological Review, 50(6): 587-592 (in Chinese with English abstract)
[8] He B, Xu YG, Chung SL, Xiao L and Wang YM. 2003. Sedimentary evidence for a rapid, kilometer-scale crustal doming prior to the eruption of the Emeishan flood basalts. Earth and Planetary Science Letters, 213(3-4): 391-405
[9] Hou T, Zhang ZC, Pirajno F. 2012. A new metallogenic model of the Panzhihua giant V-Ti iron oxide deposit in the Emeishan large province: Based on high-Mg olivine-bearing wehrlites and new field evidence. International Geology Review, 54(15): 1721-1745
[10] Hou T, Zhang ZC, Encarnacion J, Santosh M and Sun Y. 2013. The role recycled oceanic crust in magmatism and metallogenesis: Os-Sr-Nd isotpes, U-Pb geochronology and geochemistry of picritic dykes in the Panzhihua giant Fe-Ti oxide deposit, central Emeishan large igneous province. Contributions to Mineralogy and Petrology, 165(4): 805-822
[11] Hou ZQ, Lu JR and Lin SZ. 2005. The axial zone consisting of pyrolite and eclogite in the Emei mantle plume: Major, trace element and Sr-Nd-Pb isotope evidence. Acta Geologica Sinica, 79(2): 200-219 (in Chinese with English abstract)
[12] Hu RZ, Tao Y, Zhong H, Huang ZL and Zhang ZW. 2005. Mineralization systems of a mantle plume: A case study from the Emeishan igneous province, Southwest China. Earth Science Frontiers, 12(1): 42-54 (in Chinese with English abstract)
[13] Hunter RH and Sparks RSJ. 1987. The differentiation of the Skaergaard intrusion. Contribution to Mineralogy and Petrology, 95(4): 451-461
[14] Jang YD, Naslund HR and McBirney AR. 2001. The differentiation trend of the Skaergaard Intrusion and the timing of magnetite crystallization: Iron enrichment revisited. Earth and Planetary Science Letters, 189(3-4): 189-196
[15] Jang YD and Naslund HR. 2003. Major and trace element variation in ilmenite in the Skaergaard intrusion: Petrologic implications. Chemical Geology, 193(1-2): 109-125
[16] Klemm DD, Henckel J, Dehm RM and von Gruenewaldt G. 1985. The geochemistry of titanomagnetite in magnetite layers and their host rocks of the Eastern Bushveld Complex. Economic Geology, 80(4): 1075-1088
[17] Namur O, Charlier B, Toplis J, Higgins MD, Liegeois JP and Auwera JV. 2010. Crystallization sequence and magma chamber processes in the ferrobasaltic septiles layered intrusion, Canada. Journal of Petrology, 51(6): 1203-1236
[18] Pang KN, Zhou MF, Lindsley D, Zhao DG and Malpas J. 2008. Origin of Fe-Ti Oxide ores in mafic intrusions: Evidence from the Panzhihua Intrusion, SW China. Journal of Petrology, 49(2): 295-313
[19] Pang KN, Li CS, Zhou MF and Ripley EM. 2009. Mineral compositional constraints on petrogenesis and oxide ore genesis of the Late Permian Panzhihua layered gabbroic intrusion, SW China. Lithos, 110(1-4): 199-214
[20] Reynolds IM. 1985. The nature and origin of titaniferous magnetiterich layers in the Upper Zone of the Bushveld complex: A review and synthesis. Economic Geology, 80(4): 1089-1108
[21] Song XY, Zhou MF, Hou ZQ, Cao ZM, Wang YL and Li YG. 2001. Geochemical constraints on the mantle source of the Upper Permian Emeishan continental flood basalts, southwestern China. International Geology Review, 43(3): 213-225
[22] Song XY, Zhou MF, Cao ZM and Robinson PT. 2004. Late Permian rifting of the South China Craton caused by the Emeishan mantle plume? Journal of the Geological Society London, 161(5): 773-781
[23] Song XY, Zhang CJ, Hu RZ, Zhong H, Zhou MF, Ma RZ and Li YG. 2005. Genetic links of magmatic deposits in the Emeishan large igneous province with dynamics of mantle plume. Journal of Mineralogy and Petrology, 25(4): 35-44 (in Chinese with English abstract)
[24] Song XY, Keays RR, Long X, Qi HW and Ihlenfeld C. 2009. Platinum-group element geochemistry of the continental flood basalts in the central Emeisihan large igneous province, SW China. Chemical Geology, 262(3-4): 246-261
[25] Song XY, Qi HW, Hu RZ, Chen LM, Yu SY and Zhang JF. 2013. Formation of thick stratiform Fe-Ti oxide layers in layered intrusion and frequent replenishment of fractionated mafic magma: Evidence from the Panzhihua intrusion, SW China. Geochemistry Geophysics Geosystems, 14(3): 712-732
[26] Tegner C, Duncan RA, Bernstein S, Brooks CK, Bird DK and Storey M. 1998. 40Ar-39Ar geochronology of Tertiary mafic intrusions along the East Greenland rifted margin: Relation to flood basalts and the Iceland hotspot track. Earth and Planetary Science Letters, 156(1-2): 75-88
[27] Toplis MJ and Carrol MR. 1996. Differentiation of ferro-basaltic magmas under conditions open and closed to oxygen: Implications for the Skaergaard intrusion and other natural systems. Journal of Petrology, 37(4): 837-858
[28] Wang DH. 1998. Mantle Plume and Mineralization. Beijing: Seismic Press, 1-160 (in Chinese with English abstract)
[29] Wilmart E, Demaiffe D and Duchesne JC. 1989. Geochemical constraints on the genesis of the Tellnes ilmenite deposit, Southwest Norway. Economic Geology, 84(5): 1047-1056
[30] Xiao L, Xu YG and He B. 2003. Emei mantle plume-subcontinental lithosphere interaction: Sr-Nd and O isotopic evidences from low-Ti and high-Ti basalts. Geological Journal of China Universities, 9(2): 207-217 (in Chinese with English abstract)
[31] Xiao L, Xu YG, Mei HJ, Zheng YF, He B and Pirajno F. 2004. Distinct mantle sources of low-Ti and high-Ti basalts from the western Emeishan large igneous province, SW China: Implications for plume-lithosphere interaction. Earth and Planetary Science Letters, 228(3-4): 525-546
[32] Xu YG and Zhong SL. 2001. The Emeishan large igneous province: Evidence for mantle plume activity and melting conditions. Geochimica, 30(1): 1-9 (in Chinese with English abstract)
[33] Xu YG, Chung SL, Jahn BM and Wu GY. 2001. Petrologic and geochemical constraints on the petrogenesis of Permian-Triassic Emeishan flood basalts in southwestern China. Lithos, 58(3-4): 145-168
[34] Xu YG, Mei HJ, Xu JF, Huang XL, Wang YJ and Chung SL. 2003. Origin of two differentiation trends in the Emeishan flood basalts. Chinese Science Bulletin, 48(4): 383-387 (in Chinese)
[35] Xu YG, He B, Chung SL, Menzies MA and Frey FA. 2004. Geologic, geochemical, and geophysical consequences of plume involvement in the Emeishan flood-basalt province. Geology, 32(10): 917-920
[36] Zhang XQ, Zhang JF, Song XY, Deng YF, Guan JX and Zheng WQ. 2011. Implications of compositions of plagioclase and olivine on the formation of the Panzhihua V-Ti magnetite deposit, Sichuan Province. Acta Petrologica Sinica, 27(12): 3675-3688 (in Chinese with English abstract)
[37] Zhang ZC, Mahoney JJ, Mao JW and Wang FS. 2006. Geochemistry of picritic and associated basalt flows of the western Emeishan flood basalt province, China. Journal of Petrology, 47(10): 1997-2019
[38] Zhang ZC, Zhi XC, Chen L, Saunders AD. and Reichow MK. 2008. Re-Os isotopic compositions of picrites from the Emeishan flood basalt province, China. Earth and Planetary Science Letters, 276(1-2): 30-39
[39] Zhang ZC, Mao JW, Saunders AD, Ai Y, Li Y and Zhao L. 2009. Petrogenetic modeling of three mafic-ultramafic layered intrusions in the Emeishan large igneous province, SW China, based on isotopic and bulk chemical constraints. Lithos, 113(3-4): 369-392
[40] Zhang ZC, Hou T, Santosh M, Li HM, Li JW, Zhang ZH, Song XY and Wang M. 2014. Spatio-temporal distribution and tectonic settings of the major iron deposits in China: An overview. Ore Geology Reviews, 57: 247-263
[41] Zhong H, Yao Y, Hu SF, Zhou XH, Liu BG, Sun M, Zhou MF and Viljeon MJ. 2003. Trace-element and Sr-Nd isotopic geochemistry of the PGE-bearing Hongge layered intrusion, southwestern China. International Geology Review, 45(4): 371-382
[42] Zhong H and Zhu WG. 2006. Geochronology of layered mafic intrusions from the Pan-Xi area in the Emeishan large igneous province, SW China. Mineralium Deposita, 41(6): 599-606
[43] Zhou MF, Malpas J, Song XY, Robinson PT, Sun M, Kennedy AK, Lesher CM and Keays RR. 2002. A temporal link between the Emeishan large igneous province (SW China) and the end-Guandalupian mass extinction. Earth and Planetary Science Letters, 196(3-4): 113-122
[44] Zhou MF, Robinson PT, Lesher CM, Keays RR, Zhang CJ and Malpas JM. 2005. Geochemistry, petrogenesis and metallogenesis of the Panzhihua gabbroic layered intrusion and associated Fe-Ti-V oxide deposits, Sichuan Province, SW China. Journal of Petrology, 46(11): 2253-2280
[45] 范蔚茗, 王岳军, 彭头平, 苗来成, 郭锋. 2004. 桂西晚古生代玄武岩Ar-Ar和U-Pb年代学及其对峨眉山玄武岩省喷发时代的约束. 科学通报, 49(18): 1892-1900
[46] 郝艳丽, 张招崇, 王福生, Mahonet JJ. 2004. 峨眉山大火成岩省"高钛玄武岩"和"低钛玄武岩"成因探讨. 地质论评, 50(6): 587-592
[47] 侯增谦, 卢记仁, 林盛中. 2005. 峨眉地幔柱轴部的榴辉岩-地幔岩源区:主元素、痕量元素及Sr、Nd、Pb同位素证据. 地质学报, 79(2): 200-219
[48] 胡瑞忠, 陶琰, 钟宏, 黄智龙, 张正伟. 2005. 地幔柱成矿系统:以峨眉山地幔柱为例. 地学前缘, 12(1): 42-54
[49] 宋谢炎, 胡瑞忠, 张成江, 钟宏, 周美夫, 马润则, 李佑国. 2005. 峨眉火成岩省岩浆矿床成矿作用与地幔柱动力学过程的耦合关系. 矿物岩石, 25(4): 35-44
[50] 王登红. 1998. 地幔柱及其成矿作用. 北京: 地震出版社, 1-160
[51] 肖龙, 徐义刚, 何斌. 2003. 峨眉地幔柱-岩石圈的相互作用:来自低钛和高钛玄武岩的Sr-Nd和O同位素证据. 高校地质学报, 9(2): 207-217
[52] 徐义刚, 钟孙霖. 2001. 峨眉山大火成岩省: 地幔柱活动的证据及其熔融条件. 地球化学, 30(1): 1-9
[53] 徐义刚, 梅厚钧, 许继峰, 黄小龙, 王岳军, 钟孙霖. 2003. 峨眉山大火成岩省两类岩浆分异趋势及其成因. 科学通报, 48(4): 383-387
[54] 张晓琪, 张加飞, 宋谢炎, 邓宇峰, 官建祥, 郑文勤. 2011. 斜长石和橄榄石成分对四川攀枝花钒钛磁铁矿床成因的指示意义. 岩石学报, 27(12): 3675-3688
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