云南香格里拉可麦洛新生代碱性侵入岩地球化学特征及意义
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摘要
分布于扬子地台西缘、哀牢山-红河断裂带的新生代碱性侵入岩为研究板内岩浆系统中的壳幔作用及地球化学循环提供了理想的研究窗口。研究选择对香格里拉地区可麦洛碱性侵入岩的元素地球化学特征进行测试分析,结果显示该岩体具有高铝(w_(Al2)O_313.50%～15.50%,平均14.63%)、碱值(w_(Na2)O+K_2O为6.79%～9.95%,平均8.74%)的特征;w(MgO)为1.74%～5.25%,平均为3.21%;w(Ni)为25.17×10~(-6)～127.16×10~(-6),平均54.47×10~(-6);w(Cr)为12.86×10~(-6)～48.23×10~(-6),平均26.76×10~(-6),与滇西新生代碱性岩相比富含亲稀土元素(644.55×10~(-6)～402.09×10~(-6)),Eu异常不明显(Eu/Eu~*=0.89～1.09)。微量元素蛛网图显示出较强的负K,Ti(Ti/Ti~*=0.38～0.45)异常,Nb异常变化较大(Nb/Nb~*=1.29～0.47)。综合分析该侵入岩可能起源于壳幔过渡带的部分熔融,其源区残留有石榴石、角闪石和金云母。软流圈上涌及下地壳拆沉很可能导致扬子地台西缘下伏岩石圈地幔与下地壳形成物质能量交换,而长期的壳幔反应会造成岩石圈地幔弱化,局部出现低强度的弱化岩石圈地幔,形成壳幔过渡带。
Cenozoic alkaline intrusions occurred on the east side of the Ailaoshan-Red River shear zone in the western Yangtze craton provide an opportunity for understanding of the crust-mantle interaction and geochemical cycling in the intra-plate magmatic system.The analyzed ten samples from the Kemailuo alkaline intrusions,Shangri-La County are characterized by high contents of w(Al_2O_3)(13.50%～15.50%),alkaline(6.79%～9.95%),w(MgO)(1.74%～5.25%),w(Ni)(25.17×10~(-6)～127.16×10~(-6)) and w(Cr)(12.86×10~(-6)～48.23×10~(-6)).Light rare earth element(644.55×10~(-6)～402.09×10~(-6)) in these samples are higher than other Cenozoic alkaline rocks in Western Yunnan.In addition,these samples show nearly flat heavy rare earth element(HREE) patterns and insignificant Eu anomalies(Eu/Eu~*=0.89～1.09).Trace element spider diagram displays strong negative K,Ti(Ti/Ti~*=0.38～0.45) anomalies and variable Nb anomalies(Nb/Nb~*=1.29～0.47).Trace element modeling indicates that garnet,amphibole and phlogopite may be present in the residua during source partial melting.Through comprehensive analysis,it is considered that the crust-mantle transition zone might be the source of Kemailuo alkaline intrusions,and the upwelling of the asthenosphere and delamination of lower crust lead to the exchange of material energy between the lower lithosphere mantle and the lower crust in the west margin of Yangtze craton.
Cenozoic alkaline intrusions occurred on the east side of the Ailaoshan-Red River shear zone in the western Yangtze craton provide an opportunity for understanding of the crust-mantle interaction and geochemical cycling in the intra-plate magmatic system.The analyzed ten samples from the Kemailuo alkaline intrusions,Shangri-La County are characterized by high contents of w(Al_2O_3)(13.50%～15.50%),alkaline(6.79%～9.95%),w(MgO)(1.74%～5.25%),w(Ni)(25.17×10~(-6)～127.16×10~(-6)) and w(Cr)(12.86×10~(-6)～48.23×10~(-6)).Light rare earth element(644.55×10~(-6)～402.09×10~(-6)) in these samples are higher than other Cenozoic alkaline rocks in Western Yunnan.In addition,these samples show nearly flat heavy rare earth element(HREE) patterns and insignificant Eu anomalies(Eu/Eu~*=0.89～1.09).Trace element spider diagram displays strong negative K,Ti(Ti/Ti~*=0.38～0.45) anomalies and variable Nb anomalies(Nb/Nb~*=1.29～0.47).Trace element modeling indicates that garnet,amphibole and phlogopite may be present in the residua during source partial melting.Through comprehensive analysis,it is considered that the crust-mantle transition zone might be the source of Kemailuo alkaline intrusions,and the upwelling of the asthenosphere and delamination of lower crust lead to the exchange of material energy between the lower lithosphere mantle and the lower crust in the west margin of Yangtze craton.
引文
[1] Lu Y J,Kerrich R,Mccuaig T C, et al.Geochemical,Sr-Nd-Pb,and zircon Hf-O isotopic compositions of Eocene-Oligocene shoshonitic and potassic adakite-like felsic intrusions in western Yunnan,SW China:petrogenesis and tectonic implications[J].Journal of Petrology,2013,54:1 309-1 348.
[2] Xu Y G,Menzies M A,Thirlwall M F, et al.Exotic lithosphere mantle beneath the western Yangtze craton:petrogenetic links to Tibet using highly magnesian ultrapotassic rocks[J].Geology,2001,29:863-866.
[3] Zhang Z C,Xiao X C,Wang J, et al.Post-collisional Plio-Pleistocene shoshonitic volcanism in the western Kunlun Mountains,NW China:Geochemical constraints on mantle source characteristics and petrogenesis[J].Journal of Asian Earth Sciences,2008,31:379-403.
[4] Ding L,Kapp P,Zhong D L, et al.Cenozoic volcanism in Tibet:evidence for a transition from oceanic to continental subduction[J].Journal of Petrology,2003,44:1 833-1 865.
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[6] Guo Z F,Hertogen J,Liu J Q, et al.Potassic magmatism in western Sichuan and Yunnan provinces,SE Tibet,China:petrological and geochemical constraints on petrogenesis[J].Journal of Petrology,2005,46:33-78.
[7] 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,1989,42:313-345.
[8] Huang X L,Niu Y L,Xu Y, 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,2010,51:1 617-1 654.
[9] Jiang Y H,Jiang S Y,Ling H F, et al.Low-degree melting of a metasomatized lithospheric mantle origin of Cenozoic Yulong monzogranite-porphyry,east Tibet:geochemical and Sr-Nd-Pb-Hf isotopic constraints[J].Earth and Planetary Science Letters,2006,241:617-633.
[10] 邓万明,孙宏娟,张玉泉.囊谦盆地新生代钾质火山岩成因岩石学研究[J].地质科学,2001,36(3):304-318.
[11] Castillo P R.Adakite petrogenesis[J].Lithos,2012,134:304-316.
[12] 邹光富,毛英,毛琼,等.西南三江地区大地构造演化与成矿作用[J].矿物岩石,2017,37(1):15-29.
[13] Li X H,Zhou H W,Liu Y, et al.Shoshonitic intrusive suite in SE Guangxi:petrology and geochemistry[J].Chinese Science Bulletin,2000,45:653-658.
[14] 侯增谦,侯立纬,叶庆同,等.三江义敦岛弧碰撞造山过程与成矿系统[M].北京:地质出版社,2003.
[15] Pearce J A.Trace element characteristics of lavas from destructive plate boundaries.In:Thorpe RS (ed) Andesites:Orogenic Andesites and related rocks[M].Wiley,Chichester,1982,525-548.
[16] Pearce J A,Harris N B W,Tindle A G.Trace element discrimination diagrams for the tectonic interpretation of granitic rocks[J].Journal of Petrology,1984,25:956-983.
[17] Furman T,Graham D.Erosion of lithospheric mantle beneath the East African Rift system:geochemical evidence from the Kivu volcanic province[J].Lithos,1999,48:237-262.
[18] Hastie AR,Kerr AC,McDonald I, et al.Geochronology,geochemistry and petrogenesis of rhyodacite lavas in eastern Jamaica:A new adakite subgroup analogous to early Archaean continental crust? [J].Chemcal Geology,2010,276:344-359.
[19] 赖绍聪,张国伟,秦江锋,等.青藏高原东北缘伯阳地区第三系流纹岩地球化学及岩石成因[J].地学前缘,2006,13(4):212-220.
[20] Jung S,Masberg P,Mihm D, et al.Partial melting of diverse crustal sources-constraints from Sr-Nd-O isotopic compositions of quartz diorite-granodiorite-leucogranite associations (Kaoko Belt,Namibia) [J].Lithos,2009,111:236-251.
[21] Cai K D,Sun M,Yuan C, et al.Geochronology,petrogenesis and tectonic significance of peraluminous granites from the Chinese Altai,NW China[J].Lithos,2011,127:261-281.
[22] 邓万明,钟大赉.壳-幔过渡带及其在岩石圈构造演化中的地质意义[J].科学通报,1997,42(23):2 474-2 482.
[23] Gallagher K,Hawkesworth C.Dehydration melting and the generation of continental flood basalts[J].Nature,1992,358:57-59.
[24] Deng J,Wang Q F,Li G J, et al.Cenozoic tectono-magmatic and metallogenic processes in the Sanjiang region,southwestern China[J].Earth-Science Reviews,2014,138:268-299.
[25] Wang J H,Yin A,Harrison T M, et al.A tectonic model for Cenozoic igneous activities in the eastern Indo-Asian Collision Zone[J].Earth and Planetary Science Letters,2001,188:123-133.
[26] Gilley L D,Harrison T M,Leloup P H, et al.Direct dating of left-lateral deformation along the Red River shear zone,China and Vietnam[J].Journal of Geophysical Research Solid Earth,2003,108(B2):14-21.
[27] 赵甫峰,刘显凡,卢秋霞,等.云南六合正长斑岩中花岗岩包体锆石U-Pb定年及其地质意义[J].地质学报,2011,85(10):1 574-1 584.
[28] 路凤香,郑建平,张瑞生,等.地壳与弱化岩石圈地幔的相互作用:以燕山造山带为例[J].地球科学-中国地质大学学报,2006,31(1):1-7.
[29] 路凤香,郑建平,张瑞生,等.华北克拉通东部显生宙地幔演化[J].地学前缘,2005,12(1):61-67.
[30] 刘建华,刘福田,何建坤,等.攀西古裂谷的地震成像研究——壳幔构造特征及其演化推断[J].中国科学D辑,2000,30(B12):9-15.
(1)云南省地质矿产勘察开发局.1∶25×104中甸幅区地质调查报告.2003.
[2] Xu Y G,Menzies M A,Thirlwall M F, et al.Exotic lithosphere mantle beneath the western Yangtze craton:petrogenetic links to Tibet using highly magnesian ultrapotassic rocks[J].Geology,2001,29:863-866.
[3] Zhang Z C,Xiao X C,Wang J, et al.Post-collisional Plio-Pleistocene shoshonitic volcanism in the western Kunlun Mountains,NW China:Geochemical constraints on mantle source characteristics and petrogenesis[J].Journal of Asian Earth Sciences,2008,31:379-403.
[4] Ding L,Kapp P,Zhong D L, et al.Cenozoic volcanism in Tibet:evidence for a transition from oceanic to continental subduction[J].Journal of Petrology,2003,44:1 833-1 865.
[5] Chen J L,Xu J F,Wang B D, et al.Origin of Cenozoic alkaline potassic volcanic rocks at KonglongXiang,Lhasa terrane,Tibetan Plateau:Products of partial melting of a mafic lower-crustal source? [J].Chemcal Geology,2010,273:286-299.
[6] Guo Z F,Hertogen J,Liu J Q, et al.Potassic magmatism in western Sichuan and Yunnan provinces,SE Tibet,China:petrological and geochemical constraints on petrogenesis[J].Journal of Petrology,2005,46:33-78.
[7] 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,1989,42:313-345.
[8] Huang X L,Niu Y L,Xu Y, 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,2010,51:1 617-1 654.
[9] Jiang Y H,Jiang S Y,Ling H F, et al.Low-degree melting of a metasomatized lithospheric mantle origin of Cenozoic Yulong monzogranite-porphyry,east Tibet:geochemical and Sr-Nd-Pb-Hf isotopic constraints[J].Earth and Planetary Science Letters,2006,241:617-633.
[10] 邓万明,孙宏娟,张玉泉.囊谦盆地新生代钾质火山岩成因岩石学研究[J].地质科学,2001,36(3):304-318.
[11] Castillo P R.Adakite petrogenesis[J].Lithos,2012,134:304-316.
[12] 邹光富,毛英,毛琼,等.西南三江地区大地构造演化与成矿作用[J].矿物岩石,2017,37(1):15-29.
[13] Li X H,Zhou H W,Liu Y, et al.Shoshonitic intrusive suite in SE Guangxi:petrology and geochemistry[J].Chinese Science Bulletin,2000,45:653-658.
[14] 侯增谦,侯立纬,叶庆同,等.三江义敦岛弧碰撞造山过程与成矿系统[M].北京:地质出版社,2003.
[15] Pearce J A.Trace element characteristics of lavas from destructive plate boundaries.In:Thorpe RS (ed) Andesites:Orogenic Andesites and related rocks[M].Wiley,Chichester,1982,525-548.
[16] Pearce J A,Harris N B W,Tindle A G.Trace element discrimination diagrams for the tectonic interpretation of granitic rocks[J].Journal of Petrology,1984,25:956-983.
[17] Furman T,Graham D.Erosion of lithospheric mantle beneath the East African Rift system:geochemical evidence from the Kivu volcanic province[J].Lithos,1999,48:237-262.
[18] Hastie AR,Kerr AC,McDonald I, et al.Geochronology,geochemistry and petrogenesis of rhyodacite lavas in eastern Jamaica:A new adakite subgroup analogous to early Archaean continental crust? [J].Chemcal Geology,2010,276:344-359.
[19] 赖绍聪,张国伟,秦江锋,等.青藏高原东北缘伯阳地区第三系流纹岩地球化学及岩石成因[J].地学前缘,2006,13(4):212-220.
[20] Jung S,Masberg P,Mihm D, et al.Partial melting of diverse crustal sources-constraints from Sr-Nd-O isotopic compositions of quartz diorite-granodiorite-leucogranite associations (Kaoko Belt,Namibia) [J].Lithos,2009,111:236-251.
[21] Cai K D,Sun M,Yuan C, et al.Geochronology,petrogenesis and tectonic significance of peraluminous granites from the Chinese Altai,NW China[J].Lithos,2011,127:261-281.
[22] 邓万明,钟大赉.壳-幔过渡带及其在岩石圈构造演化中的地质意义[J].科学通报,1997,42(23):2 474-2 482.
[23] Gallagher K,Hawkesworth C.Dehydration melting and the generation of continental flood basalts[J].Nature,1992,358:57-59.
[24] Deng J,Wang Q F,Li G J, et al.Cenozoic tectono-magmatic and metallogenic processes in the Sanjiang region,southwestern China[J].Earth-Science Reviews,2014,138:268-299.
[25] Wang J H,Yin A,Harrison T M, et al.A tectonic model for Cenozoic igneous activities in the eastern Indo-Asian Collision Zone[J].Earth and Planetary Science Letters,2001,188:123-133.
[26] Gilley L D,Harrison T M,Leloup P H, et al.Direct dating of left-lateral deformation along the Red River shear zone,China and Vietnam[J].Journal of Geophysical Research Solid Earth,2003,108(B2):14-21.
[27] 赵甫峰,刘显凡,卢秋霞,等.云南六合正长斑岩中花岗岩包体锆石U-Pb定年及其地质意义[J].地质学报,2011,85(10):1 574-1 584.
[28] 路凤香,郑建平,张瑞生,等.地壳与弱化岩石圈地幔的相互作用:以燕山造山带为例[J].地球科学-中国地质大学学报,2006,31(1):1-7.
[29] 路凤香,郑建平,张瑞生,等.华北克拉通东部显生宙地幔演化[J].地学前缘,2005,12(1):61-67.
[30] 刘建华,刘福田,何建坤,等.攀西古裂谷的地震成像研究——壳幔构造特征及其演化推断[J].中国科学D辑,2000,30(B12):9-15.
(1)云南省地质矿产勘察开发局.1∶25×104中甸幅区地质调查报告.2003.