新疆西准噶尔谢米斯台一带志留纪流纹岩地球化学特征及构造意义
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摘要
谢米斯台一带志留纪火山岩主要为一套中酸性火山岩及其火山碎屑岩建造,流纹岩大面积出露,具有高Si(SiO_2>70.53%)、低镁(MgO=0.12%~0.58%)、富K贫Na(Na_2O=1.71%~4.45%,K_2O=4.21%~5.72%,Na_2O/K_2O=0.38~0.91)、富Al贫Ca(Al_2O_3=11.04%~15.2%,CaO=0.3%~1.94%)等特征,大离子亲石元素(LILE)相对富集,高场强元素(HFSE)相对亏损,Eu具有弱—中等的负异常,且Nb/La、Ti/Y比值较低,Hf/Ta、La/Ta、La/Yb、Ta/Yb等比值均较高,显示具典型岛弧火山岩地球化学特征。结合区域构造演化特征,推测在谢米斯台一带,准噶尔洋在志留纪开始进入强烈的俯冲消减作用,在壳幔结合部位可能俯冲板片与富集地幔局部熔融引起下地壳物质大规模的部分熔融或重熔,经历了一定程度的分离结晶和大量地壳物质的混染形成的酸性岩浆喷发形成流纹岩,是陆壳垂向增生的一个主要阶段。早古生代晚期,谢米斯台地区处于萨吾尔复合岛弧的南部边缘岛弧环境。
The Silurian volcanic rocks are mainly composed of medium-acid volcanic rocks and volcaniclastic rocks in Xiemisitai area. The geochemical characteristics of rhyolite are sililar to those of typical island arc volcanic rocks. For example, the rhyolites have high-SiO_2(SiO_2>70.53%), low-Mg(MgO=0.12%-0.58%), Krich and Na-depletion(Na_2O=1.71%-4.45%, K_2O=4.21%-5.72%, Na_2O/K_2O=0.38-0.91), Al-rich and Ca-depletion(Al_2O_3=11.04%-15.2%, CaO=0.3%-1.94%), relatively enriched LILE, relatively depleted HFSE, and weak-moderate negative anomaly Eu. The rhyolites have low ratios of Nb/La, Ti/Y and high ratios of Hf/Ta, La/Ta, La/Yb, Ta/Yb. It suggests that the Junggar Ocean began to enter into strong subduction subtraction in the Silurian in the Xiemisitai area based on the background of regional tectonic evolution. The rhyolites maybe the product of partial melting in the mantle wedge region through the local melting of the subducted slab, and experienced a certain degree of separation and crystallization, which is a major stage in the vertical accretion of continental crust in the late Early Paleozoic.
The Silurian volcanic rocks are mainly composed of medium-acid volcanic rocks and volcaniclastic rocks in Xiemisitai area. The geochemical characteristics of rhyolite are sililar to those of typical island arc volcanic rocks. For example, the rhyolites have high-SiO_2(SiO_2>70.53%), low-Mg(MgO=0.12%-0.58%), Krich and Na-depletion(Na_2O=1.71%-4.45%, K_2O=4.21%-5.72%, Na_2O/K_2O=0.38-0.91), Al-rich and Ca-depletion(Al_2O_3=11.04%-15.2%, CaO=0.3%-1.94%), relatively enriched LILE, relatively depleted HFSE, and weak-moderate negative anomaly Eu. The rhyolites have low ratios of Nb/La, Ti/Y and high ratios of Hf/Ta, La/Ta, La/Yb, Ta/Yb. It suggests that the Junggar Ocean began to enter into strong subduction subtraction in the Silurian in the Xiemisitai area based on the background of regional tectonic evolution. The rhyolites maybe the product of partial melting in the mantle wedge region through the local melting of the subducted slab, and experienced a certain degree of separation and crystallization, which is a major stage in the vertical accretion of continental crust in the late Early Paleozoic.
引文
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[31]张海洋,沈晓明,马林,等.新疆北部富蕴县埃达克岩的同位素年代学及其对古亚洲洋板块俯冲时限的制约[J].岩石学报,2008,24(5):1054-1058.
[32]赵振华,王强,熊小林,等.新疆北部的两类埃达克岩[J].岩石学报,2006,22(5):1249-1265.
[33]赵振华,王强,熊小林,等.新疆北部的富镁火成岩[J].岩石学报,2007,23(7):1696-1707.
[34]牛贺才,单强,于学元,等.扎河坝蛇绿混杂岩内富铌玄武(安山)岩的地球化学特征及其地质意义[J].岩石学报,2009,25(4):916-924.
[35]牛贺才,单强,张兵,等.东扎河坝蛇绿混杂岩中的石榴角闪岩[J].岩石学报,25(6):1484-1491.
[36]杨维,王国灿,纵瑞文,等.西准噶尔志留纪—泥盆纪弧盆格局的确定及其区域构造演化意义[J].地球科学,2015,40(3):448-460.
[37]朱永峰,徐新,陈博,等.西准噶尔蛇绿混杂岩中的白云石大理岩和石榴角闪岩:早古生代残余洋壳深俯冲的证据[J].岩石学报,2008,24(12):2767-2777.
[38]孟磊,申萍,沈远超,等.新疆谢米斯台地区中段火山岩岩石学、地球化学及其含矿性研究[J].地质科学,45(2):551-563.
[2]肖序常,等.试论新疆北部大地构造演化[J].地质科学第一辑,北京:地质出版社,1990:47-68.
[3]Buslov M,Saphonova I Y,Watanabe T,et al.2001.Evolution of the Paleo-Asian Ocean(Altai-Sayan Region,Central Asia)and collision of possible Gondwana-derived terranes with the southern marginal part of the Siberian continent[J].Geosciences Journal,5(3):203-224.
[4]Buslov M,Watanabe T,Fujiwara Y,et al.2004.Late Paleozoic faults of the Altai region,central Asia:Tectonic pattern and model of formation[J].Journal of Asian Earth Sciences,23(5):655-671.
[5]Xiao W,Han C,Yuan C,et al.2008.Middle Cambrian to Permian subduction-related accretionary orogenesis of Northern Xinjiang,NW China:Implications for the tectonic evolution of central Asia[J].Journal of Asian Earth Sciences,32(2):102-117.
[6]何国琦,李茂松,刘德权,等.中国新疆古生代地壳演化及成矿[M].新疆:新疆人民出版社,1984.
[7]肖序常,汤耀庆,李锦铁,等.新疆北部及其邻区大地构造[M].北京:地质出版社,1992.
[8]王章棋,江秀敏,郭晶,等.新疆西准噶尔谢米斯台地区发现早古生代火山岩地层:野外地质学和年代学证据[J].大地构造与成矿学,2014,38(3):670-685.
[9]Gill J B.Orogenic Andesites and Plate Tectonics[M].New York:Springer-verlag,1981.
[10]Atherton M P,Petford N.1993.Generation of sodium-rich magmas from newly underplated basaltic crust[J].Nature,362:144-146.
[11]Belousova EA,Griffin WL,O’Reilly SY,et al.2002.Igneous zircon:Trace element composition as an indicator of source rocktype[J].Contributions to Mineralogy and Petrology,143(5):602-622.
[12]Wu YB and Zheng YF.2004.Genesis of Zircon and its constraints on interpretation of U-Pb age[J].Chinese Science Bulletin,49(15):1544-1569.
[13]Siebel W,Blaha U,Chen FK,et al.2005.Geochronology and geochemistry of a dyke-host rock association and implications for the formation of the Bavarian Pfahl shear zone,Bohemian Massif[J].International Journal of Earth Sciences,94(1):8-23.
[14]Shen P,Shen Y,Liu T,et al.2008.Geology and geochemistry of the Early Carboniferous Eastern Sawur caldera complex and associated gold epithermal mineralization,Sawur Mountains,Xinjiang,China[J].Journal of Asian Earth Sciences,32(2):259-279.
[15]孟磊,申萍,沈远超,等.新疆谢米斯台中段火山岩岩石地球化学特征、锆石U-Pb年龄及其地质意义[J].岩石学报,2010,26(10):3047-3056.
[16]Walker J D,Geissman J,Bowring S,et al.2013.The Geological Society of America Geologic Time Scale[J].Geological Society of America Bulletin,125(3-4):259-272.
[17]Xiao WJ,Han CM,Yuan C,et al.2008.Middle Cambrianto Permiansub ductionrelated accretionary orogenesis of northern Xinjiang,NW China:Implications for the tectonic evolution of central Asia[J].Journal of Asian Earth Sciences,32:102-117.
[18]肖序常,汤耀庆,冯益民.新疆北部及其邻区大地构造[M].北京:地质出版社,1992:1-169.
[19]何国琦,李茂松,刘德权,等.中国新疆古生代地壳演化及成矿[M].香港:香港文化教育出版社,1994:1-437.
[20]王广瑞.新疆北部及邻区地质构造单元与地质发展史[J].新疆地质,1996,14(1):12-27.
[21]李锦轶,何国琦,徐新,等.新疆北部及邻区地壳构造格架及其形成过程的初步探讨[J].地质学报,2006,80(1):148-168.
[22]Rollison HR.1993.Using Geochemical Data:Evaluation,Presentation,Interpretation[M].London:Longman Group UK Ltd,1-267.
[23]Salters VJM and Hart SR.1991.The mantle sources of ocean ridges,island arcs:The Hf-isotope connection[J].Earth Planet,Sci.Lett.,104:364-380.
[24]Pearce JA,Harris NBW and Tindle AG.1984.Trace element discrimination diagrams for the tectonic interpretation of granitic rocks[J].J.Petrol.,25(4):956-983.
[25]Ajaji T,Weis D and Giret A.1998.Coeval potassic and sodic calcalkaline series in the postcollisional Hercynian Tanncherfi intrusive complex,northeastern Morocco:Geochemical,isotopic and geochronological evidenc.Lithos,45:371-393.
[26]王金荣,贾志磊,李泰德,等.新疆西准噶尔发现早泥盆世埃达克岩:大地构造及成矿意义[J].岩石学报,2013,29(3):841-852.
[27]孙敏,龙晓平,蔡克大,等.阿尔泰早古生代末期洋中脊俯冲:锆石Hf同位素组成突变的启示[J].中国科学(D辑),39(7):935-948.
[28]Yuan C,Sun M,Xiao WJ,et al.2007.Accretionary orogenesis of the Chinese Altai:Insights from Paleozoic granitoids[J].Chemical Geology,242(1-2):22-39.
[29]Sun M,Yuan C,Xiao WJ,et al.2008.Zircon U-Pb and Hf isotopic study of gneissic rocks from the Chinese Altai:Progressive accretionary history in the Early to Middle Palaeozoic[J].Chemical Geology,247(3-4):352-383.
[30]张海洋,牛贺才,Sato H,等.新疆北部晚古生代埃达克岩、富铌玄武岩组合:古亚洲洋板块南向俯冲的证据[J].高校地质学报,2004,10(1):106-113.
[31]张海洋,沈晓明,马林,等.新疆北部富蕴县埃达克岩的同位素年代学及其对古亚洲洋板块俯冲时限的制约[J].岩石学报,2008,24(5):1054-1058.
[32]赵振华,王强,熊小林,等.新疆北部的两类埃达克岩[J].岩石学报,2006,22(5):1249-1265.
[33]赵振华,王强,熊小林,等.新疆北部的富镁火成岩[J].岩石学报,2007,23(7):1696-1707.
[34]牛贺才,单强,于学元,等.扎河坝蛇绿混杂岩内富铌玄武(安山)岩的地球化学特征及其地质意义[J].岩石学报,2009,25(4):916-924.
[35]牛贺才,单强,张兵,等.东扎河坝蛇绿混杂岩中的石榴角闪岩[J].岩石学报,25(6):1484-1491.
[36]杨维,王国灿,纵瑞文,等.西准噶尔志留纪—泥盆纪弧盆格局的确定及其区域构造演化意义[J].地球科学,2015,40(3):448-460.
[37]朱永峰,徐新,陈博,等.西准噶尔蛇绿混杂岩中的白云石大理岩和石榴角闪岩:早古生代残余洋壳深俯冲的证据[J].岩石学报,2008,24(12):2767-2777.
[38]孟磊,申萍,沈远超,等.新疆谢米斯台地区中段火山岩岩石学、地球化学及其含矿性研究[J].地质科学,45(2):551-563.