中天山南缘代京却克却二长花岗岩年代学研究及构造意义
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摘要
新疆中天山南缘地区广泛分布晚古生代侵入岩,对中天山南缘代京却克却地区二长花岗岩进行LA-ICP-MS锆石U-Pb定年,获得岩体结晶年龄为(394.7±2.9)Ma,属中泥盆世。岩石地球化学结果表明,该二长花岗岩为一套高钾钙碱性系列过铝质岩石,大离子亲石元素Rb,Th,K相对富集,高场强元素Nb,Ta,Ti,P相对亏损。结合区域地质背景,认为中天山南缘代京却克却地区二长花岗岩形成于火山弧环境,是幔源岩浆底侵带来的大量热能使得晚古生代下地壳物质发生部分熔融的产物。综合分析认为,该岩体可能代表了中泥盆世南天山洋向中天山微地块之下的俯冲岩浆活动记录。
Late Palaeozoic.Intrusive rocks are widely distributed in southern margin area of Central Tianshan Mountain.The LA-ICP MS age of zircon which are located in the Daijingquekeque are(394.7±2.9) Ma,Geochemistry results show that devonianmonzonitic granite major elements belong to High potassium peraluminous calc-alkaline rocks Series,which display LILE enrichment of Rb,Th and K,and HFSE depletion of Nb,Ta,Ti,P;Monzonitic granite that REEs are characterized by right type distribution patterns.The geochemical characteristics show that Devonian monzonitic granit,which was the product of Late Palaeozoic lower crust partial melting because of mantle-derived magma underplating brings a lot of heat,have characteristics of volcanic arc granites. Therefore,devonian monzonitic are considered as the earliest magma record of South Tianshan ocean basin northward subduction in the Daijingquekeque area,Central Tianshan Mountains.
Late Palaeozoic.Intrusive rocks are widely distributed in southern margin area of Central Tianshan Mountain.The LA-ICP MS age of zircon which are located in the Daijingquekeque are(394.7±2.9) Ma,Geochemistry results show that devonianmonzonitic granite major elements belong to High potassium peraluminous calc-alkaline rocks Series,which display LILE enrichment of Rb,Th and K,and HFSE depletion of Nb,Ta,Ti,P;Monzonitic granite that REEs are characterized by right type distribution patterns.The geochemical characteristics show that Devonian monzonitic granit,which was the product of Late Palaeozoic lower crust partial melting because of mantle-derived magma underplating brings a lot of heat,have characteristics of volcanic arc granites. Therefore,devonian monzonitic are considered as the earliest magma record of South Tianshan ocean basin northward subduction in the Daijingquekeque area,Central Tianshan Mountains.
引文
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[25]王守敬,王居里.新疆巴伦台钾长花岗岩的地球化学及年代学[J].西北大学学报(自然科学版),2010, 30(1):105-110.
[26] Dong Y P, Zhang G W, Li W, et al. Syn-and post-collisional granitoids in the Central Tianshan orogen:Geochemistry, geochronology and implications for tectonic evolution[J]. Gondwana Research, 2011, 20:568-581.
[27] Shi Y R, Jian P, Ma H D, et, al. Zircon ages and Hf isotopic compositions of plutonic rocks from the Central Tianshan(Xinjiang,northwest China)and their significance for early to mid-Palaeozoic crustal evolution[J]. International Geology Review, 2014,56:1413-1434.
[2] Xiao W J, Zhang L C, Li J L, et al. Paleozoic accretionary and collisional tectonics of the eastern Tianshan(China):implication for the continental growth of central Asia[J]. American Journal of Science, 2004b, 304:370-395.
[3]董云鹏,周鼎武,徐静刚,等.中天山北缘干沟蛇绿混杂岩带的地质地球化学[J].岩石学报,2006, 22(1):49-56.
[4]高俊,龙灵利,Klemd R.南天山晚古生代还是三叠纪碰撞造山带[J].岩石学报,2006, 22(5):1049-1061.
[5]李锦轶,王克桌,朱志新,等.天山山脉地貌特征、地壳组成与地质演化[J].地质通报,2006, 25(8):895-909.
[6]韩宝福,郭召杰,何国琦.“钉合岩体”与新疆北部主要缝合带的形成时限[J].岩石学报,2010, 26(8):2233-2246.
[7]朱志新,李锦轶,徐仕琪.新疆西天山古生代侵入岩的地质特征及构造意义[J].地学前缘,2011,18(2):170-179.
[8] Ma X X, Shu L S, Meert J G. Early Permian slab breakoff in the Chinese Tianshan belt inferred from the post-collisional granitoids[J]. Gondwana Research, 2015, 27:228-243.
[9]李平,朱志新,穆利修,等.新疆中天山巴伦台地区花岗质侵入体地球化学、年代学研究及构造意义[J].地质学报,2017,91(1):80-93.
[10]韩宝富,郭召杰,何国琦.“钉合岩体”与新疆北部主要缝合带的形成时限[J].岩石学报,2010, 26(8):2233-2246.
[11]张喜,高俊,钱青,等.新疆中天山乔霍特铜矿区I型花岗岩锆石LA-ICP-MS-U-Pb年龄及其地质意[J].岩石学报,2011, 27(6):1637-1648.
[12]田亚洲,杨经绥,高健,等.新疆布鲁斯台辉长岩岩石学特征及对南天山洋俯冲时限的制约[J].岩石学报,2014, 30(8):2363-2380.
[13] Liu Y S, Hu Z C, Gao S. In-situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J]. Chemical Geology, 2008, 257:34-43.
[14] Ludwing K R. ISOPLOT 3.00/A Geochronnlogical Toolkit for Microsoft Excel[J]. Berkeley Geochronology Center Special Publication, 2003, 4:1-70.
[15]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):1589-1604.
[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(4):956-983.
[17] Rapp R P, Watson E B. 1995. Dehydration melting of metabasalt at 8-32 kbar:Implications for continental growth and crust-mantle recycling[J]. Journal of Petrology, 36(4):891-931.
[18] Barth M G, Nough W F,Rudnick R L.Tracking the budget of Nb and Ta in the continental crust[J]. Chemical Geology,2000, 165(99):197-213.
[19] Bea F, Arzamastsev A, Montero P, et al. 2001.Anomalous alkaline rocks of Soustov Kola:Evidence of mantle derived metasomatic fluids affecting crustal materials[J]. Contributions to Mineralogy and Petrology, 140(5):554-566.
[20] Zhang L F, Ai Y L, Liu J G, et al. Triassic collision of western Tianshan orogenic belt, China:evidence from SHRIMP U-Pb dating of zircon from HP/UHP eclogitic rocks[J]. Lithos, 2007a, 96:266-280.
[21]李曰俊,孙龙德,彭更新,等.南天山西端乌帕塔尔坎群发现石炭-二叠纪放射虫化石[J].地质科学,2005, 40(2):220-226.
[22]舒良树,卢华复,王博,等.中-南天山古生代增生-碰撞事件和变形运动学研究[J].南京大学学报(自然科学版),2003, 39(1):17-30.
[23]舒良树,朱文斌,丁海峰,等.新疆古块体的形成与演化[J].中国地质,2013, 40(1):43-60.
[24]夏林祈,张国伟,李向民.天山古生代洋盆开启、闭合时限的岩石学约束—来自震旦纪、石炭纪火山岩的证据[J].地质通报,2002, 21(2):55-65.
[25]王守敬,王居里.新疆巴伦台钾长花岗岩的地球化学及年代学[J].西北大学学报(自然科学版),2010, 30(1):105-110.
[26] Dong Y P, Zhang G W, Li W, et al. Syn-and post-collisional granitoids in the Central Tianshan orogen:Geochemistry, geochronology and implications for tectonic evolution[J]. Gondwana Research, 2011, 20:568-581.
[27] Shi Y R, Jian P, Ma H D, et, al. Zircon ages and Hf isotopic compositions of plutonic rocks from the Central Tianshan(Xinjiang,northwest China)and their significance for early to mid-Palaeozoic crustal evolution[J]. International Geology Review, 2014,56:1413-1434.